PERTUSSIS TOXIN BINDING PROTEIN

TECHNICAL FIELD

The invention relates to the field of biomedicine, and an anti-pertussis toxin (PT) single domain antibody and derivative protein thereof are disclosed. Specifically, a pertussis toxin-binding protein and use thereof are disclosed.

BACKGROUND

Bordetella pertussis (B. pertussis) is a Gram-negative bacterium that infects the upper respiratory tract to cause uncontrollable violent coughing. According to the World Health Organization, Bordetella pertussis infection causes an estimated 300,000 deaths worldwide every year, mainly among young unvaccinated infants. Babies with pertussis often need to be hospitalized in the pediatric intensive care unit, and their treatment usually involves mechanical ventilation. Pertussis in adults usually leads to chronic cough. The incidence of pertussis increased due to the exposure of unvaccinated and under-vaccinated individuals (including infants who have not been fully vaccinated), individuals whose immunity has weakened over time and asymptomatic carriers.

The previous pertussis vaccines were reported not to provide long-term protection. There is no approved therapeutic vaccine for pertussis. Antibiotics do not play a primary role in the course of pertussis due to not neutralizing pertussis toxin proteins, although Bordetella pertussis bacteria can be eliminated from respiratory tract by treatment. Furthermore, in the developing world, it is inconsistent and very difficult to obtain the existing pertussis vaccine (although defective). Therefore, a more effective treatment for pertussis is still needed.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides a pertussis toxin-binding protein capable of specifically binding to pertussis toxin and comprising at least one immunoglobulin single variable domain comprising CDR1, CDR2 and CDR3 selected from the group consisting of:

(1) CDR1 shown in SEQ ID NO: 1, CDR2 shown in SEQ ID NO: 2, and CDR3 shown in SEQ ID NO: 3;

(2) CDR1 shown in SEQ ID NO: 4, CDR2 shown in SEQ ID NO: 5, and CDR3 shown in SEQ ID NO: 6;

(3) CDR1 shown in SEQ ID NO: 7, CDR2 shown in SEQ ID NO: 8, and CDR3 shown in SEQ ID NO: 9;

(4) CDR1 shown in SEQ ID NO: 10, CDR2 shown in SEQ ID NO: 11, and CDR3 shown in SEQ ID NO: 12;

(5) CDR1 shown in SEQ ID NO: 13, CDR2 shown in SEQ ID NO: 14, and CDR3 shown in SEQ ID NO: 15;

(6) CDR1 shown in SEQ ID NO: 16, CDR2 shown in SEQ ID NO: 17, and CDR3 shown in SEQ ID NO: 18;

(7) CDR1 shown in SEQ ID NO: 19, CDR2 shown in SEQ ID NO: 20, and CDR3 shown in SEQ ID NO: 21;

(8) CDR1 shown in SEQ ID NO: 22, CDR2 shown in SEQ ID NO: 23, and CDR3 shown in SEQ ID NO: 24;

(9) CDR1 shown in SEQ ID NO: 25, CDR2 shown in SEQ ID NO: 26, and CDR3 shown in SEQ ID NO: 27;

(10) CDR1 shown in SEQ ID NO: 28, CDR2 shown in SEQ ID NO: 29, and CDR3 shown in SEQ ID NO: 30;

(11) CDR1 shown in SEQ ID NO: 31, CDR2 shown in SEQ ID NO: 32, and CDR3 shown in SEQ ID NO: 33;

(12) CDR1 shown in SEQ ID NO: 34, CDR2 shown in SEQ ID NO: 35, and CDR3 shown in SEQ ID NO: 36;

(13) CDR1 shown in SEQ ID NO: 37, CDR2 shown in SEQ ID NO: 38, and CDR3 shown in SEQ ID NO: 39.

In one aspect, the present invention provides a nucleic acid molecule encoding the pertussis toxin binding protein of the present invention.

In one aspect, the present invention provides an expression vector comprising the nucleic acid molecule of the present invention operably linked to an expression regulatory element.

In one aspect, the present invention provides a recombinant cell comprising the nucleic acid molecule of the present invention or transformed with the expression vector of the present invention, and capable of expressing the pertussis toxin binding protein.

In one aspect, the present invention provides a method for producing the pertussis toxin binding protein of the present invention, comprising:

a) culturing the recombinant cell of the present invention under conditions allowing the expression of the pertussis toxin binding protein;

b) recovering the pertussis toxin binding protein expressed by the recombinant cells from the culture obtained from step a); and

c) optionally further purifying and/or modifying the pertussis toxin binding protein obtained from step b).

In one aspect, the present invention provides a pharmaceutical composition comprising the pertussis toxin binding protein of the present invention and a pharmaceutically acceptable carrier.

In one aspect, the present invention provides a method for treating Bordetella pertussis infection in a subject, the method comprising administering to the subject an effective amount of pertussis toxin binding protein of the present invention or pharmaceutical composition of the present invention.

In one aspect, the present invention provides a method for preventing Bordetella pertussis infection in a subject, the method comprising administering to the subject an effective amount of pertussis toxin binding protein of the present invention or pharmaceutical composition of the present invention.

In one aspect, the present invention provides a method for detecting the presence and/or amount of pertussis toxin in a biological sample, the method comprising:

(a) contacting the biological sample and the control sample with the pertussis toxin binding protein of the present invention respectively under conditions allowing the formation of complex between the pertussis toxin binding protein and pertussis toxin;

(b) detecting the formation of the complex,

wherein the difference in the complex formation between the biological sample and the control sample indicates the presence and/or amount of pertussis toxin in the sample.

In one aspect, the present invention provides a kit comprising the pertussis toxin binding protein of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a survival curve of protection against PT toxin with single-dose administration of 20 μg/dose.

FIG. 2 is a survival curve of protection against PT toxin with single-dose administration of 40 μg/dose.

FIG. 3 is a survival curve of protection against PT toxin with multiple-dose administration of 20 μg/dose.

FIG. 4 is a survival curve of protection against PT toxin with multiple-dose administration of 40 μg/dose.

FIG. 5 is a survival curve of protection against PT toxin with multiple-dose administration of 20 μg/dose or 40 μg/dose.

FIG. 6 shows the amino acid sequence alignment of iPT7 humanized variants.

FIG. 7 shows the amino acid sequence alignment of iPT15 humanized variants.

FIG. 8 shows the amino acid sequence alignment of iPT42 humanized variants.

DETAILED DESCRIPTION OF THE INVENTION

Unless otherwise indicated or defined, all used terms have the common meaning in the field, which will be understood by those skilled in the field. See, for example, the standard manual, such as Sambrook et al., “Molecular cloning: a laboratory manual” (2nd edition), volumes 1-3. Cold Spring Harbor Laboratory Press (1989); Lewin, “Genes IV”, Oxford University Press, New York (1990); and Roitt et al., “Immunology” (2nd edition). Gover Medical Publishing, London. New York (1989), and the general prior art cited herein; in addition, unless otherwise stated, all the methods, steps, techniques and operations that are not specifically detailed may and have been performed in a manner known per se, which will be understood by those skilled in the art. Also see, for example, the standard manual, the above general prior art, and other references cited therein.

Unless otherwise specified, the terms “antibody” and “immunoglobulin” used interchangeably, whether referring to a heavy chain antibody or a conventional 4-chain antibody herein, are used as general terms to include a full-length antibody, its single chain and all parts, domains or fragments thereof (including but not limited to antigen-binding domains or fragments, such as VHH domains or VH/VL domains, respectively). In addition, the term “sequence” as used herein (for example, in the terms “immunoglobulin sequence”, “antibody sequence”, “single variable domain sequence”, “VHH sequence” or “protein sequence”, etc.) should generally be understood to include not only the relevant amino acid sequence, but also the nucleic acid sequence or nucleotide sequence encoding the sequence, unless a more limited explanation is required herein.

As used herein, the term “domain” (of a polypeptide or protein) refers to a folded protein structure, which can maintain its tertiary structure independent of the rest of the protein. Generally speaking, the domain is responsible for the individual functional properties of the protein, and in many cases, it can be added, removed or transferred to other proteins without losing the functions of the rest of the protein and/or the domain.

As used herein, the term “immunoglobulin domain” refers to a spherical region of an antibody chain (for example, a chain of a conventional 4-chain antibody or a heavy chain antibody), or a polypeptide basically composed of such spherical regions. The immunoglobulin domain is characterized by maintaining the immunoglobulin folding characteristics of antibody molecules.

As used herein, the term “immunoglobulin variable domain” refers to an immunoglobulin domain which is basically composed of four “framework regions” called “framework region 1” or “FR1”, “framework region 2” or “FR2”, “framework region 3” or “FR3”, and “framework region 4” or “FR4” in the field and hereinafter, respectively, wherein the framework regions are spaced apart by three “complementarity determining regions” called “complementarity determining region 1” or “CDR1”, “complementarity determining region 2” or “CDR2” and “complementarity determining region 3” or “CDR3”, respectively. Therefore, the general structure or sequence of immunoglobulin variable domain may be expressed as follows: FR1-CDR1-FR2-CDR2-FR3-CDR3-FR4. The immunoglobulin variable domain endows the antibody with specificity for antigen because of its antigen-binding site.

As used herein, the term “immunoglobulin single variable domain” refers to an immunoglobulin variable domain that can specifically bind to an epitope without pairing with other immunoglobulin variable domains. An example of immunoglobulin single variable domain within the meaning of the present invention is a “domain antibody”, such as immunoglobulin single variable domains VH and VL (a VH domain and a VL domain). Another example of the immunoglobulin single variable domain is the “VHH domain” (or simply “VHH”) of Camelidae as defined below.

The “VHH domain”, also known as the heavy chain single domain antibody, VHH domain, VHH antibody fragment and VHH antibody, is the variable domain of antigen-binding immunoglobulin called “heavy chain antibody (i.e., an antibody devoid of light chains)” (Hamers-Casterman C, Atarhouch T, Muyldermans S, Robinson G, Hamers C, Songa E B, Bendalman N, Hamers R.; “Naturally occurring antibodies devoid of light chains”; Nature 363, 446-448(1993)), The term “VHH domain” is used to distinguish the variable domain from the heavy chain variable domain (which is referred to herein as “VH domain”) and the light chain variable domain (which is referred to herein as “VL domain”) both existing in the conventional 4-chain antibody. The VHH domain specifically binds to the epitope without other antigen binding domains (this is contrary to the VH or VL domain in the conventional 4-chain antibody, in which case the epitope is recognized by the VL domain together with the VH domain). The VHH domain is a small, stable and efficient antigen recognition unit formed by a single immunoglobulin domain.

In the context of the present invention, the terms “heavy chain single domain antibody”, “VHH domain”, “VHH”. “VHH domain”. “VHH antibody fragment” and “VHH antibody” can be used interchangeably.

For example, as shown in FIG. 2 in Riechmann and Muyldermans, J. Immunol. Methods 231, 25-38 (1999), the amino acid residues used in the VHH domain of Camelidae can be numbered according to the general numbering method for VH domain given by Kabat et al. (Kabat et al. Sequences of Proteins of Immunological Interest, 5th Ed. Public Health Service, National Institutes of Health, Bethesda, Md. (1991)).

Alternative methods of numbering amino acid residues of the VH domain are also known in the art. For example, Chothia CDR refers to the position of the structural loop (Chothia and Lesk, J. mol. Biol. 196:901-917 (1987)). AbM CDR represents the compromise between Kabat hypervariable region and Chothia structural loop, and is used in the antibody modeling software Oxford Molecular's AbM. The “Contact” CDR is based on the analysis of the crystal structure of the available complex. The residues of CDR from each method are described as follows:

Loop
Kabat
AbM
Chothia
Contact

LCDR1
L24-L34
L24-L34
L26-L32
L30-L36

LCDR2
L50-L56
L50-L56
L50-L52
L46-L55

LCDR3
L89-L97
L89-L97
L91-L96
L89-L96

HCDR1 (Kabat
H31-H35B
H26-H35B
H26-H32
H30-H35B

numbering)

HCDR1 (Chothia
H31-H35
H26-H35
H26-H32
H30-H35

numbering)

HCDR2
H50-H65
H50-H58
H53-H55
H47-H58

HCDR3
H95-H102
H95-H102
H96-H101
H93-H101

However, it should be noted that, as well known for the VH domain and VHH domain in the art, the total number of amino acid residues in each CDR may be different and may not correspond to the total number of amino acid residues indicated by the Kabat numbering (that is, one or more positions according to the Kabat numbering system may not be occupied in the actual sequence, or the actual sequence may comprise more amino acid residues than allowed by the Kabat numbering). This means that, in general, the numbering according to Kabat may or may not correspond to the actual numbering of amino acid residues in the actual sequence.

For example, CDR can include an extended CDR, such as 24-36 or 24-34 (LCDR1), 46-56 or 50-56 (LCDR2) and 89-97 or 89-96 (LCDR3) in the VL; 26-35 (HCDR1), 50-65 or 49-65 (HCDR2) and 93-102, 94-102 or 95-102 (HCDR3) in the VH.

The total number of amino acid residues in the VHH domain will usually be in the range of 110 to 120, often between 112 and 115. However, it should be noted that smaller and longer sequences may also be suitable for the purpose described herein.

Other structural and functional properties of the VHH domain and a polypeptide containing the same can be summarized as follows:

The VHH domain, which has been naturally “designed” to functionally bind to the antigen devoid of the light chain variable domain and without interaction with the light chain variable domain, can be used as a single and relatively small functional antigen-binding structural unit, domain or polypeptide. This differentiates the VHH domain from the VH and VL domains of a conventional 4-chain antibody which are usually not suitable for practical application per se as a single antigen-binding protein or an immunoglobulin single variable domain, but need to be combined in some form or another form to provide functional antigen-binding units (such as in the form of conventional antibody fragments such as Fab fragments; or in the form of scFv composed of VH domains covalently linked to VL domains).

