The Mycobacterium tuberculosis BCG-a protein has homology with the Escherichia coli GroES protein

Anti-obesity effect and protection of liver-kidney functions by Codium fragile sulphated polysaccharide on high fat diet induced obese rats

The present study investigates the hypolipidemic effects of sulphated polysaccharide obtained from Codium fragile (CFSP) in induced obese rats (HFD). The results showed an increase in body weight of HFD rats by 21.56% as compared to control normal rats. Moreover, serum lipase activity underwent an increase which led to an increase in the levels of total cholesterol (T-Ch), triglycerides (TG) and low density lipoprotein cholesterol (LDL-Ch) in serum associeted with a decrease in the level of high density lipoprotein cholesterol (HDL-Ch) in untreated HFD rats. This diet has disrupted the antioxidant status by decreasing the activities of antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX)) and subsequently an increase in thiobarbituric acid reactive substances (TBARS) level in liver and kidney of obese rats. All these disturbances are significantly corrected by CFSP administration with no fatty deposits in the liver and a protective effect against renal histological alteration. This confirms the important role of this polysaccharide in the fight against oxidative stress and the prevention of hyperlipidemia.

Multiple chaperonins in bacteria--novel functions and non-canonical behaviors

Chaperonins are a class of molecular chaperones that assemble into a large double ring architecture with each ring constituting seven to nine subunits and enclosing a cavity for substrate encapsulation. The well-studied Escherichia coli chaperonin GroEL binds non-native substrates and encapsulates them in the cavity thereby sequestering the substrates from unfavorable conditions and allowing the substrates to fold. Using this mechanism, GroEL assists folding of about 10-15 % of cellular proteins. Surprisingly, about 30 % of the bacteria express multiple chaperonin genes. The presence of multiple chaperonins raises questions on whether they increase general chaperoning ability in the cell or have developed specific novel cellular roles. Although the latter view is widely supported, evidence for the former is beginning to appear. Some of these chaperonins can functionally replace GroEL in E. coli and are generally indispensable, while others are ineffective and likewise are dispensable. Additionally, moonlighting functions for several chaperonins have been demonstrated, indicating a functional diversity among the chaperonins. Furthermore, proteomic studies have identified diverse substrate pools for multiple chaperonins. We review the current perception on multiple chaperonins and their physiological and functional specificities.

Effect of Mycobacterium tuberculosis chaperonins on bronchial eosinophilia and hyper-responsiveness in a murine model of allergic inflammation

BACKGROUND

Epidemiological evidence suggests that infection with Mycobacterium tuberculosis protects children against asthma. Several laboratories have shown that, in mouse models of allergic inflammation, administration of the whole live tuberculosis vaccine, Mycobacterium bovis bacillus Calmette-Guerin (BCG), prevents ovalbumin (OVA)-induced pulmonary eosinophilia.

OBJECTIVE

The aim of this study was to characterize specific M. tuberculosis molecules that are known to modulate immune responses to see if they affected pulmonary eosinophilia and bronchial hyper-responsiveness.

METHODS

C57Bl/6 mice were sensitized to OVA on days 0 and 7 and subsequently challenged with OVA on day 14 over a 3-day period. Pulmonary eosinophilia and bronchial hyper-responsiveness were measured 24 h following the last antigen challenge. In some groups, mice were pre-treated with M. tuberculosis or M. tuberculosis chaperonins (Cpns)60.1, 60.2 and 10, and the effect of this treatment on the allergic inflammatory response to aerosolized OVA was established.

RESULTS

We show that M. tuberculosis Cpns inhibit allergen-induced pulmonary eosinophilia in the mouse. Of the three Cpns produced by M. tuberculosis, Cpn60.1, Cpn10 and Cpn60.2, the first two are effective in preventing eosinophilia when administered by the intra-tracheal route. Furthermore, the increase in airways sensitivity to inhaled methacholine following OVA challenge of immunized mice was suppressed following treatment with Cpn60.1. The allergic inflammatory response was also characterized by an increase in Th2 cytokines IL-4 and IL-5 in bronchoalveolar lavage fluid, which was also suppressed following treatment with Cpn60.1.

CONCLUSION

These data show that bacterial Cpns can suppress eosinophil recruitment and bronchial hyper-responsiveness in a murine model of allergic inflammation.

