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

Culture filtrate proteins from BCG act as adjuvants for cytotoxic T lymphocyte induction

Mycobacterium bovis bacilli Calmette-Guerin (BCG) is a licensed vaccine against tuberculosis. It requires attenuated live bacteria to be effective, possibly because actively secreted proteins play a critical role in inducing anti-tuberculosis immunity. BCG also functions as an effective adjuvant. Moreover, the effects of BCG components as adjuvants are not important as those of attenuated live BCG, which is used in cancer immunotherapy. However, the BCG secreted proteins have not been paid attention in anticancer immunity. To understand mycobacterial secreted proteins' function, we investigate immune responses to BCG culture filtrate proteins (CFP). Here, CFP strongly induce both antigen-specific CD4+ T cells and specific CD8+ T cells, which may be functional cytotoxic T lymphocytes (CTLs). In this study, we clearly demonstrate that CFP acts as an adjuvant for CTL induction against specific co-administered proteins and propose CFP as a new protein adjuvant. The CTL response shows potent anticancer effects in mice. These findings could provide insight into the contribution of mycobacterial secreted proteins in both anticancer and antimycobacterial immunity.

Possible Cross-Reactivity between SARS-CoV-2 Proteins, CRM197 and Proteins in Pneumococcal Vaccines May Protect Against Symptomatic SARS-CoV-2 Disease and Death

Various studies indicate that vaccination, especially with pneumococcal vaccines, protects against symptomatic cases of SARS-CoV-2 infection and death. This paper explores the possibility that pneumococcal vaccines in particular, but perhaps other vaccines as well, contain antigens that might be cross-reactive with SARS-CoV-2 antigens. Comparison of the glycosylation structures of SARS-CoV-2 with the polysaccharide structures of pneumococcal vaccines yielded no obvious similarities. However, while pneumococcal vaccines are primarily composed of capsular polysaccharides, some are conjugated to cross-reacting material CRM197, a modified diphtheria toxin, and all contain about three percent protein contaminants, including the pneumococcal surface proteins PsaA, PspA and probably PspC. All of these proteins have very high degrees of similarity, using very stringent criteria, with several SARS-CoV-2 proteins including the spike protein, membrane protein and replicase 1a. CRM197 is also present in Haemophilus influenzae type b (Hib) and meningitis vaccines. Equivalent similarities were found at lower rates, or were completely absent, among the proteins in diphtheria, tetanus, pertussis, measles, mumps, rubella, and poliovirus vaccines. Notably, PspA and PspC are highly antigenic and new pneumococcal vaccines based on them are currently in human clinical trials so that their effectiveness against SARS-CoV-2 disease is easily testable.

Recombinant human HSP60 produced in ClearColi™ BL21(DE3) does not activate the NFκB pathway

HSP60, an intracellular molecular chaperone has been largely described as an alarmin or damage-associated molecular pattern when released outside the cell. HSP60 has been reported as a possible ligand of TLR2 or TLR4 inducing NFκB-dependant signaling pathway leading to cytokine secretion. However, recent publications suggested that HSP60 could not act as an activator of TLR4 by itself. The observed effect could be due to the presence of endotoxin in HSP60 preparation especially LPS. In order to clarify the controversy, we produced recombinant human HSP60 in two different strains of Escherichia coli, standard strain for protein overproduction, BL21(DE3), and the new ClearColi BL21(DE3) strain which lacks LPS-activity through TLR4. Undoubtedly, we have shown that recombinant HSP60 by itself was not able to induce NFκB-dependant signaling pathway in a model of THP1 monocyte cell line. Our data suggest that HSP60 needs either pathogen-associated molecules, specific post-translational modification and/or other host factors to activate immune cells via NFκB activation.

Biochemical and immunological characterization of a cpn60.1 knockout mutant of Mycobacterium bovis BCG

Pathogenic mycobacteria possess two homologous chaperones encoded by cpn60.1 and cpn60.2. Cpn60.2 is essential for survival, providing the basic chaperone function, while Cpn60.1 is not. In the present study, we show that inactivation of the Mycobacterium bovis BCG cpn60.1 (Mb3451c) gene does not significantly affect bacterial growth in 7H9 broth, but that this knockout mutant (Δcpn60.1) forms smaller colonies on solid 7H11 medium than the parental and complemented strains. When growing on Sauton medium, the Δcpn60.1 mutant exhibits a thinner surface pellicle and is associated with higher culture filtrate protein content and, coincidentally, with less protein in its outermost cell envelope in comparison with the parental and complemented strains. Interestingly, in this culture condition, the Δcpn60.1 mutant is devoid of phthiocerol dimycocerosates, and its mycolates are two carbon atoms longer than those of the wild-type, a phenotype that is fully reversed by complementation. In addition, Δcpn60.1 bacteria are more sensitive to stress induced by H(2)O(2) but not by SDS, high temperature or acidic pH. Taken together, these data indicate that the cell wall of the Δcpn60.1 mutant is impaired. Analysis by 2D gel electrophoresis and MS reveals the upregulation of a few proteins such as FadA2 and isocitrate lyase in the cell extract of the mutant, whereas more profound differences are found in the composition of the mycobacterial culture filtrate, e.g. the well-known Hsp65 chaperonin Cpn60.2 is particularly abundant and increases about 200-fold in the filtrate of the Δcpn60.1 mutant. In mice, the Δcpn60.1 mutant is less persistent in lungs and, to a lesser extent, in spleen, but it induces a comparable mycobacteria-specific gamma interferon production and protection against Mycobacterium tuberculosis H37Rv challenge as do the parental and complemented BCG strains. Thus, by inactivating the cpn60.1 gene in M. bovis BCG we show that Cpn60.1 is necessary for the integrity of the bacterial cell wall, is involved in resistance to H(2)O(2)-induced stress but is not essential for its vaccine potential.

Evaluation of signal peptide prediction algorithms for identification of mycobacterial signal peptides using sequence data from proteomic methods

Secreted proteins play an important part in the pathogenicity of Mycobacterium tuberculosis, and are the primary source of vaccine and diagnostic candidates. A majority of these proteins are exported via the signal peptidase I-dependent pathway, and have a signal peptide that is cleaved off during the secretion process. Sequence similarities within signal peptides have spurred the development of several algorithms for predicting their presence as well as the respective cleavage sites. For proteins exported via this pathway, algorithms exist for eukaryotes, and for Gram-negative and Gram-positive bacteria. However, the unique structure of the mycobacterial membrane raises the question of whether the existing algorithms are suitable for predicting signal peptides within mycobacterial proteins. In this work, we have evaluated the performance of nine signal peptide prediction algorithms on a positive validation set, consisting of 57 proteins with a verified signal peptide and cleavage site, and a negative set, consisting of 61 proteins that have an N-terminal sequence that confirms the annotated translational start site. We found the hidden Markov model of SignalP v3.0 to be the best-performing algorithm for predicting the presence of a signal peptide in mycobacterial proteins. It predicted no false positives or false negatives, and predicted a correct cleavage site for 45 of the 57 proteins in the positive set. Based on these results, we used the hidden Markov model of SignalP v3.0 to analyse the 10 available annotated proteomes of mycobacterial species, including annotations of M. tuberculosis H37Rv from the Wellcome Trust Sanger Institute and the J. Craig Venter Institute (JCVI). When excluding proteins with transmembrane regions among the proteins predicted to harbour a signal peptide, we found between 7.8 and 10.5 % of the proteins in the proteomes to be putative secreted proteins. Interestingly, we observed a consistent difference in the percentage of predicted proteins between the Sanger Institute and JCVI. We have determined the most valuable algorithm for predicting signal peptidase I-processed proteins of M. tuberculosis, and used this algorithm to estimate the number of mycobacterial proteins with the potential to be exported via this pathway.

