Patent Application
20190293645
Incorporated by reference in its entirety herein is a computer-readable sequence listing submitted concurrently herewith and identified as follows: One 19,513 Byte ASCII (Text) file named “sequence_listing.txt,” created on Nov. 22, 2017.
The invention relates to infectious disease, in particular to medical diagnostics and methods of detecting tuberculosis infections.
Traditionally, the diagnosis of tuberculosis (TB) is based on signs and symptoms suggestive of TB together with appropriate chest x-ray changes and demonstration of mycobacteria in the sputum (smear-positive TB) and positive cultures for TB. In order to get a positive smear, the number of TB organisms in the sputum sample must exceed certain detection threshold. TB cultures are often slow and laborious, and many labs may not have the appropriate facilities and expertise. As a result, a TB skin test, the tuberculin skin test (TST) is often used in addition to smears and cultures to establish a TB diagnosis in patients with relevant symptoms and x-ray changes. The tuberculin skin test could be used to diagnose latent tuberculosis, but it requires two visits and skilled personnel for test placement and interpretation. In addition, the tuberculin skin test often does not separate latent tuberculosis infection from prior immunization with Mycobacterium bovis Bacille Calmette Guerin (BCG) or infection with environmental mycobacteria since the TST utilizes tuberculin purified protein derivatives (PPD) as the antigen components. A major advance was the identification of early secreted antigenic target 6 kD protein (ESAT-6) and culture filtrate protein 10 (CFP10). ESAT-6 and CFP-10 are secreted by all M. tuberculosis and pathogenic M. bovis strains but are absent from all Bacille Calmette-Guérin (BCG) vaccine strains and from commonly encountered nontuberculous mycobacteria (NTM) except M. kansasii, M. szulgai, and M. marinum. Colangeli et al., Infect. Immun. 2000; 68:990-993; Harboe et al., Infect. Immun. 1996; 64:16-22.
Given the cumbersome nature of these assays—smears, cultures and TST,—time consuming, requiring unique expertise and facility (culturing), return visit to the clinics (TST), there have been intense interests at other blood markers that could be used to establish the diagnosis of TB. Advances in these areas have led to at least two commercially available assays—TSPOT-TB and QuantiFeronTB-Gold. Both of these tests essentially detect blood T-cells that react with antigens (ESAT6 and CFP10) specific to M. tuberculosis. These tests involve stimulating blood lymphocytes with the antigens in the form of peptides corresponding to the ESAT6 and CFP10 or the full length recombinant antigens, followed by measurement of interferon-γ (IFN-γ) secreted by the T-cells by enzyme-linked immunoassay (QuantiFeronTB-Gold) or by detection of interferon-γ-producing cells by enzyme-linked immunospot assay (TSPOT-TB).
While these T-cell based TB tests in ELISA format are a definite improvement over the TST in the diagnosis of TB, there are still a number of caveats and issues. For instance, the laboratory intensive nature of these IGRAs which are based on the ELISA format is problematic, especially under resource poor settings. An alternative to T-cell based tests are assays based on the detection of tuberculosis-specific antibodies.
A serological test with appropriate sensitivity and specificity to detect tuberculosis-specific antibodies in blood/serum/saliva samples can have significant advantages over currently available tests. Unlike the tuberculin skin test (TST), assays of antibody responses to M. tuberculosis antigens is less invasive and dangerous (adverse effects) and saves time. These tests also do not require the patient to return to the clinic for evaluation. These advantages are similar to those of IGRAs. In addition, the serological assay to detect TB-specific antibodies can also be casted into user-friendly and field-ready rapid formats. These rapid formats can reduce the heavy laboratory dependence of T-cell based assays. The responses with rapid formats can also be calibrated in such a way that the ambiguity in result interpretation might be avoided as found in previous studies. Liebeschuetz et al. Lancet 364(9452):2196-203; Goodwin, D. J. (2010) Operational issues for QFT-GIT testing. Tri-Service TB screening and testing policy review. Joint Preventive Medicine Policy Group. Rosslyn, Va.; October 2010. (88ABW-2010-5700). This process can be achieved in rapid tests by tuning, i.e. positive responses observed only above certain pre-determined threshold. The observable threshold is determined through extensive screening with field samples.
One major issue with the serological assay to detect TB-specific antibodies is which antigen(s) can be used in the assay. Over the past hundred years, our understanding of the antibody response has changed dramatically. Also, new antigens have been identified and several recombinant antigens have been produced. However, the accuracy of existing serological assays is modest, and these tests have not been clinically useful. Steingart et al. Thorax 2007; 62:911-8; Steingart et al., PLoS Med. 2007; 4:e202; Steingart et al., Clin. Vaccine Immunol. 2009; 16:260-76; Abebe et al., Scand. J. Immunol. 2007; 66:176-91. Nevertheless, efforts towards discovery of novel additional antigens and better methodological strategies for developing efficient serological assays have continued.
There is a significant need to develop new assays and screens to detect tuberculosis infections in patients.
This background information is provided for informational purposes only. No admission is necessarily intended, nor should it be construed, that any of the preceding information constitutes prior art against the present invention.
It is to be understood that both the foregoing general description of the embodiments and the following detailed description are exemplary, and thus do not restrict the scope of the embodiments.
In one aspect, the invention relates to a protein combination that can be used in diagnostics to detect tuberculosis.
In another aspect, the invention provides isolated Rv0222 protein or protein(s) with high sequence identity (>80% sequence identity), whole or immunogenic peptides to be used singly or in combination with other antigens in diagnostics/detection devices to detect antibodies which specifically bind to Rv0222 and which are present in a bodily fluid sample (serum, whole blood, plasma, saliva).
In another aspect, the invention provides isolated Rv3120 protein or protein(s) with high sequence identity (>80% sequence identity), to be used singly or in combination with other antigens in diagnostics/detection devices to detect antibodies which specifically bind to Rv3120 and which are present in a bodily fluid sample (serum, whole blood, plasma, saliva).
In another aspect, the invention provides isolated Rv1989c protein or protein(s) with high sequence identity (>80% sequence identity), to be used singly or in combination with other antigens in diagnostics/detection devices to detect antibodies which specifically bind to Rv1989c and which are present in a bodily fluid sample (serum, whole blood, plasma, saliva).
In another aspect, the invention provides isolated Rv3118 protein or protein(s) with high sequence identity (>80% sequence identity), whole or immunogenic peptides to be used singly or in combination with other antigens in diagnostics/detection devices to detect antibodies which specifically bind to Rv3118 and which are present in a bodily fluid sample (serum, whole blood, plasma, saliva).
In another aspect, the invention provides isolated Rv1636 protein or protein(s) with high sequence identity (>80% sequence identity), whole or immunogenic peptides to be used singly or in combination with other antigens in diagnostics/detection devices to detect antibodies which specifically bind to Rv1636 and which are present in a bodily fluid sample (serum, whole blood, plasma, saliva).
In another aspect, the invention provides isolated Rv3426 protein or protein(s) with high sequence identity (>80% sequence identity), whole or immunogenic peptides to be used singly or in combination with other antigens in diagnostics/detection devices to detect antibodies which specifically bind to Rv3426 and which are present in a bodily fluid sample (serum, whole blood, plasma, saliva).
In another aspect, the invention provides a diagnostics tool such as a TB lateral flow rapid diagnostic test or an enzyme-linked immunoassay detecting interferon-γ (IFN-γ) released by the T-cells or an enzyme-linked immunospot assay detecting IFN-γ-producing cells, and others that utilizes the Rv0222 or protein(s) with high sequence identity (>80% sequence identity), full-length, or immunogenic fragments thereof is a native protein, conjugated to a molecule, or part of a complex of multiple polypeptide chains.
In another aspect, the invention provides a diagnostics tool such as a TB lateral flow rapid diagnostic test or an enzyme-linked immunoassay detecting interferon-γ (IFN-γ) released by the T-cells or an enzyme-linked immunospot assay detecting IFN-γ-producing cells, and others that utilizes the Rv3120 or protein(s) with high sequence identity (>80% sequence identity), full-length, or immunogenic fragments thereof is a native protein, conjugated to a molecule, or part of a complex of multiple polypeptide chains.
In another aspect, the invention provides a diagnostics tool such as a TB lateral flow rapid diagnostic test or an enzyme-linked immunoassay detecting interferon-γ (IFN-γ) released by the T-cells or an enzyme-linked immunospot assay detecting IFN-γ producing cells, and others that utilizes the Rv1989c or protein(s) with high sequence identity (>80% sequence identity), full-length, or immunogenic fragments thereof is a native protein, conjugated to a molecule, or part of a complex of multiple polypeptide chains.
In another aspect, the invention provides a diagnostics tool such as a TB lateral flow rapid diagnostic test or an enzyme-linked immunoassay detecting interferon-γ (IFN-γ) released by the T-cells or an enzyme-linked immunospot assay detecting IFN-γ-producing cells, and others that utilizes the Rv3118 or protein(s) with high sequence identity (>80% sequence identity), full-length, or immunogenic fragments thereof is a native protein, conjugated to a molecule, or part of a complex of multiple polypeptide chains.
In another aspect, the invention provides a diagnostics tool such as a TB lateral flow rapid diagnostic test or an enzyme-linked immunoassay detecting interferon-1 (IFN-γ) released by the T-cells or an enzyme-linked immunospot assay detecting IFN-γ-producing cells, and others that utilizes the Rv1636 or protein(s) with high sequence identity (>80% sequence identity), full-length, or immunogenic fragments thereof is a native protein, conjugated to a molecule, or part of a complex of multiple polypeptide chains.
In another aspect, the invention provides a diagnostics tool such as a TB lateral flow rapid diagnostic test or an enzyme-linked immunoassay detecting interferon-γ (IFN-γ) released by the T-cells or an enzyme-linked immunospot assay detecting IFN-γ-producing cells, and others that utilizes the Rv3426 or protein(s) with high sequence identity (>80% sequence identity), full-length, or immunogenic fragments thereof is a native protein, conjugated to a molecule, or part of a complex of multiple polypeptide chains.
In another aspect, the invention provides a diagnostics tool such as a TB lateral flow rapid diagnostic test or an enzyme-linked immunoassay detecting interferon-γ (IFN-released by the T-cells or an enzyme-linked immunospot assay detecting IFN-γ-producing cells, and others that utilizes a combination of the Rv0222 and/or Rv3120 and/or Rv1989c or protein(s) with highly similar sequence identity (>80% sequence identity), full-length, or immunogenic fragments, thereof is a native protein, conjugated to a molecule, or part of a complex of multiple polypeptide chains, with the following combinations Rv0222 and Rv3120, Rv0222 and Rv1989c, Rv3120 and Rv1989c, Rv0222 and Rv3120 and Rv1989c.