Because of these unique properties, the use of VHH domain—alone or as a part of a larger polypeptide—provides many significant advantages superior to that using conventional VH and VL domains, scFv or conventional antibody fragments (such as Fab- or F(ab′)2-fragments): only a single domain is needed to bind to antigen with high affinity and selectivity, so that there is neither need to exist two separate domains nor need to ensure that these two domains exist in an appropriate spatial conformation and configuration (for example, scFv generally needs specially designed linkers); the VHH domain can be expressed from a single gene without post-translational folding or modification; the VHH domain can be easily transformed into multivalent and multispecific formats (formatting); the VHH domain is highly soluble and has no aggregation tendency, the VHH domain is highly stable to heat, pH, protease and other denaturants or conditions, and therefore can be prepared, stored or transported without using freezing equipment, thereby saving cost, time and environment; the VHH domain is easy to prepare and relatively cheap, even on the scale required for production; compared with a conventional 4-chain antibody and its antigen-binding fragments, the VHH domain is relatively small (about 15 kDa or 1/10 of the size of conventional IgG), which shows higher tissue permeability and can be administered at a higher dose, as still compared with the conventional 4-chain antibody and its antigen-binding fragments; the VHH domain can show the so-called cavity binding properties (especially due to its extended CDR3 loop compared with the conventional VH domain), thus reaching the targets and epitopes that the conventional 4-chain antibody and its antigen binding fragments cannot reach.

Methods for obtaining VHH binding to specific antigens or epitopes have been previously disclosed in the following documents: R. van der Linden et al., Journal of Immunological Methods, 240 (2000) 185-195; Li et al., J Biol Chem., 287 (2012) 13713-13721; Deffar et al., African Journal of Biotechnology Vol. 8 (12). pp. 2645-2652, 17 Jun., 2009 and WO94/04678.

The VHH domain derived from Camelidae can be humanized by replacing one or more amino acid residues in the amino acid sequence of the original VHH sequence with one or more amino acid residues existing at the corresponding positions in the VH domain of a human conventional 4-chain antibody (also referred to as “sequence optimization” herein, besides humanization. “sequence optimization” can also encompass other modifications of the sequence by one or more mutations providing VHH improvement properties, such as deleting potential post-translational modification sites). A humanized VHH domain can contain one or more complete human framework sequences. The humanization may be achieved by humanization of amino acids on the protein surface (resurfacing) and/or CDR grafting to a universal framework, such as examples illustrated herein.

As used herein, the term “epitope” or “antigenic determinant” used interchangeably refers to any antigenic determinant on the antigen to which the complementary site of an antibody binds. Generally, antigenic determinants comprise chemically active surface groups of molecules, such as amino acids or sugar side chains, and usually have specific three-dimensional structure characteristics and specific charge characteristics. For example, the epitope usually includes at least 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15 continuous or discontinuous amino acids in a unique spatial conformation, which can be a “linear” epitope or “conformational” epitope. See, for example. Epitope mapping protocols in methods in molecular biology, Vol. 66. G. E. Morris. Ed. (1996). In the linear epitope, all interaction points between proteins and interacting molecules (such as antibodies) exist linearly along the primary amino acid sequence of proteins. In the conformational epitope, the interaction points exist across protein amino acid residues separately from one another.

Many epitope mapping techniques well known in the art can be used to identify the epitope of a given antigen. See, for example, Epitope Mapping Protocols in Methods in Molecular Biology. Vol. 66. G. E. Morris, Ed. (1996). For example, linear epitopes can be determined by, for example, the method as follows: synthesizing a large number of peptides on a solid support at the same time, wherein these peptides correspond to various parts of protein molecules, and reacting these peptides while still being linked to the support with antibodies. These techniques are known in the art and described in, for example, U.S. Pat. No. 4,708,871; Geysen et al. (1984) Proc. Natl. Acad. Sci. USA 81:3998-4002; Geysen et al. (1986) Molec. Immunol. 23:709-715. Similarly, a conformational epitope can be identified by determining the spatial configuration of amino acids by, for example, X-ray crystallography and 2-dimensional nuclear magnetic resonance. See, for example, Epitope Mapping Protocols (supra).

Antibodies can be screened for competitively binding to the same epitope using conventional techniques known to those skilled in the art. For example, competitive and cross-competitive studies may be conducted to obtain antibodies that compete or cross-compete with each other for binding to antigens. A high-throughput method for obtaining antibodies that bind to the same epitope based on their cross-competition is described in the international patent application WO03/48731. Therefore, the conventional techniques known to those skilled in the art may be used to obtain antibodies and antigen-binding fragments thereof which compete with the antibody molecules of the present invention for binding to the same epitope on pertussis toxin.

Generally speaking, the term “specificity” refers to the number of different types of antigens or epitopes that a specific antigen-binding molecule or antigen-binding protein (such as the immunoglobulin single variable domain of the present invention) can bind to. The specificity of antigen binding proteins can be determined based on their affinity and/or affinity. The affinity expressed by the dissociation equilibrium constant (KD) between an antigen and an antigen-binding protein is a measure of the binding strength between an epitope and an antigen-binding site on the antigen-binding protein: the smaller KD value, the stronger the binding strength between the epitope and the antigen-binding protein (or, the affinity can also be expressed as the association constant (KA), which is 1/KD). As will be understood by those skilled in the art, the affinity can be determined in a known manner, depending on the specific antigen of interest. The affinity is a measure of the binding strength between an antigen-binding protein (such as immunoglobulin, antibody, immunoglobulin single variable domain or polypeptide comprising the same) and the associated antigen. The affinity is related to both the affinity between the antigen-binding sites on the antigen-binding protein and the number of associated binding sites present on the antigen-binding protein.

As used herein, the term “pertussis toxin binding protein” means any protein capable of specifically binding to pertussis toxin. The pertussis toxin binding protein may include an antibody against pertussis toxin as defined herein. The pertussis toxin binding protein also encompasses immunoglobulin superfamily antibodies (IgSF) or CDR grafted molecules.

“Pertussis toxin” is a multi-subunit protein toxin derived from Bordetella pertussis (B. pertussis), which may act specifically on G proteins to inhibit the function of signaling pathway of G proteins. The pertussis toxin comprises subunit S1, subunit S2, subunit S3, subunit S4 and subunit S5, the amino acid sequences of which were logged in the UniProtKB database, with the corresponding accession numbers being: P04977, P04978, P04979, P0A3R5 and P04981, respectively.

The “pertussis toxin binding protein” of the present invention may comprise at least one immunoglobulin single variable domain (e.g., VHH) that binds to pertussis toxin. In some embodiments, the “pertussis toxin binding molecule” of the present invention may comprise 2, 3, 4 or more immunoglobulin single variable domains (e.g., VHH) that bind to pertussis toxin. In addition to the immunoglobulin single variable domain binding to pertussis toxin, the pertussis toxin binding protein of the present invention may still comprise a linker and/or a moiety with effector function, such as a half-life extending moiety (for example, the immunoglobulin single variable domain binding to serum albumin), and/or a fusion partner (e.g., serum albumin) and/or a conjugated polymer (e.g., PEG) and/or a Fc region. In some embodiments, the “pertussis toxin binding protein” of the present invention also encompasses bispecific antibodies, which contain immunoglobulin single variable domains that bind to different antigens.

Generally, the pertussis toxin binding protein of the present invention may bind to the antigen of interest (i.e. pertussis toxin) with a dissociation constant (KD) of preferably 10⁻⁷-10⁻¹⁰mol/L (M), more preferably 10⁻⁸-10⁻¹⁰mol/L, even more preferably 10⁻⁹-10⁻¹⁰mol/L or even more less and/or with an association constant (KA) of at least 10⁷M⁻¹, preferably at least 10⁸M⁻¹, more preferably at least 10⁹M⁻¹, even more preferably at least 10¹⁰M⁻¹, as measured by Biacore or KinExA or Fortibio assay. Any KD value greater than 10⁻⁴m is generally regarded as an indicator of nonspecific binding. Specific binding of antigen-binding proteins to antigens or epitopes can be determined in any known suitable way, including, for example, surface plasmon resonance (SPR) assay, Scatchard assay and/or competitive binding assay (such as radioimmunoassay (RIA), enzyme immunoassay (EIA) and sandwich and competitive assay) described herein.

The amino acid residues will be represented according to the standard three-letter or single-letter amino acid code as well known and agreed in the art. When comparing two amino acid sequences, the term “amino acid difference” refers to an addition, deletion or substitution of a specified number of amino acid residues at a certain position in the reference sequence compared with another sequence. In the case of substitution, the substitution will preferably be a conservative amino acid substitution, which means that the amino acid residue is replaced by another amino acid residue with similar chemical structure, which has little or no influence on the functions, activity or other biological properties of the polypeptide. The conservative amino acid substitution is well known in the art, for example, the conservative amino acid substitution is preferably that one amino acid in the following groups (i)-(v) is replaced by another amino acid residue in the same group: (i) smaller aliphatic nonpolar or weakly polar residues: Ala, Ser, Thr, Pro and Gly; (ii) polar negatively charged residues and their (uncharged) amides: Asp, Asn. Glu and Gln, (iii) polar positively charged residues: His, Arg and Lys; (iv) larger aliphatic nonpolar residues: Met, Leu, Ile, Val and Cys; and (v) aromatic residues: Phe, Tyr and Trp. Particularly preferred conservative amino acid substitutions are as follows: Ala-to-Gly/Ser substitution; Arg-to-Lys substitution; Asn-to-Gln/His substitution; Asp-to-Glu substitution; Cys-to-Ser substitution; Gln-to-Asn substitution; Glu-to-Asp substitution; Gly-Ala/Pro substitution; His-to-Asn/Gln substitution; Ile-to-Leu/Val substitution; Leu-to-Ile/Val substitution; Lys-to-Arg/Gln/Glu substitution; Met-to-Leu/Tyr/Ile substitution; Phe-to-Met/Leu/Tyr substitution; Ser-to-Thr substitution; Thr-to-Ser substitution; Trp-to-Tyr substitution; Tyr-to-Trp/Phe substitution; Val-to-Ile/Leu substitution.

“Sequence identity” between two polypeptide sequences indicates the percentage of identical amino acids between the two sequences. “Sequence similarity” indicates the percentage of amino acids that are the same or represent conservative amino acid substitutions. A method for evaluating the degree of sequence identity between amino acids or nucleotides is known to those skilled in the art. For example, the amino acid sequence identity is usually measured using a sequence analysis software. For example, a BLAST program of NCBI's database may be applied to determine the identity. For determination of sequence identity, see, for example, Computational Molecular Biology. Lesk, A. M., ed., Oxford University Press, New York, 1988: Biocomputing: Informatics and Genome Projects, Smith. D. W., ed., Academic Press, New York, 1993; Computer Analysis of Sequence Data, Part I, Griffin, A. M., and Griffin. H. G., eds., Humana Press, New Jersey, 1994; Sequence Analysis in Molecular Biology, von Heinje, G., Academic Press, 1987 and Sequence Analysis Primer, Gribskov, M. and Devereux, J., eds., M Stockton Press, New York, 1991.

Compared with the natural biological source of a polypeptide or nucleic acid molecule and/or the reaction medium or culture medium used for obtaining the polypeptide or nucleic acid molecule, when the polypeptide or nucleic acid molecule has been separated from at least one other usually associated component (such as another protein/polypeptide, another nucleic acid, another biological component or macromolecule or at least one pollutant, impurity or trace component) in the source or medium (culture medium), the polypeptide or nucleic acid molecule is regarded as “isolated”. In particular, a polypeptide or nucleic acid molecule is considered as “isolated” when it has been purified at least 2 times, especially at least 10 times, more particularly at least 100 times and up to 1000 times or more. The “isolated” polypeptide or nucleic acid molecules are preferably substantially homogeneous as determined by suitable techniques (for example, suitable chromatographic techniques, such as polyacrylamide gel electrophoresis).

An “effective amount” means that the amount of pertussis toxin binding protein or pharmaceutical composition of the present invention may result in a decrease in the severity of disorder symptoms, an increase in the frequency and duration of the asymptomatic period of the disorder, or the prevention of injury or disability as a result of suffering from the disorder.

As used herein, the term “subject” refers to a mammal, especially a primate mammal, in particular a human.

The Pertussis Toxin Binding Protein of the Present Invention

The invention provides a pertussis toxin binding protein, which comprises at least one immunoglobulin single variable domain capable of specifically binding to pertussis toxin.

In some embodiments, the at least one inmmunoglobulin single variable domain comprises CDR1, CDR2 and CDR3 in VHH shown in any one of SEQ ID NOs: 40-52. The CDRs can be Kabat CDRs, AbM CDRs, Chothia CDRs or Contact CDRs. In some embodiments, the CDRs are Kabat CDR.

In some embodiments, the at least one immunoglobulin single variable domain comprises CDR1, CDR2 and CDR3 selected from the group consisting of:

(1) CDR1 shown in SEQ ID NO: 1, CDR2 shown in SEQ ID NO: 2, and CDR3 shown in SEQ ID NO: 3 (corresponding to CDRs of iPT 3):

(2) CDR1 shown in SEQ ID NO: 4, CDR2 shown in SEQ ID NO: 5, and CDR3 shown in SEQ ID NO: 6 (corresponding to CDRs of iPT 7);

(3) CDR1 shown in SEQ ID NO: 7, CDR2 shown in SEQ ID NO: 8, and CDR3 shown in SEQ ID NO: 9 (corresponding to CDRs of iPT 12):

(4) CDR1 shown in SEQ ID NO: 10, CDR2 shown in SEQ ID NO: 11, and CDR3 shown in SEQ ID NO: 12 (corresponding to CDRs of iPT 13);

(5) CDR1 shown in SEQ ID NO: 13, CDR2 shown in SEQ ID NO: 14, and CDR3 shown in SEQ ID NO: 15 (corresponding to CDRs of iPT 15);

(6) CDR1 shown in SEQ ID NO: 16, CDR2 shown in SEQ ID NO: 17, and CDR3 shown in SEQ ID NO: 18 (corresponding to CDRs of iPT 20);

(7) CDR1 shown in SEQ ID NO: 19, CDR2 shown in SEQ ID NO: 20, and CDR3 shown in SEQ ID NO: 21 (corresponding to CDRs of iPT 21);

(8) CDR1 shown in SEQ ID NO: 22, CDR2 shown in SEQ ID NO: 23, and CDR3 shown in SEQ ID NO: 24 (corresponding to CDRs of iPT 22);

(9) CDR1 shown in SEQ ID NO: 25, CDR2 shown in SEQ ID NO: 26, and CDR3 shown in SEQ ID NO: 27 (corresponding to CDRs of iPT 26);

(10) CDR1 shown in SEQ ID NO: 28, CDR2 shown in SEQ ID NO: 29, and CDR3 shown in SEQ ID NO: 30 (corresponding to CDRs of iPT 28);

(11) CDR1 shown in SEQ ID NO: 31, CDR2 shown in SEQ ID NO: 32, and CDR3 shown in SEQ ID NO: 33 (corresponding to CDRs of iPT 35);

(12) CDR1 shown in SEQ ID NO: 34, CDR2 shown in SEQ ID NO: 35, and CDR3 shown in SEQ ID NO: 36 (corresponding to CDRs of iPT 36);

(13) CDR1 shown in SEQ ID NO: 37, CDR2 shown in SEQ ID NO: 38, and CDR3 shown in SEQ ID NO: 39 (corresponding to CDRs of iPT 42).