T-cell recognition of mycobacterial GroES peptides in Thai leprosy patients and contacts

We report here the mapping of T-cell-stimulatory determinants of the GroES 10-kDa heat shock protein homologues from Mycobacterium leprae and Mycobacterium tuberculosis, which are known as major immunogens in mycobacterial infections. Peripheral blood mononuclear cells (PBMC) from treated tuberculoid leprosy or lepromatous leprosy patients and from healthy household or hospital staff contacts of the patients were cultured with 20 16-mer peptides covering the entire sequences of both M. leprae and M. tuberculosis GroES. The total number of recognized peptides was found to be the largest in family contacts, while responder frequencies to the individual tested peptides varied (5 to 80%) with specificity between the patient and contact groups. Proliferative responses to some peptides showed positive or negative associations of low statistical significance with DR and DQ alleles, though responses to most GroES peptides were genetically permissive. Notably, the sequence of the 25-40 peptide of M. leprae, but not that of M. tuberculosis, was more frequently stimulatory in tuberculoid leprosy patients than in either group of sensitized healthy contacts. This peptide bound to a number of HLA-DR molecules, of which HLA-DRB5*0101 had the strongest affinity. The epitope core binding to this allele was localized to the 29-to-37 sequence, and its key residue was localized to the M. leprae-specific glutamic acid at position 32. This epitope may be of interest for the development of a blood test- or skin test-based diagnostic reagent for tuberculoid leprosy, subject to further clinical evaluation in untreated patients.

Predominant recognition of species-specific determinants of the GroES homologues from Mycobacterium leprae and M. tuberculosis

The Mycobacterium leprae and M. tuberculosis 10,000 MW heat-shock protein homologues of GroES have previously been identified as major immunogens for human T cells. We used synthetic peptides to characterize the determinants recognized by murine T cells. The findings suggest that, despite 90% sequence identity between these two proteins, T cells recognize prominently the species-specific determinants localized within amino acid residues 21-40 and 49-72. Analysis of the molecular determinants of species-specificity for the M. leprae GroES sequence 25-40, using T-cell hybridomas and major histocompatibility complex (MHC)-binding assays, led to the identification of epitope cores and critical residues. Interestingly, closely overlapping epitope cores were found to be restricted by either H-2Ad (24-34) or H-2Ed (28-34). Furthermore, the site recognized by the M. leprae-specific monoclonal antibodies ML06 and ML10 was also localized in the overlapping sequences 25-31 and 25-29. In conclusion, we demonstrated that immunodominant species-specific T- and B-cell epitopes can be found in a mycobacterial heat-shock protein despite its highly conserved amino acid sequence. This finding suggests the feasibility of identifying a sufficient number of M. leprae-specific determinants for a composite T-cell immunodiagnostic reagent for tuberculoid leprosy.

An mpb-64 flanking sequence specific for Mycobacterium bovis

A clone carrying a plasmid with the mpb-64 gene and 3' flanking sequences (plasmid pMBA122) was detected during the screening of a Mycobacterium bovis genomic library with sera from infected cattle. When the pMBA122 insert was used as a probe in Southern blots against PvuII-digested mycobacterial DNA, it distinguished the different M. tuberculosis complex species. This probe hybridized with a 7-kb band in M. tuberculosis, a 5-kb band in M. bovis and a 3-kb band in M. tuberculosis complex strains from wild seals. Smal genomic digestions enabled us to locate this polymorphic region downstream of the mpb-64 gene. In order to clone this particular region, we designed a pair of PCR primers. Unexpectedly, these primers amplified only M. bovis DNA; no amplification was seen in M. tuberculosis DNA. When the annealing temperature was lowered from 70 to 55 degrees C, an amplification product of the same size was obtained with M. tuberculosis. This product was cloned and sequenced, and showed partial homology to the M. bovis amplified fragment. Therefore, this region comprises M. bovis sequences with a lower homology with M. tuberculosis than other compared sequences. This suggests that a more precise differentiation method at the species level for the M. tuberculosis complex could be achieved using PCR directed to this region.

Human humoral responses to antigens of Mycobacterium tuberculosis: immunodominance of high-molecular-mass antigens

