Recombinant BCG coexpressing Ag85B, ESAT-6 and mouse-IFN-gamma confers effective protection against Mycobacterium tuberculosis in C57BL/6 mice

In this study, the protective efficacy of a novel recombinant bacille Calmette Géurin (BCG) strain (rBCG-AEI) expressing fusion protein the antigen 85B (Ag85B)- the 6-kDa early secreted antigen target (ESAT-6)-IFN-gamma against Mycobacterium tuberculosis H37Rv in mice was evaluated. The immunogenicity study showed that rBCG-AEI could induce higher specific antibody titers and significantly increase cellular immune response than BCG, or rBCG-A strain (expressing Ag85B), or rBCG-AE strain (expressing fusion protein Ag85B-ESAT-6). The protective experiment demonstrated that rBCG-AEI could confer similar or even better protective efficacy against M. tuberculosis infection compared with others in organ bacterial loads, lung histopathology and net weight gain or loss. The results suggested that rBCG-AEI is a potential candidate for further study.     

Murine T cell-stimulatory peptides from the 19-kDa antigen of Mycobacterium tuberculosis. Epitope-restricted homology with the 28-kDa protein of Mycobacterium leprae.

Fifteen overlapping synthetic peptides, spanning the entire amino acid sequence of the Mycobacterium tuberculosis 19-kDa protein, were used to identify epitopes recognized by murine T cells. Five of the 15 peptides tested were able to elicit in vitro lymph node T cell proliferative responses in C57BL/10 mice primed by footpad inoculation with homologous peptide. Analysis in congenic strains of mice revealed H-2 restriction in the response to four peptides. However, one peptide, 19.7 (residues 61 to 80), induced T cell responses in all four haplotypes tested. This peptide was also unique in being able to stimulate lymph node cells from C57BL/10 mice immunized with recombinant 19-kDa protein, killed M. tuberculosis, or live bacillus Calmette Guerin infection. T cell lines specific for peptide 19.7 were of the CD4 phenotype. Significantly, sequence analysis revealed that residues 61 to 80 of the 19-kDa protein exhibited considerable homology with a single 20-amino acid sequence (residues 120 to 140), but not with any other region of the 28-kDa protein expressed in Mycobacterium leprae. This finding is the first evidence of epitope-restricted homology between otherwise structurally unrelated microbial Ag.     

Identification of T cell stimulatory peptides from the 38-kDa protein of Mycobacterium tuberculosis.

T cell specificity to individual antigenic epitopes could determine the distinction between protective and pathogenic host reactions in tuberculous infections. Therefore, T cell stimulatory epitopes of the Mycobacterium tuberculosis 38-kDa lipoprotein, of known structure and specificity and of prominent immunogenicity, have been examined. To identify potential T cell epitopes, eight peptides, seven of which were predicted to form amphiphatic helices, were used for immunization of various inbred mice and for elicitation of in vitro T cell proliferative responses. Three different response patterns were observed. 1) Lymph node cells from mice immunized with peptide, recombinant 38-kDa Ag, killed M. tuberculosis strain H37Ra, or live Mycobacterium bovis bacillus Calmette Guerin infection responded to peptide 38.G (residues 350 to 369). Responses were observed in mice of H-2b, H-2d, and H-2k haplotypes. 2) Peptide 38.C (residues 201 to 220) induced proliferation of lymph node cells from 38-kDa protein-, but not from peptide-immunized mice. 3) Peptide 38.F (residues 285 to 304) only elicited a response of the homologous peptide-primed cells. Analysis of CD4+ T cell lines confirmed the distinct specificities and stimulatory features of peptides 38.F and 38.G. The described attributes of peptide 38.C and 38.G could be of potential interest for diagnostic evaluation in tuberculous infections.     