In some embodiments, the at least one immunoglobulin single variable domain in the pertussis toxin binding protein of the present invention is a VHH. In some embodiments, the VHH comprises any one of the amino acid sequences shown in SEQ ID NOs: 40-52.

In some embodiments, the at least one immunoglobulin single variable domain in the pertussis toxin binding protein of the present invention is a humanized VHH.

In some embodiments, the at least one immunoglobulin single variable domain in the pertussis toxin binding protein of the present invention is a humanized VHH, which comprises an amino acid sequence having at least 80%, preferably at least 90%, more preferably at least 95%, even more preferably at least 99% sequence identity to any one of the sequences shown in SEQ ID NOs: 40-52. In some embodiments, the humanized VHH comprises one or more amino acid substitutions as compared to any one of the amino acid sequences shown in SEQ ID NOs: 40-52. For example, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 conservative amino acid substitutions are comprised.

In some embodiments, at least one immunoglobulin single variable domain in the pertussis toxin binding protein of the present invention is a humanized VHH, wherein the humanized VHH comprises any one amino acid sequence shown in SEQ ID NOs: 53-85.

In some embodiments, the pertussis toxin binding protein comprises one immunoglobulin single variable domain that specifically binds to pertussis toxin.

In some embodiments, the pertussis toxin binding protein comprises at least two, such as 2, 3, 4 or more immunoglobulin single variable domains that specifically bind to pertussis toxin.

In some embodiments, the at least two immunoglobulin single variable domains bind to the same epitope or compete or partially compete for binding to the same epitope, for example, the at least two immunoglobulin single variable domains are the same.

In some embodiments, the at least two immunoglobulin single variable domains bind to different epitopes or do not compete for binding to the same epitope.

Whether two antibody or immunoglobulin single variable domains bind to or compete for binding to the same epitope can be determined by epitope binning using Bio-Layer Interferometry (BLI), as exemplified in the examples of the present invention.

In some embodiments, the at least two immunoglobulin single variable domains that specifically bind to pertussis toxin are directly connected to each other.

In some embodiments, the at least two immunoglobulin single variable domains that specifically bind to pertussis toxin are interconnected by a linker. The linker may be a nonfunctional amino acid sequence having 1-20 or more amino acids in length, without secondary and above structure. For example, the linker is a flexible linker, such as GGGGS, GS, GAP, (GGGGS)×3, and so on.

In some embodiments, the pertussis toxin binding protein comprises a first immunoglobulin single variable domain and a second immunoglobulin single variable domain, wherein the first immunoglobulin single variable domain is located at the N-terminal of the second inmmunoglobulin single variable domain, and

wherein the first inmmunoglobulin single variable domain comprises CDR1 shown in SEQ ID NO: 4, CDR2 shown in SEQ ID NO: 5 and CDR3 shown in SEQ ID NO: 6, and the second immunoglobulin single variable domain comprises CDR1 shown in SEQ ID NO: 13, CDR2 shown in SEQ ID NO: 14 and CDR3 shown in SEQ ID NO: 15; or

wherein the first immunoglobulin single variable domain comprises CDR1 shown in SEQ ID NO: 13, CDR2 shown in SEQ ID NO: 14 and CDR3 shown in SEQ ID NO: 15, and the second immunoglobulin single variable domain comprises CDR1 shown in SEQ ID NO: 4, CDR2 shown in SEQ ID NO: 5 and CDR3 shown in SEQ ID NO: 6; or

wherein the first immunoglobulin single variable domain comprises CDR1 shown in SEQ ID NO: 4, CDR2 shown in SEQ ID NO: 5 and CDR3 shown in SEQ ID NO: 6, and the second immunoglobulin single variable domain comprises CDR1 shown in SEQ ID NO: 22, CDR2 shown in SEQ ID NO: 23 and CDR3 shown in SEQ ID NO: 24; or

wherein the first immunoglobulin single variable domain comprises CDR1 shown in SEQ ID NO: 22, CDR2 shown in SEQ ID NO: 23 and CDR3 shown in SEQ ID NO: 24, and the second immunoglobulin single variable domain comprises CDR1 shown in SEQ ID NO: 4, CDR2 shown in SEQ ID NO: 5 and CDR3 shown in SEQ ID NO: 6; or

wherein the first immunoglobulin single variable domain comprises CDR1 shown in SEQ ID NO: 4, CDR2 shown in SEQ ID NO: 5 and CDR3 shown in SEQ ID NO: 6, and the second immunoglobulin single variable domain comprises CDR1 shown in SEQ ID NO: 37, CDR2 shown in SEQ ID NO: 38 and CDR3 shown in SEQ ID NO: 39; or

wherein the first immunoglobulin single variable domain comprises CDR1 shown in SEQ ID NO: 37, CDR2 shown in SEQ ID NO: 38 and CDR3 shown in SEQ ID NO: 39, and the second immunoglobulin single variable domain comprises CDR1 shown in SEQ ID NO: 4, CDR2 shown in SEQ ID NO: 5 and CDR3 shown in SEQ ID NO: 6; or

wherein the first immunoglobulin single variable domain comprises CDR1 shown in SEQ ID NO: 7, CDR2 shown in SEQ ID NO: 8 and CDR3 shown in SEQ ID NO: 9, and the second immunoglobulin single variable domain comprises CDR1 shown in SEQ ID NO: 31, CDR2 shown in SEQ ID NO: 32 and CDR3 shown in SEQ ID NO: 33; or

wherein the first immunoglobulin single variable domain comprises CDR1 shown in SEQ ID NO: 31. CDR2 shown in SEQ ID NO: 32 and CDR3 shown in SEQ ID NO: 33, and the second immunoglobulin single variable domain comprises CDR1 shown in SEQ ID NO: 7, CDR2 shown in SEQ ID NO: 8 and CDR3 shown in SEQ ID NO: 9; or

wherein the first immunoglobulin single variable domain comprises CDR1 shown in SEQ ID NO: 13, CDR2 shown in SEQ ID NO: 14 and CDR3 shown in SEQ ID NO: 15, and the second immunoglobulin single variable domain comprises CDR1 shown in SEQ ID NO: 31, CDR2 shown in SEQ ID NO: 32 and CDR3 shown in SEQ ID NO: 33; or

wherein the first immunoglobulin single variable domain comprises CDR1 shown in SEQ ID NO: 13, CDR2 shown in SEQ ID NO: 14 and CDR3 shown in SEQ ID NO: 15, and the second immunoglobulin single variable domain comprises CDR1 shown in SEQ ID NO: 37, CDR2 shown in SEQ ID NO: 38 and CDR3 shown in SEQ ID NO: 39; or

wherein the first immunoglobulin single variable domain comprises CDR1 shown in SEQ ID NO: 31, CDR2 shown in SEQ ID NO: 32 and CDR3 shown in SEQ ID NO: 33, and the second immunoglobulin single variable domain comprises CDR1 shown in SEQ ID NO: 37, CDR2 shown in SEQ ID NO: 38 and CDR3 shown in SEQ ID NO: 39; or

wherein the first immunoglobulin single variable domain comprises CDR1 shown in SEQ ID NO: 7, CDR2 shown in SEQ ID NO: 8 and CDR3 shown in SEQ ID NO: 9, and the second immunoglobulin single variable domain comprises CDR1 shown in SEQ ID NO: 13, CDR2 shown in SEQ ID NO: 14 and CDR3 shown in SEQ ID NO: 15; or

wherein the first immunoglobulin single variable domain comprises CDR1 shown in SEQ ID NO: 13, CDR2 shown in SEQ ID NO: 14 and CDR3 shown in SEQ ID NO: 15, and the second immunoglobulin single variable domain comprises CDR1 shown in SEQ ID NO: 7, CDR2 shown in SEQ ID NO: 8 and CDR3 shown in SEQ ID NO: 9; or

wherein the first immunoglobulin single variable domain comprises CDR1 shown in SEQ ID NO: 7, CDR2 shown in SEQ ID NO: 8 and CDR3 shown in SEQ ID NO: 9, and the second immunoglobulin single variable domain comprises CDR1 shown in SEQ ID NO: 37, CDR2 shown in SEQ ID NO: 38 and CDR3 shown in SEQ ID NO: 39; or

wherein the first immunoglobulin single variable domain comprises CDR1 shown in SEQ ID NO: 37, CDR2 shown in SEQ ID NO: 38 and CDR3 shown in SEQ ID NO: 39, and the second immunoglobulin single variable domain comprises CDR1 shown in SEQ ID NO: 7, CDR2 shown in SEQ ID NO: 8 and CDR3 shown in SEQ ID NO: 9.

the first immunoglobulin single variable domain comprises the amino acid sequence shown in one of SEQ ID NOs: 41, 53-63 and the second immunoglobulin single variable domain comprises the amino acid sequence shown in one of SEQ ID NOs: 44, 64-74; or

the first immunoglobulin single variable domain comprises the amino acid sequence shown in one of SEQ ID NOs: 44, 64-74 and the second immunoglobulin single variable domain comprises the amino acid sequence shown in one of SEQ ID NOs: 41, 53-63; or

the first immunoglobulin single variable domain comprises the amino acid sequence shown in SEQ ID NO: 47 and the second immunoglobulin single variable domain comprises the amino acid sequence shown in one of SEQ ID NOs: 41, 53-63; or

the first immunoglobulin single variable domain comprises the amino acid sequence shown in one of SEQ ID NOs: 52, 75-85 and the second immunoglobulin single variable domain comprises the amino acid sequence shown in one of SEQ ID NOs: 41, 53-63; or

the first immunoglobulin single variable domain comprises the amino acid sequence shown in SEQ ID NO: 42 and the second immunoglobulin single variable domain comprises the amino acid sequence shown in SEQ ID NO: 50; or

the first immunoglobulin single variable domain comprises the amino acid sequence shown in SEQ ID NO: 50 and the second immunoglobulin single variable domain comprises the amino acid sequence shown in SEQ ID NO: 42; or

the first immunoglobulin single variable domain comprises the amino acid sequence shown in SEQ ID NO: 63 and the second immunoglobulin single variable domain comprises the amino acid sequence shown in SEQ ID NO: 70; or

the first immunoglobulin single variable domain comprises the amino acid sequence shown in SEQ ID NO: 80 and the second immunoglobulin single variable domain comprises the amino acid sequence shown in SEQ ID NO: 74; or

In some embodiments, the pertussis toxin binding protein of the present invention comprises the amino acid sequence selected from SEQ ID NOs: 87-105.

In some embodiments, the pertussis toxin binding protein of the present invention comprises an immunoglobulin Fc region in addition to at least one inmmunoglobulin single variable domain capable of specifically binding to pertussis toxin. The inclusion of immunoglobulin Fc region in the pertussis toxin binding protein of the present invention allows for the formation of dimer molecules by the binding proteins, while prolonging the half-life of the binding proteins in vivo. The Fc region may be from different subtypes of immunoglobulin, such as IgG (e.g., an IgG1, IgG2, IgG3, or IgG4 subtype), IgA1. IgA2, IgD, IgE, or IgM. The immunoglobulin Fc region generally includes the hinge region or part of the hinge region, CH2 region and CH3 region of the immunoglobulin constant region.

In some embodiments, mutations can be introduced into the wild-type Fc sequence to change the associated activity mediated by Fc. The mutations include, but are not limited to: a) mutations that change Fc-mediated CDC activity; b) mutations that change Fc-mediated ADCC activity; or c) mutations that change the half-life in vivo mediated by FcRn. Such mutations are described in the following documents: Leonard G Presta. Current Opinion in Immunology 2008, 20:460-470; Esohe E. Idusogie et al., J Immunol 2000, 164; 4178-4184, RAPHAEL A. CLYNES et al., Nature Medicine, 2000, Volume 6, Number 4: 443-446; Paul R. Hinton et al., J Immunol. 2006, 176:346-356. For example, a mutation of 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 amino acids in CH2 region can be used to increase or remove the activity of ADCC or CDC mediated by Fc or to increase or decrease the affinity of FcRn. In addition, the stability of the protein can be increased by a mutation of 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 amino acids in the hinge region.

In some embodiments, mutations can be introduced into the Fc sequence to make the mutated Fc more easier to form a homodimer or heterodimer. For example, the knob-hole model mentioned in Ridgway. Presta et al. 1996 and Carter 2001, makes it easier to form heterodimers between different Fc mutations, which makes use of spatial effects of amino acid side chain groups at Fc contact interfaces; for another example, in CN 102558355A or CN 103388013A, by changing the charge of amino acids at Fc contact interfaces to change the ionic interaction between Fc contact interfaces, it is easier to form heterodimers between different Fc mutation pairs (CN 102558355A), or form homodimers between Fcs with the same mutation (CN 103388013A).

The immunoglobulin Fc region is preferably the human immunoglobulin Fc region, more preferably the Fc region of human IgG1. In some embodiments, the amino acid sequence of the immunoglobulin Fc region is shown in SEQ ID NO: 86.

In some embodiments, in the pertussis toxin binding protein of the present invention, the at least one immunoglobulin single variable domain capable of specifically binding to pertussis toxin is directly linked to the immunoglobulin Fc region or linked via a linker. The linker may be a nonfunctional amino acid sequence having 1-20 or more amino acids in length, without no secondary and above structure. For example, the linker is a flexible linker, such as GGGGS. GS, GAP, and so on. In some embodiments, the immunoglobulin Fc region is located at the C-terminal of the at least one immunoglobulin single variable domain that specifically binds to pertussis toxin.

In some embodiments, the pertussis toxin binding protein of the present invention comprises a first amino acid sequence selected from one of SEQ ID NOs: 40-85 and 87-105, and a second amino acid sequence shown in SEQ ID NO: 86 directly linked to the first amino acid sequence or linked via a linker, wherein the second amino acid sequence is located at the C-terminal of the first amino acid sequence.

In some embodiments, the pertussis toxin binding protein of the present invention comprises the amino acid sequence selected from SEQ ID NOs: 106-109.

In some embodiments, the pertussis toxin binding protein of the present invention comprises an immunoglobulin single variable domain that specifically binds to pertussis toxin, which is directly connected or connected via a linker to an immunoglobulin Fc region which allows the pertussis toxin binding protein to form a dimer molecule comprising two pertussis toxin binding domains. Such pertussis toxin binding protein is also called a bivalent pertussis toxin binding protein. In some embodiments, the dimer is a homodimer.