In another aspect, the invention provides a diagnostics tool such as a TB lateral flow rapid diagnostic test or an enzyme-linked immunoassay detecting interferon-γ (IFN-γ) released by the T-cells or an enzyme-linked immunospot assay detecting IFN-γ-producing cells, and others that utilizes a combination of the Rv3118 and/or Rv1636 and/or Rv3426 or protein(s) with highly similar sequence identity (>80% sequence identity), full-length, or immunogenic fragments, thereof is a native protein, conjugated to a molecule, or part of a complex of multiple polypeptide chains, with the following combinations Rv3118 and Rv1636, Rv3118 and Rv3426, Rv1636 and Rv3426, Rv3118 and Rv1636 and Rv3426.
In another aspect, the invention provides a diagnostics tool such as a TB lateral flow rapid diagnostic test or an enzyme-linked immunoassay detecting interferon-γ (IFN-γ) released by the T-cells or an enzyme-linked immunospot assay detecting IFN-γ-producing cells, and others that utilizes a combination of the Rv0222 and/or Rv3120 and/or Rv1989c and/or Rv3118 and/or Rv1636 and/or Rv3426 and/or Rv2185c and/or Rv3354 protein(s) with highly similar sequence identity (>80% sequence identity), full-length, or immunogenic fragments, thereof is a native protein, conjugated to a molecule, or part of a complex of multiple polypeptide chains. In some embodiments, the following combinations are used: Rv0222 and Rv3118; Rv0222 and Rv1636; Rv0222 and Rv3426; Rv0222 and Rv3354; Rv0222 and Rv2185c; Rv0222 and Rv3118 and Rv1636; Rv0222 and Rv3118 and Rv3426; Rv0222 and Rv1636 and Rv3426; Rv0222 and Rv3354 and Rv2185c; Rv1989c and Rv3118; Rv1989c and Rv1636; Rv1989c and Rv3426; Rv1989c and Rv3354; Rv1989c and Rv2185c; Rv1989c and Rv3118 and Rv1636; Rv1989c and Rv3118 and Rv3426; Rv1989c and Rv1636 and Rv3426; Rv1989c and Rv3354 and Rv2185c; Rv3120 and Rv3118; Rv3120 and Rv1636; Rv3120 and Rv3426; Rv3120 and Rv3354; Rv3120 and Rv2185c; Rv3120 and Rv3118 and Rv1636; Rv3120 and Rv3118 and Rv3426; Rv3120 and Rv1636 and Rv3426; Rv3120 and Rv3354 and Rv2185c; Rv0222 and Rv1989c and Rv3118; Rv0222 and Rv1989c and Rv1636; Rv0222 and Rv1989c and Rv3426; Rv0222 and Rv1989c and Rv3354; Rv0222 and Rv1989c and Rv2185c; Rv0222 and Rv1989c and Rv3118 and Rv1636; Rv0222 and Rv1989c and Rv3118 and Rv3426; Rv0222 and Rv1989c and Rv1636 and Rv3426; Rv0222 and Rv1989c and Rv3354 and Rv2185c; Rv0222 and Rv3120 and Rv3118; Rv0222 and Rv3120 and Rv1636; Rv0222 and Rv3120 and Rv3426; Rv0222 and Rv3120 and Rv3354; Rv0222 and Rv3120 and Rv2185c; Rv0222 and Rv3120 and Rv3118 and Rv1636; Rv0222 and Rv3120 and Rv3118 and Rv3426; Rv0222 and Rv3120 and Rv1636 and Rv3426; Rv022 and Rv3120 and Rv3354 and Rv2185c; Rv1989c and Rv3120 and Rv3118; Rv1989c and Rv3120 and Rv1636; Rv1989c and Rv3120 and Rv3426; Rv1989c and Rv3120 and Rv3354; Rv1989c and Rv3120 and Rv2185c; Rv1989c and Rv3120 and Rv3118 and Rv1636; Rv1989c and Rv3120 and Rv3118 and Rv3426; Rv1989c and Rv3120 and Rv1626 and Rv3426; Rv1989c and Rv3120 and Rv3354 and Rv2185c; Rv0222 and Rv1989c and Rv3120 and Rv3118, Rv0222 and Rv1989c and Rv3120 and Rv1636; Rv0222 and Rv1989c and Rv3120 and Rv3426; Rv0222 and Rv1989c and Rv3120 and Rv3354; Rv0222 and Rv1989c and Rv3120 and Rv2185c; Rv0222 and Rv1989c and Rv3120 and Rv3118 and Rv1636; Rv0222 and Rv1989c and Rv3120 and Rv3118 and Rv3426, Rv0222 and Rv1989c and Rv3120 and Rv1636 and Rv3426; Rv0222 and Rv1989c and Rv3120 and Rv3354 and Rv2185c; Rv0222 and Rv1989c and Rv3120 and Rv3118 and Rv1636 and Rv3426; and Rv0222 and Rv1989c and Rv3120 and Rv3354 and Rv2185c and Rv3118 and Rv1636 and Rv3426.
In another aspect, the invention provides a diagnostics tool such as a TB lateral flow rapid diagnostic test or an enzyme-linked immunoassay detecting interferon-γ (IFN-γ) released by the T-cells or an enzyme-linked immunospot assay detecting IFN-γ-producing cells, and others that utilizes a combination of the Rv0222, and/or Rv1989c, and/or Rv3120, and/or Rv3118, and/or Rv1636, and/or Rv3426 and/or with other TB antigens.
In another aspect, the invention provides a method of detecting antibodies in a sample from a subject, wherein the antibodies bind to epitopes of Mycobacterium tuberculosis antigens, comprising
In another aspect, the invention provides a method for assaying interferon-γ production from a sample comprising T cells from a subject, comprising
In another aspect, the invention provides a method for detecting interferon-γ producing T cells from a sample from a subject, comprising
In some embodiments, the sample is incubated with the two or more isolated polypeptides or antigenic fragments or variants thereof for between 4 and 24 hours prior to detecting the presence of interferon-γ produced by the T cells. In some embodiments, the T cells are freshly isolated. The method of any of claims 44-46, wherein the T cells are in blood or isolated from blood. In some embodiments, the T cells comprise CD4+ and CD8+ T cells. In some embodiments, the T cells comprise CD4+ immediate effector T cells. In some embodiments, the subject has been infected with Mycobacterium tuberculosis. In some embodiments, the sample is selected from the group consisting of blood, serum, plasma, lymph nodes, skin, saliva, urine, cerebrospinal fluid and milk.
In another aspect, the invention provides a device, wherein the device comprises two or more isolated polypeptides or antigenic fragments or variants thereof, wherein the polypeptides comprise polypeptides selected from the group consisting of SEQ ID NOS:1, 3, 5, 7, 9, 11, 13, and 15. In some embodiments, the two or more isolated polypeptides or antigenic fragments or variants thereof are attached or immobilized to a solid support. In some embodiments, the two or more isolated polypeptides or antigenic fragments or variants thereof are attached or immobilized to a bead, a flow path in a lateral flow immunoassay device, a well in a microtiter plate, or a flow path in a rotor. In some embodiments, the device is for assaying for the presence of antibodies in a sample from a subject, wherein the antibodies bind to epitopes of Mycobacterium tuberculosis antigens.
Other objects, features and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating specific embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
The skilled artisan will understand that the drawings, described below, are for illustration purposes only. The drawings are not intended to limit the scope of the present teachings in any way.
The present invention is based, in part, on the discovery that a combination of polypeptides from Mycobacterium tuberculosis, or antigenic fragments or variants thereof provide for robust detection of immune system responses—an antibody response or T-cell response against Mycobacterium tuberculosis infection. In some embodiments, the invention provides an assay and device having the appropriate sensitivity and specificity to detect tuberculosis-specific antibodies in patient samples and having significant advantages over currently available tests. Accordingly, in some embodiments, the invention provides compositions, devices, methods, and kits useful for the detection of antibodies that bind to Mycobacterium tuberculosis antigens and the diagnosis of tuberculosis in subjects.
Reference will now be made in detail to the presently preferred embodiments of the invention which, together with the drawings and the following examples, serve to explain the principles of the invention. These embodiments describe in sufficient detail to enable those skilled in the art to practice the invention, and it is understood that other embodiments may be utilized, and that structural, biological, and chemical changes may be made without departing from the spirit and scope of the present invention. Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art.
In some embodiments, the practice of the present invention employs various techniques of molecular biology (including recombinant techniques), microbiology, cell biology, biochemistry and immunology. See, e.g., Sambrook et al. Molecular Cloning: A Laboratory Manual, 2nd edition (1989); Current Protocols in Molecular Biology (F. M. Ausubel et al. eds. (1987)); the series Methods in Enzymology (Academic Press, Inc.); PCR: A Practical Approach (M. MacPherson et al. IRL Press at Oxford University Press (1991)); PCR 2: A Practical Approach (M. J. MacPherson, B. D. Hames and G. R. Taylor eds. (1995)); Antibodies, A Laboratory Manual (Harlow and Lane eds. (1988)); Using Antibodies, A Laboratory Manual (Harlow and Lane eds. (1999)); and Animal Cell Culture (R. I. Freshney ed. (1987)).
Definitions of common terms in molecular biology may be found, for example, in Benjamin Lewin, Genes VII, published by Oxford University Press, 2000 (ISBN 019879276X); Kendrew et al. (eds.); The Encyclopedia of Molecular Biology, published by Blackwell Publishers, 1994 (ISBN 0632021829); and Robert A. Meyers (ed.), Molecular Biology and Biotechnology: a Comprehensive Desk Reference, published by Wiley, John & Sons, Inc., 1995 (ISBN 0471186341).
For the purpose of interpreting this specification, the following definitions will apply and whenever appropriate, terms used in the singular will also include the plural and vice versa. In the event that any definition set forth below conflicts with the usage of that word in any other document, including any document incorporated herein by reference, the definition set forth below shall always control for purposes of interpreting this specification and its associated claims unless a contrary meaning is clearly intended (for example in the document where the term is originally used). The use of “or” means “and/or” unless stated otherwise. As used in the specification and claims, the singular form “a,” “an” and “the” include plural references unless the context clearly dictates otherwise. For example, the term “an antibody” includes a plurality of antibodies, including mixtures thereof. The use of “comprise,” “comprises,” “comprising,” “include,” “includes,” and “including” are interchangeable and not intended to be limiting. Furthermore, where the description of one or more embodiments uses the term “comprising,” those skilled in the art would understand that, in some specific instances, the embodiment or embodiments can be alternatively described using the language “consisting essentially of” and/or “consisting of.”