Hsp65与IL-2融合蛋白诱导小鼠细胞免疫应答及保护力

目的研究Hsp65与hIL-2的融合蛋白在小鼠体内诱导的免疫应答及保护力。方法在大肠杆菌中诱导表达Hsp65与hIL-2的融合蛋白,通过Ni-NTA亲合柱纯化后的蛋白经鉴定后,与佐剂DDA和MPL联合免疫小鼠,连续免疫3次,每次间隔2周,最后一次免疫结束后两周,分离5只小鼠脾淋巴细胞,测定淋巴细胞增殖指数,IFN-γ和IL-2水平,以及特异性淋巴细胞杀伤功能,其余5只免疫小鼠用于MTB毒株攻击实验。结果获得融合蛋白可分别与抗Hsp65和抗hIL-2的单抗发生特异性反应。融合蛋白免疫小鼠后,小鼠脾淋巴细胞被有效活化,诱导产生的-γIFN和IL-2的水平以及CTL杀伤功能均显著高于BCG和单纯Hsp65免疫组（P〈0.05）。融合蛋白免疫组可有效抵抗MTB毒株攻击,脾脏细菌数显著减少（4.36±0.48）,提供的保护力与BCG相当（4.30±0.53）。结论Hsp65与hIL-2的融合蛋白是一种有效的亚单位疫苗,可用于TB的预防。     

IgG antibodies from patients with bullous pemphigoid bind to localized epitopes on synthetic peptides encoded by bullous pemphigoid antigen cDNA.

Bullous pemphigoid (BP) is an autoimmune blistering disease characterized in part by the presence of tissue-bound and circulating antibodies specific for basement membrane zone proteins, the BP Ag. The purpose of the present study was to determine seroreactivity of patients with BP to six nonoverlapping synthetic peptides representing sequences in the carboxyl domain of the recently cloned 230-kDa BP Ag. Sera from 40 patients with BP, 57 normal subjects, and 18 patients with other autoimmune blistering skin diseases were examined in an ELISA for binding to six synthetic peptides varying between 17 and 19 amino acids in length. The binding of IgG from patients with BP to three synthetic peptides, P1-2, P1-1, and P3-1, was significantly different from that seen in the normal controls (p less than 0.001, Fisher's exact test). Affinity-purified anti-P1-2 antibody from a patient with BP bound in a characteristic linear band to the epidermal side of 1 M NaCl split skin and immunoprecipitated the native 230-kDa BP Ag. Serum IgG antibodies from a rabbit immunized with a BP fusion protein that contains the sequences for P1-1 and P1-2, bound on ELISA to P1-2 but not to P1-1. These data suggest that multiple epitopes on the 230-kDa BP Ag are recognized by circulating autoantibodies in patients with this disease, and that an epitope encoded within the synthetic peptide P1-2 is expressed on the native molecule and may be relevant in the generation of an immune response both in man and in an animal model.     

Protective efficacy of a cloned Brugia malayi antigen in a mouse model of microfilaremia

Immunization of mice with irradiated Brugia larvae or parasite extracts has been shown to induce partial resistance to microfilaremia and enhance clearance of infective larvae. We recently reported the cloning of a 548 amino acid 62-kDa Brugia malayi Ag identified on the basis of reactivity with antisera to a subset of protective microfilarial Ag. Our study describes the protective efficacy against microfilaremia in mice, immunogenicity, and parasite stage-specificity of this candidate vaccine molecule. Immunization of Swiss or BALB/c mice with 1 to 3 micrograms of a 92-kDa trpE fusion protein encoding amino acids 1-479 reduced the intensity of microfilaremia by 40 to 60% compared to control animals given buffer or bacterial trpE (p less than 0.01 to 0.001). Mice immunized with the 92-kDa fusion protein developed delayed-type hypersensitivity reactivity to B. malayi as assessed by enhanced footpad swelling 24 and 48 h after intradermal injection of adult worm extract and in vitro lymph node mononuclear cell proliferation (3H-thymidine uptake) in response to the fusion protein (mean +/- SD stimulation index 4.7 +/- 0.8 vs 2.0 +/- 1.4 for trpE, p less than 0.05). Proliferative responses of lymph node cells coincubated with three other fusion proteins corresponding to the filarial protein truncated from its carboxyl-terminus suggest that dominant T cell epitopes of the 62-kDa Ag are encompassed by amino acids 437-479. Rabbit antibody to the 92-kDa trpE fusion protein immunoprecipitated a 62-kDa polypeptide from [35S] methionine biosynthetically labeled B. malayi microfilariae, adult female, and adult male worms. These data indicate that a recombinant Ag expressed in several developmental stages of B. malayi is capable of inducing partial resistance against microfilariae and Ag-specific T cell responses in mice.     