Multiple chaperonins in bacteria--why so many?

A significant proportion of bacteria express two or more chaperonin genes. Chaperonins are a group of molecular chaperones, defined by sequence similarity, required for the folding of some cellular proteins. Chaperonin monomers have a mass of c. 60 kDa, and are typically found as large protein complexes containing 14 subunits arranged in two rings. The mechanism of action of the Escherichia coli GroEL protein has been studied in great detail. It acts by binding to unfolded proteins and enabling them to fold in a protected environment where they do not interact with any other proteins. GroEL can assist the folding of many proteins of different sizes, sequences, and structures, and homologues from many different bacteria can functionally replace GroEL in E. coli. What then are the functions of multiple chaperonins? Do they provide a mechanism for cells to increase their general chaperoning ability, or have they become specialized to take on specific novel cellular roles? Here I will review the genetic, biochemical, and phylogenetic evidence that has a bearing on this question, and show that there is good evidence for at least some specificity of function in multiple chaperonin genes.

Gamma interferon responses induced by a panel of recombinant and purified mycobacterial antigens in healthy, non-mycobacterium bovis BCG-vaccinated Malawian young adults

We have previously shown that young adults living in a rural area of northern Malawi showed greater gamma interferon (IFN-gamma) responses to purified protein derivatives (PPD) prepared from environmental mycobacteria than to PPD from Mycobacterium tuberculosis. In order to define the mycobacterial species to which individuals living in a rural African population have been exposed and sensitized, we tested T-cell recognition of recombinant and purified antigens from M. tuberculosis (38 kDa, MPT64, and ESAT-6), M. bovis (MPB70), M. bovis BCG (Ag85), and M. leprae (65 kDa, 35 kDa, and 18 kDa) in >600 non-M. bovis BCG-vaccinated young adults in the Karonga District of northern Malawi. IFN-gamma was measured by enzyme-linked immunosorbent assay (ELISA) in day 6 supernatants of diluted whole-blood cultures. The recombinant M. leprae 35-kDa and 18-kDa and purified native M. bovis BCG Ag85 antigens induced the highest percentages of responders, though both leprosy and bovine tuberculosis are now rare in this population. The M. tuberculosis antigens ESAT-6 and MPT64 and the M. bovis antigen MPB70 induced the lowest percentages of responders. One of the subjects subsequently developed extrapulmonary tuberculosis; this individual had a 15-mm-diameter reaction to the Mantoux test and responded to M. tuberculosis PPD, Ag85, MPT64, and ESAT-6 but not to any of the leprosy antigens. We conclude that in this rural African population, exposure to M. tuberculosis or M. bovis is much less frequent than exposure to environmental mycobacteria such as M. avium, which have antigens homologous to the M. leprae 35-kDa and 18-kDa antigens. M. tuberculosis ESAT-6 showed the strongest association with the size of the Mantoux skin test induration, suggesting that among the three M. tuberculosis antigens tested it provided the best indication of exposure to, or infection with, M. tuberculosis.

Specific delayed-type hypersensitivity responses to ESAT-6 identify tuberculosis-infected cattle

Human and bovine tuberculosis have long been detected by skin testing with purified protein derivative (PPD), a complex mix of partly denatured mycobacterial antigens with suboptimal specificity. In the present study, skin tests based on ESAT-6, a recombinantly produced antigen highly specific for tuberculosis infection, were investigated. Although ESAT-6 was strongly recognized in vitro and induced high levels of gamma interferon, initial investigations demonstrated that higher doses of ESAT-6 than of PPD were needed to induce substantial delayed-type hypersensitivity reactions. Also, the kinetics of the skin test response differed for the two reagents; PPD showed maximal response at 72 h, but the response to ESAT-6 often peaked later at 96 h. Tests based on an optimized strategy (400 micro g of ESAT-6 measured between 72 and 96 h), in cattle infected with Mycobacterium bovis (n = 22) and animals sensitized by exposure to environmental mycobacteria showed ESAT-6 to have a promising diagnostic potential (sensitivity, 82%; specificity, 100%; optimal cutoff, 3 mm), compared with PPD (sensitivity, 86%; specificity, 90%; optimal cutoff, 4 mm). Larger investigations are required to refine cutoff points for any new diagnostic test, but the present results indicate great potential for skin tests based on specific antigens for accurate in vivo diagnosis of tuberculosis.

Heat shock protein 70 is a potent activator of the human complement system

According to new hypotheses, extracellular heat shock proteins (Hsps) may represent an ancestral danger signal of cellular death or lysis-activating innate immunity. Recent studies demonstrating a dual role for Hsp70 as both a chaperone and cytokine, inducing potent proinflammatory response in human monocytes, provided support for the hypothesis that extracellular Hsp is a messenger of stress. Our previous work focused on the complement-activating ability of human Hsp60. We demonstrated that Hsp60 complexed with specific antibodies induces a strong classical pathway (CP) activation. Here, we show that another chaperone molecule also possesses complement-activating ability. Solid-phase enzyme-linked immunosorbent assay was applied for the experiments. Human Hsp70 activated the CP independently of antibodies. No complement activation was found in the case of human Hsp90. Our data further support the hypothesis that chaperones may messenger stress to other cells. Complement-like molecules and primitive immune cells appeared together early in evolution. A joint action of these arms of innate immunity in response to free chaperones, the most abundant cellular proteins displaying a stress signal, may further strengthen the effectiveness of immune reactions.

Improved immunogenicity and protective efficacy of a tuberculosis DNA vaccine encoding Ag85 by protein boosting

C57BL/6 mice were vaccinated with plasmid DNA encoding Ag85 from Mycobacterium tuberculosis, with Ag85 protein in adjuvant, or with a combined DNA prime-protein boost regimen. While DNA immunization, as previously described, induced robust Th1-type cytokine responses, protein-in-adjuvant vaccination elicited very poor cytokine responses, which were 10-fold lower than those observed with DNA immunization alone. Injection of Ag85 DNA-primed mice with 30 to 100 microg of purified Ag85 protein in adjuvant increased the interleukin-2 and gamma interferon (IFN-gamma) response in spleen two- to fourfold. Further, intracellular cytokine analysis by flow cytometry also showed an increase in IFN-gamma-producing CD4(+) T cells in DNA-primed-protein-boosted animals, compared to those that received only the DNA vaccination. Moreover, these responses appeared to be better sustained over time. Antibodies were readily produced by all three methods of immunization but were exclusively of the immunoglobulin G1 (IgG1) isotype following protein immunization in adjuvant and preferentially of the IgG2a isotype following DNA and DNA prime-protein boost vaccination. Finally, protein boosting increased the protective efficacy of the DNA vaccine against an intravenous M. tuberculosis H37Rv challenge infection, as measured by CFU or relative light unit counts in lungs 1 and 2 months after infection. The capacity of exogenously given protein to boost the DNA-primed vaccination effect underlines the dominant role of Th1-type CD4(+) helper T cells in mediating protection.

