Patent Application
20210138089
The present application includes a Sequence Listing in electronic format as a text file titled “Seq_Listing.txt” which was created on Feb. 29, 2016 and has a size of 6 kilobytes. The contents of txt file “Seq_Listing.txt” are incorporated by reference herein.
The allergic reaction, type I hypersensitivity, is a complex immune reaction to innocuous compounds such as food, environmental factors and drugs. These reactions can trigger symptoms from harmless skin irritation to a life-threatening anaphylaxic reaction and require sophisticated techniques to diagnose and treat. Approximately 1.6% of the U.S. population is at risk for an allergy mediated anaphylaxis response. In the U.S., anaphylaxis reactions account for over three hundred thousand emergency room visits per year. Currently, there are no known FDA approved preventative treatments for type I hypersensitivity. Drugs, such as steroids and antihistamines, treat allergy symptoms, but not the underlying response.
Type I hypersensitivity is characterized by the release of inflammatory cytokines such as histamine from mast cells after exposure to an allergen, also known as a degranulation response. The response is initiated when immunoglobulin constant fragment epsilon receptors (FcεRI) binds the Fc region of an allergen specific IgE, forming the IgE-FcεRI complex. The event is marked by the clustering of the complex on mast cells, inducing an intracellular signaling cascade which causes degranulation. This event, also known as crosslinking, is triggered by several IgEs binding multivalently to a single allergen protein.
One major hurdle for current research, both clinical and at the bench top, is the determination and evaluation of the allergen epitopes, which are regions where IgEs bind to trigger degranulation. Determination and evaluation require binding assays using either genetically modified allergen protein or the use of linear peptide fragments or sequences taken from an allergen protein. However, there have been complexities associated with genetically modifying and expressing allergen proteins and controlling mutagenic sites. Another drawback is that, unlike epitope sequences in folded proteins, linear peptide mimetics of protein epitopes, as allergen mimetics, undergo an increase in conformational entropy. The use of linear peptide mimetics of protein epitopes decreases binding affinity, therefore, any method utilizing this technique could overlook moderate-to-low affinity epitopes that are important or critical for degranulation response.
Another disadvantage is that the binding assays require copious amounts of purified IgE and patient serum. Additionally, they are only capable of measuring monovalent IgE-epitope binding. This form of binding is not representative of degranulation response in vivo. Epitope antigenicity, which is the ability for a molecule to stimulate degranulation response, is not directly correlated with binding affinity. Rather, epitope antigenicity is dependent on multivalent reactions and intercellular regulatory responses. Therefore, there is a need for a method for determining allergen epitope antigenicity that is representative of degranulation response in vivo. Moreover, while various techniques for diagnosing allergy sensitivity exist, none of these techniques alone are suitable for determining the binding sites on allergen proteins. The present disclosure addressed these needs.
Embodiments herein relate to the field of nanoparticles, and more particularly to liposomal nanoparticles for diagnostic applications. As will be described further hereinbelow, the invention provides an allergen presentation platform. The platform is a liposomal nanoparticle that can have one or more presented above the surface of the nanoparticle that can elicit an allergic reaction, for example, an IgE dependent reaction.
Accordingly, the invention provides a liposomal nanoparticle comprising:
about 0.1 mol % to about 20 mol % of a synmimotope-lipid conjugate;
about 2 mol % to about 10 mol % of a polyethylene glycol-lipid (PEG-lipid) conjugate; and
about 80 mol % to about 97 mol % of a phospholipid.
The nanoparticle has a spherical lipid bilayer comprising the phospholipid and the synmimotope-lipid conjugate, the spherical lipid bilayer having an interior surface and an exterior surface; the exterior surface of the spherical lipid bilayer comprises the PEG-lipid conjugate wherein PEG moieties of the PEG-lipid conjugate form a coating over the exterior surface of the nanoparticle, and one or more synmimotope moieties of synmimotope-lipid conjugates protrude above the coating formed by the PEG moieties.
The synmimotope-lipid conjugate comprises a conjugate of Formula I:
A-B-C-D-E-(F)n (I)
wherein
A is a synmimotope, wherein the synmimotope is a mimotope, a hapten, or a peptide sequence of known or suspected allergen epitopes;
B is a first linker or a direct bond, wherein the first linker, when present, comprises one or more ethylene glycol moieties or saccharide moieties covalently attached to synmimotope (A) and second linker (C) by amide bonds;
C is a second linker, wherein the second linker (C) comprises an amino acid or an oligomer of a charged amino acid or a polar amino acid, wherein the amino acid or oligomer is covalently attached by amide bonds to first linker (B) or the synmimotope (A) if first linker (B) is a direct bond, and to third linker (D);
D is a third linker, wherein the third linker (D) comprises an oligomer of ethylene glycol attached covalently at distal ends by amide bonds to second linker (C), and tag (E);
E is a tag, wherein the tag comprises a monomer or dimer of an amino acid, optionally further comprising a chromophore or fluorophore (e.g., tryptophan);
F is a (C8-C22)acyl moiety, such as a palimitoyal moiety, covalently attached to tag (E) by an amide bond; and
n is 1 or 2;
wherein the diameter of the nanoparticle is about 20 nm to about 2 μm. See, for example, the lipid conjugates of
In one embodiment, the synmimotope (A) of the synmimotope-lipid conjugate is a known or suspected allergen epitope selected from the group of allergen epitopes consisting of SEQ ID NO: 1-4; SEQ ID NO: 5-12; SEQ ID NO: 13-16; SEQ ID NO: 17-23; and SEQ ID NO: 24-31.
In another embodiment, the synmimotope (A) of the synmimotope-lipid conjugate is a hapten. The hapten can be any small molecules that elicit an immune response, that can be conjugated to form the lipid conjugate of Formula I. Conjugation chemistry is well known in the art (see Hermanson, Bioconjugate Techniques, Academic Press, San Diego, Calif. (1996)). In various embodiments, the hapten can be selected from the group consisting of 2,4-dinitrophenol (DNP), dansyl, penicillin, a sulfa drug (e.g., celecoxib, sulfasalazine, prontosil, sulfamethoxazole, sulfasalazine, sulfadiazine, and the anti-retrovirals amprenavir, or fosamprenavir), and a platinum drug (e.g., cisplatin or oxalaplatin).
In one embodiment, the PEG-lipid conjugate comprises about 10 to about 200 ethylene glycol residues and the lipid is a (C5-C22)acyl moiety or a phospholipid, wherein the ethylene glycol residues and the lipid are optionally linked by an amide bond.
In some embodiments, the phospholipid comprises one or two (C5-C22)acyl moieties. In a specific embodiment, the phospholipid is 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) or 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC).
In one embodiment, second linker (C) comprises a charged amino acid. The charged amino acid can be, for example, aspartic acid, glutamic acid, lysine, or and arginine. In another embodiment, second linker (C) comprises a polar amino acid. The polar amino acid can be, for example, glutamine, asparagine, histidine, serine, threonine, or methionine.
In one embodiment, the tag (E) is a tryptophan residue, or a monomer or dimer of lysine. In various embodiments, moiety (F) is a (C16)acyl moiety or a (C18)acyl moiety.
In some specific embodiments, the nanoparticle has a diameter of about 10 nm to about 300 nm. In other specific embodiments, the nanoparticle can have a diameter of about 80 nm to about 220 nm, or about 100 nm to about 160 nm.
In one embodiment, the nanoparticle has a plurality of mimotopes, e.g., epitopes, protruding above the coating formed by the PEG moieties, wherein the plurality of epitopes is homogeneous or heterogeneous.
In one embodiment, the nanoparticle comprises: about 2 mol % mimotope-lipid conjugate; about 5 mol % PEG-lipid conjugate; and about 93 mol % 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC).
In various embodiments, the nanoparticle can further comprise about 1 mol % to about 35 mol % cholesterol, with respect to the molar amount of the phospholipid.
In another embodiment, the nanoparticle comprises: about 2% mimotope-lipid conjugate; about 5% polyethylene glycol-lipid (PEG-lipid) conjugate; about 93% 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC); wherein the mimotope-lipid conjugate comprises: a mimotope; an ethylene glycol linker; an oligo-lysine linker; a tryptophan residue; and a palmitoyl tail;
wherein the mimotope is a known or suspected allergen epitope selected from the group of allergen epitopes consisting of SEQ ID NO: 1-4, SEQ ID NO: 5-12, SEQ ID NO: 13-16, SEQ ID NO: 17-23, and SEQ ID NO: 24-31;
wherein said PEG-lipid conjugate comprises PEG conjugated to a hydrophilic region of a lipid, wherein said lipid comprises a hydrophilic region and a hydrocarbon tail; and wherein the diameter of the nanoparticle is about 20 nm to about 300 nm.
The invention further provides a method of diagnosing an allergy comprising:
providing sera from an allergy sensitive subject; contacting said sera to cells in culture; adding a nanoparticle that contains a synmimotope as described herein; and evaluating degranulation results; thereby determining if an allergy is present in the subject.
The evaluation of degranulation results of the nanoparticle can be by a standard beta hexosaminidase assay. The the nanoparticle can include a mimotope of any one of SEQ ID NO: 1-31. In various embodiments, the mimotope is selected from the (e.g., five membered) group consisting of SEQ ID NO: 1-4, SEQ ID NO: 5-12, SEQ ID NO: 13-16, SEQ ID NO: 17-23, and SEQ ID NO: 24-31. A plurality of the nanoparticles can be added to the sera and cells in culture. The nanoparticle can be used for identifying a specific subject's sensitivity to a particular set of epitopes. The nanoparticle can be used for predicting a symptomatic clinical response. Furthermore, the nanoparticle can be used to evaluate epitopes alone or in combination to determine the ability to trigger allergic responses.
The invention also provides a method of diagnosing an allergy comprising: providing blood containing basophils; adding a nanoparticle that contains a synmimotope as described herein to the blood; and evaluating degranulation results; thereby diagnosing the presence or character of an allergy. The evaluation of degranulation results of the nanoparticle can be, for example, by fluorescence-activated cell sorting (FACS) to identify activated basophils.
The invention further provides a method of diagnosing an allergy comprising: providing a nanoparticle that contains a synmimotope as described herein; contacting the nanoparticle to a subject's skin; delivering the nanoparticle to said subject subcutaneously; and evaluating immunological response; thereby diagnosing the presence or character of an allergy. The nanoparticle can be contacted to subject's skin using a scratch test. The nanoparticle can be contacted to subject's skin using a microneedle. The microneedle can include a plurality of nanoparticles. The nanoparticles can comprise a spatial array of a plurality of mimotopes selected from the group consisting of SEQ ID NO: 1-4, SEQ ID NO: 5-12, SEQ ID NO: 13-16, SEQ ID NO: 17-23, and SEQ ID NO: 24-31. The microneedle can comprise at least one mimotope for an allergen of interest.