As used herein, the term “about” means plus or minus 10% of the numerical value of the number with which it is being used.
The term “antigen,” as used herein, refers to a molecule capable of being recognized by an antibody. An antigen can be, for example, a peptide or a modified form thereof. An antigen can comprise one or more epitopes.
The term “epitope,” as used herein, is a portion of an antigen that is specifically recognized by an antibody. An epitope, for example, can comprise or consist of a portion of a peptide (e.g., a peptide of the invention). An epitope can be a linear epitope, sequential epitope, or a conformational epitope. In certain embodiments, epitopes may comprise non-contiguous regions.
The terms “nucleic acid,” “oligonucleotide” and “polynucleotide” are used interchangeably herein and encompass DNA, RNA, cDNA, whether single stranded or double stranded, as well as chemical modifications thereof.
Single letter amino acid abbreviations used herein have their standard meaning in the art, and all peptide sequences described herein are written according to convention, with the N-terminal end to the left and the C-terminal end to the right.
In one embodiment, the invention provides a method of detecting antibodies in a sample from a subject, wherein the antibodies bind to epitopes of Mycobacterium tuberculosis antigens, comprising
The sample is not particularly limiting. In some embodiments, the sample is selected from the group consisting of blood, serum, plasma, lymph nodes, skin, saliva, urine, cerebrospinal fluid and milk.
The Mycobacterium tuberculosis antigens comprise polypeptides comprising SEQ ID NOS:1, 3, 5, 7, 9, 11, 13, and/or 15. The amino acid and nucleic acid sequences of the Mycobacterium tuberculosis antigens are shown below.
In accordance with the method, the sample is contacted with two or more isolated polypeptides or antigenic fragments or variants thereof, wherein the polypeptides comprise polypeptides selected from the group consisting of SEQ ID NOS:1, 3, 5, 7, 9, 11, 13, and 15.
The Mycobacterium tuberculosis polypeptides, variants and antigenic fragments can be prepared in any suitable manner. Such polypeptides include isolated naturally occurring polypeptides, recombinantly produced polypeptides, synthetically produced polypeptides, or polypeptides produced by a combination of these methods.
In some embodiments, the Mycobacterium tuberculosis polypeptides are optimized for high level expression in E. coli using codons that are preferred in E. coli. In some embodiments, engineered antigenic fragments of Mycobacterium tuberculosis polypeptides (nucleic acid and amino acid sequences), which are optimized for expression in E. coli can be used, and which harbor an affinity tag (e.g., a histidine tag) to facilitate purification of the protein. As used herein, a codon that is “optimized for high level expression in E. coli” refers to a codon that is relatively more abundant in E. coli in comparison with all other codons corresponding to the same amino acid. In some embodiments, at least 40% of the codons are optimized for high level expression in E. coli. In some embodiments, at least 50%, at least 60%, at least 70%, at least 80%, at least 85%, at least 90%, at least 95%, or at least 99% of the codons are optimized for high level expression in E. coli. In some embodiments, the gene is cloned into an expression vector, such as pET30B to add an N-terminal hexahistidine tag and/or protease cleavage site.
In some embodiments, the polypeptides of the invention may be in substantially purified form. They may be in substantially isolated form, in which case they will generally comprise (for example about or at least) 90%, such as (for example about or at least) 95, 97 or 99% of the polypeptide in the preparation.
The two or more isolated polypeptides include at least two of the polypeptides selected from SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, and SEQ ID NO:15 as well as antigenic fragments and variants thereof which have at least 80% identity thereto. In some embodiments, the polypeptides have at least 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or greater identity to the polypeptides of NO:1, SEQ ID NO:3, SEQ ID NO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, and SEQ ID NO:15 and antigenic fragments thereof. In some embodiments, the polypeptides have at least 100% identity to the polypeptide of NO:1, SEQ ID NO:3, SEQ ID NO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, and SEQ ID NO:15 and antigenic fragments thereof.
Methods for aligning polynucleotides or polypeptides are codified in computer programs, including the GCG program package (Devereux et al., Nuc. Acids Res. 12:387 (1984)), BLASTP, BLASTN, FASTA (Atschul et al., J Molec. Biol. 215:403 (1990)), and Bestfit program (Wisconsin Sequence Analysis Package, Version 8 for Unix, Genetics Computer Group, University Research Park, 575 Science Drive, Madison, Wis. 53711) which uses the local homology algorithm of Smith and Waterman (Adv. App. Math., 2:482-489 (1981)). For example, the computer program ALIGN which employs the FASTA algorithm can be used, with an affine gap search with a gap open penalty of −12 and a gap extension penalty of −2.
When using any of the sequence alignment programs to determine whether a particular sequence is, for instance, about 95% identical to a reference sequence, the parameters are set such that the percentage of identity is calculated over the full length of the reference polynucleotide and that gaps in identity of up to 5% of the total number of nucleotides in the reference polynucleotide are allowed.
In some embodiments, the variant polypeptides, including those which have 80% or more identity to the Mycobacterium tuberculosis polypeptides described herein or antigenic fragments thereof, are recognized by an antibody that binds a polypeptide selected from the group consisting of SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, and SEQ ID NO:15 and antigenic fragments thereof. In some embodiments, the variant has 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more identity to a Mycobacterium tuberculosis polypeptide described herein and is recognized by an antibody that binds a Mycobacterium tuberculosis polypeptide selected from the group consisting of SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, and SEQ ID NO:15 and antigenic fragments thereof.
In some embodiments, the Mycobacterium tuberculosis polypeptides, variants or antigenic fragments are part of a larger protein such as a fusion protein. It is often advantageous to include additional amino acid sequence which contains secretory or leader sequences, pro-sequences, sequences which aid in purification such as multiple histidine residues, or additional sequence for stability during recombinant production.
An antigenic fragment is a polypeptide having an amino acid sequence that entirely is the same as part but not all of the amino acid sequence of one of the aforementioned Mycobacterium tuberculosis polypeptides. The antigenic fragment can be “free-standing,” or comprised within a larger polypeptide of which they form a part or region, most preferably as a single continuous region.
In some embodiments, the antigenic fragments include, for example, truncation polypeptides having the amino acid sequence of the Mycobacterium tuberculosis polypeptides, except for deletion of a continuous series of residues that includes the amino terminus, or a continuous series of residues that includes the carboxyl terminus or deletion of two continuous series of residues, one including the amino terminus and one including the carboxyl terminus. In some embodiments, fragments are characterized by structural or functional attributes such as fragments that comprise alpha-helix and alpha-helix forming regions, beta-sheet and beta-sheet-forming regions, turn and turn-forming regions, coil and coil-forming regions, hydrophilic regions, hydrophobic regions, alpha amphipathic regions, beta amphipathic regions, flexible regions, surface-forming regions, and high antigenic index regions.
The antigenic fragment can be of any size. In some embodiments the fragment is capable of inducing an immune response in a subject or be recognized by a specific antibody. In some embodiments, the specific antibody recognizes the full-length protein. In some embodiments, the fragment corresponds to an amino-terminal truncation mutant. In some embodiments, the number of amino terminal amino acids missing from the fragment ranges from 1-100 amino acids. In some embodiments, it ranges from 1-75 amino acids, 1-50 amino acids, 1-40 amino acids, 1-30 amino acids, 1-25 amino acids, 1-20 amino acids, 1-15 amino acids, 1-10 amino acids and 1-5 amino acids.
In some embodiments, the fragment can be, e.g., at least 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, or 44 amino acids in length. The fragment can be contiguous or can include one or more deletions (e.g., a deletion of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more amino acid residues). In some embodiments, peptides of the invention that comprise a fragment of a peptide sequence described herein can further comprise an additional N-terminal peptide sequence, an additional C-terminal peptide sequence, or a combination thereof. In some embodiments, the additional N-terminal and/or C-terminal peptide sequences can be non-native sequences.
In some embodiments, the fragment corresponds to carboxyl-terminal truncation mutant. In some embodiments, the number of carboxyl terminal amino acids missing from the fragment ranges from 1-100 amino acids. In some embodiments, it ranges from 1-75 amino acids, 1-50 amino acids, 1-40 amino acids, 1-30 amino acids, 1-25 amino acids, 1-20 amino acids, 1-15 amino acids, 1-10 amino acids and 1-5 amino acids.
In some embodiments, the fragment corresponds to an internal fragment that lacks both the amino and carboxyl terminal amino acids. In some embodiments, the fragment is 7-200 amino acid residues in length. In some embodiments, the fragment is 10-150 amino acid residues, 15-85 amino acid residues, 25-65 amino acid residues or 30-50 amino acid residues in length. In some embodiments, the fragment is 7 amino acids, 10 amino acids, 12 amino acids, 15 amino acids, 20 amino acids, 25 amino acids, 30 amino acids, 35 amino acids, 40 amino acids, 45 amino acids, 50 amino acids 55 amino acids, 60 amino acids, 80 amino acids or 100 amino acids in length.
Larger antigenic fragments are also useful according to the present invention, as are fragments corresponding to most, if not all, of the amino acid sequence of SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, and SEQ ID NO:15.
In some embodiments, the polypeptides useful in the methods of the invention include polypeptides having an amino acid sequence at least 80% identical to that of SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, and SEQ ID NO:15 or antigenic fragments thereof. In some embodiments, the variants are those that vary from the reference by conservative amino acid substitutions, i.e., those that substitute a residue with another of like characteristics. Typical substitutions are among Ala, Val, Leu and Ile; among Ser and Thr; among the acidic residues Asp and Glu; among Asn and Gln; and among the basic residues Lys and Arg, or aromatic residues Phe and Tyr. In some embodiments, the polypeptides are variants in which several, 5 to 10, 1 to 5, or 1 to 2 amino acids are substituted, deleted, or added in any combination.
In some embodiments, peptides of the invention are modified. The peptides of the invention may be modified by a variety of techniques, such as by denaturation with heat and/or a detergent (e.g., SDS). In some embodiments, peptides of the invention may be modified by association with one or more further moieties. The association can be covalent or non-covalent, and can be, for example, via a terminal amino acid linker, such as lysine or cysteine, a chemical coupling agent, or a peptide bond. The additional moiety can be, for example, a ligand, a ligand receptor, a fusion partner, a detectable label, an enzyme, or a substrate that immobilizes the peptide.