The selection of antigens of Mycobacterium tuberculosis for most studies of humoral responses in tuberculosis patients has been restricted to molecules that were either immunodominant in immunized animals or amenable to biochemical purification rather than those that were reactive with the human immune system. Delineation of antigens that elicit humoral responses during the natural course of disease progression in humans has been hindered by the presence of cross-reactive antibodies to conserved regions on ubiquitous prokaryotic antigens in sera from healthy individuals and tuberculosis patients. The levels of cross-reactive antibodies in the sera were reduced by preadsorption with Escherichia coli lysates, prior to studying their reactivity against a large panel of M. tuberculosis antigens to which the human immune system may be exposed during natural infection and disease. Thus, reactivity against pools of secreted, cellular, and cell wall-associated antigens of M. tuberculosis was assessed by an enzyme-linked immunosorbent assay (ELISA). Initial results suggested that the secreted protein preparation contained antigens most frequently recognized by the humoral responses of pulmonary tuberculosis patients. The culture filtrate proteins were subsequently size fractionated by preparative polyacrylamide gel electrophoresis, characterized by reaction with murine monoclonal antibodies to known antigens of M. tuberculosis by an ELISA, and assessed for reactivity with tuberculous and nontuberculous sera. Results show that a secreted antigen of 88 kDa elicits a strong antibody response in a high percentage of patients with pulmonary tuberculosis. This and other antigens identified on the basis of their reactivity with patient sera may prove useful for developing serodiagnosis for tuberculosis.

Expression and functional characterisation of the clpC gene of Mycobacterium leprae: ClpC protein elicits human antibody response

This paper reports the expression of a previously described gene [Nath and Laal, Nucleic Acids Res. 18 (1990) 4935], currently identified as the clpC gene of Mycobacterium leprae, using an in vitro rabbit reticulocyte lysate-coupled transcription/translation system. The produced protein moved as a 95-kDa band on SDS-PAGE. An additional band of 79 kDa was seen which may have resulted from a GTG codon downstream to the initiating ATG in the clpC sequence. A threefold increase in synthesis of the 95-kDa protein was achieved by altering the translation codon context sequence of the ATG start codon. The ClpC (caseinolytic protease C) amino acid sequence, which contained two nucleotide-binding sites, exhibited in vitro ATP binding. Of functional significance was its immunoreactivity in human subjects with mycobacterial infection. Leprosy and tuberculosis patients with active disease had antibodies which recognised ClpC in dot ELISA.

The large, free-living amoebae: wonderful cells for biological studies

The large, free-living amoebae have been widely used as model cells for studying a variety of biological phenomena, including cell motility, nucleocytoplasmic interactions, membrane function, and symbiosis. Results of studies by our group on amoebae as moving cells, as material for micrurgical manipulations, and as hosts for intracellular symbionts are summarized here. In particular, our recent studies of the amoeba as a microcosm, in which spontaneously infecting foreign microbes have become integrated as necessary cell components, are described in some detail. These processes have involved an initial microbial infection, mutual adaptation by the host and symbionts, and development of obligatory symbiosis. Evidence is presented to show that symbiont-derived macromolecules are involved in the protection of symbionts from digestion, the symbionts have acquired regulatory elements on their chromosomal genes to enhance production of beneficial gene products, and symbionts apparently utilize host-derived macromolecules to their benefit. These studies involved morphological observations both at light and electron microscopic levels, physiological and genetic studies, production and use of poly- and monoclonal antibodies, and molecular-biological approaches including gene cloning and sequencing. It is shown that amoebae are uniquely suited as model cells with which to study these phenomena.

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.

Structural proteins of mycobacteriophage I3: cloning, expression and sequence analysis of a gene encoding a 70-kDa structural protein

The structural proteins of mycobacteriophage I3 have been analysed by sodium dodecyl sulfate-polyacrylamide-gel electrophoresis (SDS-PAGE), radioiodination and immunoblotting. Based on their abundance the 34- and 70-kDa bands appeared to represent the major structural proteins. Successful cloning and expression of the 70-kDa protein-encoding gene of phage I3 in Escherichia coli and its complete nucleotide sequence determination have been accomplished. A second (partial) open reading frame following the stop codon for the 70-kDa protein was also identified within the cloned fragment. The deduced amino-acid sequence of the 70-kDa protein and the codon usage patterns indicated the preponderance of codons, as predicted from the high G+C content of the genomic DNA of phage I3.

Identification of bovine T-cell epitopes for three Mycobacterium bovis antigens: MPB70, 19,000 MW and MPB57

Bovine tuberculosis remains a serious problem in several regions, partly due to a lack of specific diagnostic tests. The aim of this study was to identify bovine T-cell epitopes for defined Mycobacterium bovis antigens using an experimental model of the natural disease. Panels of synthetic peptides (16-mers with five residue overlaps) were produced from published amino acid sequences for MPB70, the 19,000 MW antigen and MPB57. In vitro lymphocyte proliferation assays were used to identify T-cell epitopes. Lymphocytes from experimentally infected cattle proliferated in response to five epitopes (residues 88-105 and 144-163 for MPB70; 1-16 and 67-84 for the 19,000 MW antigen; and 85-100 for MBP57). These epitopes were not recognized by control, non-infected animals, but were recognized by field reactors to intradermal tuberculin testing. All five epitopes were recognized by three different breeds of cattle (Friesian, Charolais and Simmental). In addition, the bovine T-cell epitopes identified for the 19,000 MW antigen in this study were similar to epitopes previously reported for man and mouse. Thus, as well as identifying candidate reagents for improved diagnostic tests and vaccination, this study provides evidence for genetic promiscuity T-cell recognition of major myobacterial epitopes.

