Enzyme-linked immunosorbent assay for distinguishing serological responses of lepromatous and tuberculoid leprosies to the 29/33-kilodalton doublet and 64-kilodalton antigens of Mycobacterium tuberculosis

Astrocytes: From the Physiology to the Disease

Astrocytes are key cells for adequate brain formation and regulation of cerebral blood flow as well as for the maintenance of neuronal metabolism, neurotransmitter synthesis and exocytosis, and synaptic transmission. Many of these functions are intrinsically related to neurodegeneration, allowing refocusing on the role of astrocytes in physiological and neurodegenerative states. Indeed, emerging evidence in the field indicates that abnormalities in the astrocytic function are involved in the pathogenesis of multiple neurodegenerative diseases, including Alzheimer's Disease (AD), Parkinson's Disease (PD), Huntington's Disease (HD) and Amyotrophic Lateral Sclerosis (ALS). In the present review, we highlight the physiological role of astrocytes in the CNS, including their communication with other cells in the brain. Furthermore, we discuss exciting findings and novel experimental approaches that elucidate the role of astrocytes in multiple neurological disorders.

Tackling tuberculosis: Insights from an international TB Summit in London

Tuberculosis (TB) poses a grave predicament to the world as it is not merely a scientific challenge but a socio-economic burden as well. A prime cause of mortality in human due to an infectious disease; the malady and its cause, Mycobacterium tuberculosis have remained an enigma with many questions that remain unanswered. The ability of the pathogen to survive and switch between varied physiological states necessitates a protracted therapeutic regimen that exerts an excessive strain on low-resource countries. To complicate things further, there has been a significant rise of antimicrobial resistance. Existing control measures, including treatment regimens have remained fairly uniform globally for at least half a century and require reinvention. Overcoming the societal and scientific challenges requires an increase in dialog to identify key regions that need attention and effective partners with whom successful collaborations can be fostered. In this report, we explore the discussions held at the International TB Summit 2015 hosted by EuroSciCon, which served as an excellent platform for researchers to share their recent findings. Ground-breaking results require outreach to affect policy design, governance and control of the disease. Hence, we feel it is important that meetings such as these reach a wider, global audience.

Mycobacterium tuberculosis H(37)Ra ESAS-7-An excretory-secretory antigen fraction of immunodiagnostic potential in pulmonary tuberculosis

A mycobacterial excretory-secretory protein fraction ESAS-7 purified by 50% ammonium sulphate precipitation followed by SDS-PAGE fractionation was evaluated by penicillinase enzyme linked immuno-sorbent assay (ELISA) for its sensitivity and specificity in the diagnosis of pulmonary tuberculosis. At a "cut off" serum dilution of 600, 38 (90%) of 42 sera from bacteriologically confirmed tuberculosis cases, 15 (100%) of 15 sera from bacteriogically negative but anti tubercular therapy (ATT) responded cases, 3 (7%) of 43 sera from normal healthy subjects and 4 (8%) of 48 sera from non tuberculous disease control cases gave positive reaction for tubercular antibody to ESAS-7 antigen fraction containing predominantly 33-kDa protein with a sensitivity of 90% in bacteriologically confirmed cases and specificity of 92%. Further, this diagnostic assay using the ESAS-7 antigen is more sensitive requiring as little as one nanogram antigen per test compared to use of 100 nanogram EST-6 antigen reported earlier. Thus use of ESAS-7 antigen for antibody detection has good diagnostic potential with improved specificity in pulmonary tuberculosis.