A further method for using the nanoparticle thus includes, but is not limited to, providing sera from an allergy sensitive individual for an in vitro application. IgE molecules in sera can be allowed to bind to receptors on cell surface. Degranulation using nanoallergens can be monitored using, for example, a standard beta hexosaminidase assay. The nanoparticle can include a plurality of nanoparticles with single or different combinations of mimotope-lipid conjugates loaded to trigger allergic responses. The nanoparticle can be used to identify a specific patient's sensitivity to a set of epitopes and predict a symptomatic clinical response. An in vivo application of using nanoallergen includes animal testing of allergen molecules and immunological responses. Another in vivo application includes using nanoallergens in a clinical application similar to a scratch test.
The following drawings form part of the specification and are included to further demonstrate embodiments or various aspects of the present disclosure. In some instances, embodiments of the disclosure can be best understood by referring to the accompanying drawings in combination with the detailed description presented herein. The description and accompanying drawings may highlight a certain specific example, or a certain aspect of the disclosure. However, one skilled in the art will understand that portions of the example or aspect may be used in combination with other examples or aspects of the invention.
In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which are shown by way of illustration embodiments that may be practiced. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope. Thus, the following detailed description is not to be taken in a limiting sense, and the scope of embodiments is defined by the appended claims and their equivalents.
Various operations may be described as multiple discrete operations in turn, in a manner that may be helpful in understanding embodiments; however, the order of description should not be construed to imply that these operations are order dependent.
The description may use the terms “embodiment” or “embodiments,” which may each refer to one or more of the same or different embodiments. Furthermore, the terms “comprising,” “including,” “having,” and the like, as used with respect to embodiments, are synonymous. The use of the word “a” or “an” when used in conjunction with the term “comprising” in the claims and/or the specification may mean “one,” but it is also consistent with the meaning of “one or more,” “at least one,” and “one or more than one.” Some embodiments of the present disclosure may consist of or consist essentially of one or more elements, method steps, and/or methods of the invention. It is contemplated that any method or composition described herein can be implemented with respect to any other method or composition described herein.
The terms “coupled” and “connected,” along with their derivatives, may be used. It should be understood that these terms are not intended as synonyms for each other. Rather, in particular embodiments, “connected” may be used to indicate that two or more elements are in direct physical or electrical contact with each other. “Coupled” may mean that two or more elements are in direct physical or electrical contact. However, “coupled” may also mean that two or more elements are not in direct contact with each other, but yet still cooperate or interact with each other.
For the purposes of the description, a phrase in the form “A/B” or in the form “A and/or B” means (A), (B), or (A and B). For the purposes of the description, a phrase in the form “at least one of A, B, and C” means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B and C). For the purposes of the description, a phrase in the form “(A)B” means (B) or (AB) that is, A is an optional element.
In various embodiments, methods, apparatuses, and systems for nanoallergens are provided. In exemplary embodiments, a computing system may be employed to perform, or to control devices employed to perform, one or more methods as disclosed herein.
The term “contact”, as used herein, refers to an addition to or an interaction between, at least, two molecules, that causes an increase or decrease in the magnitude of a certain activity or function of the molecules compared to the magnitude of the activity or function observed in the absence of, at least, one of the molecules. Example includes, but is not limited to, contact of sera to cells in culture.
As used herein, “subject” refers to a person, an individual, or animal that is the object of medical or scientific study or a patient. In another aspect, the present disclosure provides a composition of matter and method of administrating said composition of matter to a subject, preferably a human, or in a format that can be diluted or reconstituted for administration to the subject.
The term “immunoglobulin E” (hereinafter, used interchangeably with “IgE”),” as used herein, collectively means proteins that participate in the body's protective immunity by selectively acting against antigens. Immunoglobulins are composed of two identical light chains and two identical heavy chains. The light and heavy chains comprise variable and constant regions. There are five distinct types of heavy chains based on differences in the amino acid sequences of their constant regions: gamma (γ), mu (μ), alpha (a), delta (δ) and epsilon (ε) types, and the heavy chains include the following subclasses: gamma 1 (γ1), gamma 2 (γ2), gamma 3 (γ3), gamma 4 (γ4), alpha 1 (α1) and alpha 2 (α2). Also, there are two types of light chains based on differences in the amino acid sequences of their constant regions: kappa (κ) and lambda (λ) types (Coleman et al., Fundamental Immunology, 2nd Ed., 1989, 55-73). According to the features of the constant regions of the heavy chains, immunoglobulins are classified into five isotypes: IgG, IgA, IgD, IgE and IgM.
As used herein, an “epitope,” “epitope protein,” “epitope peptide,” “allergen epitope,” “allergenic protein” or “allergy protein” is a mimotope, peptide, cyclic peptide, peptidomimetic, or other molecule that binds to IgE to trigger degranulation and any polypeptide determinant capable of specific binding to an immunoglobulin or T-cell receptor. In certain embodiments, epitope determinants include chemically active surface groupings of molecules such as amino acids, sugar side chains or moieties, phosphoryl, or sulfonyl moieties, and, in certain embodiments, may have specific three dimensional structural characteristics, and/or specific charge characteristics. An epitope is a region of an antigen that is bound by an antibody. In certain embodiments, an antibody is said to specifically bind an antigen when it preferentially recognizes its target antigen in a complex mixture of proteins and/or macromolecules. Examples include, but are not limited to, peanut allergen proteins such as Ara h1, Ara h2, Ara h6 and shrimp allergen protein, Pen al or any known or suspected allergen.
As used herein, a “mimotope” is a macromolecule or peptide that mimics the structure of an “epitope”. A mimotope can be a known or suspected peptide sequence of allergen epitopes. Examples include, but are not limited to, peptide sequences of allergen epitopes such as Ara h1, Ara h2, Ara h6 and, Pen al, or any known or suspected peptide sequence of allergen epitopes, such as one or more of the sequences described herein.
As used herein, a “synmimotope” is a mimotope, an epitope, a hapten, a peptidomimetic, or an allergen metabolite (e.g., a metabolite of penicillin). Therefore, a synmimotope includes mimitopes, which are macromolecules or peptides that mimic the structure of an epitope, as well as small molecules (e.g., sulfa drugs or chemotherapeutics), allergen metabolites, and actual epitopes that can elicit an immune response. Haptens are small molecules that elicit an immune response only when attached to a large carrier such as a protein or a lipid of the lipid conjugates described herein. Thus, a “synmimotope-lipid conjugate” is a mimotope, an epitope, a hapten, a peptidomimetic, or an allergen metabolite conjugated to a carrier such as a lipid described herein.
As used herein, a “first linker” can be a sugar, an oligosaccharide, an amino acid, peptides, or other molecules that can provide favorable results in epitope display and binding. Examples of a first linker include, but are not limited to, ethylene glycol molecules.
As used herein, a “second linker” can be any moiety that will improve mimotope-lipid water solubility profile. The second linker increases hydrophilicity and improves epitope display on the liposomal surface. Examples include, but are not limited to, charged amino acids such as aspartic acid (D), glutamic acid (E), lysine (K) and arginine (R) or polar amino acids, such as, glutamine (Q), asparagine (N), histidine (H), serine (S), threonine (T), and methionine (M).
As used herein, a “fluorophore residue”, “fluorophore” or “chromophore” can be any moiety that can aid in purification of the epitope-lipid conjugate. An example of a fluorophore includes, but is not limited to, tryptophan.
As used herein, a “lipid” or “bulk lipid” is any compatible lipid that has a hydrophilic region and a hydrocarbon tail that can facilitate the incorporation of epitope-lipid conjugate into a lipid membrane. Examples include, but are not limited to, phospholipids, such as 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC), and fatty acids, such as palmitic acid.
As used herein, “nanoparticle” refers to any partially or wholly lipid-coated nanostructure having a cross-section length (“diameter”) in the range of 1 to 3000 nanometers (nm) (i.e., 1 nm to 3 microns). As used herein, cross-section length refers to the measurement of the longest cross-section length of the nanoparticle (e.g., the longest distance that can be measured between two points of a cross-section of the nanoparticle). In some instances, such particles will have a cross-section length in the range of 10 nm to 50 nm, 50 to 1000 nm, 50 to 900 nm, 50 to 800 nm, 50 to 700 nm, 50 to 600 nm, 50 to 500 nm, 50 to 400 nm, 50 to 300 nm, 50 to 200 nanometers, and/or 50 to 100 nm. The lower end of these ranges may alternatively be about 100 nm. In some instances, the particles will have a cross-section length of greater than 1 micron. The size of the nanoparticle is therefore predetermined and controlled as is the size of its nanostructure core.
As used herein, the term “component” can refer to one molecule of a particular species, for example, one molecule of component 160, or to a plurality of molecules of a particular species (eg. two or more molecules of component 160). Nanoparticle may include components 110, 120, 130, 140, 150, 160, 170, 180 and/or combinations thereof in various ratio. As used herein, a “molecular ratio” may be provided to indicate the number of molecules of two or more components (e.g., 160, 170, 180) in a nanoparticle. The number of molecules of a component in a nanoparticle may also be described in terms of a “mole percentage,” which is calculated by dividing the number of molecules of that component by the number of molecules in the nanoparticle. For example, in a nanoparticle with 100 component molecules, 93 of which are component 180, 5 of which are component 170, 2 of which are component 160, the “molecular ratio” of the components (160:170:180) is 93:5:2, and the mole percentages of the three components are 93%, 5% and 2%, respectively. If not specifically identified, percentages referenced herein are molar percentages (mol %), unless the context specifically indicates otherwise.
Referring now to
Optionally, component 170 can be made to enhance the stability and/or circulation time of nanoparticle 100. In some embodiments, component 170 may include a polymer 110 conjugated or otherwise coupled to lipid molecule 180 to form 170. Polymer 110 can be a water-soluble polymer, such as polyethylene glycol (PEG). In some other embodiments, polymer 110 can be coupled to lipid molecules 180 to form a PEG-lipid block polymer 170 (e.g., PEG2000-DSPE conjugate or PEG-lipid conjugate). Optionally, Nanoallergens 100 can include cholesterol to improve particle stability.