Induction of Mycobacterium avium gene expression following phagocytosis by human macrophages

Little is known about the bacterial factors that enable pathogenic mycobacteria to survive and multiply within the macrophages of the infected host. By preparing cDNA from Mycobacterium avium bacilli grown in human-derived macrophages and in broth culture and using subtractive hybridization to remove commonly expressed genes, a procedure was developed to identify genes of M. avium that are specifically expressed when the bacilli are growing within macrophages. Total RNA was isolated from M. avium recovered 5 days after infection of human macrophages and from bacilli grown in vitro in broth. Mycobacterial mRNAs were converted to cDNA by reverse transcription. Biotin-modified cDNAs prepared from M. avium grown in broth culture were used to subtract the housekeeping genes from the cDNAs of the macrophage-derived M. avium. After each round of subtraction, a sample of the unsubtracted cDNA was amplified, labeled, and hybridized to cosmid clones of M. avium DNA. After three rounds of subtraction, the amplified DNA hybridized to approximately 1% of the cosmid clones under stringent conditions. Although the majority of the genes that are induced in phagocytized M. avium cells are expressed in the broth-grown bacilli, one DNA fragment that was identified coded for an mRNA that is highly specific for M. avium in phagosomes. This procedure will be especially useful for identifying genes that are expressed in response to growth in specific environments from organisms with genetic systems that are not well characterized.

Immunological evaluation of a 12-kilodalton protein of Mycobacterium tuberculosis by enzyme-linked immunosorbent assay

OBJECTIVE

To purify and study the seroreactivity of native and recombinant 12-kilodalton protein of Mycobacterium tuberculosis H37Rv.

DESIGN

M. tuberculosis H37Rv cells and Escherichia coli XL-1 containing the plasmid PRL4 encoding the M. tuberculosis heat shock protein GroES homolog were used as sources for the purification of native and recombinant 12 kD of M. tuberculosis respectively. The seroreactivity of the 12 kDs was studied by ELISA using sera from 35 leprosy and 25 active pulmonary tuberculosis (TB) patients, and from 10 normal healthy controls.

RESULTS

The 12 kD protein was purified from H37Rv extract (s12 kD) and from recombinant E. coli (r12 kD) by ultrafiltration and MonoQ fast pressure liquid chromatography (FPLC). Analysis of s12 kD and r12 kD by SDS-PAGE revealed a single protein band in both cases with an approximate molecular weight of 12,000 which was recognized by monoclonal antibody SA-12 in immunoblotting. Both the proteins exhibited a pI of approximately 4.6 by isoelectric focusing. Both the 12 kD proteins exhibited 96% positivity with TB sera as compared to normal control sera (P < 0.01). Only one serum sample from the 35 leprosy sera tested exhibited binding to both the s12 kD and r12 kD proteins. Delayed type hypersensitivity reaction to the 12 kD proteins was elicited in guinea pigs that had been immunized with H37Rv sonicate.

CONCLUSION

The 12 kD protein could be easily purified and could serve as a valuable serodiagnostic tool in the screening of TB cases from a large population in an endemic area.

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)

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.

Nucleotide sequence analysis and serologic characterization of a 27-kilodalton Mycobacterium intracellulare lipoprotein

Disseminated mycobacteremia resulting from Mycobacterium avium-Mycobacterium intracellulare complex (MAC) infections frequently contribute to the morbidity and mortality seen in AIDS patients. To better understand the immunopathology of MAC disease and to identify molecules that may have potential diagnostic and vaccine utility, an immunoreactive M. intracellulare protein (MI43) and the gene encoding this antigen were characterized. Southern blot hybridizations demonstrated that MI43 gene probes reacted only with genomic DNA from M. intracellulare, M. avium, and Mycobacterium asiaticum and not with DNA isolated from 11 other mycobacterial species. Nucleotide sequence analysis showed that the MI43 gene encodes a 27-kDa protein which contains a consensus bacterial lipoprotein processing sequence. Detergent-phase separations and metabolic labeling with [3H]palmitate also suggested that MI43 is a lipoprotein. Serological assays demonstrated that recombinant MI43 fusion proteins react with sera from M. avium-infected mice, sera from patients with MAC disease, and sera from patients with active tuberculosis. These results further suggest that mycobacterial lipoproteins are important immunogens that should be considered in the development of improved mycobacterial vaccines and diagnostic reagents.