The mapping of epitopes of the 18-kDa protein of Mycobacterium leprae recognized by murine T cells in a proliferation assay

The 18-kDa protein of Mycobacterium leprae was purified from recombinant plasmids pUL108 and pML-3 grown in Saccharomyces cerevisiae and Escherichia coli, respectively. Significant lymphoproliferative responses were observed when T cells from immunized mice were challenged in culture with purified 18-kDa protein. Synthetic peptides have been prepared that span most of the 148 amino acid residues that constitute the sequence of the 18-kDa protein and used to map epitopes recognized by T cells. When mice were immunized with 18-kDa protein and lymph node cells subsequently prepared and challenged in microculture proliferative assays by using synthetic peptides, only one region of the intact protein appeared stimulatory. This T cell epitope was located between residues 116 and 121, adjacent to an epitope between residues 110 and 115 which we have previously shown to bind the L5 mAb. Immunization of mice with peptides, and subsequent challenge of lymph node cells in assays by using the 18-kDa protein as Ag revealed that residues 111-125 were the most effective in priming responses. Furthermore, the ability of 18-kDa primed lymph node cells to recognize determinants on both M. leprae and Mycobacterium tuberculosis indicates that in addition to possessing an M. leprae-specific B cell determinant, the 18-kDa protein contains a cross-reactive T cell epitope(s).     

Pepstatin A-sensitive aspartic proteases in lysosome are involved in degradation of the invariant chain and antigen-processing in antigen presenting cells of mice infected with Leishmania major

We previously reported that CA074, a specific inhibitor of cathepsin B, significantly deviated immune responses from the disease-promoting Th2 type to the protective Th1 type in BALB/c mice infected with Leishmania major. Herein, we found that pepstatin A-sensitive aspartic proteases (PSAP) in lysosomes seem to play a different role from that of cathepsin B in antigen-processing and Ii-degradation. That is, cathepsin B appears to digest 16-, 28-, and 31-kDa peptides of soluble leishmania antigen (SLA), whereas PSAP seems to process mainly 28-kDa peptides. Furthermore, the latter protease contributed to the degradation of Ii but cathepsin B did not. Following treatment with pepstatin A, both Th1 and Th2 responses were profoundly suppressed in resistant DBA/2 mice (H-2(d)) and in susceptible BALB/c mice (H-2(d)), and both strains of mice became markedly susceptible compared with the untreated groups, probably owing to failure in degradation of Ii and partly to failure in digestion of 28-kDa peptide.     