PEGylated nanoparticles provide a combination of high circulation times, increased stability, and a defined size range of 1-5 nm, 1-10 nm, 1-50 nm, 1-100 nm, 1-200 nm or 1-300 nm. In some embodiments, nanoparticles ranging from 50 nm to 200 nm in size can be used in cellular experiments. In other embodiments, nanoparticles can be synthesized from a couple 10s of nanometers to several 10s or 100s of micrometers, for example, in animal or human testing. An important characteristic of nanoparticles is that they present particularly attractive scaffolds for multivalent display of allergen epitope peptides and other multiple functional groups on their surfaces. In some embodiments, nanoallergen may include, but are not limited to gold, silicon, dedramer, or any molecule that provides multivalent display other than a liposome.
Prior to liposome formation, desired epitopes 150 are covalently conjugated to lipid tails 120 with a linker 140 and the product, epitope-lipid 160, is purified. The lipid tails 120 provide the moiety that seamlessly integrates into the liposomal membrane and anchors the epitope 150 to the liposomal particle surface permanently. Following the synthesis and the purification the epitope-lipid 160 can then be incorporated into nanoallergens 100 during liposomal nanoparticle synthesis at the desired precise ratios to form nanoallergens 100.
By displaying multiple copies of the epitope on the liposome surface, nanoallergens provide a highly multivalent vehicle to assess the epitope's immunogenicity and not merely its monovalent IgE binding affinity. The nanoallergen platform is extremely versatile and can have varying particle sizes and epitope loading. Most importantly, nanoallergens can display multiple epitopes on a single particle, allowing multivalent binding to IgEs specific to a variety of epitopes, simulating allergen proteins. Through systematic removal of individual epitopes from a heterogeneous nanoallergen, the most crucial epitopes for an allergen protein's immunogenicity can be evaluated through either in vitro or potentially in vivo experiments. Such precise control over epitope ratios can also be utilized to study the more nuanced biological interactions in mast cell degranulation as well.
The epitope-lipid conjugates that are displayed on nanoallergens are synthesized and purified before liposome formation. The design of the epitope-lipid conjugate consists of five components. The components include a mimotope, a first linker (such as oligo-lysine linker) to increase hydrophilicity and to improve epitope display on the liposomal surface, a second linker, such as, but is not limited to ethylene glycol linker to further aid epitope display, a chromophore or fluorophore (such as, but not limited to, tryptophan) to aid purification and a lipid (such as, but not limited to, palmitic acid tail) to facilitate the component's incorporation into a lipid membrane. These five components can be chemically linked together using Fmoc Solid Phase Peptide Synthesis (SPPS), cleaved from the resin and purified using reverse phase high performance liquid chromatography (RP-HPLC). Nevertheless, there are many other potential synthetic methods that can be used to achieve the desired products including but are not limited to in solution synthetic methods and other solid phase synthesis methodologies. The epitopes are typically linear peptide sequences, but could be cyclic peptides and/or mimotopes of the epitope sequences, taken from either current literature or from the peptide sequence of a given allergen protein and then synthesized using SPPS methods.
Embodiments of the present disclosure provide a nanoparticle based platform, named nanoallergens for identifying, evaluating and studying allergen epitopes as multiple copies of a single epitope, as well as, in various combinations at any desired ratio against each other on the same particle. Nanoallergens can display multiple epitopes on a single particle, allowing multivalent binding to IgEs specific to a variety of epitopes, simulating allergen proteins. The disclosed nanoallergen platform is extremely versatile and can have varying particle sizes and epitope loading. Nanoparticles can be composed to include various molecular ratios of components. The molar/molecular ratios of nanoparticle components may vary for various embodiments. In some embodiments, a nanoparticle includes 0.1-40% mimotope conjugated to lipid molecule (mimotope-lipid conjugate). The nanoparticle may further include about 85-94.9% lipid, such as, but is not limited to, DSPC (1,2-distearoyl-sn-glycero-3-phosphocholine). The mimotope-lipid conjugate further includes a mimotope, a first linker, and lipid molecule. The mimotope can be a known or suspected allergenic epitope, such as, but is not limited to, Ara h 1, Ara h 2, Ara h 6 and Pen al. The lipid can have a hydrophobic region and hydrocarbon tail.
In some embodiments, the first linker can be, but is not limited to, a carbohydrate or sugar, such as an oligosaccharide, ethylene glycol, an amino acid, or peptide, to aid in peptide display. In another embodiment, nanoparticle includes a second linker, such as charged or polar amino acid.
In some embodiments, a nanoparticle includes a polymer conjugated to a hydrophobic region of lipid molecule. The polymer can be water-soluble polymer, such as polyethylene glycol (PEG). The polymer can be conjugated to hydrophobic region of lipid molecule to form 5% lipid-PEG block polymer, such as DSPE-PEG2000. In other embodiments, polymers can be poly(lactic-co-glycolic acid) (PLGA), polymeric sugars (e.g., oligosaccharides) or other biocompatible water-soluble molecules.
In some embodiments, a nanoparticle can include a molecule that can improve stability of the nanoparticle, such as, but is not limited to 0.1-35% cholesterol.
In some embodiments, the mimotope-lipid conjugate can be synthesized by using single amino acids. The amino acids can be separated from the rest of the mimotope-lipid conjugate with a first linker. Thereafter, using fluorenylmethyloxycarbonyl(Fmoc)-LysButyloxycarbonyl(Boc)-OH, a second linker is added. A variable length of the first linker is added using an Fmoc protected first linker molecule. Fmoc-Lys(Boc)-OH is added followed by addition of lipid tails. Mimotope-lipid conjugate molecules protected with terminal acid groups can be activated with HBTU and a four-fold molar excess of DIEA for 5 minutes and conjugated to resin over 30 minutes. Thereafter, Fmoc is deprotected with 20% piperdine in DMF and IvDdE is deprotected using 2% hydrazine in DMF. The mimotope-lipid conjugate is cleaved using a 95:2.5:2.5 TFA:water:TIS solution for 45 minutes. The mimotope-lipid conjugate is purified using 1200 Agilent RP-HPLC using a semi-preparative Zorbax C3 column with a two phase water and 70:20:10 IPA:ACN:water mix with a gradient of 60-100% IPA mix over 10 minutes at a flow rate of 3 mL/min. Nevertheless, there are many other potential synthetic methods than can be used to achieve the desired products including, but are not limited to, in solution synthetic methods and other solid-phase synthesis methodologies.
An epitope can be, but is not limited to, linear peptide sequences, cyclic or mimotopes of the epitope sequences taken from either current literature or from the peptide sequence of a given allergen protein and synthesized using solid-phase peptide synthesis (SPPS) methods.
In the examples below, nanoallergens are used to systematically evaluate which epitopes are crucial in degranulation responses with an in vitro technique. The efficacy of the technique is demonstrated with the major peanut allergen proteins, Ara h 2 and Ara h6. The nanoallergens serve a multivalent platform for studying and evaluating the potency of peanut allergy epitopes.
Materials. NovaPEG Rink Amide resin, HBTU [2-(H-benzotriazol-1-yl)-1,1,3,3 tetramethyluroniumhexafluorophosphate], all Fmoc conjugated amino acids and BSA (Bovine Serum Albumin) were purchased from EMD Biosciences. DIEA (N,N-diisopropylethylamine), TFA (trifluoroacetic acid), triisopropylsilane (TIS), hydrazine, cholesterol, dichloromethane, 2-proponol, ACN(acetonitrile), ethanol, all Kaiser test reagents, G418 salt and Bovine serum albumin (BSA), tween 20 and piperidine were purchased from Sigma. DMF (dimethylformamide) (>99.8%), chloroform, penicillin, L-glutamine and Eagle's Minimum Essential Media were obtained from Thermo Fisher. 1,2-Distearoyl-sn-glycero-3-phosphocholine (DSPC), DSPE-mPEG2000 (1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-methoxy(polyethylene glycol)-2000] (ammonium salt)), membranes and all mini extruder components were purchased from Avanti Polar Lipids (Alabaster, Al, USA). Fmoc-EG6-OH was purchased from Quanta Biodesign. DiD fluorescent dye (3H-Indolium, 2-(5-(1,3-dihydro-3,3-dimethyl-1-octadecyl-2H-indol-2-ylidene)-1,3-pentadienyl)-3,3-dimethyl-1-octadecyl-, perchlorate) and fluorescein 5(6) isothiocyanate was purchased from Invitrogen. Western blot reagents, gels and equipment were obtained from Bio-Rad. Goat anti-rabbit IgG (ab6721), anti BTK IgG (ab50659) and anti-BTK (phospho Y223 IgG (ab68217) and anti-human IgE were obtained from Abcam. RIPA buffer and phosphatase inhibitor I was purchased from Boston Bioproducts (Boston). Anti-rabbit-HRP IgG was purchased from Jackson ImmunoResearch. Human serum samples were purchased from PlasmaLab International (Everett, Wash.).
The lipid-epitope conjugates were synthesized with standard Fmoc solid phase peptide synthesis (SPPS) chemistry using NovaPEG Rink Amide resin as previously described. A sample lipid-epitope conjugate is shown in
Nanoallergen Preparation. Liposomal nanoallergens were prepared using a procedure as previously described. Briefly, DSPC, mPEG-2000-DSPC, cholesterol, and lipid-epitope conjugates were dissolved in chloroform, lyophilized for 30 minutes, rehydrated in PBS at 60° C. and then extruded through a 200, 100, 80 or 50 nm polycarbonate filter (Avanti).
Particle Characterization. The size of liposomes was confirmed using DLS analysis via the 90Plus nanoparticle size analyzer (Brookhaven Instruments Corp., Long Island, N.Y.), using 658 nm light observed at a fixed angle of 90° at 20° C.
Cell Culture. RBL-SX38 cells were a generous gift from Dr. Jean-Pierre Kinet from Harvard University. RBL-SX38 cells were cultured in Minimum Essential Media (Gibco) with 10% fetal bovine serum (Gemini BioProducts, Sacramento Calif.) and 1.2 mg/mL of G418 salt (Sigma) as previously described.
Degranulation Assays. Degranulation assays were performed as previously described using nanoallergens as the allergen. RBL cells were plated into 96-well dishes for 24 hrs and then incubated with 10% of human sera in cell culture media for an additional 24 hrs prior to the degranulation assay.