Antibody responses to the chlamydial heat shock proteins hsp60 and hsp70 are H-2 linked

The effects of both H-2 and non-H-2 genes on antibody responses to two Chlamydia trachomatis heat shock proteins (hsp60 and hsp70) were investigated. These chlamydial proteins are homologs of Escherichia coli GroEL (hsp60) and DnaK (hsp70) and are highly sequence conserved between bacterial and mammalian sources. Antibody responses among 17 different strains of mice immunized with C. trachomatis serovar B and serovar C elementary bodies were evaluated by immunoblot, radioimmunoprecipitation and enzyme-linked immunosorbent assay. Antibody responses to the two proteins displayed host genetic restriction. Of six distinctive H-2 haplotypes, only H-2d generated high antibody responses to hsp70. Five of the six H-2 haplotypes, i.e., H-2a, H-2d, H-2k, H-2q, and H-2s, produced high antibody responses to hsp60. Only the H-2b-bearing strain had low antibody responses to hsp60. By using congenic and H-2 recombinant strains, the genes responsible for regulating antibody responses to hsp70 and hsp60 were mapped to the K-IA region of the H-2 locus. In F1 hybrid crosses between high and low responders, high responses to hsp60 and hsp70 were dominant traits. Other genes outside the H-2 locus also influenced antibody responses to hsp60 and hsp70, since inbred strains of identical H-2 but different background genes displayed variable antibody responses to the proteins. The genetic control of murine immune responses to C. trachomatis hsp60, a putative chlamydial immunopathologic antigen, suggests that a similar genetic mechanism may also exist in humans, and this observation may help to explain the observed variability in the spectrum of chlamydial diseases seen in humans.

Cloning, sequencing, and molecular analysis of the groESL operon of Clostridium acetobutylicum

The groESL operon of Clostridium acetobutylicum was cloned in Escherichia coli by using a gene probe of E. coli groESL. Sequencing of a positively reacting 2.2-kbp HindIII fragment contained in the recombinant plasmid pFN1 and a 2.5-kbp XbaI fragment present in pFN4 revealed that both fragments partially overlapped and together spanned 3,493 bp of the clostridial chromosome. Two complete open reading frames (288 and 1632 bp) were found and identified as the groES- and groEL-homologous genes of C. acetobutylicum, respectively. The 3' end of a third gene (orfZ), which was divergently transcribed, showed no significant homology to other sequences available in the EMBL and GenBank data bases. The length of the groESL-specific mRNA (2.2 kb), a transcription terminator downstream of groEL, and a transcription start site upstream of groES, identified by primer extension analysis, indicated that groES and groEL of C. acetobutylicum are organized in a bicistronic operon. From the transcription start site, the promoter structure 5'-TTGCTA (17 bp) TATTAT that shows high homology to the consensus promoter sequence of gram-positive bacteria as well as E. coli was deduced. Transcription of the groESL operon was strongly heat inducible, and maximum levels of mRNA were detected 15 min after heat shock from 30 to 42 degrees C. An 11-bp inverted repeat, located between promoter and translation start sites of groES and partially identical with similar structures in front of several heat shock genes of other bacteria, may play an important role in the regulation of heat shock gene expression in this organism.

Nucleotide sequence analysis and serologic characterization of the Mycobacterium intracellulare homologue of the Mycobacterium tuberculosis 19 kDa antigen

Disseminated Mycobacterium avium/Mycobacterium intracellulare complex (MAC) disease is a frequent complication in patients with the acquired immune deficiency syndrome (AIDS). In this report, we present the nucleotide sequence of the M. intracellulare MI22 gene. Computer sequence comparisons reveal that the MI22 gene, which encodes a serologically active protein, has 78% DNA sequence identity and 77% protein sequence identity with the seroreactive 19 kDa Mycobacterium tuberculosis lipoprotein antigen. Southern blot hybridizations indicate that an MI22 gene probe binds similar-sized restriction fragments in M. tuberculosis and M. intracellular genomic DNA. In addition, immunoblot analyses demonstrate that MI22 is recognized by sera from tuberculosis patients. These data further support the existence of 19 kDa MAC and M. tuberculosis protein homologues. Phase partitioning experiments and the presence of a consensus lipid modification site in the deduced MI22 protein sequence strongly suggest that M122 is also a lipoprotein. Comparative analyses of these mycobacterial antigenic homologues may provide the basis for the design of species-specific diagnostic reagents.