In some embodiments, the pertussis toxin binding protein of the present invention comprises two immunoglobulin single variable domains that specifically bind to pertussis toxin, which are directly interconnected or interconnected via a linker, and an immunoglobulin Fc region which allows the pertussis toxin binding protein to form a dimer molecule comprising four pertussis toxin binding domains. Such pertussis toxin binding protein is also called a tetravalent pertussis toxin binding protein. In some embodiments, the dimer is a homodimer.

Nucleic Acid, Vector and Host Cell

In another aspect, the invention relates to a nucleic acid molecule that encodes the pertussis toxin-binding proteins of the invention. The nucleic acid of the invention may be RNA, DNA or cDNA. According to one embodiment of the invention, the nucleic acid of the invention is in essentially isolated form.

The nucleic acid of the invention may also be in the form of, may be present in and/or may be part of a vector, such as for example a plasmid, cosmid or YAC. The vector may especially be an expression vector, i.e. a vector that can provide for expression of the pertussis toxin-binding protein in vitro and/or in vivo (i.e. in a suitable host cell, host organism and/or expression system). Such expression vector generally comprises at least one nucleic acid of the invention that is operably linked to one or more suitable regulatory elements, such as promoter(s), enhancer(s), terminator(s), and the like. Such elements and their selection in view of expression of a specific sequence in a specific host are common knowledge of the skilled person. Specific examples of regulatory elements and other elements useful or necessary for expressing pertussis toxin-binding protein of the invention include such as promoters, enhancers, terminators, integration factors, selection markers, leader sequences, reporter genes, and the like.

The nucleic acids of the invention may be prepared or obtained in a manner known per se (e.g. by automated DNA synthesis and/or recombinant DNA technology), based on the information on the amino acid sequences for the polypeptides of the invention given herein, and/or can be isolated from a suitable natural source.

In another aspect, the invention relates to recombination host cells that express or are capable of expressing one or more pertussis toxin-binding protein of the invention; and/or that contain a nucleic acid of the invention. According to a particularly preferred embodiment, said host cells are bacterial cells; other useful cells are yeast cells, fungal cells or mammalian cells.

Suitable bacterial cells include cells from gram-negative bacterial strains such as strains of Escherichia coli, Proteus, and Pseudomonas, and gram-positive bacterial strains such as strains of Bacillus, Streptomyces, Staphylococcus, and Lactococcus. Suitable fungal cell include cells from species of Trichoderma, Neurospora, and Aspergillus.

Suitable fungal cell include cells from species of Trichoderma, Neurospora, and Aspergillus. Suitable yeast cells include cells from species of Saccharomyces (for example, Saccharomyces cerevisiae), Schizosaccharomyces (for example, Schizosaccharomyces pombe), Pichia (for example, Pichia pastoris and Pichia methanolica), and Hansenula.

Suitable mammalian cells include for example HEK293 cells, CHO cells. BHK cells, HeLa cells, COS cells, and the like.

However, amphibian cells, insect cells, plant cells, and any other cells used in the art for the expression of heterologous proteins can be used as well.

The invention further provides methods of manufacturing a pertussis toxin-binding protein of the invention, such methods generally comprise the steps of:

- culturing host cells of the invention under conditions that allow expression of the pertussis toxin-binding protein of the invention; and
- recovering the pertussis toxin-binding protein expressed by the host cells from the culture; and
- optionally further purifying and/or modifying the pertussis toxin-binding protein of the invention.

Pertussis toxin-binding proteins of the invention may be produced in a cell as set out above either intracellularly (e.g. in the cytosol, in the periplasma or in inclusion bodies) and then isolated from the host cells and optionally further purified; or they can be produced extracellularly (e.g. in the medium in which the host cells are cultured) and then isolated from the culture medium and optionally further purified.

Methods and reagents used for the recombinant production of polypeptides, such as specific suitable expression vectors, transformation or transfection methods, selection markers, methods of induction of protein expression, culture conditions, and the like, are known in the art. Similarly, protein isolation and purification techniques useful in a method of manufacture of a pertussis toxin-binding protein of the invention are well known to the skilled person.

However, the pertussis toxin-binding proteins of the invention can also be obtained by other methods for production of proteins known in the art, such as, chemical synthesis, including solid phase or liquid phase synthesis.

Pharmaceutical Compositions

In another aspect, the present invention provides a composition. e.g., a pharmaceutical composition, containing one or a combination of pertussis toxin-binding protein of the present invention, formulated together with a pharmaceutically acceptable carrier. Such compositions may include one or a combination of (e.g., two or more different) pertussis toxin-binding proteins of the invention. For example, a pharmaceutical composition of the invention can comprise a combination of antibody molecules that bind to different epitopes on the target antigen (pertussis toxin).

As used herein, “pharmaceutically acceptable carrier” includes any and all solvents, dispersion media, coatings, antibacterial and antifungal agents, isotonic and absorption delaying agents, and the like that are physiologically compatible. Preferably, the carrier is suitable for intravenous, intramuscular, subcutaneous, parenteral, spinal or epidermal administration (e.g., by injection or infusion). Depending on the route of administration, the active compound, i.e., antibody, or immunoconjugate, may be coated in a material to protect the compound from the action of acids and other natural conditions that may inactivate the compound.

The pharmaceutical compounds of the invention may include one or more pharmaceutically acceptable salts. A “pharmaceutically acceptable salt” refers to a salt that retains the desired biological activity of the parent compound and does not impart any undesired toxicological effects (see e.g., Berge. S. M., et al. (1977) J. Pharm. Sci. 66:1-19). Examples of such salts include acid addition salts and base addition salts. Acid addition salts include those derived from nontoxic inorganic acids, such as hydrochloric, nitric, phosphoric, sulfuric, hydrobromic, hydroiodic, phosphorous and the like, as well as from nontoxic organic acids such as aliphatic mono- and dicarboxylic acids, phenyl-substituted alkanoic acids, hydroxy alkanoic acids, aromatic acids, aliphatic and aromatic sulfonic acids and the like. Base addition salts include those derived from alkaline earth metals, such as sodium, potassium, magnesium, calcium and the like, as well as from nontoxic organic amines, such as N,N′-dibenzylethylenediamine. N-methylglucamine, chloroprocaine, choline, diethanolamine, ethylenediamine, procaine and the like.

A pharmaceutical composition of the invention also may include a pharmaceutically acceptable anti-oxidant. Examples of pharmaceutically acceptable antioxidants include: (1) water soluble antioxidants, such as ascorbic acid, cysteine hydrochloride, sodium bisulfate, sodium metabisulfite, sodium sulfite and the like; (2) oil-soluble antioxidants, such as ascorbyl palmitate, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), lecithin, propyl gallate, alpha-tocopherol, and the like; and (3) metal chelating agents, such as citric acid, ethylenediamine tetracetic acid (EDTA), sorbitol, tartaric acid, phosphoric acid, and the like.

These compositions may also contain adjuvants such as preservatives, wetting agents, emulsifying agents and dispersing agents.

Prevention of presence of microorganisms may be ensured both by sterilization procedures, supra, and by the inclusion of various antibacterial and antifungal agents, for example, paraben, chlorobutanol, phenol sorbic acid, and the like. It may also be desirable to include isotonic agents, such as sugars, sodium chloride, and the like into the compositions. In addition, prolonged absorption of the injectable pharmaceutical form may be brought about by the inclusion of agents which delay absorption such as aluminum monostearate and gelatin.

Pharmaceutically acceptable carriers include sterile aqueous solutions or dispersions and sterile powders for the extemporaneous preparation of sterile injectable solutions or dispersion. The use of such media and agents for pharmaceutically active substances is known in the art. Except insofar as any conventional media or agent is incompatible with the active compound, use thereof in the pharmaceutical compositions of the invention is contemplated. Supplementary active compounds can also be incorporated into the compositions.

Therapeutic compositions typically must be sterile and stable under the conditions of manufacture and storage. The composition can be formulated as a solution, microemulsion, liposome, or other ordered structure suitable to high drug concentration. The carrier can be a solvent or dispersion medium containing, for example, water, ethanol, polyol (for example, glycerol, propylene glycol, and liquid polyethylene glycol, and the like), and suitable mixtures thereof. The proper fluidity can be maintained, for example, by the use of a coating such as lecithin, by the maintenance of the required particle size in the case of dispersion and by the use of surfactants.

Sterile injectable solutions can be prepared by incorporating the active compound in the required amount in an appropriate solvent with one or a combination of ingredients enumerated above, as required, followed by sterilization microfiltration. Generally, dispersions are prepared by incorporating the active compound into a sterile vehicle that contains a basic dispersion medium and the required other ingredients from those enumerated above. In the case of sterile powders for the preparation of sterile injectable solutions, the preferred methods of preparation are vacuum drying and freeze-drying (lyophilization) that yield a powder of the active ingredient plus any additional desired ingredient from a previously sterile-filtered solution thereof.

The amount of active ingredient which can be combined with a carrier material to produce a single dosage form will vary depending upon the subject being treated, and the particular mode of administration. The amount of active ingredient which can be combined with a carrier material to produce a single dosage form will generally be that amount of the composition which produces a therapeutic effect. Generally, out of one hundred percent, this amount will range from about 0.01 percent to about ninety-nine percent of active ingredient, preferably from about 0.1 percent to about 70 percent, most preferably from about 1 percent to about 30 percent of active ingredient in combination with a pharmaceutically acceptable carrier.

Dosage regimens are adjusted to provide the optimum desired response (e.g., a therapeutic response). For example, a single bolus may be administered, several divided doses may be administered over time or the dose may be proportionally reduced or increased as indicated by the exigencies of the therapeutic situation. It is especially advantageous to formulate parenteral compositions in dosage unit form for ease of administration and uniformity of dosage. Dosage unit form as used herein refers to physically discrete units suited as unitary dosages for the subjects to be treated; each unit contains a predetermined quantity of active compound calculated to produce the desired therapeutic effect in association with the required pharmaceutical carrier. The specification for the dosage unit forms of the invention are dictated by and directly dependent on (a) the unique characteristics of the active compound and the particular therapeutic effect to be achieved, and (b) the limitations inherent in the art of compounding such an active compound for the treatment of sensitivity in individuals.

For administration of the antibody molecule, the dosage ranges from about 0.0001 to 100 mg/kg, and more usually 0.01 to 20 mg/kg, of the subject body weight. For example dosages can be 0.3 mg/kg body weight, 1 mg/kg body weight, 3 mg/kg body weight, 5 mg/kg body weight, 10 mg/kg body weight, 20 mg/kg body weight or 30 mg/kg body weight or within the range of 1-30 mg/kg. An exemplary treatment regime entails administration once per week, once every two weeks, once every three weeks, once every four weeks, once a month, once every 3 months or once every three to 6 months, or with a short administration interval at the beginning (such as once per week to once every three weeks), and then an extended interval later (such as once a month to once every three to 6 months).

Alternatively, antibody can be administered as a sustained release formulation, in which case less frequent administration is required. Dosage and frequency vary depending on the half-life of the antibody in the patient. In general, human antibodies show the longest half-life, followed by humanized antibodies, chimeric antibodies, and nonhuman antibodies. The dosage and frequency of administration can vary depending on whether the treatment is prophylactic or therapeutic. In prophylactic applications, a relatively low dosage is administered at relatively infrequent intervals over a long period of time. Some patients continue to receive treatment for the rest of their lives. In therapeutic applications, a relatively high dosage at relatively short intervals is sometimes required until progression of the disease is reduced or terminated, and preferably until the patient shows partial or complete amelioration of symptoms of disease. Thereafter, the patient can be administered a prophylactic regime.

Actual dosage levels of the active ingredients in the pharmaceutical compositions of the present invention may be varied so as to obtain an amount of the active ingredient which is effective to achieve the desired therapeutic response for a particular patient, composition, and mode of administration, without being toxic to the patient. The selected dosage level will depend upon a variety of pharmacokinetic factors including the activity of the particular compositions of the present invention employed, or the ester, salt or amide thereof, the route of administration, the time of administration, the rate of excretion of the particular compound being employed, the duration of the treatment, other drugs, compounds and/or materials used in combination with the particular compositions employed, the age, sex, weight, condition, general health and prior medical history of the patient being treated, and like factors well known in the medical arts.

A composition of the present invention can be administered via one or more routes of administration using one or more of a variety of methods known in the art. As will be appreciated by the skilled artisan, the route and/or mode of administration will vary depending upon the desired results. Preferred routes of administration for pertussis toxin-binding proteins of the invention include intravenous, intramuscular, intradermal, intraperitoneal, subcutaneous, spinal or other parenteral routes of administration, for example by injection or infusion. The phrase “parenteral administration” as used herein means modes of administration other than enteral and topical administration, usually by injection, and includes, without limitation, intravenous, intramuscular, intraarterial, intrathecal, intracapsular, intraorbital, intracardiac, intradermal, intraperitoneal, transtracheal, subcutaneous, subcuticular, intraarticular, subcapsular, subarachnoid, intraspinal, epidural and intrasternal injection and infusion.

Alternatively, a pertussis toxin-binding protein of the invention can be administered via a non-parenteral route, such as a topical, epidermal or mucosal route of administration, for example, intranasally, orally, vaginally, rectally, sublingually or topically.

Disease Prevention and Treatment

The present invention relates to a method for treating Bordetella pertussis infection in a subject, the method comprising administering to the subject the pertussis toxin binding protein of the present invention or pharmaceutical composition of the present invention (in an effective amount, for example).

In another aspect, the present invention relates to a method for preventing Bordetella pertussis infection in a subject, the method comprising administering to the subject the pertussis toxin binding protein of the present invention or pharmaceutical composition of the present invention (in an effective amount, for example). In some embodiments, the subject is at risk of Bordetella pertussis infection (for example, the patient is a pre-vaccinated baby and/or the patient has been exposed to pertussis toxin).

In another aspect, the present invention relates to a method for neutralizing pertussis toxin in a subject, the method comprising administering to the subject pertussis toxin binding protein of the present invention or pharmaceutical composition of the present invention (in an effective amount, for example). In some embodiments, the subject is infected with Bordetella pertussis.

In another aspect, the present invention relates to a method for treating Bordetella pertussis infection-related diseases or disorders in a subject, the method comprising administering to the subject pertussis toxin binding protein of the present invention or pharmaceutical composition of the present invention (in an effective amount, for example).