A 46-kDa antigen associated with estrogen receptor in human breast cancer

A 65-kDa estrogen receptor (ER) protein has been demonstrated both by sucrose gradient analysis and by immunoblot, using anti-ER monoclonal antibodies (MAbs). Since the ER is denatured in many experimental situations, such as formaldehyde fixing of samples for histochemistry and electroimmunoblotting studies, in this work we used a denatured 60-70-kDa ER-rich protein preparation as antigen for mice immunization in order to raise anti-ER MAbs. That material was obtained by affinity purification on an allyl-estradiol matrix of the MCF-7 cytosolic ER, followed by further isolation and enrichment by PAGE. NS-1 myeloma cells and spleen lymphocytes from the immunized mice were fused, and resultant hybridoma colonies were screened by [125I]-estradiol-labelled nuclear ER immunoprecipitation. The isolated MAb, E476, shows a moderate ability to precipitate ER and reacts strongly with a 46-kDa antigen in Western blot assay. The 46-kDa antigen was not detectable in native cytosol but became reactive after 50% ammonium sulfate precipitation of cytosolic proteins. The 46-kDa antigen appeared concentrated in the NaSCN plus estradiol eluate of the affinity column used for cytosolic ER purification. Freshly prepared 60-70-kDa material from the preparative gel electrophoresis did not show any E476 reactivity. However, when the 60-70-kDa proteins were frozen, thawed and speed vacuum concentrated, the 46-kDa antigen became detectable. Storage increased the reactivity of the 60-70-kDa material with the E476 MAb. The 46-kDa antigen was present only in the ER positive cell lines, and was absent in all negative cell lines tested. The 46-kDa protein is also present in the ER positive human breast cancer specimens. We conclude that the 46-kDa protein identified with the E476 MAb in human breast cancer is probably a naturally occurring ER fragment.     

T lymphocytes from healthy individuals with specificity to self-epitopes shared by the mycobacterial and human 65-kilodalton heat shock protein

The immune response to mycobacterial pathogens comprises a significant percentage of T cells with specificity for a 65-kDa heat shock protein (hsp) which is highly conserved in bacteria and man. PBMC were activated in vitro with killed Mycobacterium tuberculosis and afterward tested for CTL activity on autologous target cells primed with 1) killed M. tuberculosis, 2) intact recombinant 65-kDa hsp of Mycobacterium bovis/M. tuberculosis; or 3) tryptic fragments of the recombinant 65-kDa hsp. Strong CTL activity was observed on targets primed with killed M. tuberculosis or with tryptic fragments of the 65-kDa hsp, but not on those primed with the intact 65-kDa hsp. M. tuberculosis activated T cells from 2/13 donors tested exerted killer activity against unprimed targets. To assess whether T cell responses were directed against self-epitopes shared by the mycobacterial and human 65-kDa hsp, four peptides of at least 10 amino acids length were synthesized corresponding to fully or almost identical regions of these molecules. Peripheral blood T cells from 8/9 individuals tested, after activation with killed M. tuberculosis, expressed strong CTL activity toward autologous targets primed with one or more of these synthetic peptides. By using HLA-DR transfected murine L cells we found that the epitopes were recognized in the context of histocompatible HLA-DR (class II) molecules. We conclude that the demonstration of T cells with specificity to self-epitopes in vitro is not indicative for autoimmune disease. However, if at certain stages of infection such T cells are activated by crossreactive microbial epitopes they could cause autoimmune responses.     

Immune responses to the 18-kDa protein of Mycobacterium leprae. Similar B cell epitopes but different T cell epitopes seen by inbred strains of mice.

Antibody responses to the 18-kDa protein of Mycobacterium leprae have been analyzed in different strains of mice. High, intermediate, and low responder strains have been identified and these response patterns show clear linkage to genes encoded in the H-2 complex. Three peptides, residues 1-50, 51-100, and 101-148 have been synthesized, as well as a series of 20-mer peptides, which span the entire 18-kDa protein. Repeated immunization of different strains of mice with the 18-kDa protein resulted in IgG responses to epitopes found on all three synthetic peptides. Immunization of BALB/cJ and B10.BR mice, two high responder strains, with 18-kDa protein resulted in high levels of IgG antibody to epitopes found on peptides 1-20, 16-35, 31-50, 46-65, and 76-95. B10.BR mice also contained IgG that bound peptide 61-80 and BALB/cJ mice produced IgG that bound peptide 91-110. Although B10.BR mice produced IgG that bound the 50-mer peptide 101-148, this IgG was not detected by binding to peptides 91-110, 106-125, 121-140, and 131-148. Immunization of B10.BR mice with individual overlapping 20-mer peptides as Ag revealed that peptides 1-20, 16-35, 31-50, and 76-95 elicited high titers of IgG that bound both the immunizing peptide as well as 18-kDa protein. As these peptides induce antibody synthesis they must contain both B cell and T cell epitopes. By contrast, immunization of BALB/cJ mice with the same 20-mer peptides, all of which contain B cell epitopes for this strain, failed to elicit IgG responses with one exception. Peptide 91-110 induced IgG that bound peptide 91-110, but not the intact 18-kDa protein. We conclude that peptides 1-20, 16-35, 31-50, and 76-95 either lack T cell epitopes for BALB/cJ mice, or activate different T cell subpopulations in the two strains. We suggest that the induction of IgG responses to small peptide Ag is an in vivo assay of the activity of Th2 cell subpopulations.     