Immunohistological analysis of in situ expression of mycobacterial antigens in skin lesions of leprosy patients across the histopathological spectrum. Association of Mycobacterial lipoarabinomannan (LAM) and Mycobacterium leprae phenolic glycolipid-I (PGL-I) with leprosy reactions

The presence of mycobacterial antigens in leprosy skin lesions was studied by immunohistological methods using monoclonal antibodies (MAbs) to Mycobacterium leprae-specific phenolic glycolipid I (PGL-I) and to cross-reactive mycobacterial antigens of 36 kd, 65 kd, and lipoarabinomannan (LAM). The staining patterns with MAb to 36 kd and 65 kd were heterogeneous and were also seen in the lesions of other skin diseases. The in situ staining of PGL-I and LAM was seen only in leprosy. Both antigens were abundantly present in infiltrating macrophages in the lesions of untreated multibacillary (MB) patients, whereas only PGL-I was occasionally seen in scattered macrophages in untreated paucibacillary lesions. During treatment, clearance of PGL-I from granulomas in MB lesions occurred before that of LAM, although the former persisted in scattered macrophages in some treated patients. This persistence of PGL-I in the lesions paralleled high serum anti-PGL-I antibody titers but was not indicative for the presence of viable bacilli in the lesions. Interestingly, we also observed a differential expression pattern of PGL-I and LAM in the lesions of MB patients with reactions during the course of the disease as compared with those without reactions. In conclusion, the in situ expression pattern of PGL-I and LAM in MB patients may assist in early diagnosis of reactions versus relapse.

Effect of intestinal resection on serum antibodies to the mycobacterial 45/48 kilodalton doublet antigen in Crohn's disease

Interest in the role of mycobacterial infection in Crohn's disease has been revived by the cultural detection of Mycobacterium paratuberculosis in patients with Crohn's disease. This hypothesis was examined serologically using assays with high specificity for Crohn's disease. The effect of intestinal resection on serum antibodies specific for Crohn's disease was investigated with an immunoblot assay and an enzyme linked immunosorbent assay using the 45/48 kilodalton doublet antigen of Mycobacterium tuberculosis. Antibodies were detected in 64.7% of patients with Crohn's disease (n = 17), 10% of patients with ulcerative colitis (n = 10), 5% of patients with carcinoma of the colon (n = 20), and none of 10 healthy subjects with the immunoblot assay. Statistical comparison of the Crohn's disease patients with each control group resulted in p = 0.0000236. Immunoglobulin G was essentially unchanged 75 days (mean) after surgery. After more than 180 days, however, the antibody response was reduced in all of five patients studied, and was no longer demonstrable in two of them (40%). Simultaneously, the Crohn's disease activity index (CDAI) decreased. Both the high specificity of this assay for Crohn's disease and the diminished antibody response after intestinal resection in parallel with decreased CDAI support a mycobacterial aetiology of Crohn's disease.

Lack of cytotoxic activity against Mycobacterium leprae 65-kD heat shock protein (hsp) in multibacillary leprosy patients

Cytotoxic T cells play an important role in host defence mechanisms, as well as in the immunopathology of leprosy. In this study, we evaluated whether Mycobacterium leprae hsp18, hsp65 and Myco. tuberculosis hsp71 could induce cytotoxic T cell activity against autologous macrophages pulsed with these hsp. Paucibacillary (PB) patients and normal controls generated more effector cells than multibacillary (MB) patients with all three hsp tested. There was no cross-reactivity between any of the hsp tested. Mycobacterium leprae hsp65 induced cytotoxic responses only in those MB patients undergoing an erythema nodosum leprosum (ENL) episode. Although hsp65 and hsp18 induced similar proliferation in MB patients, a high proportion of these patients did not generate cytotoxic effector cells in response to hsp65. Hence, those T cells reacting to hsp65 may play an important role in the control of Myco. leprae infection.

IgG humoral response against the antigen 85 complex homologues in leprosy

Antigen 85 complex is the major protein component present in M. bovis BCG culture filtrate (CF). It consists of a family of three proteins: 85A, 85B and 85C. Combining isoelectric focusing and Western blot analysis, we have previously identified different antigenically related proteins present in the CF of other mycobacteria (M. tuberculosis, M. kansasii, M. avium, M. gordonae, M. fortuitum and M. phlei) using monoclonal antibodies (MoAbs) directed against the antigen 85 complex of M. bovis BCG. Humoral immune response directed against these cross-reactive homologues was analysed in sera from 20 patients with multibacillary leprosy (BL/LL), from 20 patients with paucibacillary leprosy (BT/TT) and from 15 healthy leprosy contacts. All the antigen 85 homologues identified in the seven CFs by MoAbs were also recognized by IgG present in sera from multibacillary leprosy patients, but not or very faintly in sera from paucibacillary leprosy patients or from healthy subjects. These results suggest that some of the M. leprae epitopes inducing a significant humoral response in multibacillary leprosy are common to the various 85 antigenically related proteins present in all mycobacterial species.