Molecular characterization of the dnaK gene region of Clostridium acetobutylicum, including grpE, dnaJ, and a new heat shock gene

The dnaK gene region of Clostridium acetobutylicum was cloned in Escherichia coli by using the pBluescript SK+ and pUC18 vectors. By using the E. coli dnaK gene as a probe and by in vivo chromosome walking, three positive clones harboring the recombinant plasmids pKG1, pKG2, and pKG3 containing 1.2-kbp HindIII, 3.55-kbp EcoRV, and 1.2-kbp PstI fragments of the chromosome of C. acetobutylicum, respectively, were isolated. The cloned fragments partially overlapped, and together they spanned 4,083 bp of the clostridial genome that were completely sequenced. On one strand, four open reading frames of which the last was obviously truncated were identified. The last three genes showed high homology to the grpE, dnaK, and dnaJ heat shock genes of E. coli, respectively. They were preceded by an open reading frame (orfA) without any homology to sequences available in the EMBL or GenBank data bases. Typical translational start sites could be found in front of all four genes. Northern (RNA) blot analysis revealed transcripts of this region with a maximum length of 5.0 kb. Thus, these genes are probably organized in an operon. A transcription terminator could be found between the dnaK and dnaJ genes. By primer extension analysis, a major heat-inducible transcription start site was identified 49 bases upstream of orfA. This site was preceded by a region (5'-TTGACA[17 bp]TATTTT) that exhibited high homology to the consensus promoter sequences of gram-positive bacteria as well as sigma 70-dependent E. coli. Between this promoter and the initiation codon of orfA, a hairpin-loop structure with a possible regulatory role in the expression of these genes was found. Additional heat-inducible transcription start sites were located 69 bases upstream of orfA and 87 bases upstream of grpE; the corresponding promoter regions showed less similarity to other known promoter sequences. Maximum mRNA levels of this heat shock operon were found about 15 min after a heat shock from 30 to 42 degrees C. Our results indicate that orfA codes for an unknown heat shock protein.

A major T cell antigen of Mycobacterium leprae is a 10-kD heat-shock cognate protein

Several mycobacterial antigens, identified by monoclonal antibodies and patient sera, have been found to be homologous to stress or heat-shock proteins (hsp) defined in Escherichia coli and yeast. A major antigen recognized by most Mycobacterium leprae-reactive human T cell lines and cell wall-reactive T cell clones is a 10-kD protein that has now been cloned and sequenced. The predicted amino acid sequence of this protein is 44% homologous to the hsp 10 (GroES) of E. coli. The purified native and recombinant 10-kD protein was found to be a stronger stimulator of peripheral blood T cell proliferation than other native and recombinant M. leprae proteins tested. The degree of reactivity paralleled the response to intact M. leprae throughout the spectrum of leprosy. Limiting-dilution analysis of peripheral blood lymphocytes from a patient contact and a tuberculoid patient indicated that approximately one third of M. leprae-reactive T cell precursors responded to the 10-kD antigen. T cell lines derived from lepromin skin tests were strongly responsive to the 10-kD protein. T cell clones reactive to both the purified native and recombinant 10-kD antigens recognized M. leprae-specific epitopes as well as epitopes crossreactive with the cognate antigen of M. tuberculosis. Further, the purified hsp 10 elicited strong delayed-type hypersensitivity reactions in guinea pigs sensitized to M. leprae. The strong T cell responses against the M. leprae 10-kD protein suggest a role for this heat-shock cognate protein in the protective/resistant responses to infection.