Immunological properties of recombinant Mycobacterium bovis bacillus Calmette-Guérin strain expressing fusion protein IL-2-ESAT-6

The live vaccine Mycobacterium bovis bacillus Calmette-Guérin (BCG) provides variable efficacy against adult pulmonary tuberculosis (TB). Recombinant BCG, expressing either immunodominant antigens or Th1 cytokines, is a promising strategy for developing a new TB vaccine. However, not much is known about whether the introduction of cytokine and specific antigen genes concurrently into the BCG strain could improve the immunogenicity of BCG. In this study, a recombinant BCG strain (rBCG) expressing the fusion protein human interleukin (IL)-2 and ESAT-6 (early secreted antigenic target-6 kDa) antigen of Mycobacterium tuberculosis was constructed. Six weeks after BALB/c mice (H-2d) were immunized with 106 colony forming units (CFUs) BCG or rBCG, splenocyte proliferation was determined with MTT [3-(4,5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide] assay, IL-4 and interferon (IFN)-gamma produced by splenocytes were tested by enzyme linked immunosorbent assay (ELISA,) and the cytotoxicity of splenocytes from immunized mice to P815 cells (H-2d) expressing ESAT-6 protein was measured using CytoTox 96 Non-Radioactive Cytotoxicity Assay. Compared with native BCG-vaccinated mice, rBCG induced stronger Th1 responses that were confirmed by high lymphoproliferative responses and IFN-gamma production to culture filtrate protein (CFP) or ESAT-6 protein. Moreover, rBCG induced significant enhanced CTL responses against P815-ESAT-6 cells. Results from rBCG-immunized mice demonstrated that introducing the il-2 and esat-6 genes into BCG could enhance Th1 type immune responses to ESAT-6. Further investigation is needed by introducing other Th1 cytokines and antigens into BCG to optimize the protective efficacy against TB.     

Calcium-activated neutral protease purified from beef lung: properties and use in defining structure of epidermal growth factor receptors

Ca2+-Requiring proteases degrade cytosolic and integral membrane proteins as well as alter, by limited proteolysis, the activity of certain protein kinases. When cells are lysed, a Ca2+-requiring protease degrades the epidermal growth factor (EGF) receptor, an integral membrane protein with an intrinsic kinase activity, from its 170-kDa form to a 150-kDa form. This Ca2+-requiring protease has all of the characteristics of calcium-activated neutral protease (CANP). To show that CANP is the protease uniquely responsible for the degradation of the native EGF receptor in vitro, CANP was highly purified from beef lung. This affinity purified CANP had properties previously described for other CANPs: heterodimer of 80 and 30 kDa; neutral pH optimum; activation by millimolar Ca2+; and inhibition by an endogenous, heat-stable proteinaceous inhibitor, by leupeptin, and by sulfhydryl alkylating agents. Using the EGF receptor labeled by covalent attachment to 125I-EGF, this purified CANP quantitatively generated the 150-kDa form from the native receptor in A-431 cell membranes. As with the native receptor, the 150-kDa receptor forms produced by the endogenous Ca2+-requiring protease, by CANP, by chymotrypsin, and by elastase were all capable of EGF-stimulated autophosphorylation. When the 150-kDa receptor forms were generated by the three exogenously added proteases, autophosphorylation with [gamma-32P]ATP followed by trypsinization produced 32P-labeled peptides that were not the same. However, the tryptic 32P-labeled peptides from the autophosphorylated 150-kDa receptor form produced by CANP or by the endogenous Ca2+-requiring protease were identical. These data indicate that CANP is identical to the endogenous Ca2+-requiring protease responsible for producing the autophosphorylating 150-kDa receptor form from the native EGF receptor when cells are lysed.     