Peptides useful in the invention can be conjugated to a ligand, such as biotin (e.g., via a cysteine or lysine residue), a lipid molecule (e.g., via a cysteine residue), or a carrier protein (e.g., serum albumin, keyhole limpet hemocyanin (KLH), immunoglobulin Fc domain via e.g., a cysteine or lysine residue). Attachment to ligands, such as biotin, can be useful for associating the peptide with ligand receptors, such as avidin, streptavidin, polymeric streptavidin (see e.g., US 2010/0081125 and US 2010/0267166, both of which are herein incorporated by reference), or neutravidin. Avidin, streptavidin, polymeric streptavidin, neutravidin, in turn, can be linked to a signaling moiety (e.g., a moiety that can be visualized, such as colloidal gold, a fluorescent moiety, or an enzyme (horseradish peroxidase or alkaline phosphatase) or a solid substrate (e.g., an Immobilon or nitrocellulose membrane). In some embodiments, the peptides of the invention can be fused or linked to a ligand receptor, such as avidin, streptavidin, polymeric streptavidin, or neutravidin, thereby facilitating the association of the peptides with the corresponding ligand, such as biotin and any moiety (e.g., signaling moiety) or solid substrate attached thereto. Examples of other ligand-receptor pairs are well-known in the art and can similarly be used. In some embodiments, the peptides of the invention can be linked or conjugated to a signaling moiety directly.
In some embodiments, peptides useful in the invention can be fused or conjugated to a fusion partner (e.g., a peptide or other moiety). In some embodiments, a fusion partner can facilitate purification, expression of the peptide in a host cell, detection, stabilize the peptide, connecting the peptide to a surface or other entities, etc. Examples of suitable compounds for fusion partners include carrier proteins (e.g., serum albumin, immunoglobulin Fc domain, dendrimer, etc.), beta-galactosidase, glutathione-S-transferase, a histidine tag, etc. The fusion can be achieved by means of, e.g., a peptide bond. For example, peptides of the invention and fusion partners can be fusion proteins and can be directly fused in-frame or can comprise a peptide linker, as discussed above in the context of additional N-terminal and C-terminal peptide sequences. In some embodiments, a mixture of peptides of the invention can be linked by a dendrimer, e.g., as in a MAPS structure.
In addition, peptides of the invention may be modified to include any of a variety of known chemical groups or molecules. Such modifications include, but are not limited to, glycosylation, acetylation, acylation, ADP-ribosylation, amidation, covalent attachment to polyethylene glycol (e.g., PEGylation), covalent attachment of flavin, covalent attachment of a heme moiety, covalent attachment of a nucleotide or nucleotide derivative, covalent attachment of a lipid or lipid derivative, covalent attachment of phosphatidylinositol, cross-linking, cyclization, disulfide bond formation, demethylation, formation of covalent cross-links, formation of cystine, formation of pyroglutamate, formylation, gamma carboxylation, glycosylation, GPI anchor formation, hydroxylation, iodination, methylation, myristoylation, oxidation, proteolytic processing, phosphorylation, prenylation, racemization, selenoylation, sulfation, ubiquitination, modifications with fatty acids, transfer-RNA mediated addition of amino acids to proteins such as arginylation, etc. Analogues of an amino acid (including unnatural amino acids) and peptides with substituted linkages are also included. Peptides of the invention that consist of any of the sequences discussed herein may be modified by any of the discussed modifications. Such peptides still “consist of” the amino acids.
Modifications as set forth above are well-known to those of skill in the art and have been described in great detail in the scientific literature. Several particularly common modifications, glycosylation, lipid attachment, sulfation, gamma-carboxylation of glutamic acid residues, hydroxylation and ADP-ribosylation, for instance, are described in many basic texts, such as Proteins-Structure and Molecular Properties, 2nd ed., T. E. Creighton, W.H. Freeman and Company, New York (1993). Many detailed reviews are available on this subject, such as by Wold, F., Posttranslational Covalent Modification of Proteins, B. C. Johnson, Ed., Academic Press, New York 1-12 (1983); Seifter et al. (1990) Meth. Enzymol. 182:626-646 and Rattan et al. (1992) Ann. N.Y. Acad. Sci. 663:48-62.
The subject is not necessarily limiting. In some embodiments, the subject has been infected with Mycobacterium tuberculosis. In some embodiments, the subject can have active tuberculosis, latent tuberculosis, or be tuberculosis-negative. A positive result also includes the possibility of a previous infection that has been completely cleared and no possibility of latent tuberculosis. In some embodiments, the method is performed as a screen for tuberculosis in mass populations in developing countries. In some embodiments, the method could be utilized as a community-based triage or referral test to identify people suspected of having tuberculosis. A triage test can be a test that can be used by first-contact providers in the community (for example, community health workers or informal providers) to test persons with any symptoms or risk factors suggestive of tuberculosis who are seeking care (that is, it would not be used for active case-finding) to rule out TB (identify those who are triage-test negative) and direct individuals who require further evaluation (those who are triage-test positive) to a confirmatory test. The triage test can have higher accuracy than symptom screening. Symptom-only screening has very low specificity.
The subject is generally a human but may be an animal, typically one which can be naturally or artificially infected by a mycobacterium. The subject can be a mammal, such as a primate, cow, sheep, pig, badger or rodent, e.g. a mouse or rat. In some embodiments, the subject typically has an active or latent mycobacterial infection, or has had such an infection recently. The subject may test positive or negative in a Mantoux test. In some embodiments, the subject may be at risk of a mycobacterial infection, typically for socio-economic reasons or may have a genetic or acquired predisposition to mycobacterial infection. In some embodiments, the subject is a healthy contact who has been exposed to a mycobacterium. In some embodiments, the exposure is to pulmonary tuberculosis, such as ‘open’ pulmonary tuberculosis which is sputum a. f. b. (acid-fast bacillus) smear positive. In some embodiments, the method may be used to trace the healthy contacts of individuals with such tuberculosis infections. The method may also be used to carry out population surveys to measure the number of individuals in a population who have a mycobacterial infection or are healthy contacts.
In some embodiments, the method can help distinguish between a subject that has “active” tuberculosis and a subject that has “latent” tuberculosis. In some embodiments, active tuberculosis can be screened wherein the sample from the subject is contacted with SEQ ID NO:9 or an antigenic fragment or variant thereof; SEQ ID NO:11 or an antigenic fragment or variant thereof; SEQ ID NO:13 or an antigenic fragment or variant thereof; and SEQ ID NO:15 or an antigenic fragment or variant thereof; followed by detecting formation of antibody-peptide complexes comprising said isolated polypeptides or antigenic fragments or variants thereof; wherein formation of said complexes is indicative of the presence of the antibodies to epitopes of Mycobacterium tuberculosis antigens in said sample, wherein the sample is from a subject that has “active” tuberculosis. These B-cell antigens (SEQ ID NO: 9, 11, 13 and 15) induce antibody immune responses that seem to be confined to various categories of “active” TB (smear positive, smear negative, smear negative/culture negative/chest X-ray positive with improvement with treatment) while exhibit little antibody responses (5-10%) in patients with LTBI (smear negative/culture negative/QuantiFERON-TB positive category).
In accordance with the method, the sample is contacted with two or more isolated polypeptides or antigenic fragments or variants thereof, wherein the polypeptides comprise polypeptides selected from the group consisting of SEQ ID NOS:1, 3, 5, 7, 9, 11, 13, and 15. In some embodiments, the sample is contacted with at least two, three, four, five, six, seven, eight or more isolated polypeptides or antigenic fragments or variants thereof. In some embodiments, the two or more polypeptides comprise at least SEQ ID NO:9 or an antigenic fragment or variant thereof. In some embodiments, at least one of the polypeptides, antigenic fragments or variants thereof comprises a non-native sequence, such as an affinity tag to facilitate purification of the polypeptide. In some embodiments, the affinity tag can include 6×-His, HA, GST, or FLAG. In some embodiments, all of the polypeptides, antigenic fragments or variants thereof comprise non-native sequences, such as an affinity tag. In some embodiments, at least two of the polypeptides are conjugated to each other, or part of a fusion protein.
In some embodiments, the sample is contacted with SEQ ID NO:5 or an antigenic fragment or variant thereof; SEQ ID NO:7 or an antigenic fragment or variant thereof; and SEQ ID NO:9 or an antigenic fragment or variant thereof.
In some embodiments, the sample is contacted with SEQ ID NO:1 or an antigenic fragment or variant thereof; SEQ ID NO:3 or an antigenic fragment or variant thereof; SEQ ID NO:5 or an antigenic fragment or variant thereof; SEQ ID NO:7 or an antigenic fragment or variant thereof; and SEQ ID NO:9 or an antigenic fragment or variant thereof.
In some embodiments, the sample is contacted with SEQ ID NO:9 or an antigenic fragment or variant thereof; SEQ ID NO:11 or an antigenic fragment or variant thereof; SEQ ID NO:13 or an antigenic fragment or variant thereof; and SEQ ID NO:15 or an antigenic fragment or variant thereof.
In some embodiments, the accuracy/sensitivity of detecting antibody-peptide complexes in the sample from a subject infected with Mycobacterium tuberculosis is at least 70%, at least 80%, at least 90%, or at least 95%.
In some embodiments, the polypeptides are attached to or immobilized upon a solid support. In some embodiments, the solid support is a bead (e.g., a colloidal particle, nanoparticle, latex bead, etc.), a flow path in a lateral flow immunoassay device (e.g., a porous membrane), a flow path in an analytical rotor, or a tube or a well (e.g., in a plate suitable for an ELISA assay). In some embodiments, the solid support comprises metal, glass, a cellulose-based material (e.g., nitrocellulose), or a polymer (e.g., polystyrene, polyethylene, polypropylene, polyester, nylon, polysulfone, etc.). In some embodiments, the peptide or mixture of different peptides is attached to a dendrimer and/or incorporated into a MAPS system.
In some embodiments, the detecting step comprises performing an ELISA assay. In other embodiments, the detecting step comprises performing a lateral flow immunoassay. In other embodiments, the detecting step comprises performing an agglutination assay. In other embodiments, the detecting step comprises spinning the sample in an analytical rotor. In other embodiments, the detecting step comprises analyzing the sample using a Western blot, a slot blot, or a dot blot. In still other embodiments, the detecting step comprises analyzing the sample with an electrochemical sensor, an optical sensor, or an opto-electronic sensor. In some embodiments, the two or more isolated polypeptides or antigenic fragments or variants thereof is conjugated to a ligand. In some embodiments, the two or more isolated polypeptides or antigenic fragments or variants thereof are biotinylated. In some embodiments, the two or more isolated polypeptides or antigenic fragments or variants thereof are conjugated to streptavidin.