Evidence for specific and non-covalent binding of lipids to natural and recombinant Mycobacterium bovis BCG hsp60 proteins, and to the Escherichia coli homologue GroEL

Heat-shock proteins (Hsps) from various origins are known to share a conserved structure and are assumed to be key partners in the biogenesis of proteins. Fractionation of the mycobacterial Hsp60, a 65 kDa protein also called Cpn60, from Mycobacterium bovis BCG zinc-deficient culture filtrate on phenyl-Sepharose followed by Western blotting revealed the existence of four Hsp60-1 and Hsp60-2 forms, based on their hydrophobicity behaviour. Hsp60-2 species were further purified by ion-exchange chromatography and partial amino acid sequences of cyanogen bromide (CNBr) peptides of purified Hsp60-2 species showed identity with the amino acid sequence deduced from the hsp60-2 gene, indicating that the various Hsp60-2 forms are encoded by the same gene. In addition, the mycobacterial Hsp60-2 was overexpressed in E. coli using the pRR3Hsp60-2 plasmid and analysed on phenyl-Sepharose. The elution pattern of the recombinant Hsp60-2, as well as that of Escherichia coli GroEL, was similar to that of the native Hsp60-2 from the culture filtrate of M. bovis BCG and entirely different from that of the mycobacterial antigen 85. Extraction of mycobacterial Hsp60-2 forms, recombinant BCG Hsp60-2 and E. coli GroEL with organic solvents releases various amounts of non-covalently bound lipids. The presence of lipids on Hsp60-2 was confirmed by labelling M. bovis BCG with radioactive palmitate. The radioactivity was specifically associated with Hsp60 in the aqueous phase and the 19 and 38 kDa lipoproteins in the Triton X-114 phase. Analysis of the lipids extracted from purified Hsp60-2, recombinant BCG Hsp60-2 and E. coli GroEL by TLC showed the same pattern for all the samples. Acid methanolysis of the lipids followed by GC analysis led to the identification of C(16:0), C(18:0) and C(18:1) as the major fatty acyl constituents, and of methylglycoside in these proteins. Altogether, these data demonstrate that lipids are non-covalently bound to Hsp60-2 and homologous proteins.

Lack of protection in mice and necrotizing bronchointerstitial pneumonia with bronchiolitis in guinea pigs immunized with vaccines directed against the hsp60 molecule of Mycobacterium tuberculosis

In this study, the hsp60 and hsp70 heat shock protein antigens of Mycobacterium tuberculosis were tested as potential vaccine candidates, using purified recombinant protein antigens or antigens encoded in the form of a DNA plasmid vaccine. Guinea pigs vaccinated with a mixture of the two proteins showed no evidence of resistance to low-dose aerosol challenge infection and quickly developed severe lung damage characterized by necrotizing bronchointerstitial pneumonia and bronchiolitis. As a result, we turned instead to a DNA vaccination approach using a plasmid encoding the hsp60 antigen of M. tuberculosis. Although immunogenic in mice, vaccination with plasmid DNA encoding hsp60 was not protective in that model or in the guinea pig model and again gave rise to similar severe lung damage. This study seriously questions the safety of vaccines against tuberculosis that target highly conserved heat shock proteins.

Overexpression, purification and characterization of Mycobacterium bovis BCG alcohol dehydrogenase

A previous study of the effect of zinc deprivation on Mycobacterium bovis BCG pointed out the potential importance of an alcohol dehydrogenase for maintaining the hydrophobic character of the cell envelope. In this report, the effect of the overexpression of the M. bovis BCG alcohol dehydrogenase (ADH) in Mycobacterium smegmatis and M. bovis BCG is described. The purification of the enzyme was performed to apparent homogeneity from overexpressing M. bovis BCG cells and its kinetic parameters were determined. The enzyme showed a strong preference for both aromatic and aliphatic aldehydes while the corresponding alcohols were processed 100-1000-fold less efficiently. The best kcat/Km values were found with benzaldehyde > 3-methoxybenzaldehyde > octanal > coniferaldehyde. A phylogenetic analysis clearly revealed that the M. bovis BCG ADH together with the ADHs from Bacillus subtilis and Helicobacter pylori formed a sister group of the class C medium-chain alcohol dehydrogenases, the plant cinnamyl alcohol dehydrogenases (CADs). Comparison of the kinetic properties of our ADH with some related class C enzymes indicated that the mycobacterial enzyme substrate profile resembled that of the CADs involved in plant defence rather than those implicated in lignification. A possible role for the M. bovis BCG ADH in the biosynthesis of the lipids composing the mycobacterial cell envelope is proposed.

Human 60-kDa Heat-Shock Protein: A Danger Signal to the Innate Immune System

Mammalian 60-kDa heat-shock protein (hsp60) is a key target of T cell and Ab responses in chronic inflammation or atherosclerosis. We show in this study that human hsp60 is also an Ag recognized by cells of the innate immune system, such as macrophages. Both mouse and human macrophages respond to contact with exogenous human hsp60 with rapid release of TNF-α; mouse macrophages in addition produce nitric oxide. The proinflammatory macrophage response is hsp60 dose dependent and similar in kinetics and extent to LPS stimulation. Human hsp60 was found to synergize with IFN-γ in its proinflammatory activity. Finally, human hsp60 induces gene expression of the Th1-promoting cytokines IL-12 and IL-15. These findings identify autologous hsp60 as a danger signal for the innate immune system, with important implications for a role of local hsp60 expression/release in chronic Th1-dependent tissue inflammation.

Mycobacterium tuberculosis chaperonin 10 forms stable tetrameric and heptameric structures. Implications for its diverse biological activities

The chaperonin activity of sequence-related chaperonin 10 proteins requires their aggregation into heptameric structures. We describe size-exclusion chromatography and ultracentrifugation studies that reveal that while Escherichia coli chaperonin 10 exists as a heptamer, the Mycobacterium tuberculosis chaperonin 10 is tetrameric in dilute solutions and in whole M. tuberculosis lysate. At high protein concentration and in the presence of saturating amounts of divalent ions, the protein is heptameric. Human chaperonin 10 is predominantly heptameric, although smaller oligomers were detected. These differences in structural assembly between species may explain differences in biological activity such as antigenicity. Using C-terminal and N-terminal fragments, sequence 1-25 was identified as indispensable for aggregation. CD spectroscopy studies revealed that (i) a minimum at 202-204 nm correlates with aggregation and characterizes not only the spectrum of the mycobacterial protein, but also those of E. coli and human chaperonin 10 proteins; (ii) the interactions between subunits are of the hydrophobic type; and (iii) the anti-parallel beta-pleated sheet is the main secondary structure element of subunits in both tetrameric and heptameric proteins.