Identification of immunodominant epitope of F1 antigen of Yersinia pestis

The F1 antigen of Yersinia pestis has been identified as one of the major protective antigens of this bacterium. The present study aims to delineate major and minor antigenic sites of F1 antigen. Using algorithmic predictions, five peptide sequences (P1, P2, P3, P4 and P5) spanning the C-terminal region were identified and synthesized. Antibodies were generated in mice against the peptides, native F1 protein and polymerized F1 antigen using liposomes as mode of immunization. Cross-reactivity between F1 antigen and peptides was tested using both solid and solution phase assays. Similar assays were done with rabbit anti-F1 sera. Competitive inhibition assays using a different combination of antisera and competing antigen identified P2 peptide FFVRSIGSKGGKLAAGKYTDAVTV (142-165) as the immunodominant sequence. The results indicate that this sequence appears to be exposed on the surface of F1 molecule. In a solid phase binding assay, P2 peptide was recognized even at high F1 antisera dilution. However, when antisera raised to different peptides were tested for binding to F1 antigen, antisera to P4 peptide showed maximal immunoreactivity. This implies more accessibility of this region during immobilization on solid surface. There was consistency in the results obtained for different strains of mice as well as for the rabbit antisera. Such a sequence of F1 antigen, which is recognized widely in animals of different genetic background, would be useful for diagnosis and subunit vaccine.     

Protective immunity in mice vaccinated with the Schistosoma mansoni P-28-1 antigen

The P28-1 Ag induces a strong protective immunity toward Schistosoma mansoni infection in various experimental models. T lymphocytes of mice immunized with the recombinant P28-1 Ag were stimulated in vitro by schistosome Ag of different development stages and by three P28-1 Ag-derived synthetic peptides. The most significant stimulation was achieved with the 24-43 peptide. The use of two fragments of this peptide showed that the P28-1 T lymphocyte specificity concerned essentially the NH2 terminal sequence of the 24-43 peptide. Moreover, T lymphocytes specific for the 24-43 peptide were stimulated by both schistosome Ag and the recombinant P28-1 protein. The passive transfer of (Th + Ts) lymphocytes recovered from P28-1 Ag-immunized mice increased the IgG response to P28-1 and its peptides during infection but did not protect against a challenge infection, such as the passive transfer of anti-P28-1 sera. In contrast, P28-1 specific Th cell lines maintained in culture for 2 mo, passively transferred a strong protection (50%) to infected mice. Supernatants of P28-1-specific T cells obtained after stimulation with the corresponding Ag, were able to confer cytotoxic properties to platelets and macrophages. The presence of IFN-gamma for the cytotoxicity mediated by platelets and macrophage activating factor for the cytotoxicity mediated by macrophages in these supernatants is in a large part responsible for the parasite killing observed. Finally, a preliminary immunogenetic approach with H-2 congenic mice on BALB background showed that the P28-1 Ag T cell response was under the control of the MHC and that the H-2b haplotype determined a low response to P28-1 Ag and its peptides while H-2d and k haplotypes determined high responders.     