ELISA Assay. A high binding 96-well plate was incubated with anti-Human IgE in Carbonate-Bicarbonate buffer (Sigma) at a concentration of 3 nM for 16 hours at 4° C. Plate was washed with washing buffer (PBS with 0.5% tween 20) and then blocked with blocking buffer (5% BSA in PBS with 0.1% tween 20) for 1 hr at room temperature. Plate was washed with automatic plate washer (AquaMax 2000), then varying concentrations of either Ara h 2-Biotin (Indoors Biotechnologies) or FITC-peptide 2 conjugate in blocking buffer for 1 hour. Plate was washed again and then either streptavidin-HRP (1:5 000 dilution) or anti-FITC HRP IgG (1:5000 dilution) was added in blocking buffer. After washing, Amplex Red substrate was added (Invitrogen) and plate fluorescence read at 5 minute intervals according to manufacturers instructions.
Western Blot. Stimulated RBL cells were analyzed for intracellular activity with a Western blotting technique previously described. RBL-SX38 cells were plated at approximately 0.5×106 cells per mL into a 3 mL dish for 24 hours. Cells were then incubated in 10% patient serum in cell culture media for 24 hours. Cells were then washed with Tyrodes buffer and incubated with Tyrodes from 30 minutes at 37° C. Ara h 2 or nanoallergens were then added at varying concentrations and incubated at 37° C. for 3 minutes. Cells were washed with ice cold PBS, then incubated in RIPA with phosphatase inhibitor lysis buffer, scrapped and sonicated for a minute intervals over the course of 30 minutes on ice. Lysates were then spun down at 15000 RPM for 10 minutes and their protein concentration determined by Bradford Assay. Laemmli buffer and PBS were added to all lysates so that their protein concentration was 0.5 mg/mL or would be 0.5 mg/mL prior to immunoprecipitation. Samples were boiled for 5 minutes; centrifuged and 20 uL of each was added to a 10% SDS-PAGE gel. Samples ran on the gel for 1 hr, were transferred to nitrocellulose paper for 1.5 hrs, and blocked with 5% BSA in TBS-T for 1 hr. Primary antibodies were added at the manufacturer's suggested dilutions in blocking buffer, washed with TBS-T, then appropriate secondary antibodies with HRP conjugates were added according to manufacturer's dilutions (typically 1:10000). The membranes were washed, and incubated in with Clarity™ Western ECL Blotting Substrate (Bio-Rad) for 5 minutes. Bands were exposed onto Kodak Chemiluminescence Film for times ranging from 1-30 minutes.
Peanut allergies are one of the most common food allergies and affect 0.6% of the U.S. population or 1.8 million people. Therefore, peanut allergy proteins have been extensively studied, revealing potential allergen proteins. One of these is Ara h 2, a 17.5 kDa 2S albumin seed storage protein comprised of five alpha helices bound by four disulfide bonds. This is the major peanut protein, which has immuno-reactivity with over 90% of the clinical peanut allergy population. A study by Stanley et al. proposed potential IgE binding epitopes for Ara h 2. Through computational studies and various IgE binding assays using patient sera, several other studies have also evaluated IgE binding epitopes of Ara h2. Applicants have performed a thorough evaluation of current literature on Ara h 2 IgE binding epitopes and have chosen eight potential IgE binding epitopes (SEQ ID NO: 5-12,
The synthetic allergens, herein nanoallergens, are modified liposomes, which are spherical nanoparticles formed from a lipid bilayer of phospholipids. Liposomes have been used for many years as drug delivery vehicles and more recently have employed active targeting of disease relevant proteins through the use of targeting ligands expressed on the liposome surface. Recent advances in applicants' laboratory have developed techniques for precise loading of targeting elements by synthesizing peptide-lipid conjugates, purifying them and then forming liposomes. The techniques allow for precise control over particle size, formulation, peptide loading and the possibility for heterogeneous particles. Nanoallergens utilized similar peptide-lipid conjugates, where the peptide was a linear peptide sequence from an allergen protein, in this case, Ara h 2.
The most crucial component of the disclosed nanoallergens is the epitope-lipid conjugate, which was synthesized using well-established peptide-lipid conjugate chemistry developed in our laboratory. The epitope-lipid conjugates consist of three moieties: epitope peptides from Ara h 2, an ethylene glycol (EG) linker and two palmitate (C16) tails to facilitate the molecule's insertion into lipid membranes (SEQ ID NO: 5-12,
The primary goals of this study were (1) to demonstrate the effectiveness of nanoallergens to induce degranulation in vitro using allergy reactive human sera and (2) to determine crucial antigenic epitopes of Ara h2 in the clinical population. Therefore, applicants' first concern was to demonstrate that nanoallergens can stimulate degranulation of mast-like cells in vitro with the same sensitivity and specificity of natural allergens. Using the mast-like rat basophil leukemia SX38 (RBL) cell line that has been transfected to express the human FcεRI on their surface, applicants can use peanut reactive patient sera in applicants' cellular degranulation assays (
Decreasing degranulation responses at higher allergen concentrations is likely due to an increase of inhibitory cascades caused by overstimulation. Applicants performed a series of Western blots to observe increases in activating and inhibitory cascades in the presence of both Ara h 2 and nanoallergens with 2% epitope 2. Applicants observed phosphorylation of Bruton's tyrosine kinase (BTK) indicating activating signaling pathways. Applicants observed an increase in phosphorylation BTK nanoallergens, demonstrating their similar intracellular responses (
In addition to epitope 2 nanoallergens, applicants formed nanoallergens using all eight of the potential IgE binding epitopes. As demonstrated by
Applicants formulated nanoallergens using varying ratios of several allergy epitopes while maintaining the total epitope loading at 2% of total lipid. First, applicants combined the low antigenic epitope 3 with the highly antigenic epitope 2 at various ratios and observed the results. This was done in order to simulate allergen proteins that generally possess both high and low affinity epitopes on the same protein molecule. As the ratio of high to low affinity epitope decreases, it appears to increase the degranulation response (
Allergens possess more than just two IgE binding epitopes on a single allergen protein. For example, Ara h2 has demonstrated up to seven IgE binding epitopes for a single clinical sample. To more accurately simulate multiple IgE binding to a single allergen protein, applicants increased the number of different epitopes on a single nanoallergen while maintaining a constant total epitope loading of 2%. Applicants decided to keep an even ratio of different epitopes in order to model the 1:1 ratio of epitopes that are present on a single allergen protein. As demonstrated by
Using the epitope 2, 3, 5 nanoallergens, applicants can then determine which of these epitopes is most crucial for such high degranulation responses. This high degranulation response can be evaluated by omitting an epitope from a nanoallergen formulation or co-incubating an excess of free epitope peptide to monovalently bind epitope reactive IgEs and inhibit them. Applicants omitted each epitope one by one from the formulation and observed the results. When epitope 2 was prevented from interacting with its specific IgEs either by omission or addition of free peptide, a greater than 1000-fold increase in the maximum degranulation concentration occurred (1 pM to >5000 pM,
Given the variability of IgE binding epitopes in the clinical population, it was prudent to also test nanoallergens on additional patient serum. In light of the variability, applicants chose three additional patient serums that have both high peanut specific IgE concentrations and showed degranulation responses to Ara h 2 (Table 2,
All four samples demonstrated similar moderate responses to epitope 5 and 6 and low responses to epitope 7 and no response to 4 or 8 (
The studies presented herein demonstrate that nanoallergens can be effectively used in vitro with patient serum to identify immunodominant IgE binding epitopes. Nanoallergens offer more information about the immunogenicity of IgE binding epitopes than current epitope binding studies. This platform is versatile, tunable and, as this study demonstrates, can provide addition information about allergens and type I hypersensitivity-induced degranulation.
One of the most crucial aspects of nanoallergens is their ability to more directly describe the immunogenicity of an individual IgE binding epitope. By using a highly multivalent platform, nanoallergens more accurately simulate how the epitope would participate in crosslinking of FcεRI receptors. Additionally, even at 2% epitope loading and assuming half of them are confined to the inner core of the liposome, these particles would display around 800 epitopes each. The high degree of valency allows nanoallergens to overcome the decreased monovalent affinity for free peptides due to increases in conformational entropy. Therefore, nanoallergens can characterize epitopes that might not have high enough affinity to be detected with conventional binding studies such as ELISA.
The typical method for assessing IgE binding epitopes is either with a microarray or ELISA type assay for determining if binding occurs and to obtain an estimate of monovalent affinity. However, these metrics do not necessarily translate to physiological degranulation responses in vivo. One study by Osku et al. demonstrates that the estimate of affinity for an individual epitope does not necessarily correlate to clinical responses. Linear peptides not in the context of the protein are limited in that they do not demonstrate their unique contribution to the overall avidity of the allergen protein and because crosslinking reactions are inherently multivalent, this information is critical. Nanoallergens offer a more robust metric for epitope immunogenicity and even demonstrate the importance of lower affinity epitope that might be overlooked by ELISA assays. For example, in our study, epitope 3 and 5 did not demonstrate any binding through ELISA, but could trigger degranulation in a nanoallergen (
More importantly, heterogeneous nanoallergens provide information about which epitopes are most crucial for trigger degranulation. By systematically removing a single epitope from a heterogeneous nanoallergen, applicants can provide a measure of how the single epitope impacts the immunogenicity of the allergen protein as a whole. The information gleaned from this data would be invaluable for future inhibitor designs. Additionally, with multiple patient seras, applicants demonstrate trends in immunogenic epitopes for Ara h 2 (
Nanoallergens can be used to also reveal new aspects of allergens and the degranulation response. Epitope 2 had a higher affinity than other epitope peptides, given that it was able to be detected binding by ELISA (
Overall, nanoallergens provide important immunogenic information about potential IgE binding epitopes. Nanoallergens could even be used to screen for new potential IgE binding epitopes with greater ease than conventional binding studies. Epitope-lipid conjugates are easy to synthesize with standard peptide synthesis techniques and can rapidly be incorporated into nanoallergens allowing epitopes to be quickly characterized. Applicants also repeated this study with the second major peanut allergen protein, Ara h 6, and demonstrated the utility of nanoallergens with other allergen proteins (
Type I hypersensitivity is primarily caused by immune recognition of otherwise innocuous molecules, resulting in degranulation reactions in mast cells, releasing histamine, inflammatory cytokines, and other inflammation causing molecules into circulation.1 Mast cell degranulation is typically triggered by the crosslinking of the high affinity immunoglobulin E receptor (FcεRI) through multivalent interactions between the allergen specific FcεRI bound immunoglobulin E (IgE) antibodies and the allergen protein. Here, we describe a new liposome based synthetic allergen platform—nanoallergens—for stimulating degranulation responses that offer precise control over allergen characteristics such as antigen valency and epitope heterogeneity. The results of this study establish nanoallergens as a potent and versatile platform delivering reproducible outcomes that can be used to elucidate novel intricacies of allergen-IgE interactions and degranulation responses.