Suitable immunoassay methods typically include: receiving or obtaining (e.g., from a patient) a sample of body fluid or tissue likely to contain antibodies; contacting (e.g., incubating or reacting) a sample to be assayed with a peptide of the invention, under conditions effective for the formation of a specific peptide-antibody complex (e.g., for specific binding of the peptide to the antibody); and assaying the contacted (reacted) sample for the presence of an antibody-peptide reaction (e.g., determining the amount of an antibody-peptide complex). The presence of an elevated amount of the antibody-peptide complex indicates that the subject was exposed to and infected with an infectious Mycobacterium tuberculosis. A peptide, including a modified form thereof, which “binds specifically” to (e.g., “is specific for” or binds “preferentially” to) an antibody against a Mycobacterium tuberculosis antigen interacts with the antibody, or forms or undergoes a physical association with it, in an amount and for a sufficient time to allow detection of the antibody. By “specifically” or “preferentially,” it is meant that the peptide has a higher affinity (e.g., a higher degree of selectivity) for such an antibody than for other antibodies in a sample. For example, the peptide can have an affinity for the antibody of at least about 1.5-fold, 2-fold, 2.5-fold, 3-fold, or higher than for other antibodies in the sample. Such affinity or degree of specificity can be determined by a variety of routine procedures, including, e.g., competitive binding studies. In an ELISA assay, a positive response is defined as a value 2 or 3 standard deviations greater than the mean value of a group of healthy controls.
Conditions for reacting peptides and antibodies so that they react specifically are well-known to those of skill in the art. See, e.g., Current Protocols in Immunology (Coligan et al., editors, John Wiley & Sons, Inc).
The methods comprise receiving or obtaining a sample of body fluid or tissue that might contain antibodies from a subject. The antibodies can be, e.g., of IgG, IgE, IgD, IgM, or IgA type. Once the peptide antigen and sample antibody are permitted to react in a suitable medium, an assay is performed to determine the presence or absence of an antibody-peptide reaction. Among the many types of suitable assays, which will be evident to a skilled worker, are immunoprecipitation and agglutination assays.
In some embodiments of the invention, the assay comprises: immobilizing the antibody(s) in the sample, e.g., directly or indirectly via binding to peptides of the invention; adding a peptide of the invention; and detecting the degree of antibody bound to the peptide, e.g., by the peptide being labeled or by adding a labeled substance, such as a labeled binding partner (e.g., streptavidin-colloidal gold complex) or a labeled antibody which specifically recognizes the peptide. In other embodiments, the assay comprises: immobilizing a peptide of the invention; adding the sample containing antibodies; and detecting the amount of antibody bound to the peptide, e.g., by adding another peptide of the invention conjugated, directly or indirectly, to a label (e.g., colloidal gold complex, fluorescent label, enzyme (e.g., horseradish peroxidase or alkaline phosphatase)) or by adding a labeled substance, such as a binding partner or a labeled antibody which specifically recognizes the sample antibodies (e.g., anti-human IgG antibodies, anti-human IgM antibodies, etc.) or combinations thereof. In some embodiments, the assay comprises: immobilizing a peptide of the invention; adding the sample containing antibodies; and detecting the amount of antibody bound to the peptide, e.g., by adding a first binding partner which specifically recognizes the sample antibodies (e.g., anti-human IgG antibodies, anti-human IgM antibodies, etc.), and further adding a second binding partner (e.g., protein A, protein G, protein L, etc.), wherein the second binding partner is labeled and recognizes said first binding partner. In still other embodiments, the assay comprises: reacting the peptide and the sample containing antibodies without any of the reactants being immobilized, and then detecting the amount of complexes of antibody and peptide, e.g., by the peptide being labeled or by adding a labeled substance, such as a labeled binding partner (e.g., streptavidin-colloidal gold complex) or a labeled antibody which specifically recognizes the peptide.
Immobilization of a peptide of the invention can be either covalent or non-covalent, and the non-covalent immobilization can be non-specific (e.g., non-specific binding to a polystyrene surface in, e.g., a microtiter well). Specific or semi-specific binding to a solid or semi-solid carrier, support or surface, can be achieved by the peptide having, associated with it, a moiety which enables its covalent or non-covalent binding to the solid or semi-solid carrier, support or surface. For example, the moiety can have affinity to a component attached to the carrier, support or surface. In this case, the moiety may be, e.g., a biotin or biotinyl group or an analogue thereof bound to an amino acid group of the peptide, such as 6-aminohexanoic acid, and the component is then avidin, streptavidin, neutravidin, or an analogue thereof. An alternative is a situation in which the moiety has the amino acid sequence His-His-His-His-His-His and the carrier comprises a Nitrilotriacetic Acid (NTA) derivative charged with Ni++ or Co++ ions. In some embodiments, the moiety is a fusion partner.
Suitable carriers, supports, and surfaces include, but are not limited to, beads (e.g., magnetic beads, colloidal particles or nanoparticles, such as colloidal gold, or nanoparticles comprising silica, latex, polystyrene, polycarbonate, or PDVF), latex of co-polymers such as styrene-divinyl benzene, hydroxylated styrene-divinyl benzene, polystyrene, carboxylated polystyrene, beads of carbon black, non-activated or polystyrene or polyvinyl chloride activated glass, epoxy-activated porous magnetic glass, gelatin or polysaccharide particles or other protein particles, red blood cells, mono- or polyclonal antibodies or Fab fragments of such antibodies.
A particularly useful assay format is a lateral flow immunoassay format. Antibodies to human or animal immunoglobulins can be labeled with a signal generator or reporter (e.g., colloidal gold) that is dried and placed on a glass fiber pad (sample application pad or conjugate pad). The diagnostic peptide is immobilized on membrane, such as nitrocellulose or a PVDF (polyvinylidene fluoride) membrane (e.g., an Immobilon membrane). When a solution of sample (blood, serum, etc.) is applied to the sample application pad (or flows through the conjugate pad), it dissolves the labeled reporter, which then binds to all antibodies in the sample. The resulting complexes are then transported into the next membrane (PVDF or nitrocellulose containing the diagnostic peptide) by capillary action. If antibodies against the diagnostic peptide are present, they bind to the diagnostic peptide striped on the membrane, thereby generating a signal (e.g., a band that can be seen or visualized). An additional antibody specific to the labeled antibody or a second labeled antibody can be used to produce a control signal.
An alternative format for the lateral flow immunoassay comprises the peptides or compositions of the invention being conjugated to a ligand (e.g., biotin) and complexed with labeled ligand receptor (e.g., streptavidin-colloidal gold). The labeled peptide complexes can be placed on the sample application pad or conjugate pad. Anti-human IgG/IgM or anti-animal (e.g., dog, mouse, deer) IgG/IgM antibodies or other peptides of the invention are immobilized on a membrane, such as nitrocellulose of PVDF, at a test site (e.g., a test line).
When sample is added to the sample application pad, antibodies in the sample react with the labeled peptide complexes such that antibodies that bind to peptides of the invention become indirectly labeled. The antibodies in the sample are then transported into the membrane (PVDF or nitrocellulose containing the diagnostic peptides) by capillary action and bind to the immobilized anti-human IgG/IgM/IgA or anti-animal IgG/IgM/IgA antibodies (or protein A, protein G, protein L, or combinations thereof) or immobilized peptides of the invention. If any of the sample antibodies are bound to the labeled peptides of the invention, the label associated with the peptides can be seen or visualized at the test site.
Alternatively, when sample is added to the sample application pad, antibodies in the sample react with the labeled anti-human IgG/IgM/IgA or anti-animal IgG/IgM/IgA antibodies (or protein A, protein G, protein L, or combinations thereof) such that antibodies that bind to peptides of the invention become indirectly labeled. The labeled antibodies in the sample are then transported into the membrane (PVDF or nitrocellulose containing the diagnostic peptides) by capillary action and bind to the immobilized peptides of the invention. If any of the sample antibodies are bound to the immobilized peptides of the invention, the label associated with the peptides can be seen or visualized at the test site.
In the embodiments utilizing the lateral flow immunoassay format described above, the lateral flow device may comprise two ports: a sample port, which is positioned between a conjugate pad (containing a labeled analyte-binding partner) and a test site or line (containing an immobilized analyte-binding partner) and a chase port, which is positioned downstream (e.g. toward the end of the device away from test site) of the conjugate pad. In such devices comprising two ports, sample is deposited downstream of the test site via the sample port and fluid flow through the conjugate pad is initiated by depositing solution (e.g. diluent, buffer, or the like) via the chase port. The “chase” solution dissolves the labeled reagents in the conjugate pad and flows through to interact with the sample and then the immobilized reagents at the test site. Alternatively, sample is deposited downstream of the test site via the sample port and migrates toward the test site(s), resulting in the capture of the analyte(s) by the immobilized agents at the test site(s). Subsequently, fluid flow through the conjugate pad is initiated by depositing solution (e.g. diluent, buffer, or the like) via the chase port. The “chase” solution dissolves the labeled reagents in the conjugate pad and flows through to interact with the captured analyte(s) at the test site(s).
In other embodiments utilizing the lateral flow immunoassay format described above, the lateral flow device may comprise one port: a sample/chase buffer port, which is positioned below a conjugate pad (containing a labeled analyte-binding partner) and the test site(s) or line(s) containing immobilized analyte-binding partner(s). In such devices, sample is deposited downstream of the test site via the sample/buffer port and fluid flow through the conjugate pad is initiated by depositing solution (e.g. diluent, buffer, or the like) via the sample/chase buffer port. The “chase” solution dissolves the labeled reagents in the conjugate pad and flows through to interact with the sample and then the immobilized reagents at the test site(s).