Guinea pig cellular immune responses to proteins secreted by Mycobacterium tuberculosis

To study the immunological activity of proteins secreted by Mycobacterium tuberculosis, we carried out comparative studies in guinea pigs infected intravenously with 2.5 x 10(3) CFU of this organism or with 2.5 x 10(4) CFU of Mycobacterium bovis BCG. Groups of infected guinea pigs were skin tested with fractions of secreted proteins covering well-defined narrow-molecular-mass regions, or such fractions were used for lymphocyte stimulation experiments. The lymphocyte stimulation experiments showed that the fraction containing proteins with molecular masses below 10 kDa had a superior stimulating capacity in tuberculous guinea pigs whereas the 24- to 30-kDa fraction gave significantly higher skin reactions in this group compared with BCG-vaccinated guinea pigs. A precise mapping within the region from 23 to 35 kDa by using a combination of narrow overlapping fractions and purified proteins enabled the identification of the 24-kDa antigen MPT64 as a molecule specific for tuberculous infection. Thus, MPT64 is a promising candidate for a specific diagnostic skin test reagent for human tuberculosis.

The expression of mycobacterial heat shock protein (HSP64) on Meth A tumour cells

Immunological cross-reactivity between Mycobacterium bovis BCG stress protein (heat shock protein: HSP64) and Meth A tumour cells was analysed by using anti-BCG HSP64 mAb whose recognition epitopes were characterized against BCG HSP64 peptides. By indirect immunofluorescence analysis (IIFA), it was found that one of seven anti-BCG HSP64 mAb, XVIIIG1, bound to the cell surface of Meth A in BALB/c mice. This result was further confirmed by western blot analysis, demonstrating the presence of a 64 kDa protein which reacted with mAb XVIIIG1 that recognizes the 110-123 amino acid peptide of the BCG HSP64. Comparison of the amino acid sequence between the mouse HSP65 and BCG HSP64 recognized by mAb XVIIIG1 revealed 50% amino acid sequence homology. It was concluded from these results that Meth A tumour cells continuously express the stress protein HSP64 as a kind of tumour-associated antigen on the surface of tumour cells.

Chemical definition, cloning, and expression of the major protein of the leprosy bacillus

The decline in prevalence of leprosy is not necessarily matched by a fall in incidence, emphasizing the need for new antigens to measure disease transmission and reservoirs of infection. Mycobacterium leprae obtained from armadillo tissues was disrupted and subjected to differential centrifugation to arrive at preparations of cell wall, cytoplasmic membrane, and cytosol. By committing 0.3 g of M. leprae to the task, it was possible to isolate from the cytosol and fully define the major cytosolic protein. Amino-terminus sequencing and chemical and enzymatic cleavage, followed by more sequencing and fast atom bombardment-mass spectrometry of fragments, allowed description of the entire amino acid sequence of a protein of 10,675-Da molecular mass. The sequence derived by chemical means is identical to that deduced previously from DNA analysis of the gene of a 10-kDa protein, a GroES analog. The work represents the first complete chemical definition of an M. leprae protein. PCR amplification of the 10-kDa protein gene, when cloned into Escherichia coli with a pTRP expression vector, allowed production of the recombinant protein. Chemical analysis of the expressed protein demonstrated that it exactly reflected the native protein. The recombinant major cytosolic protein appears to be a promising reagent for skin testing, still probably the most appropriate and pragmatic means of measuring incidence of leprosy.

Soluble Mycobacterium bovis protein antigens: studies on their purification and immunological evaluation

The eradication of bovine tuberculosis is an ultimate aim of the beef industry and the development of accurate diagnostic tests will expedite eradication. Characterization of Mycobacterium bovis antigens, and a detailed understanding of their immune reactivity will aid in the development of more specific and sensitive diagnostic tests. With this aim, studies were conducted which have resulted in the purification and immunological characterization of the major soluble M. bovis antigens. The purified antigens were found to contain cross-reactive epitopes and immunological responses to these proteins varied among individual animals. Thus if more specific diagnostic tests are to be formulated, they will have to be at the epitope level, using only species-specific epitopes and not whole proteins. Due to the genetic diversity of the response of infected cattle to individual epitopes, a large cocktail of such epitopes will be necessary for the development of a sensitive test.

Heat shock response in Actinobacillus actinomycetemcomitans

The heat shock response in Actinobacillus actinomycetemcomitans, a capnophilic Gram-negative bacterial species that is implicated in the development of certain forms of periodontitis, was characterized. Different strains of A. actinomycetemcomitans were grown at 37, 42 and 48 degrees C in the presence of 35S-methionine. The bacterial cells were lysed, run on SDS-PAGE and subsequently blotted on nitrocellulose paper. After autoradiography of the blots, several protein bands from the cultures at 42 degrees C showed an increased intensity; major bands were observed at 90, 70, and 60 kDa, but increased protein synthesis was also detected at 54, 28 and 17 kDa. Nitrocellulose blots were also incubated with a panel of monoclonal and polyclonal antibodies directed to epitopes on different heat shock proteins. Strong reactivity was found with several antibodies at the position corresponding to a molecular mass of 60 kDa. The protein is probably the GroEL homologue in A. actinomycetemcomitans, a member of the 'common bacterial antigen' family.

Murine CD8+ T suppressors against mycobacterial 65-kDa antigen compete for IL-2 and show lack of major histocompatibility complex-imposed restriction specificity in antigen recognition

The mechanism of antigen-specific suppression and reasons for aberrant major histocompatibility complex (MHC) class II restriction mediated by CD8+ T cells was investigated in a previously reported murine model of immunosuppression, generated by intraperitoneal priming with Mycobacterium vaccae. Both the CD4+ T helper cells (Th) and CD8+ T suppressor cell (Ts) of M. vaccae-primed mice recognized the 65-kDa antigen of the bacillus, presented by I-A and I-E, respectively. The CD8+ Ts could inhibit non-antigen-specific proliferation of primed CD4+ T cells induced by the exogenously added interleukin (IL)-2 (concanavalin A-stimulated culture supernatant). For inhibition, the Ts had to be activated by the 65-kDa antigen. The degree of inhibition was dependent upon the amount of added IL-2 and the relative numbers of primed CD8+ and CD4+ T cells. On incubation with antigen-presenting cells, and the 65-kDa antigen, the primed CD8+ T cells absorbed IL-2 as efficiently as primed CD4+ T cells. Based on this, it was concluded that the primed CD8+ T cells induced suppression by competition for IL-2. Employing the same model, the MHC restriction of recognition of the suppressor epitope of the 65-kDa antigen by the CD8+ Ts was investigated. The epitopes presented by diverse MHC class II molecules, such as self I-A, I-E and even allogeneic I-E were similar, because they were recognized by the same population of primed CD8+ Ts. Further, immunization of C57BL/6 mice with Ltk-cells expressing H-2 DkKk alloantigens, stimulated CD8+ T cells capable of recognizing M.vaccae 65-kDa antigen. Based on these data, it was proposed that recognition of the suppressor epitope of the 65-kDa antigen by the primed CD8+ Ts exhibits lack of restriction specificity imposed by MHC diversity.