The biochemical interactions between allergen and IgE in degranulation responses are typically complex in nature due to multivalent binding events of allergen proteins and competing intracellular pathways. A single allergen molecule binds to multiple IgE antibodies attached to FcεRI receptors causing them to cluster on cell surface.2-6 The crosslinking of receptors initiates an intracellular cascade that results in degranulation.7 Until recently, most in vitro work on allergic reactions has sought to characterize the IgE-allergen binding, assuming that IgE binding affinity necessarily equates to immunogenicity.8-11 However, clinical data does not seem to validate this assumption; multiple studies have demonstrated that there is not a direct correlation between allergen specific IgE binding affinity and clinical response to allergens.12-15 Likewise, in our laboratory, we have demonstrated the importance of weaker affinity epitope during the degranulation response.16-17
This discrepancy between IgE-allergen binding affinity and clinical response is likely due to the complexities that arise both from the biological mechanisms of degranulation response and allergen protein structure. Biological factors such as intracellular inhibitory pathways, IgE clonal variability, differences in immunogenic epitope affinities and relative IgE concentrations in patients make it very difficult to directly assess allergen immunogenicity with current laboratory techniques. 13,18-21 Additionally, B-cells may or may not produce specific IgEs to individual epitopes on allergen proteins. The number of epitopes and the positions of those epitopes that have a specific IgE will be unique to each patient and drastically affect the apparent allergen protein-IgE complex affinity and therefore the degranulation response.
In cellular based allergy research, the most commonly used experimental model is a synthetic allergy system using small molecule 2,4-dinitrophenol (DNP) as the hapten, and a monoclonal anti-DNP IgE (IgEDNP) with Rat Basophil Leukemia (RBL) cells. In order to appropriately simulate RBL cell degranulation in vitro, these DNP groups are covalently bonded to bovine serum albumin (BSA) to create a multivalent DNP-BSA allergen that can crosslink IgEDNP and trigger degranulation. Using similar methodology, other hapten-antibody pairs have also been used in degranulation studies. One of the more common is the small molecule dansyl chloride (dansyl).21-23 The hapten-BSA system, while commonly used to trigger degranulation, does not accurately mimic protein allergens. Although the BSA protein has several reactive amine groups, it is difficult to control the specific number of conjugations on each individual BSA protein. Importantly, this system also does not reflect the epitope heterogeneity or the polyclonal nature of clinical IgE's hence is not an appropriate model to simulate and study a natural response. 21,24 Likewise, BSA-hapten conjugates have a limited valency (approximately 20, given the number of lysines for binding), which restricts their ability to stimulate degranulation with low affinity peptide mimetics. Given the limitations of the BSA system, a model system for accurate and reliable allergen epitope presentation is urgently needed for successful adaption of the in vitro allergy research towards clinically relevant allergen proteins.
Our laboratory has recently developed a tetravalent allergy model that can present multiple different hapten molecules on a single scaffold that can stimulate degranulation.17,21,25-27 This design allowed control over the avidity between the allergen molecule to receptor bound IgE's. This system has been exceptionally valuable in studies of IgE-FcεRI clustering and enabled us to demonstrate the significance of weak affinity epitopes in triggering cellular degranulation.17,27 However, we identified that this system has limited functionality with clinically relevant allergens, given that protein allergens can possess up to 12 epitopes for a single allergen molecule.24,28 More importantly, natural allergen epitopes, when replicated as short peptide fragments, have a decreased affinity for their associated IgE and typically require a much higher valency to mimic protein allergens in stimulating degranulation at comparable concentrations.
In our laboratory, we have recently developed methods for effective display of different moieties on liposome surfaces. 29-32 The lipids comprising the liposome can be covalently linked with various bioactive molecules such as peptides or small molecules prior to liposome formation, giving precise control over molecule loading. This technique is well established for cancer targeting both in vivo and in vitro. 30,33,34 Precise control allows us to incorporate as many epitopes as necessary to form highly multivalent nanoparticles with tunable valency, heterogeneity and particle size, making liposomes ideal candidates to present immunoreactive epitopes and model allergens proteins. In this paper, we demonstrate the utility of the nanoallergens platform using DNP and dansyl nanoallergens. The nanoallergen platform is designed to provide a means to analyze additional aspects of allergens and determine which IgF/epitope interactions carry higher significance for stimulating the degranulation responses.
Materials and Methods
Materials. N-Fmoc-amido-dPEG6-acid [Fmoc is also known as fluoren-9-ylmethoxycarbony] was purchased from Quanta BioDesign. N-Fmoc-Glu(OtBu)-OH, Boc-Lys(Fmoc)-OH, Fmoc-lys(ivDde)-OH, NovaPEG Rink Amide resin, HBTU [2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluroniumhexafluorophosphate], Fmoc-Arg(pfb)-OH and BSA (Bovine Serum Albumin) was purchased from EMD Biosciences. IgEDNP (clone SPE-7), dansyl chloride, 1-Fluoro-2,4-dinitrobenzene (DNFB), DIEA (N,N-diisopropylethylamine), TFA (trifluoroacetic acid), Triisopropylsilane (TIS), hydrazine, Cholesterol, Dichloromethane, 2-proponol, ACN(acetonitrile) and piperidine were from Sigma and DMF (dimethylformamide) (>99.8%), chloroform, DiD fluorescent dye (3H-Indolium, 2-(5-(1,3-dihydro-3,3-dimethyl-1-octadecyl-2H-indol-2-ylidene)-1,3-pentadienyl)-3,3-dimethyl-1-octadecyl-, perchlorate), Minimum Essential Media was purchased from Thermo Fisher. IgEdansyl (clone 27-74) were purchased from BD Biosciences. DSPC (1,2-distearoyl-sn-glycero-3-phosphocholine), DSPE-mPEG2000 (1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] (ammonium salt)), membranes and all mini extruder components were purchased from Avanti Polar Lipids (Alabaster, Al, USA). DNP-BSA conjugate was purchased from Invitrogen.
Statistical Evaluation. Unless otherwise stated all error bars represent the standard deviation of triplicates in a single experiment. For degranulation experiments, the data is a representative experiment of several experiments; all others were a single experiment. EC50 values and error were calculated using Origin 7 software. All p values were calculated using an unpaired student's t test.
Synthesis of hapten-conjugated BSA molecules. The BSA-dansyl was prepared as previously described.21 Briefly, BSA at 10 mg mL−1 in 1 mL of bicarbonate buffer (0.1 M, pH 9.0) and 100 μl of 10 mg/mL of dansyl chloride DMF were combined and incubated at room temperature for 2 hours. The conjugated BSA was purified using a 0.5 ml 10 kDa molecular mass cut-off spin concentrator (Millipore). RP-HPLC was used to determine purity on an Agilent 1200 series system using a Zorbax C8 poroshell column with a two phase, 90/10 ACN/water and water mix with a flow rate of 2 mL/min at 60° C. The gradient was 5% water to 100% ACN/water mix in 5 minutes. The dansyl-BSA (elution time 4.8 min) was estimated to be >97%. There were 18 dansyl molecules per BSA as determined by the absorbance ratio of 335 nm to 280 nm.
Synthesis and purification of Lipid-Hapten conjugates. The Lipid-dansyl and Lipid-DNP conjugates were synthesized using Fmoc chemistry on solid support using NovaPEG Rink Amide resin as previously described.21 The synthetic scheme is described in
Synthesis of Hapten-BSA conjugates. Both DNP-BSA and dansyl-BSA conjugates were synthesized as described previously.21
Nanoallergen Preparation. Liposomal nanoallergens were prepared using a procedure as previously described.29,30 Briefly, DSPC, mPEG-2000-DSPC, Cholesterol, and Lipid-hapten conjugates were dissolved in chloroform, lyophilized, rehydrated in PBS at 60° C. and then extruded through a 200, 100, 80 or 50 nm polycarbonate filter (Avanti). For some homogeneous nanoallergens (i.e. only DNP or dansyl-lipid loaded), a lipid with an arginine head-group was added at 0.5% of total lipid to ensure particle homogeneity. This lipid followed a similar synthetic scheme as the hapten-lipid conjugates but with the addition of two arginine resides in place of hapten molecules.
Particle Characterization. Liposomes were measured for size using DLS (Dynamic Light Scattering) analysis via the 90Plus nanoparticle size analyzer (Brookhaven Instruments Corp.), using 658 nm light observed at a fixed angle of 90° at 20° C. Liposome samples were diluted with 0.22 μM filter sterilized PBS to a 1.25 nM liposome concentration immediately after extrusion, placed in a 50 μL quartz cuvette and particle sized.
Cell Culture. RBL-2H3 cells were cultured in Minimum Essential Media (Gibco) with 10% fetal bovine serum (Gemini BioProducts) as previously described.25
Degranulation Assays. RBL degranulation assays were performed as previously described, expect using nanoallergens as the allergen.23 Additionally, RBL cells were incubated with 1 μg/mL of total IgE overnight prior to nanoallergen incubation using 75% IgEcyclinA as an orthogonal IgE (i.e. an IgE specific to a molecule, cyclinA, which is not used in this study) to simulate physiological conditions for all degranulation assays.21
Fluorescence Quenching Assay. The binding constants for dansyl conjugates were determined as previously described.27 Briefly, Dansyl conjugates were titrated into wells containing 15 nM IgEdansyl and then the flourscence read at various concentration points (Ex=280 nm, Em=335).
Flow Cytometry. RBL-2H3 Cells were plated in 0.5 mL wells for 6 hours then incubated with 1 μg/mL of 50%/50% IgEDNP/IgEdansyl overnight. Cells were then washed with 1 mL of tyrodes buffer containing 0.05 mg/mL BSA to prevent nonspecific interactions. Nanoallergens containing 0.5% DiD were added to cells with tyrodes/BSA buffer, incubated for 5 minutes at room temperature, washed again with tyrodes/BSA buffer, quickly scrapped and analyzed with a Guava EasyCyte flow cytometer (EMD Millipore).
Kinetic Experiments. RBL-2H3 cells were diluted 1 to 3 from a confluent plate then added into a 24 well dish and allowed to adhere to the plate overnight. The cells were then incubated with 1 μg mL−1 of 25% IgEDNP using 75% IgEcyclinA as orthogonal IgE to simulate physiological conditions for 24 hours. Cells were then placed on ice for 1 hour, washed with ice cold Tyrode's buffer containing 0.05 mg/mL BSA to prevent nonspecific interactions. Nanoallergens were formed at 50, 100 and 200 nm containing 2% DNP hapten and 5% mPEG2000 and DiD dye added to ensure 600 dye molecules per liposome. These nanoallergens were added to the wells and incubated for 2-120 minutes, quickly washed with ice cold Tyrode's/BSA buffer, scrapped and analyzed with a Guava EasyCyte flow cytometer.