Another assay for the screening of blood products or other physiological or biological fluids is an enzyme linked immunosorbent assay, i.e., an ELISA. Typically, in an ELISA, isolated peptides or compositions of the invention are adsorbed to the surface of a microtiter well directly or through a capture matrix (e.g., an antibody). Residual, non-specific protein-binding sites on the surface are then blocked with an appropriate agent, such as bovine serum albumin (BSA), heat-inactivated normal goat serum (NGS), or BLOTTO (a buffered solution of nonfat dry milk which also contains a preservative, salts, and an antifoaming agent). The well is then incubated with a biological sample suspected of containing specific antibody. The sample can be applied neat, or more often it can be diluted, usually in a buffered solution which contains a small amount (0.1-5.0% by weight) of protein, such as BSA, NGS, or BLOTTO. After incubating for a sufficient length of time to allow specific binding to occur, the well is washed to remove unbound protein and then incubated with an optimal concentration of an appropriate anti-immunoglobulin antibody (e.g., for human subjects, an anti-human immunoglobulin from another animal, such as dog, mouse, cow, etc.) or another peptide of the invention that is conjugated to an enzyme or other label by standard procedures and is dissolved in blocking buffer. The label can be chosen from a variety of enzymes, including horseradish peroxidase (HRP), beta-galactosidase, alkaline phosphatase, glucose oxidase, etc. Sufficient time is allowed for specific binding to occur again, then the well is washed again to remove unbound conjugate, and a suitable substrate for the enzyme is added. Color is allowed to develop and the optical density of the contents of the well is determined visually or instrumentally (measured at an appropriate wave length). The cutoff OD value may be defined as the mean OD+3 standard deviations (SDs) of at least 50 serum samples collected from individuals from an area where TB is not endemic, or by other such conventional definitions. In the case of a very specific assay, OD+2 SD can be used as a cutoff value.
In one embodiment of an ELISA, a peptide or peptides of the invention is immobilized on a surface, such as a ninety-six-well ELISA plate or equivalent solid phase that is coated with streptavidin or an equivalent biotin-binding compound, such as avidin or nuetravidin, at an optimal concentration in an alkaline coating buffer and incubated at 4 degrees C. overnight. After a suitable number of washes with standard washing buffers, an optimal concentration of a biotinylated form of a peptide or composition of the invention, dissolved in a conventional blocking buffer, is applied to each well. A sample is then added, and the assay proceeds as above. Conditions for performing ELISA assays are well-known in the art.
In another embodiment, the methods comprise an agglutination assay. For example, in some embodiments, colloidal particles (e.g., colloidal gold, etc.) or latex beads are conjugated to peptides or compositions of the invention. Subsequently, the biological fluid is incubated with the bead/peptide conjugate, thereby forming a reaction mixture. The reaction mixture is then analyzed to determine the presence of the antibodies. In some embodiments, the agglutination assays comprise the use of a second population of particles, such as colloidal particles (e.g., colloidal gold, etc.) or latex beads, conjugated to (1) antibodies specific to the peptides of compositions of the invention, in the case of a competition assay, or (2) antibodies capable of detecting sample antibodies (e.g., anti-human IgG or IgM or IgA antibodies, etc.), in the case of a sandwich assay. Suitable agglutination methods can comprise centrifugation as a means of assessing the extent of agglutination.
It should be understood by one of skill in the art that any number of protein assay formats, particularly immunoassay formats, may be designed to utilize the isolated peptides of this invention for the detection of antibodies and infection in a subject. This invention is thus not limited by the selection of the particular assay format, and is believed to encompass assay formats that are known to those of skill in the art.
In another embodiment, the invention provides a method for assaying interferon-γ production from a sample comprising T cells from a subject, comprising
In another aspect, the invention provides a method for detecting interferon-γ producing T cells from a sample from a subject, comprising
The T cells which recognize the peptide in the method are generally T cells which have been pre-sensitized in vivo to antigen from a mycobacterium. In some embodiments, these antigen-experienced T cells are generally present in the peripheral blood of a host which has been exposed to the mycobacterium at a frequency of 1 in 106 to 1 in 103 peripheral blood mononuclear cells (PBMCs). The T cells may be CD4+ and/or CD8+ T cells.
In the method the T cells can be contacted with the peptides in vitro or in vivo, and determining whether the T cells recognize the peptide can be done in vitro or in vivo.
Determination of whether the T cells recognize the peptide is generally done by detecting an increased secretion of cytokine, such as interferon-γ, in the presence of the peptide. The interferon-γ can typically be detected by allowing it to bind to a specific binding agent and then measuring the presence of the specific binding agent/interferon-γ complex. The specific binding agent is typically an antibody, such as polyclonal or monoclonal antibodies. Antibodies to interferon-γ are commercially available, or can be made using standard techniques.
In some embodiments, the specific binding agent for interferon-γ is immobilized on a solid support. After the substance is allowed to bind the solid support it can optionally be washed to remove material which is not specifically bound to the agent. The agent/substance complex can be detected by using a second binding agent which will bind the complex. In some embodiments, the second agent binds the substance at a site which is different from the site which binds the first agent. The second agent can be an antibody that is labeled directly or indirectly by a detectable label.
In some embodiments, the second agent can be detected by a third agent which is typically labeled directly or indirectly by a detectable label. For example, the second agent may comprise a biotin moiety, allowing detection by a third agent which comprises a streptavidin moiety and typically alkaline phosphatase as a detectable label.
In one embodiment the detection system which is used is the ex-vivo ELISPOT assay described in WO 98/23960. In that assay interferon-γ secreted from the T cell is bound by a first interferon-γ specific antibody which is immobilized on a solid support. The bound interferon-γ is then detected using a second interferon-γ specific antibody which is labeled with a detectable label. Such a labeled antibody can be obtained from MABTECH (Stockholm, Sweden). Other detectable labels which can be used are discussed below.
In some embodiments, the T cells which are contacted in the method are taken from the host in a blood sample, although other types of samples which contain T cells can be used. The sample may be added directly to the assay or may be processed first. Typically, the processing may comprise diluting of the sample, for example with water or buffer. Typically, the sample is diluted from 1.5 to 100 fold, for example 2 to 50 or 5 to 10-fold.
The processing may comprise separation of components of the sample. Typically, mononuclear cells (MCs) are separated from the samples. The MCs will comprise the T cells and APCs. In some embodiments of the method the APCs present in the separated MCs can present the peptide to the T cells. In another embodiment only T cells, such as only CD4 or only CD8 T cells, can be purified from the sample. PBMCs, MCs and T cells can be separated from the sample using techniques known in the art, such as those described in Lalvani et al (1997) J. Exp. Med. 186, p 859-865.
In some embodiments, the T cells used in the assay are in the form of unprocessed or diluted whole blood samples, or are freshly isolated T cells (such as in the form of freshly isolated MCs or PBMCs) which are used directly ex vivo, i.e. they are not cultured before being used in the method. However, the T cells can be cultured before use, for example in the presence of one or more of the peptides, and generally also exogenous growth promoting cytokines During culturing the peptides are typically present on the surface of APCs, such as the APC used in the method. Pre-culturing of the T cells can lead to an increase in the sensitivity of the method.
The APC which can be present in the method can be from the same host as the T cell or from a different host. The APC can be a naturally occurring APC or an artificial APC. The APC is a cell which is capable of presenting the peptide to a T cell. It is typically a B cell, dendritic cell or macrophage. It is typically separated from the same sample as the T cell and is typically co-purified with the T cell. Thus, the APC may be present in MCs or PBMCs. The APC is typically a freshly isolated ex vivo cell or a cultured cell. It may be in the form of a cell line, such as a short term or immortalized cell line. The APC may express empty MHC class II molecules on its surface.
In some embodiments, the T cells derived from the sample can be placed into an assay with all the peptides (i.e. a pool of the peptides) which it is intended to test (the relevant panel) or the T cells can be divided and placed into separate assays each of which contain one or more of the peptides.
In one embodiment peptide per se is added directly to an assay comprising T cells and APCs. As discussed above the T cells and APCs in such an assay could be in the form of MCs. When peptides which can be recognized by the T cell without the need for presentation by APCs are used then APCs are not required. Analogues which mimic the original peptide bound to a MHC molecule are an example of such a peptide.
In one embodiment the peptide is provided to the APC in the absence of the T cell. The APC is then provided to the T cell, typically after being allowed to present the peptide on its surface. The peptide may have been taken up inside the APC and presented, or simply be taken up onto the surface without entering inside the APC.
The duration for which the peptide is contacted with the T cells will vary depending on the method used for determining recognition of the peptide. Typically, 105 to 107, preferably 5×105 to 106 PBMCs are added to each assay. In the case where peptide is added directly to the assay its concentration is from 10−1 to 103 μg/ml, preferably 0.5 to 50 μg/ml or 1 to 10 μg/ml.
Typically, the length of time for which the T cells are incubated with the peptide is from 4 to 24 hours, preferably 6 to 16 hours.
In another embodiment, the invention provides devices. In some embodiments, the devices are useful for performing an immunoassay. For example, in some embodiments, the device is a lateral flow immunoassay device. In other embodiments, the device is an analytical rotor. In other embodiments, the device is a dot blot, slot blot, or Western blot. In other embodiments, the device is a tube or a well, e.g., in a plate suitable for an ELISA assay. In still other embodiments, the device is an electrochemical sensor, an optical sensor, or an opto-electronic sensor.
In some embodiments, the device comprises at least two polypeptides, antigenic fragments or variants of Mycobacterium tuberculosis antigens as described herein. For example, in some embodiments, the device comprises two, three, four, five, six, seven or eight or more different polypeptides of the invention. In some embodiments, the peptides are attached to or immobilized upon the device. In some embodiments, peptides of the invention are attached to or immobilized on a substrate, such as a solid or semi-solid support. The attachment can be covalent or non-covalent, and can be facilitated by a moiety associated with the peptide that enables covalent or non-covalent binding, such as a moiety that has a high affinity to a component attached to the carrier, support or surface. For example, the peptide can be associated with a ligand, such as biotin, and the component associated with the surface can be a corresponding ligand receptor, such as avidin. In some embodiments, the peptide can be associated with a fusion partner, e.g., bovine serum albumin (BSA), which facilitates with the attachment of the peptide to a substrate. The peptide can be attached to or immobilized on the substrate either prior to or after the addition of a sample containing antibody during an immunoassay.
In some embodiments, the substrate is a bead, such as a colloidal particle (e.g., a colloidal nanoparticle made from gold, silver, platinum, copper, metal composites, other soft metals, core-shell structure particles, or hollow gold nanospheres) or other type of particle (e.g., a magnetic bead or a particle or nanoparticle comprising silica, latex, polystyrene, polycarbonate, polyacrylate, or PVDF). Such particles can comprise a label (e.g., a colorimetric, chemiluminescent, or fluorescent label) and can be useful for visualizing the location of the peptides during immunoassays. In some embodiments, a terminal cysteine of a peptide of the invention is used to bind the peptide directly to the nanoparticles made from gold, silver, platinum, copper, metal composites, other soft metals, etc.