Bordetella pertussis infection is characterized by leukocytosis or elevated white blood cell count. In one embodiment, the method of the present invention includes reducing the white blood cell count in a patient. In one embodiment, the method of the present invention produces accelerated reduction of leukocytosis. In another embodiment, the method of the present invention produces a decrease in the maximum white blood cell count during infection.

In one embodiment, the method of the present invention produces neutralization (inhibition or antagonism) of pertussis toxin protein. For example, the pertussis toxin binding protein of the present invention can bind to the pertussis toxin protein to partially or completely inhibit one or more biological activities of pertussis toxin protein. One of the biological activities of the pertussis toxin protein that can be inhibited or blocked by the neutralizing antibody is the ability of pertussis toxin protein to bind to cell receptors. The receptor-binding region of pertussis toxin protein consists of four polypeptide subunits, called subunit S2, subunit S3, subunit S4 and subunit S5, respectively. Examples of cellular receptors bound by subunits S2, S3, S4 and S5 of pertussis toxin protein are members of the N-linked sialoglycoprotein family, such as fetoprotein, haptoblobin and transferrin. In an exemplary embodiment, the pertussis toxin binding protein of the present invention prevents the pertussis toxin protein from binding to its cellular receptors. In another embodiment, the pertussis toxin binding protein of the present invention changes the intracellular transport steps of pertussis toxin so that the toxin will not reach the cell cytoplasm. Another important activity of pertussis toxin protein that can be inhibited by the pertussis toxin binding protein of the present invention is the enzymatic activity of pertussis toxin protein as ADP ribose enzyme against G protein. The subunit of pertussis toxin protein which is endowed with enzyme activity as ADP ribose enzyme is subunit S1. In some embodiments, the pertussis toxin protein is pertussis holothurin. The pertussis holothurin called pertussis toxin protein herein comprises all five pertussis toxin protein subunits. In other embodiments, the pertussis toxin protein is a truncated pertussis toxin protein. The truncated pertussis protein mentioned herein comprises at least one of pertussis toxin protein subunits (i.e., S1, S2, S3, S4 and S5). Various forms of pertussis toxin protein have been described in the prior art.

In various embodiments, the compositions and methods of the present invention are suitable for any stage of treating or preventing pertussis infection. For example, the incubation period of pertussis is usually 7-10 days, ranging from 4-21 days, and rarely as long as 42 days. In various embodiments, the compositions and methods of the present invention increase the length of the incubation period by making infection more difficult to occur. The clinical course of the disease is divided into three stages. The first stage, also known as catarrhal stage, begins with cold-like symptoms, such as insidious attack of rhinitis, sneezing, low fever and mild, occasional cough. Cough gradually worsens, and after 1-2 weeks, the second or paroxysmal stage begins. In various embodiments, the compositions and methods of the present invention reduce the length of the catarrhal phase and optionally prevent it from progressing to the paroxysmal phase. In various embodiments, the compositions and methods of the present invention are used to treat one or more of rhinitis, sneezing, low fever and cough. This is during the paroxysmal stage of pertussis which is usually suspected to be diagnosed. Typically, patients manifest many rapid paroxysmal cough, apparently due to the difficulty of expelling thick mucus from the tracheobronchial tree. At the end of paroxysmal cough, long inspiratory efforts are usually accompanied by a specific high-pitched “whoop” sound. During this coughing fit, the patient may become cyanotic. Especially children and infants feel very uncomfortable and painful. After coughing fits, vomiting and fatigue may usually occur. In various embodiments, the compositions and methods of the present invention reduce the amount and/or frequency of paroxysm. In various embodiments, the compositions and methods of the present invention present patients from becoming cyanotic. Paroxysmal coughing fits may occur more frequently at night, with an average of 15 times every 24 hours. In the first 1 or 2 weeks of this stage, the seizure frequency increases, stays at the same level for 2 to 3 weeks, and then gradually decreases. Paroxysmal stage usually lasts 1 to 6 weeks, but it may also last as long as 10 weeks. In various embodiments, the compositions and methods of the present invention reduce the length of this stage. During the recovery period, recovery is gradual. Paroxysmal cough may decrease and disappear in 2 to 3 weeks. In various embodiments, the compositions and methods of the present invention accelerate the onset of this stage and/or reduce its duration. Furthermore, in various embodiments, the compositions and methods of the present invention prevent or reduce paroxysmal recurrence, which may occur with subsequent respiratory infections. In various embodiments, the compositions and methods of the present invention prevent or reduce one or more of the following paroxysms: secondary bacterial pneumonia, neurological complications such as epilepsy and encephalopathy, hypoxia, otitis media, dehydration, pneumothorax, epistaxis, subdural hematoma, hernia, rectal prolapse, difficulty sleeping, urinary incontinence, pneumonia and rib fracture. Furthermore, in some embodiments, the compositions and methods of the present invention reduce or prevent necrotizing bronchiolitis, pneumonia (for example, derived from Bordetella pertussis), pulmonary edema, pulmonary hypertension and death.

In another embodiment, the method comprises administering to a subject a combination of the pertussis toxin binding protein of the present invention or the pharmaceutical composition of the present invention and an antimicrobial agent. Co-administration of the combination of the pertussis toxin binding protein of the present invention or the pharmaceutical composition of the present invention and the antimicrobial agent is expected to produce synergistic effect. Illustrative antimicrobial agents suitable for the present invention include, but are not limited to, azithromycin, clarithromycin, erythromycin, trimethoprim-sulfamethoxazole, roxithromycin, ketolide (e.g., telithromycin), ampicillin, amoxicillin, tetracycline, chloramphenicol, fluoroquinolones (e.g., ciprofloxacin, levofloxacin, ofloxacin, moxifloxacin), and cephalosporin.

In various embodiments, the subject treated by the method of the present invention is a human. In one embodiment, the subject is an infant. In one embodiment, the subject is a newborn. In another embodiment, the subject is a newborn who is less than four weeks, less than three weeks, less than two weeks, less than one week, less than six days, less than five days, less than four days, less than three days, less than two days or less than one day. In some embodiments, the human is one month old, two months old, three months old, four months old, five months old or six months old. In some embodiments, the human is at the age of about 6 to about 18 months, about 18 to about 36 months, about 1 to about 5 years, about 5 to about 10 years, about 10 to about 15 years, about 15 to about 20 years, about 20 to about 25 years, about 25 to about 30 years, about 30 to about 35 years, about 35 to about 40 years, about 40 to about 45 years, about 45 to about 50 years, about 50 to about 55 years, about 55 to about 60 years, about 60 to about 65 years, about 65 to about 70 years, about 70 to about 75 years, about 75 to about 80 years, about 80 to about 85 years, about 85 to about 90 years, about 90 to about 95 years, or about 95 to about 100 years.

On the other hand, the method of the present invention prevents Bordetella pertussis infection in a subject previously exposed to Bordetella pertussis bacteria, which comprises administering to the subject the pertussis toxin binding protein of the present invention or the pharmaceutical composition of the present invention. In various embodiments, the method provides effective preventive treatment in preventing Bordetella pertussis infection in a subject exposed to Bordetella pertussis bacteria.

In some embodiments, the pertussis toxin binding protein of the present invention or the pharmaceutical composition of the present invention is used for prophylactic application in a subject that has not been previously vaccinated against the bacteria.

It is expected that the pertussis toxin binding protein of the present invention or the pharmaceutical composition of the present invention can also serve as an adjuvant for vaccination, such as DtaP or Tdap. Furthermore, in various embodiments, the methods of the present invention treat or prevent Bordetella pertussis infection in a subject who has not been previously vaccinated against Bordetella pertussis bacteria.

Detection

On the other hand, the invention also provides a method for detecting the presence and/or amount of pertussis toxin in a biological sample, the method comprising contacting the biological sample and the control sample with the pertussis toxin binding protein of the invention under conditions allowing the formation of complex between the pertussis toxin binding protein and pertussis toxin. Then detection of the complex is performed, wherein the difference in the complex formation between the biological sample and the control sample indicates the presence and/or amount of pertussis toxin in the sample.

In some embodiments, the pertussis toxin binding protein of the present invention is also conjugated with fluorescent dyes, chemicals, polypeptides, enzymes, isotopes, labels and the like that can be used for detection or can be detected by other reagents.

In some embodiments, the biological sample is a vaccine for preventing Bordetella pertussis infection, for example, the vaccine comprises pertussis toxin.

Kits

The scope of the present invention also includes a kit for use in the method of the present invention, which includes the pertussis toxin binding protein of the present invention and instructions. The kit may further comprise at least one reagent for detection. The kit generally includes labels indicating the intended use of the contents of the kit. The term label includes any written or recorded material provided on the kit or coming with the kit or otherwise provided with the kit.

EXAMPLES

The following examples are used to further illustrate the present invention, but the scope of the present invention is not limited to these examples.

Example 1: Screening of Heavy Chain Single Domain Antibody Against Pertussis Toxin (PT)

1.1 Construction of Library:

Before immunization, 5 ml, of arterial blood from bactrian camel was collected into a vacuum blood collection tube, and the supernatant was collected as the pre-immunization serum. For the first immunization, a healthy 2-year-old Xinjiang bactrian camel was selected, 300 μg recombinant pertussis toxin protein was taken as antigen and mixed with complete Freund's adjuvant in equal volume for emulsifying the proteins completely, which was then injected into the bactrian camel's neck muscles at multiple points; for the later stage of immunization, the same amount of antigen and incomplete Freund's adjuvant were uniformly mixed in equal volume each time; immunization was performed once a week, with a total of six times of immunization on bactrian camels in the later period. At the end of the last immunization, 5 mL of bactrian camel arterial blood was collected into the vacuum blood collection tube, and the supernatant was collected as the post-immunization serum, the variation of antibody in animal serum before and after immunization were detected by ELISA, wherein, the antibody in serum increased obviously after immunization, so it was determined that the immune effect caused by antigen met the experimental requirements.

Lymphocytes were separated by density gradient centrifugation, total RNA was extracted by a RNA extraction kit provided by QIAGEN Company, all extracted RNA was reverse transcribed into cDNA by SuperScript III FIRST STRANDSUPERMIX kit according to the instructions, and nucleic acid fragments encoding the variable region of the heavy chain antibody were amplified by nested PCR.

The nucleic acid fragments of the target heavy chain single domain antibody was recovered and cloned into phage display vector pMECS by using restriction enzymes (purchased from NEB) PstI and NotI. Subsequently, the product was electrotransformed into the electroporation-competent cells TG1 of Escherichia coli, and the phage display library of anti-PT toxin immune single domain antibody was constructed and verified. Through planking with gradient dilution, the capacity of the library was calculated as 1.2×10⁸. In order to detect the insertion rate of the library, 50 clones were randomly selected for sequencing, and 50 clones with correct foreign fragment insertion were found, showing an accuracy of 100%. Through the analysis and alignment of DNAs and amino acid sequences of sequenced clones, respectively, it was confirmed that all sequences were expected camel VHH sequences, and the diversity was estimated to be more than 95%.

1.2 Panning of Antibodies Against Pertussis Toxin (PT)

Recombinant pertussis toxin protein PT was coated on a plate at 10 μg/well, and left overnight at 4° C. The next day, after being blocked with 2% skim milk at room temperature for 2 hours, 100 μL of phage (about 10¹⁰PFU) from the phage library constructed in Example 1.1 was added and functioned at room temperature for 2 hours. Afterwards, the resultant was washed 25 times with PBST (0.05% Tween 20 in PBS) to wash off unbound phages. At last, the phages specifically binding to PT protein were dissociated with Glycine (100 mM, pH 2.0) and infected with E. coli TG1 growing in logarithmic phase, the bacteria solution was collected by centrifugation and coated on a 2TYAG plate, and cultured at 37° C. overnight. The next day, E. coli on the plate was eluted and collected to obtain about 50 mL of bacteria solution. By calculating according to the OD value, about 10¹¹Escherichia coli bacteria were obtained.

1.3 Screening Sequence of Anti-PT Heavy Chain Single Domain Antibody by High-Throughput Sequencing:

2 mL of E. coli obtained in Example 1.2 was commissioned to Suzhou Hongxun Technology Co., Ltd. for high-throughput sequencing.

A total of 286.521 sequences of anti-PT single domain antibody were obtained in this high-throughput sequencing, among which the top 50 sequences with higher abundance were selected, and then 32 sequences were further selected as candidate sequences according to the individual abundance of CDR1, CDR2 and CDR3 regions in the anti-PT single domain antibody as well as the abundance of pairwise combinations.

Example 2: Preparation of FC Fusion Protein of PT Single Domain Antibody with Mammalian Cells

2.1 Preparation of Fc Fusion Plasmid of PT Single Domain Antibody

32 candidate sequences obtained in Example 1.3 were commissioned to Suzhou Hongxun Biotechnology Co., Ltd. for gene synthesis, with enzyme digestion sites added at both ends thereof.

The VHH fragment of PT single domain antibody was performed with double enzyme digestion, and fused with the DNA fragment encoding human IgG1FC, and cloned into the conventional mammalian expression vector to obtain the recombinant plasmid for expressing the Fc fusion protein of PT single domain antibody in mammals.

2.2 Preparation of Fc Fusion Protein of PT Single Domain Antibody

The vector constructed in 2.1 was transfected into HEK293 cells for transient expression of the antibody. The recombinant expression plasmid was diluted with Freestyle293 medium and added with PEI (Polyethylenimine) solution needed for transformation, and each group of plasmid/PEI mixture was added into HEK293 cell suspension and placed at 37° C., 5% CO₂for culture at 130 rpm. Four hours later, EXCELL293 medium, 2 mM glutamine were added for culture at 130 rpm. After 24 hours, 3.8 mM VPA was added, and with 4 g/L glucose after 72 hours. After culture for 5-6 days, the supernatant of the transient expression culture was collected, and the Fc fusion protein of target PT single domain antibody was obtained by purification using Protein A affinity chromatography. The purity of protein was preliminarily investigated by SDSPAGE and SECHPLC. The expression and purity analysis of a fraction of proteins were shown in Table 1 below:

TABLE 1

Expression
SDSPAGE
Main

Antibody
amount (mg/L)
purity %
peak ratio %

iPT3Fc
380
>95%
99.3

iPT7Fc
511
>95%
98.5

iPT12Fc
553
>95%
98.8

iPT13Fc
568
>95%
97.7

iPT15Fc
426
>95%
99.3

iPT20Fc
473
>95%
98.9

iPT21Fc
445
>95%
98.3

iPT22Fc
529
>95%
98.9

iPT26Fc
439
>95%
98.9

iPT28Fc
226
>95%
99

iPT35Fc
355
>95%
99.6

iPT36Fc
417
>95%
98.4

iPT42Fc
334
>95%
97.3

As can be seen, the expression levels of Fc fusion proteins of PT monoclonal antibody were all above 200 mg/L. and after one-step purification by Protein A affinity chromatography column, the concentrations of FC fusion protein were mostly above 1.0 mg/mL, and the purity was also very high.