An immunodominant 30-kDa antigen of a candidate anti-leprosy vaccine, Mycobacterium w, shares T and B cell determinants with M. leprae and M. tuberculosis

Earlier we reported that vaccination of leprosy patients with Mycobacterium w induces an immune response directed predominantly against low molecular weight antigens. One of these antigens, with a molecular mass of 30-kDa, was recognized by a majority of the vaccinated subjects as well as the tuberculoid leprosy patients and healthy contacts. In the present communication we report further characterization of this antigen. Immunofluorescence and Western blot studies with antibodies raised against this antigen demonstrate that it is associated with the cell surface and has homologues present in M. leprae and M. tuberculosis. Delayed-type hypersensitivity studies carried out in guinea pigs immunized with the 30-kDa antigen show that in addition to sharing B cell determinants, this immunodominant antigen of M. w also shares T cell determinants with M. leprae and M. tuberculosis.

The mycobacterial secreted antigen 85 complex possesses epitopes that are differentially expressed in human leprosy lesions and Mycobacterium leprae-infected armadillo tissues

The granulomatous skin lesions in leprosy are thought to be initiated by the immune response to certain antigens of the causative agent, Mycobacterium leprae. The antigen 85 complex is one of the major targets in the immune response to M. leprae infection. In the present study, a panel of previously characterized monoclonal antibodies (MAbs) (3A8, Rb2, A4g4, A2h11, Pe12, and A3c12) reacting with different epitopes of the 85 complex proteins of Mycobacterium tuberculosis and M. leprae was employed in a comparative immunohistological analysis to demonstrate the in situ expression of 85 complex antigenic epitopes in leprosy lesions across the clinical spectrum and in M. leprae-infected armadillo liver tissues. These MAbs showed a heterogeneous staining pattern in a given leprosy lesion. In highly bacilliferous borderline and lepromatous leprosy lesions, MAbs Rb2, A4g4, A2h11, and Pe12 stained clear rod-shaped M. leprae bacilli within macrophages, and the degree of staining correlated with the bacillary index of the lesion. On the other hand, MAbs 3A8 and A3c12 staining was mostly seen as a diffuse staining pattern within interstitial spaces and on the membranes of the infiltrated cells but not the bacilli. In paucibacillary borderline and tuberculoid leprosy lesions, only 3A8, Rb2, and A3c12 showed distinct staining in association with infiltrates in the granuloma. None of these MAbs showed any detectable reaction with control nonleprosy skin lesions, while MAb A3c12 positively stained the granulomas of both leprosy and control specimens. In situ reactivity of these MAbs with M. leprae-infected armadillo liver tissues also showed a heterogeneous staining pattern. Interestingly, a clear difference in expression of these epitopes was observed between armadillo tissues and human leprosy lesions. By immunogold ultracytochemistry, we further showed the differential localization of these MAb-reactive epitopes on the cell surface, in the cytosol, and at the vicinity of M. leprae within Kupffer cells of armadillo liver tissues. Our results indicate that these antigenic epitopes of the antigen 85 complex are differentially expressed in leprosy lesions and infected armadillo tissues and that they could be target determinants in the immunopathological responses during M. leprae infection.