In some embodiments, the substrate is a dot blot or a flow path in a lateral flow immunoassay device. For example, the peptides can be attached or immobilized on a porous membrane, such as a PVDF membrane (e.g., an Immobilon™ membrane), a nitrocellulose membrane, polyethylene membrane, nylon membrane, or a similar type of membrane.
In some embodiments, the substrate is a flow path in an analytical rotor. In other embodiments, the substrate is a tube or a well, such as a well in a plate (e.g., a microtiter plate) suitable for use in an ELISA assay. Such substrates can comprise glass, cellulose-based materials, thermoplastic polymers, such as polyethylene, polypropylene, or polyester, sintered structures composed of particulate materials (e.g., glass or various thermoplastic polymers), or cast membrane film composed of nitrocellulose, nylon, polysulfone, or the like. A substrate can be sintered, fine particles of polyethylene, commonly known as porous polyethylene, for example, 0.2-15 micron porous polyethylene from Chromex Corporation (Albuquerque, N. Mex.). All of these substrate materials can be used in suitable shapes, such as films, sheets, or plates, or they may be coated onto or bonded or laminated to appropriate inert carriers, such as paper, glass, plastic films, or fabrics. Suitable methods for immobilizing peptides on solid phases include ionic, hydrophobic, covalent interactions and the like.
In one aspect, the invention provides a composition comprising mixtures of at least two isolated polypeptides, fragments and/or variants thereof capable of binding to antibodies that recognize Mycobacterium tuberculosis antigens. In certain embodiments, the polypeptides are selected from the group consisting of SEQ ID NOS:1, 3, 5, 7, 9, 11, 13, 15 and combinations thereof. In some embodiments, the polypeptides comprise an affinity tag to facilitate purification of the polypeptide. In some embodiments, the affinity tag is a 6×-Histidine tag, which can be present on the N- and/or C-terminus of the protein. The mixtures of polypeptides can be useful, e.g., in diagnostic assays to detect antibodies that recognize one or more epitopes on SEQ ID NOS: 1, 3, 5, 7, 9, 11, 13, and 15. In some embodiments, the composition comprises a mixture of 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 400, 500, or more polypeptides, antigenic fragments and variants thereof as described herein. In some embodiments, the peptides are modified (e.g., by association with one or more further moieties), as described herein.
In another aspect, the invention provides nucleic acids comprising sequences encoding the polypeptides, antigenic fragments and variants thereof of the invention. Nucleic acids of the invention contain less than an entire microbial genome and can be single- or double-stranded. A nucleic acid can be RNA, DNA, cDNA, genomic DNA, chemically synthesized RNA or DNA or combinations thereof. The nucleic acids can be purified free of other components, such as proteins, lipids and other polynucleotides. For example, the nucleic acids can be 50%, 75%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% purified. The nucleic acids of the invention encode the peptides described herein. In some embodiments, the nucleic acids encode a peptide having the sequence of SEQ ID NO: 1, 3, 5, 7, 9, 11, 13 and 15 or combinations thereof. Nucleic acids of the invention can comprise other nucleotide sequences, such as sequences coding for linkers, signal sequences, TMR stop transfer sequences, transmembrane domains, or ligands useful in protein purification such as glutathione-S-transferase, histidine tag, and staphylococcal protein A.
Nucleic acids of the invention can be isolated. An “isolated” nucleic acid is one that is not immediately contiguous with one or both of the 5′ and 3′ flanking genomic sequences that it is naturally associated with. An isolated nucleic acid can be, e.g., a recombinant DNA molecule of any length, provided that the nucleic acid sequence naturally found immediately flanking the recombinant DNA molecule in a naturally-occurring genome is removed or absent. Isolated nucleic acids can also include non-naturally occurring nucleic acid molecules. Nucleic acids of the invention can also comprise fragments that encode immunogenic peptides. Nucleic acids of the invention can encode full-length polypeptides, peptide fragments, and variant or fusion peptides.
Nucleic acids of the invention can be isolated, at least in part, from nucleic acid sequences present in, for example, a biological sample, such as blood, serum, saliva, or tissue from an infected individual. Nucleic acids can also be synthesized in the laboratory, for example, using an automatic synthesizer. An amplification method such as PCR can be used to amplify nucleic acids, at least in part, from either genomic DNA or cDNA encoding the polypeptides.
Nucleic acids of the invention can comprise coding sequences for naturally occurring polypeptides or can encode altered sequences that do not occur in nature.
In some embodiments, the present invention relates to vectors that comprise a polypeptides, antigenic fragments or variants thereof from Mycobacterium tuberculosis, host cells which are genetically engineered to express the polypeptides, antigenic fragments or variants thereof and the production of polypeptides, antigenic fragments or variants thereof of the invention by recombinant techniques. Cell-free translation systems can also be employed to produce such proteins using RNAs derived from the DNA constructs of the invention.
When a polynucleotide encoding a polypeptide, antigenic fragment or variant thereof from Mycobacterium tuberculosis is used for the recombinant production of a polypeptide, the polynucleotide may include the coding sequence for the full-length polypeptide or an antigenic fragment or variant thereof, by itself; the coding sequence for the full-length polypeptide, fragment or variant thereof in reading frame with other coding sequences, such as those encoding a leader or secretory sequence, a pre-, or pro or prepro-protein sequence, or other fusion peptide portions. For example, an affinity tag that facilitates purification of the fused polypeptide can be encoded. In certain embodiments of this aspect of the invention, the marker sequence is a hexa-histidine peptide, for example, as provided in the pQE vector (Qiagen, Inc.) and described in Gentz et al., Proc Natl Acad Sci USA 86:821-824 (1989), or it may be the HA tag, which corresponds to an epitope derived from the influenza hemagglutinin protein (Wilson, I., et al., Cell 37:767, 1984). The polynucleotide may also contain non-coding 5′ and 3′ sequences, such as transcribed, non-translated sequences, ribosome binding sites and sequences that stabilize mRNA.
Representative examples of appropriate hosts include bacterial cells, such as streptococci, staphylococci, E. coli, Streptomyces, Bacillus subtilis, and fungal cells, such as yeast cells and Aspergillus cells. In some embodiments, gram negative bacteria are the host cells. A great variety of expression systems can be used, including DNA or RNA vectors. In other embodiments, the invention provides an isolated nucleic acid molecule comprising a type IV pilin operably linked to a heterologous promoter. In some embodiments, the invention further provides an isolated Mycobacterium tuberculosis nucleic acid molecule operably linked to a heterologous promoter, wherein said isolated nucleic acid molecule is capable of expressing a polypeptide when used to transform an appropriate host cell.
In some embodiments, the invention relates to an isolated nucleic acid molecule encoding an antigenic fragment or variant of Mycobacterium tuberculosis polypeptide linked to an affinity tag sequence and/or enzymatic cleavage sequence to facilitate purification. In some embodiments, the affinity tag is a 6×-Histidine tag. In some embodiments, the cleavage sequence is recognized by enterokinase. In some embodiments, the nucleic acid molecules are optimized to increase expression in E. coli without altering the amino acid sequence using preferred codons in E. coli. In some embodiments, the present invention is directed to purified polypeptides, variants and antigenic fragments of a Mycobacterium tuberculosis polypeptide as described herein.
In some embodiments, the amino acid sequence to be expressed is reverse translated for codon optimization in E. coli using a commercial tool and synthesized along with flanking restriction sites. In some embodiments, the synthetic gene is cloned into an expression vector, such as pET30B to add an N-terminal hexahistidine tag and protease cleavage site.
In some embodiments, the kits comprise polypeptides of the invention. In some embodiments, the kits comprise two, three, four, or more different polypeptides of the invention. In some embodiments, the polypeptides are attached to or immobilized on a solid support as described herein.
In some embodiments, the kits further comprise a population of beads or a plate (e.g., a plate suitable for an ELISA assay). In other embodiments, the kits further comprise a device, such as a lateral flow immunoassay device, an analytical rotor, a Western blot, a dot blot, a slot blot, an electrochemical sensor, an optical sensor, or an opto-electronic sensor. In some embodiments, the population of beads, the plate, or the device is useful for performing an immunoassay. For example, in some embodiments, the population of beads, the plate, or the device is useful for detecting formation of an antibody-peptide complex comprising an antibody from a sample and a peptide of the invention. In some embodiments, a peptide or a mixture of different peptides of the invention is attached to or immobilized on the beads, the plate, or the device.
In some embodiments, the kits further comprise an instruction. For example, in some embodiments, the kits comprise an instruction indicating how to use a peptide of the invention to detect an antibody to tuberculosis antigens or to diagnose tuberculosis disease. In some embodiments, the kits comprise an instruction indicating how to use a population of beads, a plate, or a device (e.g., comprising a peptide or a mixture of different peptides of the invention) to detect antibodies to tuberculosis antigens or to diagnose tuberculosis.
In some embodiments the kit for carrying out the method comprises one or more of the polypeptides, antigenic fragments or variants thereof and optionally a means to detect the recognition of interferon-γ secreted by a T cell. In some embodiments, the peptides are provided for simultaneous, separate or sequential use. In some embodiments, the means to detect recognition allows or aids detection based on the techniques discussed above.
The kit may additionally include a specific binding agent for the substance, such as an antibody. In some embodiments, the agent is typically specific for interferon-γ. The agent is typically immobilized on a solid support. This means that after binding the agent the substance will remain in the vicinity of the T cell which secreted it. Thus ‘spots’ of substance/agent complex are formed on the support, each spot representing a T cell which is secreting the substance. Quantifying the spots, and typically comparing against a control, allows determination of recognition of the peptide.
In some embodiments, the kit comprises a means to detect the substance/agent complex. A detectable change may occur in the agent itself after binding the substance, such as a color change. Alternatively, a second agent directly or indirectly labeled for detection may be allowed to bind the substance/agent complex to allow the determination of the spots. As discussed above the second agent may be specific for the substance, but binds a different site on the substance than the first agent.
The immobilized support may be a plate with wells, such as a microtiter plate. Each assay can therefore be carried out in a separate well in the plate.
The kit may additionally comprise medium for the T cells, detection agents or washing buffers to be used in the detection steps. The kit may additionally comprise reagents suitable for the separation from the sample, such as the separation of PBMCs or T cells from the sample. The kit may be designed to allow detection of the T cells directly in the sample without requiring any separation of the components of the sample.
The kit may comprise an instrument which allows administration of the peptide, such as intradermal or epidermal administration. In some embodiments, such an instrument comprises one or more needles. The instrument may allow ballistic delivery of the peptide. The polypeptides in the kit may be in the form of a pharmaceutical composition.