Identification of an I-Ad restricted peptide on the 65-kilodalton heat shock protein of Mycobacterium avium

The 65 kilodalton heat shock protein (Hsp65) from mycobacterial species elicits immune responses and in some cases protective immunity. Here we have used a DNA sublibrary approach to identify antigenic fragments of Mycobacterium avium Hsp65 and a synthetic peptide approach to delineate CD4+ T cell determinants. A panel of Hsp65 reactive CD4+ T cell clones was established from lymph node cells obtained from BALB/c mice immunized with recombinant Hsp65. The clones were tested for proliferative reactivity against the products of the DNA sublibrary of the hsp65 gene. A T cell epitope, restricted by the I-Ad molecule, was identified within the C-terminal region of Hsp65 and the minimal epitope (amino acid residues 489-503) delineated using overlapping peptides spanning the C-terminal fragment. Additionally, the CD4+ T cell clone recognizing this epitope also responded to native Hsp65 present in M. avium lysates by both proliferation and cytokine production, indicating that the epitope was present and processed similarly both in the native and the recombinant forms of Hsp65. This sequence identified in BALB/c mice (Hsp65 489-503) is identical in other mycobacteria, notably M. tuberculosis, M. bovis and M. leprae, suggesting the epitope may have wider application in murine models of other mycobacterial infections.     

T-helper cell and associated antibody response to synthetic peptides of the E glycoprotein of Murray Valley encephalitis virus.

A battery of 16 synthetic peptides, selected primarily by computer analysis for predicted B- and T-cell epitopes, was prepared from the deduced amino acid sequence of the envelope (E) glycoprotein of Murray Valley encephalitis (MVE) virus. We examined all of the peptides for T-helper (Th)-cell recognition and antibody induction in three strains of mice: C57BL/6, BALB/c, and C3H. Lymphoproliferative and interleukin-2 assays were performed on splenic T cells from mice inoculated with peptides in Freund's incomplete adjuvant or with MVE virus. Several peptides found to contain predicted T-cell epitopes elicited a Th-cell response in at least one strain of mice, usually with a concomitant antibody response. Peptides 145 (amino acids 145 to 169) and 17 (amino acids 356 to 376) were strongly recognized by T cells from all three inbred strains of mice. Peptide 06 (amino acids 230 to 251) primed C57BL/6 mice for Th- and B-cell reactivity with native MVE virus, and T cells from virus-immune mice were stimulated by this peptide. Peptide 06 was recognized by several Th-cell clones prepared from mice immunized with MVE, West Nile, or Kunjin virus. These results indicate that it may be feasible to design synthetic flavivirus peptides that define T-cell epitopes capable of generating a helper cell response for B-cell epitopes involved in protective immunity.     

Characterization of serologic and cell-mediated reactivity of a 38-kDa antigen isolated from Mycobacterium tuberculosis

An antigen of Mycobacterium tuberculosis with an m.w. of 38,000 has been isolated by affinity chromatography using a monoclonal antibody. This antibody bound only to an antigen found in M. tuberculosis and Mycobacterium bovis BCG. The specificity of the antigen was tested in a vertical study by immunodetection on western blots reacted with hyperimmune sera against M. tuberculosis, M. bovis, and 10 other Mycobacterium species. The antigen was detected only by antisera to M. tuberculosis and M. bovis. Specificity in cell-mediated immunity was tested by skin tests in guinea pigs sensitized with M. tuberculosis, Mycobacterium intracellulare, and Mycobacterium kansasii and by lymphocyte proliferation tests. The 38-kDa antigen induced positive skin test reactions regardless of the Mycobacterium species used to sensitize the animal. The ability of the 38-kDa antigen to sensitize for cell-mediated immunity was tested by injecting mice with the 38-kDa antigen and challenging their lymphocytes in vitro with various mycobacterial antigens. Lymphocyte proliferation was observed in the presence of 38-kDa antigen, M. tuberculosis sonicate antigen, and tuberculin purified protein derivative and to M. kansasii and M. intracellulare. The 38-kDa antigen may contain a specific epitope detected by serology, but also contains epitopes that are cross-reactive for cellular immunity.