Purification, partial characterization, and identification of a skin-reactive protein antigen of Mycobacterium bovis BCG

Biochemical and antigenic characterization of the Mycobacterium tuberculosis 71kD antigen, a member of the 70kD heat-shock protein family

A 71 kiloDalton antigen from Mycobacterium tuberculosis is recognized by antibodies and by T lymphocytes during infection (Britton et al., 1986a). Partial sequence analysis indicates a relationship between this antigen and the highly conserved family of 70-kiloDalton heat shock proteins (hsp70) (Young et al., 1988). Biochemical and serological characterization of the protein confirms its membership of the hsp70 gene family, and metabolic labelling demonstrates that it is a major component of the mycobacterial response to heat stress. The role of stress proteins as antigens during infection is discussed.

Induction of nonspecific acquired resistance and delayed-type hypersensitivity, but not specific acquired resistance in mice inoculated with killed mycobacterial vaccines

A number of nonliving mycobacterial preparations were tested in vivo for their capacity to generate various relevant parameters of cellular immunity. All preparations tested had some detectable activity in raising resistance to challenge with Mycobacterium tuberculosis or with Listeria monocytogenes and in conferring the ability to mount a delayed-type hypersensitivity response to tuberculin. This report presents the first evidence, however, that none of these preparations were able to generate protective T cells capable of adoptive immunization against virulent tuberculosis. These data are discussed in terms of the use of these preparations in generating M. tuberculosis-reactive T-cell lines and the application of these lines in the continuing search for an improved vaccine against tuberculosis.

H-2-linked control of in vitro gamma interferon production in response to a 32-kilodalton antigen (P32) of Mycobacterium bovis bacillus Calmette-Guérin

A 32-kilodalton protein antigen (P32) was previously purified to homogeneity from culture filtrate of Mycobacterium bovis BCG (J. De Bruyn, K. Huygen, R. Bosmans, M. Fauville, R. Lippens, J. P. Van Vooren, P. Falmagne, H. G. Wiker, M. Harboe, and M. Turneer, Microb. Pathog. 2:351-366, 1987). Spleen cells from BCG-sensitized mice produce significant amounts of gamma interferon (IFN-gamma) in response to this P32 protein. The amount of secreted IFN-gamma is influenced by mouse genotype, with C57BL/6 (H-2b), C57BL/10 (H-2b), and 129/Sv (H-2b) mice producing about four times more than BALB/c (H-2d), CBF1 (H-2d/b), and DBA/2 (H-2d) mice do. Analysis of seven recombinant inbred strains derived from the BALB/c x C57BL/6 cross and of congenic mice differing in major histocompatibility complex-coding chromosome 17 fragments indicates a probable H-2-linked control of this IFN-gamma induction, with H-2b cells producing high titers and H-2d cells producing low titers in response to the P32 antigen.

Immunochemical characterization of and isolation of the gene for a Borrelia burgdorferi immunodominant 60-kilodalton antigen common to a wide range of bacteria

By crossed immunoelectrophoresis and Western blotting (immunoblotting), it was shown that Borrelia burgdorferi expresses the 60-kilodalton Common Antigen (CA) that is cross-reactive with an equivalent antigen in a wide range of remotely related bacteria. B. burgdorferi CA is strongly immunogenic. A B. burgdorferi genomic library was constructed by using a plasmid cloning system. Escherichia coli recombinants were screened for expression of immunodominant B. burgdorferi antigens. One of the recombinant clones expressed the 60-kilodalton CA of B. burgdorferi. The DNA region encoding B. burgdorferi CA was localized on a 2.3-kilobase fragment of the plasmid pKH1. CA may have pathogenetic implications in Lyme borreliosis, since the CA of mycobacteria recently has been shown to play a role in the etiology of experimental autoimmune arthritis. The extensive cross-reactivity of this antigen may account for the low diagnostic specificity of the currently used serological tests in Lyme borreliosis.