Screening of a cosmid library of Mycobacterium bovis BCG in Mycobacterium smegmatis for novel T-cell stimulatory antigens

We have developed a novel method for screening a Mycobacterium bovis (BCG) cosmid library in Mycobacterium smegmatis for the detection of immunostimulatory T-cell antigens (Ag). Distinctive protein banding patterns were demonstrated in culture filtrates of three of 30 recombinant M. smegmatis clones: pBCCS13 (41 and 73 kDa); pBCCS221 (30, 50 and 68 kDa); pBCCS223 (100 kDa). Western immunoblots indicated that monoclonal antibodies (mAb) directed to the previously characterized 19-, 30-, 38-, 65- and 71-kDa mycobacterial Ag were not reactive with the distinctive recombinant proteins. Furthermore, T-cell Western blots demonstrated that fractions containing the distinctive proteins were immunostimulatory. A given tuberculin-positive donor expressed unique patterns of blastogenic reactivity to protein fractions isolated from each of the three recombinant clones. Restriction enzyme digests of the three recombinant BCG inserts revealed distinctive DNA-banding patterns. The immunostimulatory Ag, therefore, are most likely encoded within different regions of the BCG genome, as contained within three distinct inserts. T-cell Western blots further indicated a heterogeneity in the repertoire of BCG-responsive T cells since tuberculin-positive donors varied in the pattern of reactivity to protein fractions isolated from the same recombinant filtrate. Most likely, immunity to M. tuberculosis results from activation of a heterogeneous array of T cells targeted to multiple immunostimulatory Ag. The method we describe should greatly enhance our ability to define the full spectrum of T-cell Ag encoded by mycobacteria, particularly those which are secreted proteins.

Heat shock (stress) proteins and autoimmunity in rheumatic diseases

The rheumatic diseases (RDs) are characterized by acute and chronic inflammation, and autoimmunity plays a major role in their pathogenesis. RDs are for the most part of unknown etiology, but recent evidence indicates that heat shock or stress proteins (HSPs) may have an important role in the etiology/pathogenesis of RDs. HSPs are produced by prokaryotic and eukaryotic cells and are grouped according to molecular weight. Phylogenetically, HSPs are very old and are remarkably conserved molecules in evolution from bacteria to humans. HSPs are induced by a variety of cellular stresses in addition to heat; cognates are expressed constitutively and are essential in a number of normal functions. Some HSPs serve as molecular chaperones, the latter defined as proteins that mediate folding of other polypeptides and either promote their assembly into oligomeric structures or disassemble the final product. Conservation of structure and function of many HSPs may provide a link between immunity to infection and the autoimmune features of RDs. Evidence is reviewed from clinical and laboratory observations that diverse microbial agents, including viruses, bacteria, and parasites, may have putative roles in the development and pathogenesis of some RDs. HSPs also are discussed in relation to the major histocompatibility complex, HLA antigens, and disease associations and how they may alter the balance between tolerance and autoimmunity. Studies are reviewed that are supportive or nonsupportive of the concept of microbial infection associated with autoimmunity; individuals first react to microbial immunizations or infections with enhanced cellular/humoral responses to the agent's HSPs. With the enhanced immune response, cross-reactivity may occur with an HSP of the stressed host because of structural similarities to the microbial HSP. If all of these events occur, the host's homologous HSP or stressed cells now become true autoantigen(s). This sequence has implications for the etiology of immune-mediated RDs, the concept of epitope sharing, and the accompanying autoimmunity. A recurring theme emphasized in some reports to understand better the role of HSPs in autoimmunity is the need to select patients with early-onset disease. A minor subpopulation of T lymphocytes express a CD3-associated T-cell receptor (TCR) heterodimer composed of gamma and delta polypeptide chains. The gamma delta + T cells have several unique features. When analyzed by the polymerase chain reaction, lymphocytes with TCR-gamma delta appear to reflect the polyclonal expansion of preexisting gamma delta clones. They are found in peripheral lymphoid tissue in very low percentage (< 5%) but may represent the majority of T cells within epithelial tissue.(ABSTRACT TRUNCATED AT 400 WORDS)

Characterization of a stress protein from group B Neisseria meningitidis

Increased levels of a 65-kDa stress protein (Msp65) were observed in group B Neisseria meningitidis grown under stationary-growth conditions. Electron microscopy showed two apposing rings of seven subunits, a structure typical of Escherichia coli GroEL. Msp65 was not found in either the periplasmic space or the outer membrane. Several important differences between the GroEL analogs of N. meningitidis and Neisseria gonorrhoeae are discussed.

Mycobacterium tuberculosis expresses two chaperonin-60 homologs

A 65-kDa protein and a 10-kDa protein are two of the more strongly immunoreactive components of Mycobacterium tuberculosis, the causative agent of tuberculosis. The 65-kDa antigen has homology with members of the GroEL or chaperonin-60 (Cpn60) family of heat shock proteins. The 10-kDa antigen has homology with the GroES or chaperonin-10 family of heat shock proteins. These two proteins are encoded by separate genes in M. tuberculosis. The studies reported here reveal that M. tuberculosis contains a second Cpn60 homolog located 98 bp downstream of the 10-kDa antigen gene. The second Cpn60 homolog (Cpn60-1) displays 61% amino acid sequence identity with the 65-kDa antigen (Cpn60-2) and 53% and 41% identity with the Escherichia coli GroEL protein and the human P60 protein, respectively. Primer-extension analysis revealed that transcription starts 29 bp upstream of the translation start of the Cpn60-1 homolog and protein purification studies indicate that the cpn60-1 gene is expressed as an approximately 60-kDa polypeptide.

Immunization with extracellular proteins of Mycobacterium tuberculosis induces cell-mediated immune responses and substantial protective immunity in a guinea pig model of pulmonary tuberculosis

We have studied the capacity of a selected fraction of Mycobacterium tuberculosis extracellular proteins (EP) released into broth culture by mid-logarithmic-growth-phase organisms to induce cell-mediated immune responses and protective immunity in a guinea pig model of pulmonary tuberculosis. Guinea pigs infected with M. tuberculosis by aerosol but not uninfected control guinea pigs exhibit strong cell-mediated immune responses to EP, manifest by dose-dependent cutaneous delayed-type hypersensitivity and splenic lymphocyte proliferation. Guinea pigs immunized subcutaneously with EP but not sham-immunized control guinea pigs also develop strong cell-mediated immune responses to EP, manifest by dose-dependent cutaneous delayed-type hypersensitivity and splenic lymphocyte proliferation. EP is nonlethal and nontoxic to guinea pigs upon subcutaneous immunization. Guinea pigs immunized with EP and then challenged with aerosolized M. tuberculosis exhibit protective immunity. In five independent experiments, EP-immunized guinea pigs were consistently protected against clinical illness, including weight loss. Compared with EP-immunized guinea pigs, sham-immunized control guinea pigs lost 12.9 +/- 2.0% (mean +/- SE) of their total weight. EP-immunized guinea pigs also had a 10-fold reduction in viable M. tuberculosis bacilli in their lungs and spleens (P = 0.004 and 0.001, respectively) compared with sham-immunized control animals. In the two experiments in which some guinea pigs died after aerosol challenge, EP-immunized animals were protected from death. Whereas all 12 (100%) EP-immunized guinea pigs survived challenge with aerosolized M. tuberculosis, only 6 of 12 (50%) sham-immunized control guinea pigs survived challenge (P = 0.007, Fisher exact test). This study demonstrates that actively growing M. tuberculosis cells release immunoprotective molecules extracellularly, that a subunit vaccine against tuberculosis is feasible, and that extracellular molecules of M. tuberculosis are potential candidates for a subunit vaccine.