Western Blot. RBL cells were plated at approximately 50000 cells per mL into 6 well dishes. Then the cells were washed twice with Tyrode's Buffer, incubated at 37° C. for 30 minutes. RBL cells were incubated with varying concentrations of nanoallergens containing an 85/5/5/5 DSPC/HSPC-mPEG200/DNP-Lipid/Dansyl Lipid with 50% cholesterol of total lipid added for 5 minutes at room 37° C. Following stimulation, cells were washed, scraped and placed on ice and lysed with 0.5% NP-40 and 0.5% deoxycholate in 4° C. phosphorylation solubilization buffer. Samples were normalized with a Bradford assay for total protein content and immune-precipitated using agarose conjugated monoclonal anti-SHIP antibody (P1C1) from Santa Cruz Biotechnology with three subsequent washing steps with phosphorylation buffer containing 0.5% NP-40. Cell lysates were then analyzed with a western blot using anti-p-Tyr antibody (PY99) or free anti-SHIP antibody (P1C1) from Santa Cruz Biotechnology as previously described.35
Results
Nanoallergen Design. In the design of nanoallergens we used a liposomal functional group display platform that was developed in our laboratory, where the ligands are covalently attached to lipids using appropriate linkers and then purified and characterized prior to incorporating into the liposome formation.29,30 The two most commonly used haptens in modeling allergy systems are DNP and dansyl, due to their differing monovalent affinities and commercially available specific IgE clones. Anti-DNP IgE (IgEDNP) has a stronger affinity for DNP than anti-dansyl IgE (IgEdansyl) has for dansyl (KdDNP=15 nM; Kddansyl=147 nM), making them an excellent pair to study for the effects of varying epitope affinities, and thus making the system physiologically relevant (Table 8-1).17,21,25,36
In order to facilitate hapten presentation on the liposome surface, hapten-lipid conjugates were synthesized using a similar approach previously developed in our laboratory (
354 ± 70.1
222 ± 41.4
162 ± 25.8
354 ± 35.4
For most studies, the nanoallergens consisted of 2% lipid-hapten conjugate unless otherwise specified. Liposomes of 50, 80, 100 and 200 nm diameters were prepared using extrusion methods, and unless otherwise stated, 100 nm diameter particles were used for most studies. We confirmed the particle sizes by Dynamic Light Scattering analysis (Table 8-3).
19 ± 1.4
36 ± 3.3
Nanoallergens Trigger Degranulation using Single Haptens. We first evaluated the ability of a single hapten system to trigger degranulation using RBL-2H3 cells primed with either IgEDNP or IgEdansyl by using either DNP-lipid or dansyl-lipid loaded liposomes. Both DNP and dansyl presenting nanoallergens stimulated similar degranulation response to the hapten-BSA conjugated allergen at a 100 and 10 fold lower concentrations respectively demonstrating the higher potency of the platform (
To confirm that the nanoallergens were binding specifically only to those RBL cells that present the corresponding IgEs on their surface prior to initiating degranulation, we performed flow cytometry experiments. Our results indicated that both dansyl and DNP nanoallergens demonstrated specific binding to RBL cells only primed with the analogous hapten specific IgE (
Nanoallergen Particle Size and Loading Affects Degranulation Response. Particle size and peptide density can greatly affect the avidity a liposome has for the specified cell surface. We demonstrated that increasing particle size (50, 80, 100, 200 nm diameter sizes were tested) while keeping other parameters (such as hapten loading) constant results in more potent degranulation responses (
Nanoallergen Binding and Degranulation Kinetics. To further demonstrate the utility of the nanoallergen platform, we performed a kinetic binding experiment. As demonstrated in
Hapten and IgE Combinations Affect Degranulation Response. The versatility of the nanoallergen platform is best exemplified when multiple types of haptens were loaded into the bilayer. Because protein allergens present multiple IgE binding epitopes on the same allergen, nanoallergens could readily emulate protein allergens through epitope heterogeneity and precise epitope loading. By loading both DNP and dansyl haptens on the same particle, we used nanoallergens to demonstrate the effects of antigen heterogeneity on degranulation response. We loaded nanoallergens with various ratios of DNP-lipid to dansyl-lipid while maintaining the total hapten-lipid loading at 2% of total lipid. Additionally, we varied epitope specific IgE ratios when priming the RBL cells to simulate the variability in clinical IgE content (
15 ± 2.5*
DISCUSSION The results presented in this paper establish the nanoallergen platform as a versatile and effective method for reliable and reproducible activation of cellular degranulation. The platform addresses several challenges of in vitro allergy models such as the difficulty of relating allergen binding affinity directly to a degranulation response given the complex nature of degranulation. Degranulation is affected by both allergen binding attributes such as size of IgE-FcεRI clusters and number of clusters as well as cellular properties such as downstream signal transduction. Here, we used the nanoallergen platform to systematically dissect and investigate aspects of allergen binding such as valency and monovalent affinity and observe their direct effects on degranulation responses using established in vitro degranulation assays.
By using hapten molecules with known affinities, we demonstrate the complexities of the allergen binding-degranulation relationship. As stated earlier, IgEDNP and IgEdansyl have different affinities for their respective haptens. Moreover, in an effort to widen their affinity difference, we conjugated both haptens to a glutamic acid residue (
Reduced dissociation kinetics from the cell surface increases the likelihood of a second IgE-FcεRI receptor diffusing to the nanoallergen and forming larger clusters. A weaker monovalent affinity would be reflected in a larger koff for the dansyl-IgEdansyl, resulting in a shorter disassociation half-life and increasing the likelihood of nanoallergen disassociating from the cell surface before a second IgE interaction can be formed. This suggests that there is a critical spacing distance between haptens which facilitates bivalent binding to the same IgE molecule, allowing nanoallergen-cell interactions to have increased half-lives, thereby increasing the likelihood of IgE-FcεRI cluster formation. This bivalent IgE binding is a plausible explanation for the increase in degranulation response between 1% and 2% for dansyl nanoallergens (
Another important factor that impacts degranulation response was epitope heterogeneity. The higher affinity (DNP) hapten caused the strongest response at lower concentrations when it was the only epitope present, due likely to its high monovalent affinity (
The nanoallergen studies presented here also reveal several more nuanced aspects of a degranulation response. The higher the overall nanoallergen valency, the more IgE-hapten interactions can be formed and the stronger the degranulation response (Table 8-2). Additionally, avidity was not the only factor determining the potency of nanoallergens. The non-linear relationship between hapten surface density and the degranulation response demonstrated that there was an optimal avidity for the intensity of the maximum degranulation response for a given nanoallergen formulation, and this optimal response was also mediated through intracellular inhibitory cascades. Our data indicates that the maximum degranulation response did not occur when the highest number of nanoallergens was bound on the cell surface. As demonstrated in
Studies conducted using nanoallergens has the potential to reveal detailed and critical information about allergen proteins and their epitopes that even the purified natural allergen proteins themselves cannot deliver. Factors such as affinity, valency, epitope heterogeneity and intracellular inhibitory cascades are crucial complicating factors for degranulation responses. Nanoallergens allow for precise control over affinity, valency and provide immunogenic data on individual epitopes. Meanwhile, without sophisticated binding experiments, it is difficult to decipher which epitopes on allergen proteins are binding and the kinetics of these interactions. Finally, allergen proteins can only have their specific epitopes be altered with site specific directed mutagenesis, which is rather time consuming and challenging, making screening for important allergy epitopes very difficult. In addition, nanoallergens can be used to assess the kinetics of allergen binding (
In conclusion, the nanoallergen platform presented in this paper provides an efficient and versatile platform for allergy research. Nanoallergens offer several advantages over the current BSA-hapten system. The ability to generate very nanoallergens of very high valency allows them to trigger degranulation responses at similarly low (nanomolar to picomolar) concentrations as native allergen proteins. For example, peanut allergens, Ara h2 and Ara h6, have been identified to have EC50 values in cellular studies in the low picomolar range using various sera from highly allergic individuals, and these potent responses are not possible to emulate with linear peptide epitopes without a highly multivalent platform such as nanoallergens.40 Even with the high affinity DNP hapten, DNP-BSA with a valency of 18 that was used in this study as a control was only able to trigger degranulation in the nanomolar range (EC50=26±9 nM) while a 2% loaded DNP nanoallergen (valency of 800) was able to trigger degranulation in the picomolar range (EC50=180±20 pM) (
In summary, degranulation caused by type I hypersensitivity (allergies) is a complex biophysical process, and available experimental models for studying relevant immunoglobulin E (IgE) binding epitopes on allergen proteins lack the ability to adequately evaluate, rank and associate these epitopes individually and with each other. In this study, we propose a new allergy model system for studying potential allergen epitopes using nanoallergens, liposomes modified to effectively display IgE binding epitopes/haptens. By utilizing the covalently conjugated lipid tails on two hapten molecules (dinitrophenol and dansyl), hapten molecules were successfully incorporated into liposomes with high precision to form nanoallergens. Nanoallergens, with precisely controlled high particle valency, can trigger degranulation with much greater sensitivity than commonly used bovine serum albumin (BSA) conjugates. In RBL cell experiments, nanoallergens with only 2% hapten loading were able to trigger degranulation in vitro at concentrations as low as 1 nM. Additionally, unlike BSA-hapten conjugates, nanoallergens allow exact control over particle size and valency. By varying the nanoallergen parameters such as size, valency, monovalent affinity of hapten, and specific IgE ratios, we exposed the importance of these variables on degranulation intensity while demonstrating nanoallergens' potential for evaluating both high and low affinity epitopes. The data presented in this article establish nanoallergen platform as a reliable and versatile allergy model to study and evaluate allergen epitopes in mast cell degranulation.
Drug allergies are a type of adverse drug reaction that afflicts over 2 million people per year in the US. These allergies are particularly dangerous because unlike other adverse drug reactions, they are unpredictable and can have a wide variety of symptoms and triggers, and these reactions occur to very commonly used drugs such as sulfa drugs and antibiotics. In particular, immediate immunoglobulin E (IgE) mediated hypersensitivity reactions caused by drugs can be the most life threatening because they cause rapid and severe anaphylaxis reactions. Furthermore, over half of allergy fatalities are due to anaphylaxis reactions to drugs. Currently, the only FDA approved treatments for drug allergies are post-reaction treatments such as antihistamines or corticosteroids, both of which have not shown dependable prevention of anaphylaxis responses, likely due to the rapid onset of anphylaxis. The only treatment for anaphylaxis reactions to drugs is treatment with epinephrine, which only delays onset of the symptoms for several minutes so that the patient can reach proper medical care. Given the prevalence of these reactions and the lack of adequate treatments, there is a need for development of preventative and/or more rapidly acting treatments for drug reactions. In this example, we discuss the synthesis and in vitro and in vivo characterization of a new design of allergy inhibitor that can be used to prevent IgE mediated allergic reactions triggered by drug molecules.