Use of recombinant antigens expressed in Escherichia coli K-12 to map B-cell and T-cell epitopes on the immunodominant 65-kilodalton protein of Mycobacterium bovis BCG

In gene libraries of Mycobacterium bovis BCG, Mycobacterium tuberculosis, and Mycobacterium leprae, recombinants were frequently encountered that expressed an immunodominant 65-kilodalton (kDa) protein antigen that was shown to react with a high proportion of mycobacterium-reactive human and murine T cells and murine monoclonal antibodies. In this study, recombinant antigens were used to map T-cell and B-cell epitopes on the M. bovis BCG 65-kDa protein that was previously designated MbaA. Four different T-cell-epitope-containing regions (amino acid residues 1 through 16, 17 through 61, 85 through 108, and 235 through 279) were defined that were recognized by seven T-cell clones from patients with tuberculoid leprosy. These regions are distinct from two previously described T-cell epitopes recognized by T cells from a tuberculosis patient. As T-cell clones restricted by different class II determinants were shown to be specific for different regions on the 65-kDa protein, the presented data suggested that the products of different human leukocyte antigen class II loci and alleles present different parts of MbaA to the immune system. B-cell epitopes recognized by 20 monoclonal antibodies were assigned to eight different regions of MbaA. Using 15 of these antibodies, we previously showed that MbaA was antigenically related to a common antigen present in many bacterial species. The dispersed localization of the involved epitopes defined here shows that various different parts of MbaA are indeed conserved. These results show that well-defined recombinant antigens are useful tools for the localization of both B- and T-cell-epitope-containing regions of a protein. Peptides synthesized from the sequences of such regions may then exactly define the epitopes relevant for the development of specific diagnostic tests or of vaccines against mycobacteria.

Stress proteins are immune targets in leprosy and tuberculosis

To understand the immune response to infection by tuberculosis and leprosy bacilli and to develop improved vaccines, the nature of antigens that are involved in humoral and cell-mediated immunity was investigated. We have determined that five immunodominant protein antigens under study are homologues of stress proteins. This finding and observations with other pathogens suggest that infectious agents may respond to the host environment by producing stress proteins and that these proteins can be important immune targets. We postulate that abundant and highly conserved stress proteins may have "immunoprophylactic" potential for a broad spectrum of human pathogens.

Biological activity of protein antigens isolated from Mycobacterium tuberculosis culture filtrate

Mycobacterium tuberculosis culture filtrate (MTCF) protein antigens were isolated from mid-logarithmic-phase cultures grown in liquid medium and examined by high-pressure liquid chromatography and Western blot (immunoblot) analysis. A major protein band with a molecular mass of about 68 kilodaltons (kDa) and several fainter bands in the 38- and 24-kDa range were observed. The MTCF protein produced a significant delayed footpad hypersensitivity response in Mycobacterium bovis BCG-vaccinated C57BL/6 mice, comparable to that observed with standard purified protein derivative (PPD). The same proteins induced a blastogenic response in tuberculin-sensitive human peripheral blood monocytes and in T-cell clones developed from these cells. The proliferative responses to the MTCF antigens were equivalent to those observed following stimulation with PPD or M. tuberculosis sonic extracts. However, the MTCF sensitins were not recognized by five monoclonal antibodies directed against killed M. tuberculosis antigens in an enzyme immunoassay, although some response was seen with a monoclonal antibody (ML34) directed against M. leprae antigens. The ability of the MTCF to stimulate T-cell responses both in vivo and in vitro while not being recognized by antibodies directed against dead mycobacterial antigens suggests that they may be of interest as potential protective immunogens.

Generation and characterization of monoclonal antibodies to 28-, 35-, and 65-kilodalton proteins of Mycobacterium tuberculosis

Three monoclonal antibodies (H60.15, H61.3, and H105.10) directed to protein antigens of Mycobacterium tuberculosis were obtained and characterized. H60.15 recognizes a protein with a molecular mass of 28 kilodaltons (kDa) with broad cross-reactivity on a panel of 12 species and strains of mycobacteria. H61.3 reacts with a 35-kDa protein present in M. tuberculosis, Mycobacterium bovis BCG, and M. africanum. On the basis of the antigen molecular masses and competition experiments with other monoclonal antibodies, H60.15 and H61.3 seem to be the first described monoclonal antibodies to these M. tuberculosis proteins. H105.10 binds to the cross-reactive 65-kDa protein present in mycobacteria. Epitope mapping of H105.10 was performed by using the M. leprae DNA sublibrary available in bacteriophage lambda gt11 for this antigen and revealed that its epitope resides in the region from amino acids 20 to 54. The 28-, 35-, and 65-kDa antigens isolated by immunoblotting and presented on nitrocellulose to pleural effusion T cells from tuberculosis patients induced a proliferative response, indicating the presence of T-cell epitopes. These observations indicate that two protein antigens should be added to the list of antigens detectable in M. tuberculosis by monoclonal antibodies. The common feature of such proteins, the elicitation of an immune response of limited or broad cross-reactivity for mycobacteria, encourages the search for their role in the pathogenesis of mycobacterioses.