Murine and human B cell epitope mapping of the Mycobacterium tuberculosis 10-kD heat shock protein using overlapping peptides

The human immune response to the 10-kD M. tuberculosis protein was studied by a competition ELISA using monoclonal antibody (MoAb) SA-12. Twenty-five per cent of the sera from 20 patients with tuberculosis and none from 21 control subjects inhibited binding of SA-12 to the 10-kD antigen. To characterize the antigenic parts of the 10-kD antigen, overlapping decapeptides according to the amino acid sequence of the 10-kD protein were synthesized. In total, 91 sequential decapeptides, with an overlap of nine amino acids, were tested in ELISA with MoAb SA-12, human and murine sera (PEP scan). SA-12 recognized the amino acid sequence WDEDGEK (amino acid 50-56). All human sera, from patients with tuberculosis as well as from control subjects, gave almost identical undulating patterns of reactivity with the decapeptides. No relationship was found between the ability of the patients' sera to inhibit binding of MoAb SA-12 and the binding of these sera to the decapeptides comprising the epitope recognized by SA-12 in the PEP scan. Apparently, antibodies in patients' sera against the 10-kD protein are predominantly directed against discontinuous epitopes and, consequently, the continuous epitopes as presented in the PEP scan are not suitable to discriminate between patients with tuberculosis and control subjects. In the PEP scan, sera from BALB/c mice, both non-immunized and immunized with either live M. tuberculosis or the 10-kD protein gave similar patterns of reactivity, albeit different from the patterns obtained with the human sera. However, after immunization of the mice, clearly increased levels of antibodies to primary structures of the 10-kD protein were observed.

Heat shock proteins and antigens of Mycobacterium tuberculosis

The heat shock response of Mycobacterium tuberculosis has been characterized in detail by one- and two-dimensional polyacrylamide gel electrophoresis after metabolic labeling with [35S]methionine and 14C-amino acids. A temperature increase from 37 to 42 degrees C induced elevated synthesis of three major proteins corresponding to the DnaK, GroEL, and GroES proteins of M. tuberculosis previously identified as prominent antigens. At higher temperatures (45 to 48 degrees C), synthesis of GroEL decreased and novel heat shock proteins with molecular masses of 90, 28, 20, and 15 kDa were observed. These new proteins did not comigrate with known antigens during two-dimensional gel electrophoresis. The heat shock response is discussed with regard to the possible importance of transcriptional regulation of mycobacterial genes in vivo.

Identification of B- and T-cell epitopes within the MTP40 protein of Mycobacterium tuberculosis and their correlation with the disease course

Synthetic peptides derived from the amino acid sequence of MTP40, a recently characterized Mycobacterium tuberculosis protein, were tested by two different immunological assays in 91 individuals. For the purposes of this study, the population was distributed in four groups: active tuberculosis (TBC) patients with elevated bacillus loads (BK+), active TBC patients with low bacillus loads (BK-), healthy individuals living in the same household with tuberculous patients (HH), and normal individuals, who had presumably never been in contact with the bacilli (control). We found that T cells of individuals belonging to the HH group showed the highest and most frequent recognition of these peptides in a T-cell proliferation assay, while their antibodies showed the lowest recognition of these peptides when tested by enzyme-linked immunosorbent assay. In contrast, TBC patients revealed an inverse pattern of immune response. Interestingly, one of these peptides (P7) was recognized by T cells of 64% of the HH individuals and by 4.5% of normal donors. Another peptide (P4) was recognized by 55% of sera from BK+ patients and by 5.5% of normal donors. The results presented here indicate the existence of T- and B-cell epitopes within the MTP40 protein. Given the particular recognition pattern of this protein, added to the fact that it appears to be a species-specific antigen of M. tuberculosis, a detailed study of the immune response to it may be useful in the design of more accurate diagnostic tests and an improved vaccine against human TBC.

Isolation and partial characterization of major protein antigens in the culture fluid of Mycobacterium tuberculosis

Five actively secreted proteins (MPT32, MPT45, MPT51, MPT53, and MPT63) and the MPT46 protein were purified to homogeneity from Mycobacterium tuberculosis culture fluid and compared with proteins previously purified by ourselves and other investigators. Antisera were obtained by immunization of rabbits with all of the newly isolated proteins identified to be immunogenic. Two-dimensional electrophoresis of culture fluids obtained each week for 2 to 10 weeks of culturing of M. tuberculosis revealed characteristic changes, permitting identification of two distinct groups of proteins being actively secreted from the mycobacterial cells or appearing later in the culture fluids as a result of the release of soluble proteins from the cytosol after lysis of bacteria. The N-terminal amino acid sequences of five MPTs were shown to be identical to those of proteins previously isolated by other investigators and given different designations, and five new sequences are given. These sequences and the use of the antisera may serve to identify these proteins with mycobacterial constituents isolated by other investigators. The previously identified but not isolated MPT45 protein was shown to correspond to the C component of the antigen 85 complex. The 27-kDa MPT51 protein was demonstrated to cross-react with the three components of the antigen 85 complex, and the N-terminal amino acid sequences of MPT51 and MPT59 showed 60% homology. This finding and the extensive cross-reactivity between the components of the antigen 85 complex may indicate that there is a family of closely related secreted proteins in mycobacteria.