Severe drug allergy reactions are due to a process called haptenization in which drug molecules covalently bind multivalently to a carrier protein (typical serum albumins) and stimulate immune reactions. This is important because the major IgE mediated hypersensitivity response, degranulation responses are triggered by multivalent cross linking of an allergen protein with several IgE-constant fragment epsilon receptor (FcεRI) complexes, which are present on the surfaces of mast cells and basophils. This crosslinking event then triggers the release of histamine and other inflammatory compounds into systemic circulation. This haptenization process causes drug allergies to differ from food or environmental allergens in that instead of many different IgE binding epitopes on a single allergen protein, the immune system produces IgEs directed against epitopes that contain the drug molecule of interest and therefore all allergy binding epitopes for a particular drug allergy share a common target. This characteristic of severe IgE mediated drug reactions is very advantageous for potential inhibitor designs, as potentially a single inhibitor could significantly inhibit or prevent all IgE recognition of haptenized serum proteins and therefore significantly inhibit or prevent IgE hypersensitivity reactions.
β-lactam antibiotic drug allergies (e.g. penicillin drugs and penicillin derivatives) are of particular concern. β-lactam rings are reactive to primary amines and can readily haptenize serum albumins, causing allergic reactions. Although rates of severe reactions to β-lactam antibiotics are low, given the wide usage of these types of antibiotics, penicillin antibiotics account for over half of the fatal reactions to drugs. Given that β-lactam antibiotics are the most widely prescribed class of antibiotic, any potential drug that can be co-administered to assuage fears of allergic reactions would be extremely valuable. In this example, we describe the synthesis and in vitro and in vivo evaluation of a new class of allergy inhibitors we call covalent heterobivalent inhibitors (cHBIs) designed to specifically and permanently inhibit binding of drug reactive IgE molecules to haptenized proteins. We synthesized inhibitors to two compounds, Penicillin G (a β-lactam antibiotic), and a small molecule frequently used in allergy models, dansyl chloride (dansyl).
Inhibitor Design and Hapten Selection. The cHBI design consists of three unique chemical moieties that function in concert to provide specific and potent inhibition of IgE mediated degranulation reactions to a specific allergen. This molecule is similar to heterobivalent inhibitors (HBIs) previously reported in our laboratory in that these molecules contain both an antigen binding site (ABS) ligand and a nucleotide binding site (NBS) ligand. The NBS is an underutilized conserved binding site located proximal to the ABS between the heavy and light chain of all immunoglobulins (
The most crucial aspect of the cHBI design is a reactive group that can form covalent bonds with bound IgE molecules, essentially permanently inhibiting them, in contrast to HBIs which only form reversible interactions (
Due to complexities of penicilloyl group, additional design considerations were required to synthesize penicilloyl-cHBI's but the same basic molecule design was used for both cHBI's; see methods for further details.
As demonstrated in
HBI Molecule Design Increases Avidity. In order to demonstrate the importance of a bivalent system for binding, we performed fluorescence quenching binding assays on HBI molecules (e.g. cHBI molecules synthesized without an ITC moiety). In order to observe quenching, we tagged penicilloyl molecules with a dinitrophenol (DNP) group; the dansyl molecules required no DNP addition, as dansyl itself quenches fluorescence from tryptophan residues. We synthesized four molecules, a dansyl control, a dansyl-napht HBI, a penicilloyl-DNP control, and a penicilloyl-DNP HBI and tested them for binding with a monoclonal antibody for either penicillin or dansyl (Table 9-1). The results demonstrate a nearly five-fold and 20-fold increase respectively in observed Kd for the dansyl and penicilloyl molecules when the NBS ligand is added. This increase in avidity for the HBI indicates bivalent binding is occurring. It is important to note that due to the lack of commercially produced penicilloyl specific antibodies, we used a penicillin G specific antibody (e.g. specific to the penicillin molecule with an intact beta lactam ring) to test binding of the penicilloyl molecules. This explains why the monovalent affinity was measured in the micromolar range and why a bivalent approach more drastically increased apparent affinity.
cHBIs Specifically Bind Target IgEs. In order to assert that any degranulation inhibition from cHBIs is due to the proposed IgE binding mechanism rather than a non-specific cellular disruption or another phenomenon, we assessed the level of specific conjugation of cHBI molecules to a target antibody using both ELISA and flow cytometry. In order to quantify conjugation of cHBI molecules, both penicilloyl and dansyl cHBI were synthesized with biotin tags and incubated with specific antibodies, purified with membrane filtration and characterized for cHBI binding using ELISA (Table 9-1). Dansyl-biotin cHBIs demonstrated a near saturated level of conjugation at concentrations as low as 10 nM at pH 7.4 (
cHBIs Demonstrate Degranulation Inhibition In Vitro with monoclonal antibodies. After confirming the specific covalent attachment of cHBI molecules to allergy reactive IgE's, we next sought to demonstrate inhibition of allergy reactions using an in vitro system. We tested cHBIs with a well-established degranulation assay using rat basophil leukemia (RBL) cells with monoclonal IgEs and haptenized bovine serum albumin (BSA) as the IgE/allergen. As demonstrated by
cHBIs Inhibit Degranulation to Mouse Sera Primed RBL cells. In order to further examine the cHBIs inhibitory characteristics in a more physiologically relevant in vitro system, we primed RBL cells with serum taken from mice sensitized to ovalbumin (OVA) that had been haptenized with either dansyl or penicillin G (see methods section below). After incubating RBL cells with the reactive sera, degranulation was triggered with either dansyl-BSA or penicilloyl-BSA conjugates confirming the presence of hapten specific IgEs in the sera (
cHBIs Inhibit Degranulation In Vivo. Finally, in order to further evaluate cHBIs as a potential clinical tool, these molecules were administered to mice that had been previously sensitized to either dansyl or penicillin.
Conclusion. In this example, we have presented a versatile, effective and selective design for inhibitors to drug induced type I hypersensitivity basophil and mast cell degranulation. These cHBI molecules are potent and selective due to their ability to form specific covalent bonds with lysine side chains near the NBS site of antibodies, effectively permanently preventing hapten specific IgEs from participating in IgE crosslinking and degranulation of basophils and mast cells. Typically, inhibiting IgE crosslinking and degranulation responses to hapenized serum proteins is very challenging due to multiple hapten groups on serum proteins facilitating bivalent binding on single IgE molecules, greatly increasing the apparent avidity of the IgE-hapten complexes. These complexes are very stable and not inhibited by monovalent hapten molecules alone. We overcome this issue by tethering a hapten molecule to a lysine near the ABS, resulting in a large increase in effective concentration of competitive inhibitor which can effectively out-compete haptenized serum proteins for the same binding site. The innovative design of cHBIs makes them very effective and selective. As we have demonstrated in this example, these inhibitors form off target covalent interactions slowly and utilize specific bivalent binding to both ABS and NBS to facilitate a covalent linkage only to the immunoreactive antibodies of interest (
We also postulate that these inhibitors will be long lasting in a clinical setting as their inhibitory characteristics should persist throughout the course of a mast cell or basophil lifetime, which can be around a month in tissues but shorter in circulating basophils. The exact lifetime of these inhibitors in vivo will require additional research, as our RBL cell cultures restricted assay times, but we were able to demonstrate that these inhibitors completely inhibit hapten-BSA induced responses over the course of at least 72 hours (
Materials. NovaPEG Rink Amide resin, 5(6)-carboxy-fluorescein, HBTU (2-(1H-Benzotriazole-1-yl)-1,1,3,3-tetramethyluroniumhexafluorophosphate), Fmoc-Lys(IvDde)-OH, Fmoc-Arg(pfb)-OH, 10 kDa 0.5 mL centrifugal filters and BSA were purchased from EMD Millipore.
DMF (N,N-Dimethylformamide) (>99.8%), DCM (dichloromethane) (>99.8%), DIEA (N,N-Diisopropylethylamine), methanol, hydrazine, piperidine, TFA (trifluoroacetic acid), TIS (triisopropylsilane), Tryptamine, 2-Naphthaleneacetic Acid, ethylene diamine, biotin, BOC2O (Di-tert-butyl carbonate), DMAP (4-(Dimethylamino)pyridine), Succinic anhydride, CS2 (Carbon disulfide), BDI (butane diisthiolcyanate), THF (Tetrahydrafuran), TPP (triphenylphosphine), DIAD (diisopropylazocarboxylate), MeI (methyl iodine), DNFB (2,4-Dinitro-1-fluorobenzene), acetonitrile, acetic acid, methanol, carbonate-bicarbonate buffer, Tween 20, IBA (Indole-3-butyric acid), Biotin and PBS (phosphate buffered saline), Bicarbonate-carbonate buffer (Bicarb), OVA (ovalbumin), Step-HRP (streptavidin conjugated to HRP), PCMB (p-chloromercuribenzoic acid) were purchased from Sigma Aldrich.
High Binding and Non-Binding 96-well plates were purchased from Corning. Minimum Essential Media, Penicillin-Strep solution, L-glutamine, and Amplex Red ELISA kits were purchased from Life Technologies. Bovine Serum Albumin was purchased from Gemini Biosciences. 96-well Tissue Culture plates were purchased from Falcon. EG2 (Fmoc-N-amido-dPEG2-acid) and EG8 (Fmoc-N-amido-dPEG8-acid) were purchased from Quanta biodesign. FITC (Fluorescein Isothiocyanate) was purchased from Toronto Research Chemistry. Tris-Glycine buffer was purchased from VWR. Non-Fat Powdered Milk, transfer buffer (10×), and SDS-Sample Buffer (4X, reducing) were purchased from Boston BioProducts. Tris buffered Saline with 0.05% Tween 20 was purchased from KPL. Chemiluminescence substrate was purchased from Thermo scientific. Anti-dansyl IgE (clone 27-74) and anti-human cyclinA IgE (clone BF683) were purchased from BD Biosciences. Mouse IgGPenicillin (monoclonal antibody clone P2B9) was purchased from Abcam. Anti-DNP IgE (clone SPE-7) was purchased from Sigma Aldrich.