Sequence information of the variable region of the selected PT single domain antibody was as follows (the boxes from left to right of each sequence showed CDR1, CDR2 and CDR3 respectively):

iPT3

>SEQ ID NO: 40

embedded image

iPT7

>SEQ ID NO: 41

embedded image

iPT12

>SEQ ID NO: 42

embedded image

iPT13

>SEQ ID NO: 43

embedded image

iPT15

>SEQ ID NO: 44

embedded image

iPT20

>SEQ ID NO: 45

embedded image

iPT21

>SEQ ID NO: 46

embedded image

iPT22

>SEQ ID NO: 47

embedded image

iPT26

>SEQ ID NO: 48

embedded image

iPT28

>SEQ ID NO: 49

embedded image

iPT35

>SEQ ID NO: 50

embedded image

iPT36

>SEQ ID NO: 51

embedded image

iPT42

>SEQ ID NO: 52

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Example 3: Verification of Functions of FC Fusion Protein of PT Single Domain Antibody

3.1 Detection of the Affinity of Fc Fusion Protein of PT Single Domain Antibody (Bio-Layer Interferometry, BLI)

The binding kinetics of the Fc fusion protein of PT single domain antibody obtained in the above example against the recombinant human PT protein was measured by Biolayerinterferometry (BLI) using a molecular interaction instrument. The Fc fusion protein of PT single domain antibody obtained in Example 2.2 was diluted to a final concentration of 2.5 μg/mL and directly immobilized on an AHC biosensor, for kinetic measurement, PT was diluted with 0.02% PBST20 to five concentrations of 100 nM, 50 nM, 25 nM, 12.5 nM and 6.25 nM, respectively, with the sample injection time of 120 s, the dissociation time of 600 s and 10 mM glycine-HCl (pH1.7) regeneration for 5 s. The binding rate (kon) and the dissociation rate (kdis) were calculated Using simple one-to-one Languir binding model (Octet K2 data analysis software version 9.0 (Data analysis 9.0)). The equilibrium dissociation constant (kD) was calculated as the ratio of kdis/kon.

The affinity results of a fraction of Fc fusion proteins of PT single domain antibody against PT measured were shown in Table 2. Some candidate antibodies were excluded due to poor affinity (data not shown).

TABLE 2

Antibody
KD (M)
kon (1/Ms)
kdis (1/s)

iPT3Fc
1.32E09
3.88E+05
6.02E04

iPT7Fc
1.46E10
5.55E+05
1.03E04

iPT12Fc
8.91E11
6.18E+05
5.51E05

iPT13Fc
1.33E09
7.04E+05
6.19E04

iPT15Fc
1.38E10
3.93E+05
5.40E05

iPT20Fc
2.21E10
4.67E+05
9.46E05

iPT21Fc
5.37E10
5.17E+05
2.78E04

iPT22Fc
7.39E10
5.13E+05
3.79E04

iPT26Fc
3.40E10
4.27E+05
1.29E04

iPT28Fc
2.78E10
3.99E+05
1.11E04

iPT35Fc
2.74E10
3.78E+05
1.04E04

iPT36Fc
8.07E10
4.42E+05
3.57E04

iPT42Fc
3.75E10
3.86E +05
1.45E04

3.2 Identification of the Neutralizing Activity of FC Fusion Protein of PT Monoclonal Antibody Against Pertussis Toxin

PT toxin at a concentration of 434.3 μg/mL was formulated to 12 ng/mL with 10% FBS+F12K+10% FBS, and added with 50 μL to per well, according to the results of Example 3.1, the FC fusion proteins of PT monoclonal antibody with good affinity were selected to be 2×diluted from the original concentration with 10% FBS+F12K, to obtain 10 concentrations, 50 μL of which was added to each well, after stay at 37° C. for 1 hour, CHOK1 cells were collected and counted, and the number of cells was adjusted to 3×10⁵cells/mL, 50 μL of solution was added to each well of the 96-well plate, after 24 hours, 100% alcohol fixing and 0.1% crystal violet staining were carried out successively, after washing with PBS, observation and photos were taken under microscope.

The results were shown in Table 3 below: iPT13Fc, iPT21Fc, iPT28Fc and iPT36Fc showed partial neutralizing activity at the concentration of 100 μg/mL; iPT3Fc, iPT7Fc, iPT12Fc, iPT15Fc, iPT20Fc, iPT22Fc, iPT26Fc, iPT35Fc and iPT42Fc showed relatively high neutralizing activity. Some candidate antibodies were excluded due to poor neutralizing activity (data not shown).

TABLE 3

Completely neutralizing

Sample
concentration (μg/mL)

iPT3Fc
50

iPT7Fc
1.56

iPT12Fc
1.125

iPT13Fc
100

μg/mL partial neutralizing activity

iPT15Fc
1.56

iPT20Fc
50

iPT21Fc
100

μg/mL partial neutralizing activity

iPT22Fc
3.13

iPT26Fc
1.56

iPT28Fc
100

iPT35Fc
2.25

iPT36Fc
100

iPT42Fc
12.5

3.3 Detection of Different PT-Binding Epitopes of Fc Fusion Protein of PT Single Domain Antibody (Bio-Layer Interferometry (BLI): Epitope Binning)

By using the intandem method, PT-biotin was diluted with 0.02% PBST20 to 10 ug/mL and immobilized on SAbiosensor for 120 s. The Fc fusion protein of PT single domain antibody was diluted to 100 nM with 0.02% PBST20, and divided into two groups with the antibody-binding time of 300 s for each group and the regeneration solution of 10 mM glycine-HCl (pH 1.7), wherein the first antibody (saturated antibody) binded to the sensor until saturated, and then the second antibody (competitive antibody) competed with the first antibody at the same concentration, and the percentage was calculated. The percentage was calculated following the formula: Ab2 with Ab1/Ab2 without Ab1.

The results of these measurements were shown in Table 4 and Table 5. The results showed that there may be competition among iPT13, iPT20 and iPT36, and there may be competition between iPT7 and iPT12, between iPT26 and iPT35, and between iPT22 and iPT15; other antibodies have no obvious competitive relationship and have different antigen-binding epitopes.

TABLE 4

Ab1\Ab2
iPT5FC
iPT3FC
iPT7FC
iPT13FC
iPT20FC
iPT26FC
iPT36FC

iPT5FC
8.10%
85.50%
66.39%
48.14%
105.13%
19.11%
104.26%

iPT3FC
104.30%
29.80%
42.11%
43.99%
96.72%
18.41%
93.65%

iPT7FC
71.50%
63.40%
11.15%
55.60%
60.00%
70.80%
58.70%

iPT13FC
79.00%
79.75%
74.50%
22.90%
0.10%
76.50%
0.116

iPT20FC
87.10%
92.90%
93.00%
49.30%
6.72%
95.30%
0.0359

iPT26FC
49.60%
54.20%
45.60%
26.70%
13.80%
31.40%
28.00%

iPT36FC
91.60%
91.15%
92.40%
51.80%
20.30%
92.10%
8.12%

TABLE 5

Ab1\Ab2
iPT7
iPT26
iPT12
iPT15
iPT22
iPT35
iPT42

iPT7FC
11.97%
79.48%
17.43%
79.76%
41.72%
26.26%
79.59%

iPT26FC
117.29%
6.85%
110.26%
102.65%
51.00%
12.80%
93.59%

iPT12FC
16.29%
16.08%
11.88%
86.81%
53.34%
97.95%
79.00%

iPT15FC
115.91%
16.60%
108.40%
15.40%
6.73%
88.28%
79.85%

iPT22FC
82.67%
13.39%
78.47%
32.60%
7.10%
71.23%
84.19%

iPT35FC
118.80%
3.67%
119.64%
71.08%
30.57%
9.72%
98.61%

iPT42FC
110.00%
10.72%
105.09%
77.60%
45.61%
85.17%
10.48%

3.4 Detection of the Nonspecific Binding of Fc Fusion Protein of PT Single Domain Antibody to Empty Cells

CHOK1 empty cells and 293F empty cells were resuspended in 3% BSAPBS and adjusted to 6×10⁶cells/mL, and added with the Fc fusion protein of PT monoclonal antibody, obtained in Example 2.2 with a final concentration of 100 μg/mL, meanwhile the negative control and blank control were set, each being cooled in an ice bath for 30 mmi. After washing, Boster secondary antibody FITC rabbit anti-human IgG antibodies were added, with being cooled in an ice bath for 30 min After washing, the cells were resuspended in 300 μL of 1% PBSBSA Buffer, and detected by flow cytometry. The results were shown in Table 6 that there was no significant difference in the MFI between the antibody and negative control and blank control, and no non-specific binding occurred.

TABLE 6

Concentration
MFI
MFI

(μg/mL)
(CHO)
(293)

Blank
—
2.62
2.08

Negative
—
3.09
2.38

Secondary
—
3.01
2.67

antibody

iPT3Fc
100 μg/mL
2.77
2.8

iPT7Fc
100 μg/mL
2.68
2.6

iPT13Fc
100 μg/mL
2.81
2.6

iPT21Fc
100 μg/mL
2.76
2.64

iPT20Fc
100 μg/mL
2.89
2.77

iPT26Fc
100 μg/mL
2.89
2.77

iPT36Fc
100 μg/mL
2.68
2.67

Blank

2.50
2.31

Negative
—
2.87
2.40

Secondary
—
3.42
5.41

antibody

iPT12Fc
100 μg/mL.
3.54
5.69

iPT15Fc
100 μg/mL
3.6
5.78

iPT22Fc
100 μg/mL
3.61
5.59

iPT26Fc
100 μg/mL
3.79
5.84

iPT35Fc
100 μg/mL
3.76
5.95

iPT42Fc
100 μg/mL
3.66
5,56

3.6 Detection of the Thermal Stability of Fc Fusion Protein of PT Single Domain Antibodies

The trace volume of protein samples was determined by using the protein thermostability detector from UNCHAINED LABS. Heating program: initial temperature: 15° C., heating rate: 0.3° C./min, final temperature: 95° C. The fluorescence absorbance values of samples at each temperature and wavelength were recorded, and the denaturation temperature Tm was fitted using a software as the highest point of the next derivative of confidence wavelength BCM; the initial polymerization temperature Tagg was one tenth of the next derivative of static light scattering SLS at 473 nm. The higher the Tm value, the more stable the protein was. The results were shown in Table 7 below, as can be seen, each antibody had a Tm basically above 60° C. with good stability.

TABLE 7

10 mg/mL
2 mg/mL

Tm1 (° C.)
Tm2 (° C.)
Tagg (° C.)
Tm1 (° C.)
Tm2 (° C.)
Tagg (° C.)

iPT3Fc
66.3
78.9
68
66.9
81.7
74.5

iPT7Fc
64.6
81.2
66
66.9
81.6
74.5

iPT12Fc
64
78
53
63
87
74

iPT13Fc
80.9
80.9
66
67
82.2
70.2

iPT15Fc
60
79
61
64
80
74

iPT20Fc
78.6
—
66.2
84.2
84.2
78

iPT21Fc
64
—
—
65
—
64

iPT22Fc
65
80
61
65
—
66

iPT26Fc
75 5
—
60.1
67.2
—
72.1

iPT36Fc
67.2
81.9
69
68.4
83
76

iPT28Fc
49
—
—
50
—
777

iPT35Fc
58
—
58
58
—
70

iPT42Fc
67
85
70
68
83
70

Example 4: Preparation of FC Fusion Protein of PT Tetravalent Antibody with Mammalian Cells

4.1 Preparation of Fc Fusion Plasmid of PT Tetravalent Antibody

Seven antibodies iPT7, iPT12, iPT15, iPT22, iPT26, iPT35 and iPT42 were selected to be divided into four groups according to the overlapping of antigen-recognizing epitopes of antibodies (epitope binning results), sequences with small overlapping of antigen-recognizing epitopes were combined in tandem in pairs, and fused with the DNA fragment encoding human IgG1 FC, and cloned into the conventional mammalian expression vector to obtain the recombinant plasmid for expressing the Fc fusion protein of PT single domain antibody in mammals, which was expected to increase its activity by this combination; in addition, iPT12diFc and iPT15diFc were formed by combination in tandem of two identical iPT2 or iPT15 sequences, respectively, and fusion with human IgG1 Fc fragment, respectively, which were used as controls.

4.2 Preparation of Fc Fusion Protein of PT Tetravalent Antibody

The vector constructed in 4.1 was transfected into HEK293 cells for transient expression of the antibody. The recombinant expression plasmid was diluted with Freestyle293 medium and added with PEI (Polyethylenimine) solution needed for transformation, and each group of plasmid/PEI mixture was added into HEK293 cell suspension and placed at 37° C., 5% CO₂for culture at 130 rpm. Four hours later, EXCELL293 medium, 2 mM glutamine were added for culture at 130 rpm. After 24 hours, 3.8 mM VPA was added, and with 4 g/L glucose after 72 hours. After culture for 5-6 days, the supernatant of transient expression culture was collected, and the Fc fusion protein of the target PT tetravalent antibody was obtained by purification using Protein A affinity chromatography. The purity of protein was preliminarily investigated by SDSPAGE and SECHPLC. The expression and purity analysis of each protein were shown in Table 8 below, as can be seen, the expression levels of Fc fusion proteins of PT tetravalent antibody were all above 200 mg/L, and after one-step purification by Protein A affinity chromatography column, most of them had a concentration greater than 1.0 mg/mL, and the purity was also very high as shown by the SEC results.