Identification and molecular analysis of a 63-kilodalton stress protein from Neisseria gonorrhoeae

Iron limitation, glucose deprivation, and growth under low oxygen supply (environmental stress) increased the expression of several proteins of Neisseria gonorrhoeae, including a 63-kilodalton protein identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This gonococcal stress protein (GSP63) was detected in the cytosol and copurified with lithium acetate-derived outer membranes. Successful purification of the protein was achieved by sucrose density gradient centrifugation and by chromatography on phenyl-Sepharose. Gel filtration of the purified protein revealed a molecular weight of approximately 450,000, suggesting that in its native state, the protein consists of a multimer of six to eight subunits. Isoelectric focusing indicated a pI of 5.2. Immunoblotting experiments using a polyclonal antiserum raised against the purified protein demonstrated cross-reactivity with a protein of the same electrophoretic mobility as GSP63 in all eight gonococcal isolates tested. N-terminal amino acid sequencing of the protein revealed up to 65% homology with members of the Hsp60 heat shock protein family, suggesting that GSP63 is related to this group of proteins. This relationship was further substantiated by the immunological cross-reactivity of GSP63 with mycobacterial Hsp60 and the ATP-binding activity of the gonococcal stress protein.

Spleen cell cytokine secretion in Mycobacterium bovis BCG-infected mice

Three susceptible mouse strains, i.e., BALB/c (H-2d), C57BL/6 (H-2b), and major histocompatibility complex-congenic BALB.B10 (H-2b), were infected intravenously with 4 x 10(6) CFU of live Mycobacterium bovis BCG and analyzed 4 weeks later for in vitro spleen cell cytokine secretion in response to purified protein derivative (PPD), BCG culture filtrate (CF), BCG cellular extract, total BCG, the purified extracellular 30-32-kDa antigen (the fibronectin-binding antigen 85), or the intracellular 65-kDa heat shock protein. C57BL/6 and BALB.B10 mice produced 5- to 10-fold more gamma interferon and interleukin-2 (IL-2) when stimulated with CF, PPD, and antigen 85 than BALB/c mice did. When stimulated with BCG extract and whole BCG, gamma interferon and IL-2 levels were generally lower and comparable in the three strains. IL-4 was detected in spleen cell culture supernatants from infected BALB/c mice but not from C57BL/6 or BALB.B10 mice. IL-5 could not be detected. C57BL/6 and BALB.B10 spleen cells also produced more tumor necrosis factor alpha and IL-6 after stimulation with PPD and CF than BALB/c cells did. Finally, BCG vaccination generated efficient protective immunity in C57BL/6 and BALB.B10 mice but not in BALB/c mice. These data suggest that secreted mycobacterial CF antigens selectively induce a strong TH1 response in BCG-infected C57BL/6 and BALB.B10 mice, whereas in BALB/c mice this response is partly counterbalanced by TH2 cells.

The humoral immune response after BCG vaccination: an immunoblotting study using two purified antigens

The specific IgG response induced by BCG vaccination was investigated in 27 adults using two purified BCG antigens in a dot immunoblotting assay. The reflectance values increased significantly after vaccination when P64 but not when P32 was used as the antigen. The values measured after vaccination were compared with those obtained when testing sera from patients with tuberculosis. We observed that the level of anti-P64 IgG reached after BCG immunization was high enough to preclude a serological differential diagnosis with tuberculosis.

A 64 kDa protein from Mycobacterium bovis BCG shares the same antigenic determinants with line 10 hepatoma cells and has anti-line 10 tumor activity

A 64 kilodalton (kDa) surface protein was isolated from the water-extracted materials from Mycobacterium bovis strain BCG, the determinants of which are antigenically shared by a 64 kDa major surface antigenic component of line 10 hepatoma cells. The 64 kDa protein showed anti-line 10 tumor activity in pre-immunized guinea pigs, and this suggest that the BCG 64 kDa protein is probably identical with the tumor specific antigen.

Heat-shock protein 60: implications for pathogenesis of and protection against bacterial infections

In this review we have focused on antigenic features of hsp 60 related to: its ubiquitous distribution in the biosphere; its extraordinary homology among various bacteria; its high conservation from prokaryotic to eukaryotic cells; and its abundant expression under stress situations occurring during infection. These unique features make hsp 60 an excellent candidate antigen relevant to protection and pathogenesis of bacterial infections and, perhaps in a broader sense, to surveillance and autoimmunity. We will briefly discuss these possibilities in the following. Acquired resistance. If we assume that bacterial organisms contain some thousand different proteins which all represent potential antigens, the frequency of T cells with specificity for mycobacterial hsp 60 appears surprisingly high. Although, during the course of infection, high levels of hsp may be induced in bacteria, mere abundance appears to be an important though insufficient explanation. In addition, constant boosting by similar hsp 60 cognates from various microbes with which humans come into contact may contribute to dominance. This could easily explain the occurrence of hsp 60-specific T cells in healthy individuals with no clinical history of mycobacterial infections. Involvement of more sophisticated mechanisms, such as the affinity of hsp to other proteins, cannot be excluded (Flynn et al. 1989). Yet dominance does not necessarily mean protection and definite proof that hsp are protective antigens is lacking. Perhaps the immune response against epitopes shared by various mycobacterial pathogens represents a first line of defence preceding a more specific immune response. Such broadly reactive antigens would not qualify as prime candidates for vaccine design. Immunesurveillance. T cells with specificity for epitopes shared by bacterial and human hsp 60 are readily demonstrable and stressed host cells are recognized by hsp 60-specific T cells. Such T lymphocytes are endowed with the capacity to identify host cells stressed by a variety of assaults such as inflammation, infection, trauma, or transformation. Although it has been claimed that hsp-reactive gamma/delta T cells are particularly destined for such surveillance functions (Born et al. 1990, Asarnow et al. 1988), alpha/beta T cells could also participate. Pathogenesis. The mechanisms causing pathogenesis should be similar to those underlying protection and surveillance. In the former case bacterial hsp would be responsible for both induction of immunity and expression of pathogenic reactions; in the latter case an immune response stimulated by conserved regions of bacterial hsp 60 would be converted against a host-derived cognate.(ABSTRACT TRUNCATED AT 400 WORDS)

Association between the 65-kilodalton heat shock protein, Streptococcus sanguis, and the corresponding antibodies in Behçet's syndrome