The Mycobacterium tuberculosis 65-kilodalton antigen is a heat shock protein which corresponds to common antigen and to the Escherichia coli GroEL protein

Monoclonal hybridoma antibodies directed against a 65-kilodalton (kDa) mycobacterial protein could detect similarly sized antigens in many other bacterial species. In Pseudomonas aeruginosa, the cross-reacting protein corresponded to a 62-kDa antigen that has been called Common Antigen. The mycobacterial 65-kDa antigen and Common Antigen are similar in that both (i) are highly immunoreactive molecules, (ii) contain species-specific and genus-specific epitopes in addition to the broadly cross-reactive epitopes, (iii) can be isolated as homomultimers of greater than 240 kDa, and (iv) have similar amino acid compositions. In Escherichia coli, the cross-reactive protein corresponded to the GroEL protein. Both the GroEL protein and the mycobacterial 65-kDa protein are expressed as heat shock proteins.

The antigens of Mycobacterium tuberculosis, H37Rv, studied by crossed immunoelectrophoresis. Comparison with a reference system for Mycobacterium bovis, BCG

On the basis of a previously developed reference system for Mycobacterium bovis, BCG, in crossed immunoelectrophoresis (CIE), antigens of Mycobacterium tuberculosis were identified in an analogous system. A majority of the numbered lines in the BCG system were also present and identified in the M. tuberculosis system. The corresponding antigens in the two systems were identified by dual dilution in CIE, and using monospecific antisera and monoclonal antibodies. Some of the antigens were specifically identified by the demonstration of enzyme activity and by means of hydroxyapatite, concanavalin A (Con A), EDTA, and blue-Sepharose. Three antigens (nos 10, 78, and 81), which were found in high concentrations in M. tuberculosis culture fluid, were not identified or were present in low concentrations in BCG culture fluid. The high percentage of corresponding antigens confirms that there is a very close taxonomic relationship between BCG and M. tuberculosis. Corresponding antigens in BCG and M. tuberculosis did not differ in electrophoretic mobility in the antigenic preparations studied.

Antigenic relatedness of a strongly immunogenic 65 kDA mycobacterial protein antigen with a similarly sized ubiquitous bacterial common antigen

In gene libraries of Mycobacterium bovis BCG, Mycobacterium tuberculosis and Mycobacterium leprae recombinants were frequently found expressing an immunodominant 65 kDa protein antigen. In this study polyclonal and monoclonal antibodies against the 65 kDa antigen were found to react with a variety of different bacteria. Furthermore it is shown that the 65 kDa mycobacterial protein belongs to the family of antigens previously designated 'common antigen' due to their presence in a large variety of bacterial species. The molecular weight of this common antigen in 17 bacterial species was determined and it varied from 59 to 65 kDa. These bacteria included Gram-negative, Gram-positive and archae-bacteria, indicating that this antigen consists of members of an evolutionary well-conserved protein family. The 65 kDa protein was located in the cytoplasmic fraction of both Escherichia coli K12 and M. bovis BCG. Its function for the bacterial cell is presently unknown. The immunological relatedness of this common antigen to the MbaA protein might indicate a role in the etiology of rheumatoid arthritis, as was recently suggested for the mycobacterial 65 kDa antigen.

The 65kDa antigen of mycobacteria-a common bacterial protein?

The 65 kilodalton antigen of Mycobacterium tuberculosis and M. leprae is a well-characterized, strongly immunogenic protein eliciting antibody and T-cell responses in infected patients. Recent studies have disclosed regions of cross-reactivity between the 65kDa antigen and proteins in many other bacterial species. These include the product of the ams gene in E. coli which is involved in the processing of RNA. Here Douglas Young and his colleagues discuss these observations, the significance of the 65kDa antigen and its possible role in the pathogenesis of mycobacterial and other diseases.