TABLE 8

Expression
SDS PAGE
Alain peak

Antibody
amount (mg/L)
punty %
ratio %

iPT7n15Fc
281
>95%
98.9%

iPT15n7Fc
271
>95%
97.9%

iPT7n22Fc
374
>95%
98.0%

iPT22n7Fc
320
>95%
97.1%

iPT7n42Fc
308
>95%
97.6%

iPT42n7Fc
310
>95%
98.7%

iPT12n35Fc
316
>95%
98.0%

iPT35n12Fc
306
>95%
99.0%

iPT15n35Fc
328
>95%
99.3%

iPT15042Fc
320
>95%
93.0%

iPT35042Fc
290
>95%
98.4%

iPT12n15Fc
367
>95%
97.9%

iPT15n12Fc
359
>95%
98.8%

iPT12n42Fc
399
>95%
95.2%

iPT42n12Fc
254
>95%
97.4%

iPT15diFc
344
>95%
99.1%

iPT12diFc
257
>95%
95.8%

Example 5: Verification of Functions of FC Fusion Protein of PT Tetravalent Antibody

5.1 Detection of the Affinity of Fc Fusion Protein of PT Tetravalent Antibody (Bio-Layer Interferometry, BLI)

The Fc fusion protein of PT tetravalent antibody prepared in Example 4.2 was diluted to 2.5 μg/mL and immobilized on a biosensor for 60 seconds, with a curing height of about 0.8 nm. PTpuri was diluted to five gradients as 100 nM, 50 nM, 25 nM, 12.5 nM and 6.25 nm, baseline: 60 s, binding: 120 s, dissociation: 600 s. The diluent was 0.02 PBST20%, a the regeneration solution was glycine-HCl (pH 1.7), the neutralizing solution was the diluent and the biosensor was AHC, as seen from Table 9, the antibodies all showed high affinity, especially the antibody iPT15n7Fc showed the highest affinity.

TABLE 9

Sample
KD (M)
kon (1/Ms)
kdis (1/s)

iPT7n15Fc
5.24E10
1.05E+05
5.47E05

iPT1507Fc
<1.0E12
107E+05
<1.0E07

iPT7n22Fc
2.23E10
7.01E+05
1.56E04

iPT22n7Fc
2.40E10
5.73E+05
1.38E04

iPT7n42Fc
3.01E10
6.07E+05
1.82E04

iPT42n7Fc
2.67E10
6.41E+05
1.71E04

iPT12n35Fc
1.57E10
6.02E+05
9.43E05

iPT35n12Fc
1.97E10
5.42E+05
1 07E04

iPT15n42Fc
1.67E10
7.22E+05
1.21E04

iPT35n42Fc
1.24E10
5.46E+05
6.75E05

iPT15n35Fc
9.12E11
5.85E+05
5.33E05

iPT12n15Fc
2.63E10
5.67E+05
1.49E04

iPT15n12Fc
1.83E10
6.14E+05
1.12E04

iPT12n42Fc
2.42E10
5.35E+05
1.29E04

iPT42n12Fc
2.37E10
5.64E+05
1.34E04

iPT12diFc
2.67E10
3.34E+05
8.89E05

iPTISdiFc
—
—
—

5.2 Identification of the Neutralizing Activity of FC Fusion Protein of PT Tetravalent Antibody Against Pertussis Toxin

PT toxin at a concentration of 434.3 μg/ml was formulated to 12 ng/mL with 10% FBS+F12K+10% FBS, and added with 50 μL to per well, the FC fusion protein of PT tetravalent antibody with good affinity prepared in Example 4.2 was 2×diluted from the original concentration with 10% FBS+F12K, to obtain 10 concentrations, 50 μL was added to each well, after stay at 37° C. for 1 hour. CHOK1 cells were collected and counted, and the number of cells was adjusted to 3×10⁵cells/mL, then 50 μL was added to each well of the 96-well plate, after 24 hours, 100% alcohol fixing and 0.1% crystal violet staining were carried out successively, after washing with PBS, observation and photos were taken under microscope. As seen from the results shown in Table 10, tetravalent antibodies iPT7n15Fc, iPT42n7Fc, iPT12n15Fc, iPT12n42Fc, iPT12diFc, iPT15n12Fc and iPT42n12Fc all showed good neutralizing activity, and the neutralizing activity of iPT7n15Fc, iPT42n7Fc, iPT12n15Fc, iPT12n42Fc, iPT15n12Fc and iPT42n12Fc was higher than that of iPT15diFc and iPT12diFc. and still higher than that of bivalent antibody iPT12Fc, as can be seen, the neutralizing activity was improved after the combination of single-domain antibodies that recognize different epitopes.

TABLE 10

Concentration for completely

Antibody
neutralizing PTToxin (μg/mL)

iPT15n7FC
5

μg/mL partial neutralizing

iPT7n22FC
5

iPT22n7FC
100

iPT7n42FC
2.5

μg/mL partial neutralizing

iPT12n35Fc
100

iPT35n12Fc
100

iPT1Sn35Fc
20

μg/mL partial neutralizing

iPT15n42Fc
100

iPT35n42Fc
100

μg/mL partial neutralizing

iPT12Fc
0.42

iPT7n15Fc
0.1

iPT42n7Fc
0.05

iPT12n15Fc
0.111

iPT12n42Fc
0.333

iPTI2diFc
0.333

μg/mL partial neutralizing

iPT15n12Fc
0.111

iPT1SdiFc
1

μg/mL partial neutralizing

iPT42n12Fc
0.333

5.3 Detection of the Nonspecific Binding of Fc Fusion Protein of PT Tetravalent Antibody to Empty Cells

CHOK1 empty cells and 293F empty cells were resuspended in 3% BSAPBS and adjusted to 6×10⁶cells/mL, and added with the Fc fusion protein of PT monoclonal antibody obtained in Example 4.2 with a final concentration of 100 μg/mL, meanwhile the negative control and blank control were set, each being cooled in an ice bath for 30 min. After washing, Boster secondary antibody FITC rabbit anti-human IgG antibody was added, with being cooled in an ice bath for 30 min. After washing, the cells were resuspended in 300 μL of 1% PBSBSA Buffer, and detected by flow cytometry. The results were shown in Table 11, which showed that no nonspecific binding had been found.

TABLE 11

Concentration
MFI
MFI

Sample name
(μg/mL)
(293)
(CHO)

Blank
—
2.62
2.08

Negative
—
3.09
2.38

iPT12n15Fc
100
3.40
2.40

iPT12n42Fc
100
3.46
2.39

iPT12diFc
100
3.57
2.40

iPT15n12Fc
100
3.57
2.33

iPT15diFc
100
3.50
2.40

iPT42n12Fc
100
3.45
2.51

Blank
—
4.64
4.29

Negative
—
6.04
5.43

iPT7n15Fe
100
7.27
5.46

iPT42n7Fc
100
6.44
5.35

Example 6 Efficacy In Vivo Study of Fc Fusion Protein of PT Tetravalent Antibody

6.1 Protection Experiment Against PT Toxin

The NIH mice used were divided into groups with 10 mice in each group, and were injected intraperitoneally with PTtoxin at a dose of 5 μg/mouse to establish a challenged mouse model for evaluating PT toxin antibody.

In this experiment, FC fusion proteins of PT tetravalent antibody iPT7n15Fc, iPT42n7Fc, iPT15n12Fc, iPT42n12Fc and iPT12diFc were injected intraperitoneally into the challenged mouse model, and mouse mortality was recorded every day. Two hours after challenge, the FC fusion protein of PT tetravalent antibody was injected, for single dose administration, the dose was 20 μg/dose and 40 μg/dose, respectively; for multiple dose administration, it was carried out in five times, with doses being 20 μg/dose and 40 μg/dose, the day of grouping was recorded as Day 0, meanwhile the negative control was set, then weighing of mice, measuring the numbers of white blood cells and lymphocytes were carried out at DO, D5, D10 and D15, respectively, and the survival rate of mice was recorded every day.

The results were shown in Table 12 below, compared with the negative control, all antibodies had protective effect on the challenged mice, for single dose and multiple dose administration, the survival rate of mice was significantly increased when iPT15n12FC and iPT12diFC were administrated at 40 μg/dose as compared with at 20 μg/dose, and there was no significant difference among other antibodies. Survival curves for single dose administration of 20 μg/dose and 40 μg/dose were shown in FIG. 1 and FIG. 2, respectively, and survival curves for multiple dose administration of 20 μg/dose and 40 μg/dose were shown in FIG. 3 and FIG. 4, respectively.

TABLE 12

Survival rate for single
Survival rate for multiple

dose administration %
dose administration %

Antibody
20 ug/dose
40 ug/dose
20 ug/dose
40 ug/dose

name
D10
D15
D10
D15
D10
D15
D10
D15

Negative
0
0
0
0
50
50
50
50

control

group

iPT7n15Fc
40
30
70
40
90
90
90
90

iPT42n7Fc
40
40
60
20
80
80
100
90

iPT15n12Fc
20
20
60
50
60
50
90
90

iPT42n12Fc
50
40
80
30
100
100
90
90

iPT12diFc
40
20
100
50
80
70
90
90

6.2 Protection Experiment Against Bacteria

All NIH mice to be used were females, weighed in 1622 g/mouse, with 10 mice in each group, the day of grouping was recorded as Day 0, the mice were weighed, the numbers of white blood cells and lymphocytes were measured, and pertussis Bacillus was injected intraperitoneally into the NIH mice, thus establishing a challenged mouse model for evaluating PT toxin antibody by intraperitoneal injection of pertussis Bacillus.

In this experiment, FC fusion proteins of PT tetravalent antibody iPT7n15Fc, iPT42n7Fc, iPT15n12Fc, iPT42n12Fc and iPT12diFc were injected intraperitoneally into the challenged mouse model, and mouse mortality was recorded every day. Two hours after challenge, the FC fusion protein of PT tetravalent antibody was injected with multiple dose administration in five times, with doses being 20 μg/dose and 40 μg/dose, respectively, the day of grouping was recorded as Day 0, meanwhile the negative control was set, then weighing of mice, measuring the numbers of white blood cells and lymphocytes were carried out at D0, D5, D10 and D15, respectively, and the survival rate of mice was recorded every day.

The results were shown in Table 13, compared with the negative control, all antibodies had protective effect on the challenge mice, among which the antibodies iPT7n15FC and iPT42n7Fc had good protective effect, the survival rate of mice was significantly higher when administrated with iPT7n15FC and iPT15n12Fc at 40 μg/dose than at 20 μg/dose. The survival curves were shown in FIG. 5.

TABLE 13

Survival rate for multiple

dose administration %

20 μg/dose
40 μg/dose

Antibody name
D10
D15
D10
D15

Negative control
20
20
20
20

iPT7n15Fc
60
60
80
80

iPT42n7Fc
60
60
60
60

iPT15n12Fc
20
20
60
60

iPT42nl2Fc
30
30
30
30

IPTL2diFc
60
50
20
20

Example 7: Humanization of PT Single Domain Antibody

The humanization method was achieved by humanization of amino acids on the protein surface (resurfacing) and the VHH humanized universal framework transplantation method (CDR grafting to a universal framework).

The humanization steps were as follows: subjecting the antibody strains iPT7, iPT15 and iPT42 to homologous modeling by the software Modeller 9. By using NbBcII10 antibody (PDB number: 3DWT) as the reference sequence, the relative solvent accessibility of amino acids was calculated based on the three-dimensional structure of protein. If an amino acid from antibody strains iPT7, iPT15 and iPT42 was exposed to solvent, which was replaced with the amino acid at the same position in the reference humanized antibody 10HQ sequence, and finally all the substitutions were done.

The specific steps of the VHH humanized universal framework transplantation method were as follows: firstly, the universal humanized VHH framework hNbBcII10FGLA (PDB number 3EAK) designed and made according to sequence homology by Cecile Vincke et al. was obtained, which was designed based on the nanoantibody NbBcII10 antibody (PDB number: 3DWT), and the reference humanized antibody 10HQ was humanized on the amino acids on the protein surface, and the modifications of some amino acids VLP from the VHH sequence frame 1 (framework1), some amino acids GL from the VHH sequence frame 2 (framework2), some amino acids RSKRAAV of the VHH sequence frame 3 (framework3) and amino acid L of the VHH sequence frame 4 (framework4) were done. By using hNbBcII10FGLA as the framework, the CDR was replaced by the CDR region of antibody strains iPT7, iPT15 and iPT42 to accomplish the humanization of the antibody.

The antibody strains iPT7, iPT15 and iPT42 were humanized to obtain 11 humanized variants of antibody strain huPT. The sequence numbering of these humanized variants and the numbering of the amino acid residues therein were done according to Kabat, ant the comparison results of humanized sequences were shown in FIGS. 6-8.

Example 8: Preparation of FC Fusion Protein of huPT Single Domain Antibody with Mammalian Cells

8.1 Preparation of Fc Fusion Plasmid of huPT Single Domain Antibody

The coding sequences of huPT single domain antibody in Example 7 were commissioned to Suzhou Hongxun Biotechnology Co., Ltd. for gene synthesis, with enzyme digestion sites added at both ends.

The VHH fragment of huPT single domain antibody was performed with double enzyme digestion, and fused with the DNA fragment encoding human IgG1FC, and cloned into the conventional mammalian expression vector to obtain the recombinant plasmid for expressing the Fc fusion protein of PT single domain antibody in mammals.

8.2 Preparation of Fc Fusion Plasmid of huPT Single Domain Antibody

The vector constructed in 8.1 was transfected into HEK293 cells for transient expression of the antibody. The recombinant expression plasmid was diluted with Freesyle293 medium and added with PEI (Polyethylenimine) solution needed for transformation, and each group of plasmid/PEI mixture was added into HEK293 cell suspension and placed at 37° C., 5% CO₂for culture at 130 rpm. Four hours later. EXCELL293 medium, 2 mM glutamine were added for culture at 130 rpm. After 24 hours, 3.8 mM VPA was added, and with 4 g/L glucose after 72 hours. After culture for 5-6 days, the supernatant of transient expression culture was collected, and the Fc fusion protein of target huPT single domain antibody was obtained by purification using Protein A affinity chromatography. The purity of protein was preliminarily investigated by SDSPAGE and SECHPLC. The expression and purity analysis of each protein were shown in Table 14 below. The results showed that all humanized variants of iPT7 and iPT15 were not significantly different in expression level and purity, which were acceptable. However, the humanized variant of iPT42 showed certain difference in stability. Wherein, the humanized variants v1, v2, v7, v8, v10 and v11 were not desirable in either expression level or product purity.