The etiology of Behcet's syndrome (BS) is unknown, but a number of streptococcal species have been implicated. A hypothesis was postulated that a shared antigen, such as a stress protein, might account for some of these findings. Indeed, a rabbit antiserum against a 65-kDa heat shock protein of Mycobacterium tuberculosis revealed a corresponding 65-kDa band with all six Streptococcus sanguis strains examined and S. pyogenes but not with S. salivarius. By applying a panel of nine monoclonal antibodies to the mycobacterial 65-kDa heat shock protein, an approximately 65-kDa antigen was identified in the uncommon serotypes of S. sanguis ST3 and H.83 and one with a different Mr was identified in KTH-1 and S. pyogenes. Monoclonal antibodies Y1.2, C1.1, II H9, and ML30, which reacted with these streptococci, recognize residues 11 to 27, 88 to 123, 107 to 122, and 276 to 297 of the 65-kDa heat shock protein, respectively, suggesting that these residues are conserved among some uncommon serotypes of S. sanguis and S. pyogenes. Immunoblot analyses of sera from patients with BS for immunoglobulin A (IgA) and IgG antibodies revealed bands of 65 to 70 kDa with the mycobacterial heat shock protein, S. sanguis strains, and S. pyogenes, although these reactivities were also found to a lesser extent in controls. A 65- to 70-kDa band was found more frequently with S. sanguis KTH-2 or KTH-3 and IgA in serum from patients with BS than with serum from controls (P less than 0.02). Antibodies in serum were then studied by a radioimmunoassay, and in patients with BS this revealed significantly raised IgA antibodies to the recombinant 65-kDa mycobacterial heat shock protein and to soluble protein extracts of S. sanguis ST3, KTH-1, KTH-2, and KTH-3. Whereas significant anti-65-kDa heat shock protein and anti-S. sanguis ST3 antibodies were also found in sera from patients with rheumatoid arthritis and recurrent oral ulcers, the anti-S. sanguis KTH-1, KTH-2, and KTH-3 antibodies were confined to BS. The results are consistent with the hypothesis that some of the streptococcal antigens are associated with heat shock or stress proteins, which will need to be formally established by isolating heat shock proteins from streptococci.

Purification and characterization of major antigens from a Mycobacterium bovis culture filtrate

Ten major antigens from Mycobacterium bovis culture filtrate of 39, 32, 30, 25, 24, 22 (a and b forms), 19, 15, and 12 kDa have been purified and characterized by classical physicochemical methods. With monoclonal antibodies and/or N-terminal amino acid sequencing data, it was found that the antigens of 32, 30, 24, 22 (a), 19, and 12 kDa are related to M. bovis or M. tuberculosis antigens P32, MPB59, MPB64, MPB70, 19 kDa, and 12 kDa, respectively. The 39-, 25-, 22 (b)-, and 19-kDa antigens showed concanavalin A-binding properties and were positive in a glycan detection test, suggesting that they are glycoproteins. The 25- and 22 (b)-kDa proteins were found to be glycosylated forms of MPB70.

Heat-shock proteins and autoimmunity in humans

T cells and antibodies against self and non-self hsp are present in both patients and healthy controls. T cells responding to hsp65 can be involved in autoimmune diseases, this was demonstrated for two site-specific animal autoimmune diseases: AA in Lewis rats and diabetes (IDDM) in NOD mice. In human ReA there is evidence for a direct stimulation of joint T cells by antigens of the organisms causing the infection which precedes the joint inflammation. The individual antigens of the triggering bacteria still have to be defined, but hsp65 may be of importance since this is one of the molecules recognized by synovial T cells in ReA patients. In RA there are no clear data implicating an infection in the initiation of joint inflammation, but mycobacteria have been suggested to be involved. We have discussed experimental findings which are in favor of, or in contradiction with, a role of mycobacterial antigens--particularly hsp65--in the etiology of RA. T cells recognizing hsp65 and other mycobacterial antigens are present in the joint, but there is no indication for a specific involvement of one or a limited set of (myco)bacterial antigens in the pathogenesis of RA.

Genus-specific epitope on the 60-kilodalton Legionella heat shock protein recognized by a monoclonal antibody

A monoclonal antibody (MAb) immunoglobulin G2a (2125) was produced against a 60-kDa Legionella heat shock protein (HSP), recognizing a unique epitope common to all species of the genus Legionella. The antibody reacted in the immunoblot with 59 Legionella species and serogroups that were tested and showed no cross-reactivity with other bacteria, including Acinetobacter spp., Bordetella spp., Pseudomonas spp., Mycobacterium spp., and Escherichia coli. Two other MAbs (2122 and 2130) reacted with the 60-kDa Legionella protein as well but showed different cross-reactivities with other gram-negative bacteria in the same molecular mass range. The genus-specific MAb 2125 as well as the cross-reacting MAbs 2122 and 2130 were shown to be reactive with the expressed protein of the cloned gene of the 60-kDa HSP of Legionella micdadei and Legionella pneumophila. These antibodies demonstrate that Legionella-specific and nonspecific epitopes are present on this protein. A sandwich enzyme-linked immunosorbent assay (ELISA) in which the genus-specific MAb is used both as a capture antibody and as a biotinylated second antibody has been established. With this test it is possible to detect Legionella whole cells, sonicated cells, and cell fractions containing the 60-kDa HSP. The main part of the 60-kDa HSP is found in the cytoplasmic fraction. The sandwich ELISA can be used to demonstrate the increased expression of the 60-kDa protein in Legionella cells following heat shock as well as marked differences in the detection of the 60-kDa HSP on whole cells of different Legionella strains. The high specificity and sensitivity of the sandwich ELISA for sonicated cells might be very useful to screen on a genus level for Legionella cells or the 60-kDa antigen in environmental isolates or body fluids of patients.

Carrier effect of concanavalin A-reactive and -non-reactive material in tuberculin PPD

Tuberculin purified protein derivative (PPD) is a very potent T-cell reactive material in tuberculin-positive individuals, but the components responsible for this reactivity have not been adequately defined. Three purified mycobacterial proteins (MPB70, the BCG 65-kDa protein, and BCG antigen 85B) with different degrees of temperature sensitivity were iodine-labelled and added to BCG culture fluid, and the mixtures were autoclaved at 120 degrees C for 30 min to simulate the initial heating procedure used to prepare PPD. SDS-PAGE followed by protein staining and autoradiography showed that the banded pattern of unheated culture fluid was completely lost after heating, and only the labelled MPB70 preparation retained most of the radioactivity in a fraction with soluble protein of the same size. Most mycobacterial proteins are extensively denatured by these procedures, which explains the previous extensive difficulties in isolating defined constituents from PPD to characterize their behaviour in B- and T-cell reactions. In assays for the carrier effect of NIP-PPD for induction of anti-NIP production in BCG-vaccinated mice, the active fractions were heterogeneous in lectin reactivity as well as in SDS-PAGE. It appears most likely that a number of Mycobacterium tuberculosis proteins give rise to core peptides which resist proteolysis and heat denaturation to possess powerful T-cell-activating ability.