The kit may also comprise controls, such as positive or negative controls. The positive control may allow the detection system to be tested. The positive control typically mimics recognition of the peptide in any of the above methods. In some embodiments, the kits designed to determine recognition in vitro the positive control is a cytokine. In the kit designed to detect in vivo recognition of the peptide the positive control may be antigen to which most individuals should response.
The kit may also comprise a means to take a sample containing T cells from the host, such as a blood sample. The kit may comprise a means to separate mononuclear cells or T cells from a sample from the host.
Application of the teachings of the present invention to a specific problem is within the capabilities of one having ordinary skill in the art in light of the teaching contained herein. Examples of the compositions and methods of the invention appear in the following non-limiting Examples.
Comparative genomic studies have identified several Mycobacterium tuberculosis-specific genomic regions of difference (RDs) which are absent in the vaccine strains of Mycobacterium bovis BCG and which may be useful for the diagnosis of TB. Detailed information on ORF present in various RD, distributions of RD in various mycobacterial species including BCG strains, M. tuberculosis and M. bovis isolates are shown in Tables 1-3. These Tables are obtained from O. Parkash et al., Scandinavian Journal of Immunology 2009; 70(4), 345-357. The proteins encoded by these regions are called RD proteins. In recent years, a number of RD antigens have been investigated for their potential in T-cell-based cell-mediated immune response (CMI) assays. Particularly, these RD antigens have attracted attention for their potential in improving serological assays for tuberculosis diagnosis. Our work in this area has identified a number of antigens in various RDs and related M. tuberculosis genomic regions for use in serological diagnostics. The best performing antigens for use in serological TB assays that we have uncovered include the Rv0222, Rv3120, Rv1989c, Rv3118, Rv1636, Rv3426, Rv2185c, Rv3354 and others.
Mycobacterium tuberculosis H37Rv
M. tuberculosis Erdman
M. africanum
M. bovis
M. microti OV254
M. tuberculosis CSU93
M. smegmatis
M. avium
The full-length, correctly folded M. tuberculosis proteins Rv0222, Rv3120, Rv1989c, Rv3118, Rv1636, Rv3426 can be obtained as recombinant versions expressed in E. coli or any other suitable recombinant protein overexpression host organisms. A method to obtain significant quantities of purified aforementioned antigens from E. coli cells in the inventors' laboratory is described here. A DNA segment encoding the full-length Rv0222 or Rv3120, or Rv1989c or Rv3118 or Rv1636 or Rv3426 amino acid sequence (Table 4) is cloned into an E. coli protein expression of choice. Examples of suitable expression vectors include the pJexpress vector—an E. coli expression vector utilizing T5 phage promoter or our proprietary expression vector pMOS containing the pmo1 promoter. The expression vector is subsequently transformed into E. coli cells. After the recombinant protein expressing cells have been cultured and collected, the recombinant cells are lysed with an appropriate method. The cell lysate is centrifuged at 12K rpm for 15 min to separate the soluble extract from the particulate fraction. If the recombinant protein is expressed as a soluble protein, the recombinant protein can be purified from the soluble extract using chromatography, for instance, metal affinity chromatography, taking advantage of the 6×His tag at the C-terminus of the recombinant protein. If the protein is expressed as inclusion bodies, the pellet fraction obtained after centrifugation step, can be solubilized with solution containing 8M urea, refolded by slow dialysis to remove urea, and then purified using metal affinity chromatography, taking advantage of the 6×His tag at the C-terminus of the recombinant protein.
An embodiment of the invention for the use of the Rv0222, Rv3120, and Rv1989c proteins is the rapid lateral flow chromatographic test to diagnose Tuberculosis. The so-called rapid tests introduced first in the 1980s are inexpensive, disposable, membrane-based lateral flow assays that provide visual evidence of the presence of an analyte in a patient sample. The tests can be formatted either as freestanding dipsticks or as devices enclosed within plastic housings. As little as 10-100 μl of liquid sample is required to perform the test, which can be completed within 5-15 minutes. In clinical tests, the sample may be a small volume of whole blood, serum, plasma, saliva, or urine depending on the type of assay product and marker to be detected. These can be applied directly to the sample application wick for dipstick device or sample well for card device. No instrumentation is required to perform such tests, which can be used in clinics, laboratories, field locations, and the home, often by inexperienced personnel. Optional use of portable table-top or hand-held optical density or fluorescence intensity analyzing instruments is also available.
The “basic” (or classical) architecture of the lateral flow rapid test strips is shown in
The rapid lateral flow assays are also capable of detecting multiple analytes simultaneously on a single strip. Tests with up to 5 different analytes on the same strip have been developed and marketed. For our TB serodiagnostic tests, the base substrate is a nitrocellulose membrane onto which the capture antigen(s) is (are) immobilized (
There are many choices for the conjugates to be used in the assays—magnetic nanoparticles, fluorescent nanoparticles in addition to the standard of the industry—gold conjugates. As a result of their greater stability, sensitivity, precision and reproducibility, gold conjugates were introduced into membrane-based rapid tests in the late 1980s and have become the industry mainstay. Gold particles of any accurately defined size can be manufactured reproducibly under the appropriate manufacturing conditions. The visual signal is generated on the test strip by the accumulation of gold particles by the specific immunochemical reaction at the test (capture) or control line. Generally, the larger the gold particles are, the better visualization occurs. However, the trade-off between required visibility and steric hindrance dictates that, for most immunoassay applications, the optimum particle size is 40-60 nm. Larger particles may be preferred when a darker red color is desired or when the lower curvature of the particle surface would improve the molecular interaction between the antibody and antigen.
The major issue with current TB serodiagnostics/rapid tests is that these tests are known to be of inferior quality. Mostly TB rapid serodiagnostics are produced out of China and India, but poor quality standards and sloppy practices have resulted in a huge range of accuracy data, rendering them all but essentially useless.
In order to correct for this situation, the first issue in order to develop better TB serodiagnostics would be the selection of better antigens that can be used in the serological assay. Although the accuracy of existing serological rapid assays is poor and these tests have not been clinically useful, efforts towards discovery of novel TB antigens and better strategies for developing efficient serodiagnostics have continued unabatedly in the hope of discovering better-performing markers/antigens. If such a POC, highly sensitive, inexpensive, rapid serodiagnostic test could ever be developed, even with a moderate specificity (80%-90%), the impact could be very significant. These tests could be used as screening tests to triage the patients into stratified groups so that the more expensive but “definitive” testing methods (like culture or the Xpert MTB/RIF) can be focused on the highly suspected cases. Such tests would also be very useful for large-scale active case-finding approaches, where current tests are prohibitively expensive.
In order to come up with better TB antigens, we have screened by IgM/IgG ELISA a collection of smear-positive samples (>200 serum samples from various TB endemic countries) for promising antigen candidates. The antigens screened include approximately 75% of all proteins belonging to the Regions of Difference (RDs) of the M. tuberculosis genome and their vicinities, numerous antigens not in the RDs but found in various literature sources to be good antigens, as well as TB antigens known to have been utilized in other TB serodiagnostics/rapid tests. The results from these IgG/IgM screening experiments indicated the following: 1) Very few single antigen that we have investigated (>100 candidates) could provide a positive reading with >40% of the samples (both IgM and IgG). 2) TB antigens known to have been utilized previously in TB serodiagnostics/rapid tests currently in the market exhibited either very poor or poor results (20-30% positive detection rate, combined IgM and IgG). 3) A minimal combination of 3 best performing antigens was needed in order to detect >80% of the samples. Eventually we settled on a best combination of the most immunogenic antigens, Rv0222, Rv3120, Rv1989c, Rv2185c, and Rv3354 (Panel I). These antigens are among the most immuno-dominant ones that we were able to identify. Our Panel II antigens comprise of the following antigens, Rv3118, Rv1636, Rv3426, and Rv3120, which were discovered in a later screening using samples that we received from the World Health Organization (WHO).
Our TB diagnostics prototypes were evaluated by blind testing using a TB sample collection provided by the WHO. This collection contains samples in the following categories: smear positive/culture positive, smear negative/culture positive, smear negative/culture negative/chest radiology X-ray (CRX) positive (with improvement upon treatment), smear negative/culture negative/Quantiferon positive (latent TB), and non-TB (smear negative/culture negative). These samples were collected from patients from South Africa, Brazil, Peru and Vietnam.
After blind testing following a previously described protocol by the WHO (http://www.who.int/tdr/publications/documents/diagnostic-evaluation-2.pdf), the results obtained with the Panel I TB serodiagnostic prototypes can be summarized as following:
1) In the smear positive/culture positive group, our test detected 95% of these samples (n=60);
2) In the smear negative/culture positive group, our test detected 98% of these samples (n=40);
3) In the smear negative/culture negative/CRX positive group, our test detected 100% of these samples (n=15);
4) In the smear negative/culture negative/quantiferon-TB positive, our test detected 100% of these samples (n=20);
5) In the so-called Non-TB group (smear negative/culture negative), our TB test correctly predicted TB-negative status in 82% of these samples (n=60).
The “non-TB” samples in the WHO collection were evaluated only by smear microscopy and culture methods and therefore probably have included patients with latent TB. A more accurate term to refer to these “non-TB” cases is “non-active” TB. As such, the positive responses in this so-called “non-TB” group are actually LTBI cases. These testing results indicate that our Panel I TB test probably is a point-of-care equivalent of the IGRA QuantiFERON-TB test.
Our Panel 2 TB test prototypes were also evaluated using the WHO sample collection, and the following results were obtained:
1) The detection rates in the smear negative/culture positive, smear negative/culture negative/CRX positive categories are still >90%-95%;
2) The detection rate in the latent TB category (smear negative/culture negative/Quantiferon positive) is low, only 10%;
3) In the smear positive/culture positive category, the TB 2 test detected 93% of these samples while maintaining a specificity of 90% in the non-TB group.
Our TB diagnostics comprising of two Panels which can be combined into a single test or separated into 2 tests as mentioned in the Device Description Section. The test utilizing Panel I antigens is the POC equivalent of the QuantiFeron-TB test, capable of detecting almost all TB cases, including active TB and LTBI. The Panel I TB test should perform very well with HIV/TB co-infection cases since three antigens in this panel (Rv0222, Rv3154, Rv2185c) have been found to yield 85% or better responses in the TB/HIV category where current commercial serodiagnostics have performed poorly.
This application claims the benefit of U.S. Provisional Appl. No. 62/398,213, filed Sep. 22, 2016, the contents of which are hereby incorporated by reference in their entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US17/63154 | 11/22/2017 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62398213 | Sep 2016 | US |