Expression of Mycobacterium tuberculosis and Mycobacterium leprae proteins by vaccinia virus

Eight Mycobacterium tuberculosis and M. leprae genes were inserted into the vaccinia virus genome by in vivo recombination. The resulting virus recombinants were shown to express five different M. tuberculosis proteins (71, 65, 35, 19, and 12 kDa) and three M. leprae proteins (65 and 18 kDa and a biotin-binding protein) by Western immunoblot analysis, radioimmunoprecipitation, or black-plaque assay. When injected into BALB/c mice, the recombinants expressing the M. tuberculosis 71-, 65-, or 35-kDa protein and the M. leprae 65-kDa protein or the biotin-binding protein elicited antibodies against the appropriate M. tuberculosis or M. leprae protein. These vaccinia virus recombinants are being tested for the ability to elicit immune protection against M. tuberculosis or M. leprae challenge in animal model systems. The recombinants are also useful in generating target cells for assays aimed at elucidating the cellular immune responses to mycobacterial proteins in leprosy and tuberculosis. Furthermore, the M. tuberculosis 65-kDa protein and four of the other mycobacterial proteins share homology with known eucaryotic and procaryotic stress proteins, some of which may play a role in autoimmunity.

Selection and characterization of recombinant clones that produce Mycobacterium leprae antigens recognized by antibodies in sera from household contacts of leprosy patients

A Mycobacterium leprae expression library was constructed in the vectors EX1, pEX2, and pEX3 and screened with a pool of 19 well-absorbed sera from household contacts of leprosy patients. Twelve selected recombinants that were further characterized differed clearly from recombinants selected with murine monoclonal antibodies. Whereas the monoclonal antibodies recognized mainly six recombinant antigens, the human sera from contacts reacted with a range of different recombinant antigens. None of the contact recombinant antigens was identical or related to well-characterized antigens from M. leprae or other mycobacteria selected with monoclonal antibodies, including proteins of the heat shock families. Two groups of recombinant antigens could be distinguished: one that was recognized by all sera used in the pool and one that was recognized by only a limited number of sera. These antigens, selected with sera from household contacts of previously untreated lepromatous leprosy patients, may be relevant to the immune responses during the early phase of infection with M. leprae.

Molecular cloning and sequence analysis of the Sta58 major antigen gene of Rickettsia tsutsugamushi: sequence homology and antigenic comparison of Sta58 to the 60-kilodalton family of stress proteins

The scrub typhus 58-kilodalton (kDa) antigen (Sta58) of Rickettsia tsutsugamushi is a major protein antigen often recognized by humans infected with scrub typhus rickettsiae. A 2.9-kilobase HindIII fragment containing a complete sta58 gene was cloned in Escherichia coli and found to express the entire Sta58 antigen and a smaller protein with an apparent molecular mass of 11 kDa (Stp11). DNA sequence analysis of the 2.9-kilobase HindIII fragment revealed two adjacent open reading frames encoding proteins of 11 (Stp11) and 60 (Sta58) kDa. Comparisons of deduced amino acid sequences disclosed a high degree of homology between the R. tsutsugamushi proteins Stp11 and Sta58 and the E. coli proteins GroES and GroEL, respectively, and the family of primordial heat shock proteins designated Hsp10 Hsp60. Although the sequence homology between the Sta58 antigen and the Hsp60 protein family is striking, the Sta58 protein appeared to be antigenically distinct among a sample of other bacterial Hsp60 homologs, including the typhus group of rickettsiae. The antigenic uniqueness of the Sta58 antigen indicates that this protein may be a potentially protective antigen and a useful diagnostic reagent for scrub typhus fever.

The immune response to mycobacterial heat shock proteins

Several prominent protein antigens involved in antibody and T cell responses to mycobacteria have been identified as members of highly conserved heat shock protein families. The immunogenicity of heat shock proteins in a broad range of infections, along with the extensive sequence identity between corresponding host and pathogen homologues, and the potential for localized accumulation in response to stress stimuli, makes these antigens attractive candidates for theories of autoimmunity based on "molecular mimicry". The 65 kilodalton (kD) heat shock protein of mycobacteria has indeed been shown to modulate the course of autoimmune disease in experimental animals, and immune responses to this and other heat shock proteins have been demonstrated in association with human autoimmune diseases. This paper provides a brief review of the immune response to mycobacterial heat shock proteins during infection and autoimmunity.