Integration of monoclonal antibodies in quantitative immunoelectrophoresis by indirect immunoprecipitation

Characterization of the specificity of monoclonal antibody in crossed immunoelectrophoresis has been achieved by mixing the monoclonal antibody with mycobacterial antigen in the circular antigen well. After electrophoresis in the first dimension, the separated antigens and antigen complexed with monoclonal antibody were run into an intermediate gel containing rabbit anti-mouse immunoglobulin and a top gel with polyvalent rabbit anti-BCG immunoglobulin. Monoclonal antibody with bound antigen precipitated in the intermediate gel while the other antigens precipitated in their reference positions. The method was simple, efficient and sensitive. Selected monoclonal antibodies were used to demonstrate the characteristic features of the method. In rocket immunoelectrophoresis the rocket height of a monoclonal antibody may be significantly altered by adding the relevant antigen. This principle can be exploited when the polyvalent antibodies do not precipitate the antigen, and it may be used for efficient screening of monoclonal hybridoma culture supernatants. This approach may permit the quantitation of an antigen when only monoclonal antibody is available.

Induction of antigen-specific CD4+ HLA-DR-restricted cytotoxic T lymphocytes as well as nonspecific nonrestricted killer cells by the recombinant mycobacterial 65-kDa heat-shock protein

Acquired cell-mediated immunity to intracellular parasites like mycobacteria is dependent on antigen-specific T lymphocytes. We have recently found that mycobacteria not only induce helper T cells but also cytotoxic CD4+ and/or CD8+ T cells as well as nonspecific killer cells that lyse human macrophages in vitro. In addition, we have described that the recombinant heat-shock protein (hsp) 65 of Mycobacterium bovis BCG/M, tuberculosis is an important target antigen for CD4+CD8- cytotoxic T cells. We have now further investigated the cytotoxic effector cells that are induced by the hsp65 of BCG. Purified protein derivative of tuberculin (PPD)- or hsp65-specific cytotoxic T cells specifically lysed PPD, hsp65 of BCG and hsp65 of M. leprae-pulsed macrophages in an HLA-DR-restricted manner. Nonpulsed macrophages were lysed to a much lower but still significant extent. hsp65-induced effector cells expressed CD3, CD5, CD4, CD8 and CD56 markers. Depletion experiments showed that the antigen-specific HLA-DR-restricted killer cell was of the CD5+CD4+CD8-CD56- phenotype. Experiments using N-terminal truncated hsp65 fusion (cro-lacZ) proteins suggested that the N-terminal 65 amino acid residues of the 540 amino acid molecule are critical for the expression of the cytotoxic target epitope(s) in two individuals tested. In addition to inducing antigen-specific cytotoxic effector cells, the hsp65 also triggered nonspecific nonrestricted effector cells with lytic activity against nonpulsed autologous or allogeneic macrophages as well as K-562 and Daudi tumor cells. hsp65-stimulated effector cells produced both interferon and tumor necrosis factor-alpha. An important finding was that hsp65-stimulated effector cells strongly inhibited colony-forming unit formation from live BCG-infected autologous macrophages.

Chlamydial disease pathogenesis. The 57-kD chlamydial hypersensitivity antigen is a stress response protein

Chlamydia trachomatis infection of humans is commonly a localized inflammation that can result in infertility, blindness, and perhaps arthritis. The pathogenic process(es) that cause these sequelae are thought to be immunological. A 57-kD protein that is common among Chlamydia elicits ocular inflammation when introduced onto the conjunctivae of guinea pigs or nonhuman primates previously sensitized by chlamydial infection. This protein is thought to mediate the immunopathology that follows chlamydial infection. To more thoroughly characterize this chlamydial component, we cloned its gene from a C. psittaci strain and identified a particular recombinant that produced the 57-kD polypeptide. The recombinant gene product was immunoreactive with a monospecific anti-57-kD serum, and elicited an ocular inflammation similar to that produced by the 57-kD antigen isolated from chlamydiae. Sequencing identified two ORFs that encode polypeptides of 11.2 and 58.1 kD and are co-transcribed. These two polypeptides show homology with Escherichia coli groE and Coxiella burnetii htp heat-shock proteins. Striking homology (greater than 50%) was found between the 57-kD protein and the HtpB, GroEL, 65-k Mycobacterium tuberculosis and Hsp60 proteins. Thus, the 57-kD chlamydial protein, previously implicated as mediating a deleterious immunologic response to chlamydial infections, is a stress-induced protein similar to those that occur universally in both prokaryotic and eukaryotic organisms.

Serological response of patients with leprosy to a 28- to 30-kilodalton protein doublet from early cultures of Mycobacterium bovis BCG

Analysis by Western immunoblotting of Mycobacterium bovis BCG short-term culture filtrates with a pool of serum samples from lepromatous leprosy patients revealed an immunodominant protein doublet with apparent molecular masses of 28 and 30 kilodaltons (kDa). The humoral response to these antigens was also investigated by using individual serum samples from patients representative of the whole spectrum of leprosy and from tuberculosis patients, as well as from contacts of leprosy patients and control groups. The protein doublet was recognized by 92% of the sera from patients with lepromatous leprosy (51 of 56), whereas essentially negative results were obtained with sera from the other groups. Similar immunodominant bands were also detected by Western blotting analysis of sonic extracts of seven other slow- and fast-growing mycobacterial species, suggesting a broad distribution of these antigens within the genus. Analysis of the purified doublet by Western blotting after two-dimensional gel electrophoresis fractionation showed that the 28- and 30-kDa doublet consisted of at least five different components with pls from 5.2 to 5.7 and molecular masses from 28 to 31 kDa. These results indicate that the protein doublet could be used as a potential marker in the diagnosis of lepromatous leprosy.

Leprosy: understanding protective immunity

Analyses of these recombinant proteins as antigens represent the beginning of understanding the chemical nature of epitopes of M. leprae. Their role in protective immunity remains to be elucidated. The available models for analysing protective immunity include infection with M. leprae in the mouse footpad, in immuno-deficient mice, in armadillos and certain susceptible primates. None is completely satisfactory and only the mouse footpad has been applied to assess the protective efficacy of individual antigens. The workshop emphasized that the gulf between understanding immunogenicity and protective immunity is wide. Bridging this gulf is essential for the rational design of a new generation vaccine against leprosy.

Isolation of CD4- CD8- mycobacteria-reactive T lymphocyte clones from rheumatoid arthritis synovial fluid

The majority of peripheral T cells express a heterodimeric, alpha/beta T-cell receptor, which recognizes specific antigenic peptides bound to self major histocompatibility complex (MHC) molecules, and either the CD4 or CD8 surface markers. An additional subset of T cells, whose physiological function is unknown, express a distinct CD3-associated receptor composed of gamma and delta chains. This subset includes cells lacking both CD4 and CD8 surface markers, which may be involved in autoimmunity. The recognition specificity of the gamma/delta receptors is not well characterized and has been defined in only one case to date, a murine cell line which shows MHC-linked specificity. In this report, we describe the isolation of CD4- CD8-, gamma/delta TCR bearing T cell clones from the synovial fluid of a rheumatoid arthritis patient. These T cell clones respond specifically to mycobacterial antigens without MHC restriction.