TABLE 14

Expression amount
Main peak

Antibody
(mg/L)
ratio %

huPT7v1Fc
325
98.5

huPT7v2 Fc
336
98.3

huPT7v3 Fc
288
98.2

huPT7v4Fc
278
97.5

huPT7vSFc
314
98.3

huPT7v6Fc
309
97.6

huPT7v7Fc
294
98.1

huPT7v8Fc
321
97.6

huPT7v9Fc
286
98.2

huPT7v10Fc
296
97.3

huPT7v11Fc
301
97.7

huPT15v1cFc
462
97.3

huPT15v2cFc
179
94.0

huPT15v3cFc
306
95.3

huPT15v4cFc
251
66.0

huPT15v5cFc
398
92.3

huPT15v6cFc
356
95.3

huPT15v7cFc
451
97.4

huPT15v8cFc
432
94.6

huPT15v9cFc
386
96.8

huPT15v10cFc
453
97.5

huPT15v11cFc
492
96.6

huPT42v1Fc
146
32.0

huPT42v2Fc
145
18.7

huPT42v3Fc
286
90.5

huPT42v4Fc
297
91.2

huPT42v5Fc
300
92.0

huPT42v6Fc
472
95.4

huPT42v7Fc
156
56.6

huPT42v8Fc
120
42.5

huPT42v9Fc
356
95.6

huPT42v10Fc
189
38.8

huPT42v11Fc
133
53.3

Example 9: Verification of Functions of FC Fusion Protein of Humanized huPT Single Domain Antibody

9.1 Identification of PT Binding Capability of Fc Fusion Protein of huPT Single Domain Antibody (ELISA)

The recombinant human PT protein were coated on a plate with 0.3 μg/well for staying at 4° C. overnight, and reacted with the gradient dilution series of Fc fusion protein of huPT single domain antibody obtained in Example 8.2 for 2 hours at room temperature. After washing, the secondary antibody goat anti-human IgGFC horseradish peroxidase labeled antibody (Sigma) was added and reacted at room temperature for 2 hours. After washing, the developing solution was added, and the absorbance value was read at 450 nm and 650 nm, and the final absorbance value was given by subtracting the absorbance value at 650 nm from that at 450 nm. The software SotfMax Pro v5.4 was applied for data processing and mapping analysis, by using four-parameter fitting, the binding curve and EC₅₀of huPT antibody for PT protein were obtained, which reflected the affinity of the antibody for FIX. The results were shown in Table 15 below. As can be seen, all humanized variants had similar binding capacity to PT toxin protein.

TABLE 15

Antibody
EC₅₀(ng/mL)

huPT7v1Fc
34.9

huPT7v2 Fc
33.7

huPT7v3 Fc
34.2

huPT7v4Fc
36.8

huPT7v5Fc
35 7

huPT7v6Fc
35.0

huPT7v7Fc
36.0

huPT7v8Fc
33.8

huPT7v9Fc
34.6

huPT7v10Fc
35.6

huPT7v11Fe
33.3

huPTI 5v1cFc
20.2

huPTlSv2c Fc
19.8

huPT15v3e Fc
21.8

huPT15v4cFc
22.0

huPT15v5cFc
21.8

huPT15v6cFc
20.9

huPT15v7cFc
22.1

huPT15v8cFc
20.7

huPT15v9cFc
21.3

huPT15v10cFc
22.1

huPT15v11cFc
20.5

huPT42v1Fc
25.8

huPT42v2Fc
27.6

huPT42v3Fc
26.2

huPT42v4Fc
26.4

huPT42v5Fc
25.7

huPT42v6Fc
25.6

huPT427F0
22.9

huPT42v8Fc
24.9

huPT42v9Fc
27.2

huPT42v1OFc
25.5

huPT42vlIFo
25

9.2 Identification of the Neutralizing Activity of FC Fusion Protein of Humanized PT Monoclonal Antibody Against Pertussis Toxin

PT toxin at a concentration of 434.3 μg/ml was formulated to 12 ng/mL with 10% FBS+F12K+10% FBS, and added with 50 μL to per well, the FC fusion protein of PT antibody was 2×diluted from the original concentration with 10% FBS+F12K, to obtain 10 concentrations, 50 μL was added to each well, after stay at 37° C. for 1 hour, CHOK1 cells were collected and counted, and the number of cells was adjusted to 3×10⁵cells/mL, and 50 μL was added to each well of the 96-well plate, after 24 hours, 100% alcohol fixing and 0.1% crystal violet staining were carried out successively, after washing with PBS, observation and photos were taken under microscope. Three humanized variants of each of iPT7, iPT15 and iPT42 were randomly selected for investigating the neutralizing activity thereof. Among the variants of iPT42, v1, v2, v7, v8, v10 and v11 with poor stability were discarded.

The results were shown in Table 16 below, the cytotoxic neutralizing activity of the selected humanized variants were equal to or slightly better than that of the maternal antibody.

TABLE 16

Minimum neutralizing

Sample
concentration (μg/ml)

iPT15-Fe
<1

huPT15V3c-ld-Fc
<1

huPT15V7c-ld-Fc
<1

huPT15V11c-ld-Fc
<1

iPT7-Fc
<1

huPT7V1-ld-Fc
<0.5

huPT7V4-ld-Fc
<0.5

huPT7V11-ld-Fc
<0.5

iPT42-Fc
~32

huPT42V4-ld-Fc
~32

huPT42V6-ld-Fc
~16

huPT42V9-ld-Fc
~32

9.3 Detection of the Nonspecific Binding of Fc Fusion Protein of huPT Single Domain Antibody to Empty Cells

CHOK1 empty cells and 293F empty cells were resuspended in 3% BSAPBS and adjusted to 6×10⁶cells/mL, and added with the Fc fusion protein of huPT monoclonal antibody obtained in Example 8.2 with a final concentration of 100 μg/mL and 10 μg/mL, respectively, meanwhile, the negative control and blank control were set, each being cooled in an ice bath for 30 min. After washing. Boster secondary antibody FITC rabbit anti-human IgG antibody was added, with being cooled in an ice bath for 30 min. After washing, the cells were resuspended in 300 μL of 1% PBSBSA Buffer, and detected by flow cytometry. The results were shown in Table 17, which showed that no nonspecific binding had been found.

TABLE 17

Concentration
MFI
MFI

(μg/mL)
(CHO)
(293)

Blank

3.31
3.28

Negative

4.86
5.44

huPT7v1Fc
100 μg/mL
5.35
6.17

10 μg/mL
6.05
6.21

huPT7v2Fc
100 μg/mL
5.42
6.70

10 μg/mL
5.56
6.63

huPT7v4 Fc
100 μg/mL
5.83
7.69

10 μg/mL.
5.74
8.35

huPT7v7Fc
100 μg/mL
5.63
6.99

10 μg/mL
6.13
6.42

huPT7v11Ec
100 μg/mL
5.93
7.01

10 μg/mL
6.29
6.41

huPT42v4Fc
100 μg/mL
5.76
5.85

10 μg/mL
6.05
6.51

huPT42v6Fc
100 μg/mL
6.23
6.15

10 μg/mL
6.00
6.81

huPT42v9Fc
100 μg/mL
7.56
5.12

10 μg/mL
7.00
6.20

huPT15V1c-ld-Fc
100 μg/mL
7.04
6.93

10 μg/mL
7.20
6.68

huPT15V3c-ld-Fc
100 μg/mL
7.13
6.30

10 μg/mL
6.38
7.40

huPT15V7c-ld-Fc
100 μg/mL
6.54
6.00

10 μg/mL
7.37
7.06

huPT15V11c-ld-Fc
100 μg/mL
6.50
5.58

10 μg/mL
5.55
6.68

9.4 Detection of the Thermal Stability of Fc Fusion Protein of huPT Single Domain Antibody

The trace volume of protein samples was determined by using the protein thermostability detector from UNCHAINED LABS. Heating program: initial temperature: 15° C., heating rate: 0.3° C./min, final temperature: 95° C. The fluorescence absorbance values of samples at each temperature and wavelength were recorded, and the denaturation temperature Tm was fitted using a software as the highest point of the next derivative of confidence wavelength BCM; the initial polymerization temperature Tagg was one tenth of the next derivative of static light scattering SLS at 473 nm. The higher the Tm value, the more stable the protein was. The results were shown in Table 18 below, as can be seen, each antibody had a Tm basically above 60° C. with good stability.

TABLE 18

Tm1
Tagg

huPT7v4-Fc
60.8
58.5

huPT7v7-Fc
60.4
58.0

huPT7v2-Fc
60.6
58.2

huPT7v1-Fc
60.3
58.1

huPT7v11-Fc
62.1
60.0

huPT42v4-Fc
64.5
62.0

huPT42v6-Fc
67.7
72.8

huPT42v9-Fc
64.2
66.6

huPT15V1c-ld-Fc
66.8
69.6

huPT15V3c-ld-Fc
66.5
69.2

huPT15V7c-ld-Fc
66.8
69.5

huPT15V11c-ld-Fc
67.9
72.0

Example 10: Preparation of Fc Fusion Protein of Tetravalent Humanized PT Antibody

According to the method of Example 4, the humanized antibody sequences, huPT7v11, huPT15v7c and huPT42v6, which were obtained and investigated in Examples 7-9 were selected to be combined in tandem in pairs according to the overlapping of antigen-recognizing epitopes of antibodies (epitope binning results) and fused with the DNA fragment encoding human IgG1FC, to obtain tetravalent bispecific antibodies huPT7v11n15v7c-Fc, huPT7v11n15v11c-Fc, huPT42v6n15v11c-Fc and huPT42v6n7v11-Fc.

The HEK293 cells were instantly expressed and purified to obtain the Fc fusion protein of target PT tetravalent antibody.

Example 11 Further Investigation on the Activity of Fc Fusion Protein of Tetravalent Humanized PT Antibody

11.1 Investigation on the Affinity for PT Toxin

The Fc fusion protein of PT tetravalent antibody prepared in Example 10 was diluted to 2.5 μg/mL and immobilized on biosensor for 60 seconds, with a curing height of about 0.8 nm. PTpuri was diluted to five gradients as 100 nM, 50 nM, 25 nM, 12.5 nM and 6.25 nm, baseline: 60 s, binding: 120s, dissociation: 600 s. The diluent was 0.02PBST20%, the regeneration solution was glycine-HCl (pH1.7), the neutralizing solution was the diluent, the biosensor was AHC, and the results were shown in Table 19 below. Among them, 1B7 and 11E6 were used as control antibodies, which binded to PT toxin and showed the neutralizing effect. Self-cloning and preparation were carried out according to the sequences in U.S. Ser. No. 10/035,846.

TABLE 19

Sample
KD (M)
kon (1/Ms)
kdis (1/s)

huPT7n15-Fc
8.84E−11
3.75E+05
3.32E−05

huPT42n7-Fc
2.00E−10
4.59E+05
9.18E−05

huPT42n15-Fc
<1.0E−12
3.37E+05
<1.0E−07

1B7
<1.0E−12
3.87E+05
<1.0E−07

11E6
<1.0E−12
3.11E+05
<1.0E−07

11.2 Invesgation on the Neutralizing Activity of Fc Fusion Protein of Tetravalent Humanized PT Antibody and Comparison with Control Antibody

PT toxin at a concentration of 434.3 μg/ml was formulated to 12 ng/mL with 10% FBS+F-12K+10% FBS, and added with 50 μL to per well, the FC fusion protein of PT tetravalent antibody with good affinity prepared in Example 4.2 was 2×diluted from the original concentration with 10% FBS+F-12K, to obtain 10 concentrations, 50 μL was added to each well, after stay at 37° C. for 1 hour, CHO-K1 cells were collected and counted, and the number of cells was adjusted to 3×10⁵cells/mL, 50 μL was added to each well of the 96-well plate, after 24 hours, 100% alcohol fixing and 0.1% crystal violet staining were carried out successively, after washing with PBS, observation and photos were taken under microscope, 1B7 and 11E6 were control antibodies, which binded to PT toxin and showed the neutralizing effect. Self-cloning and preparation were carried out according to the sequences in U.S. Ser. No. 10/035,846.

The results were shown in Table 20, wherein, tetravalent antibodies huPT7n15-Fc, huPT42n7-Fc, huPT42n15-Fc, iPT12n42-Fc, iPT12di-Fc, iPT15n12-Fc and iPT42n12-Fc showed better neutralizing activity, and the neutralizing activity of each of iPT7n15-Fc, iPT42n7-Fc, iPT12n15-Fc, iPT12n42-Fc, iPT15n12-Fc and iPT42n12-Fc was higher than that of iPT15di-Fc and iPT12di-Fc, and also higher than that of bivalent antibody iPT12-Fc, as can be seen, the neutralizing activity was improved after the combination of single-domain antibodies that recognize different epitopes.

TABLE 20

Antibody
Minimum neutralizing

concentration

huPT7n15-Fc
0.025
μg/mL

huPT42n7-Fc
0.05
μg/mL

huPT42n15-Fc
0.1
μg/mL

1B7
1.6
μg/mL

11E6
0.8
μg/mL

1B7-11E6
(0.4 + 0.4)
μg/mL

huPT7n15-Fc + huPT42n7-Fc
(0.00625 + 0.00625)
μg/mL

huPT7n15-Fc + huPT42n15-Fc
(0.0125 + 0.0125)
μg/mL

Example 12 Comparison of Epitopes Between Fc Fusion Protein of Pt Single Domain Antibody and Control Antibody

In this example, the binding epitopes of the Fc fusion protein of PT single domain antibody of the present invention and that of the control antibody were compared by epitope binning using Bio-Layer Interferometry (BLI).

Specifically, by using the intandem method, PT-biotin was diluted with 0.02% PBST20 to 10 ug/mL and immobilized on SAbiosensor for 120 s. The Fc fusion protein of PT single domain antibody was diluted to 100 nM with 0.02% PBST20, and divided into two groups with the antibody-binding time of 300 s for each group and the regeneration solution of 10 mM glycine-HCl (pH 1.7), wherein the first antibody (saturated antibody) binded to the sensor until saturated, and then the second antibody (competitive antibody) competed with the first antibody at the same concentration, and the percentage was calculated. The percentage was calculated following the formula: Ab2 with Ab1/Ab2 without Ab1. Wherein, the control antibody (11E6, 1B7, derived from U.S. Ser. No. 10/035,846) was Ab1, and the subsequent antibody was Ab2. At the same time, the control antibody was also added to Ab2 group as a reference for the complete overlapping of antigenic epitopes.

The results were shown in Table 21 below. The results showed that, except that the epitopes of iPT12 overlapped with that of 11E6 control antibody, and the epitopes of iPT7 partially overlapped with that of 11E6 control antibody, all the other antibodies had no obvious competitive relationship with the two control antibodies and had completely non-overlapping antigen-binding epitopes.

TABLE 21

Percentage = Ab2

with Ab1/Ab2

without Ab1

Ab1

Ab2
11E6
1B7

iPT7-Fc
36%
86%

iPT12-Fc
15%
88%

iPT15-Fc
88%
85%

iPT22-Fc
76%
79%

iPT26-Fc
78%
82%

iPT35-Fc
84%
78%

iPT42-Fc
86%
88%

11E16
0.2%
—

1B7
—
1.1%

PERTUSSIS TOXIN BINDING PROTEIN

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