Methods:
cHBI Synthesis. All hapten conjugated molecules (cHBI, HBI or Hapten-ITC's) were synthesized using Fmoc solid phase peptide synthesis (SPPS) with several modifications. The basic peptide synthesis procedure is described briefly: molecules were conjugated to Rink Amide Low Loading Resin (Millipore), Fmoc-amino acids and Fmoc protected ethylene glycol spacers and Napht were dissolved at 4-fold excess in DMF, activated with a 3.6-fold excess of HBTU with 20 fold DIEA for five minutes prior to addition. DNP was added as DNFB and dansyl was added as dansyl chloride at 4 fold excesses in DMF with 20 fold DIEA. Activated Fmoc protected amino acids, haptens and Napht were reacted with amines on resin for 30 minutes for each step. After addition, resin was washed three times with DMF, and deprotected with 20% piperidine in DMF for 3 minutes three times. Following deprotection, resin was washed with DMF and DCM. Following Napht addition, the IvDdE group of lysine was deprotected using 2% hydrazine in DMF in the same fashion.
ITC domains were always added just prior to cleavage from resin. For dansyl and DNP cHBI molecules primary amines were chemically modified into ITC moieties using a modified procedure from Munch et al (
Penicillin cHBI molecules had two different chemistries in order to maintain proper ITC functionality. Prior to penicillin addition, penicillin in solution was reacted with ethylene diamine to open beta lactam ring and purified, forming a penicilloyl-NH2. Then resins with deprotected amines were reacted with succinic anhydride to leave a terminal carboxylic acid group. This group was then activated with an equimolar amount of HBTU in 5-fold excess of DIEA in DMF for 10 minutes. Resin was washed with DMF and then a 4-fold excess of penicilloyl-NH2 was added with 20-fold excess of DIEA in DMF and allowed to react for 30 minutes. The penicilloyl conjugate contains a secondary amine which is reactive to ITC. So, in order to prevent HBI cyclization, this secondary amine was methylated into a tertiary amine following a procedure by Kurosu et al. Following reaction, the resin was washed several times with DMF and synthesis continued following IvDdE deprotection. Additionally, in order to improve overall cHBI yields, ITC was conjugated by addition of bifunctional ITC molecules, BDI. BDI was added to free amines in a 10-fold excess in DMF with DIEA and allowed to react for two hours. This was the final step prior to cHBI cleavage.
Molecules were cleaved from the resin using a 95/2.5/2.5 TFA/water/TIS mixture for two cycles for 45 minutes each. The resulting solution was rotovapped to remove TFA, rehydrated in 50/50 ACN/water and purified by RP-HPLC using an Agilent 1200 series HPLC with a Zorbax C18 semi prep column using a ACN/water gradient between 20-60% ACN in 10 minutes with a flow rate of 4 mL/min. Product was collected, rotovapped, lyophilized and re-dissolved in DMSO. Concentration was determined by absorbance at 280 nm or 335 nm. All molecules were characterized using high resolution MicroTOF MS analysis. Purity was determined by analytical RP-HPLC using Zorbax Eclipse XBD-C18 with a 20-60% ACN gradient (Table 9-1).
Molecules used in ELISA and flow cytometry contained either a biotin or fluorescein (FITC) tag that was incorporated onto resin prior to molecule synthesis. In each case, Fmoc-Lys(IvDdE)-OH was attached first to the resin, deprotected on Fmoc amine, conjugated to Fmoc-EG2-OH, deprotected again and conjugated to either Biotin activated with HBTU or FITC. Then, IvDdE group is deprotected and synthesis is continued for either penicillin or dansyl cHBIs.
Fluorescence Quenching. In order to determine binding of HBI molecules to respective antibodies, we observed the quenching of tryptophan resides using a method previously described. Briefly, either IgEdansyl or IgGPenicillin was diluted into a non-binding 96-well dish at 40 nM in PBS. Then, HBI molecules which contained either a dansyl or DNP group were titrated into well and fluorescence (Ex. 280 nm, Em. 335) was observed using a SpectraMax M2 spectrophotometer. PBS and free tryptamine diluted to similar initial fluorescence values were used as controls to account for HBI fluorescence and non-specific quenching respectively.
In Solution Conjugation of cHBI Molecules. Before ELISA analysis of cHBI-antibody conjugates, we performed an in solution conjugation of cHBI molecules and antibodies allowing ITC moieties to react with primary amines on antibody proteins. Either dansyl or penicillin cHBI molecules at various concentrations were incubated with either IgEdansyl or IgEDNP (as control) or IgGPenicillin or BSA (as control) at 1 μM concentrations for various incubation times in either PBS (pH 7.4) or Bicarbonate-Carbonate Buffer (pH 9.6) at 50 μL total volumes at 37° C. After reaction, excess cHBI molecules were removed using membrane filtration with 10 kDa 0.5 mL Centrifugal Filters (Millipore) by washing antibodies three times in PBS. Purified antibodies were analyzed with a SpectraMax M5 spectrophotometer at 280 nm using an extinction coefficient of 200,000 cm−1 M−1 for IgEDNP and IgEdansyl and 150,000 cm−1 M−1 for IgGPenicillin.
ELISA. Binding of cHBI molecules to antibodies was observed using a direct ELISA. 100 μL of 2 nM antibody or BSA molecules previously reacted with cHBIs that were labeled with biotin were incubated for 2 hours in bicarbonate buffer on a high binding 96-well plate. Plates were washed with a AquaMax 2000 plate-washer to remove unbound antibody. Wells were blocked with a 5% BSA, 0.2% Tween 20 solution in PBS for 1 hour, washed and incubated with a streptavidin conjugated to HRP for 1 hour in blocking buffer. Plate was washed again and an Amplex Red Kit was used to quantify ELISA signal using a SpectraMax M5 spectrophotometer according to manufacturer's instruction.
Cell Culture. RBL-2H3 cells were cultured as previously described, split every 48-72 hours at a 1:3 dilution into fresh RBL-2H3 media. Plates for experiments were prepared at roughly 500,000 cells per mL in either 0.5 mL or 100 μL wells on tissue culture plates.
Flow Cytometry. Flow cytometry was performed on RBL-2H3 cells using a Guava easyCyte 8HT in order to demonstrate dansyl cHBI molecule attachment under more physiological conditions. RBL-2H3 cells split at 500,000 cells per mL into a 24-well dish (0.5 mL each) and allowed to attach to plate overnight. Following morning, 0.5 pg of IgEDNP or IgEdansyl was added and allowed to incubate for 24 hours. Cells were then washed twice with sterile PBS, and incubated with fresh media with dansyl cHBI-FITC between 0-1000 nM for 16 hours. Cells were then washed again with PBS and given fresh media, then chilled on ice for 30 minutes. Cells were washed with PBS and incubated in 1.5% BSA in PBS, scrapped and analyzed.
Protein-Hapten conjugates. Protein-Hapten conjugates were prepared in order to sensitize mice for allergen challenges and to trigger in vitro degranulation. Two different haptens, penicillin and dansyl chloride were used with two different protein carriers, OVA and BSA. OVA conjugates while BSA conjugates were used to trigger degranulation and perform allergen challenges. Dansyl was conjugated to OVA and BSA by dissolving 20 mg of BSA or OVA in 3 mL bicarbonate-carbonate buffer (pH 9.6) and then adding 20 mg of dansyl chloride that was dissolved in DMF. These compounds reacted under mild stirring over 24 hours at 37° C. After reaction, products were passed through a 0.22 μM filter and filtered using 10 kDa membrane filtration to remove excess dansyl. Using a dansyl extinction coefficient of 3400 cm−1 M−1 at 335 nm, and an extinction coefficient of 43800 and 30950 cm−1 M−1 at 280 nm for BSA and OVA respectively and a dansyl correction factor of 0.39 to correct for dansyl absorbance at 280 nm. Using the ratios of absorbance at 335/280 nm, we determined dansyl-BSA to have 18 dansyl per protein and dansyl-OVA to have 12 dansyl per protein.
For penicillin conjugates, performed a similar addition of hapten to protein, except using 200 mg of penicillin G salt and allowing reaction to take place over 72 hours. Penicillin-protein conjugates were filtered in a similar manner as dansyl. In order to determine conjugation efficiency, we used a Penmaldate assay from Levine et. al. We determined penicillin-BSA to have 12 penicillin per protein while penicillin-OVA had 8 penicillin per protein.
Degranulation Assay. All of these degranulation assays followed this basic procedure: (1) RBL cells previously primed with IgEs (either from monoclonal sources or mouse sera from mouse sensitization below) were incubated with cHBIs for varying amounts of time, (2) cells were washed to remove any unbound or unconjugated cHBIs, (3) allergen was added to stimulate degranulation. Briefly, 50,000 cells were incubated in a 96-well tissue culture plate and either mixtures of monoclonal antibodies (with 25% IgEdansyl and 75% orthogonal IgEcyclinA) to a final concentration of 1 μg/mL or dilutions of mouse sera were added for 24 hours. Cells were then washed with sterile PBS and cHBI compounds were added at various dilutions for varying time points. Cells were then washed with tyrodes buffer and degranulation was triggered using either dansyl-BSA or penicillin-BSA as previously described. Percent inhibition was calculated by dividing percent degranulation with cHBI's by control without cHBI for same allergen concentration. For experiments in
While specific embodiments have been described above with reference to the disclosed embodiments and examples, such embodiments are only illustrative and do not limit the scope of the invention. Changes and modifications can be made in accordance with ordinary skill in the art without departing from the invention in its broader aspects as defined in the following claims.
All publications, patents, and patent documents are incorporated by reference herein, as though individually incorporated by reference. No limitations inconsistent with this disclosure are to be understood therefrom. The invention has been described with reference to various specific and preferred embodiments and techniques. However, it should be understood that many variations and modifications may be made while remaining within the spirit and scope of the invention.
This application is a divisional of U.S. application Ser. No. 15/762,260, filed Mar. 22, 2018, which claims priority to International Application No. PCT/US2016/053816 filed Sep. 26, 2016, which claims priority to U.S. Provisional Patent Application No. 62/232,978 filed Sep. 25, 2015, each of which are hereby incorporated by reference in their entirety.
This invention was made with government support under Grant Nos. R01 AI108884 and R56 AI108884 awarded by the National Institutes of Health. The government has certain rights in the invention.
| Number | Date | Country | |
|---|---|---|---|
| 62232978 | Sep 2015 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15762260 | Mar 2018 | US |
| Child | 17126616 | US |