Identification of a novel 27-kDa protein from Mycobacterium tuberculosis culture fluid by a monoclonal antibody specific for the Mycobacterium tuberculosis complex

Mycobacterium tuberculosis antigens inducing species-specific immune responses are likely to be particularly important for serodiagnosis or for skin testing of tuberculosis. In the present study, we describe the characterization of two novel monoclonal antibodies (MoAbs) A3h4 (IgG2a) and B5g1 (IgM) that are directed to M. tuberculosis 27-kDa and 25-kDa proteins respectively. Specificity analysis by immunoblotting using 20 different species of mycobacterial sonicates revealed that MoAb A3h4 was specific for M. tuberculosis complex alone while MoAb B5g1 showed a limited cross-reactivity. Direct comparison with previously characterized MoAbs revealed that these MoAbs A3h4 and B5g1 defined new antigenic determinants of M. tuberculosis. By using M. tuberculosis complex-specific MoAb A3h4 we have identified a distinct 27-kDa protein in the M. tuberculosis H37Rv culture fluid. Since this MoAb did not bind to the previously characterized MPT44, MPT59, MPT45, MPT51 and MPT64 proteins as well as the 23-kDa superoxide dismutase (SOD) protein of M. tuberculosis, we conclude that MoAb A3h4 recognizes a novel protein in the M. tuberculosis H37Rv culture fluid. Studies of the subcellular distribution of these MoAb-reactive proteins indicate that the MoAb A3h4-reactive 27-kDa protein is present not only in the culture fluid but also in the cytosol and the cell wall of M. tuberculosis. By contrast, B5g1-reactive protein is mainly a cytosolic protein. When these MoAbs were tested in a previously established ELISA with intact mycobacteria derived from early cultures, only MoAb A3h4 showed the positive reactivity to mycobacteria belonging to the M. tuberculosis complex. In addition, during the present comparative studies of MoAbs we have also found that the previously described MoAb F116-5, which is known to recognize the mycobacterial 23-kDa SOD protein [17], cross-reacted with the MPT44, MPT59, MPT45 and MPT51 secreted proteins but not with MPT64 and MPB70. These findings indicate that the family of four secreted proteins of M. tuberculosis share a common epitope with M. tuberculosis SOD protein.

Antibodies to mycobacterial 65-kDa heat shock protein and other immunodominant antigens in patients with psoriasis

An association of microbial agents and autoimmunity has been suggested for the pathogenesis of psoriasis. Mycobacteria are common environmental microbes and their antigens, especially the highly conserved mycobacterial 65-kDa heat shock protein (hps65), have been implicated in the pathogenesis of autoimmune arthritis and other idiopathic diseases. In this context, we investigated a possible mycobacterium-induced humoral immune response in psoriasis. Sera from 17 patients with chronic plaque-type psoriasis were studied by immunoblotting using the whole sonicate of Mycobacterium tuberculosis and purified recombinant mycobacterial hsp65. Immunoblot analysis demonstrated that 58% of the psoriasis patients compared to patients with acne and DLE, and normal controls showed strong antibody activity to 65-kDa and 48/45 doublet antigens from M. tuberculosis sonicate, whereas 47% of the patients showed antibody activity to mycobacterial hsp65. Only 10-20% of the patients had an antibody response to 16-kDa and 80-kDa antigens. Similar antibody activity to 65 kDa and 48/45 kDa was also found consistently with eight different sonicated mycobacterial species by immunoblotting, indicating that these seroreactive antigens are crossreactive and are present in common environmental mycobacteria. Antibody activities to both mycobacterial 65-kDa and hsp65 showed a positive correlation (r = 0.76) with the psoriasis disease activity, whereas antibodies to 48/45-kDa doublet antigens showed a weak correlation (r = 0.54). By enzyme-linked immunosorbent assay (ELISA), 47% of the psoriasis patients showed significantly elevated antibody titers to hsp65 (p < 0.003) as compared to control groups, and the antibody response by ELISA also showed a significant positive correlation (r = 0.76) with disease activity. Anti-mycobacterial antibody activity may be related to severity of disease and may be useful in monitoring disease activity in psoriasis.

Heterogeneity of monoclonal antibody-reactive epitopes on mycobacterial 30-kilodalton-region proteins and the secreted antigen 85 complex and demonstration of antigen 85B on the Mycobacterium leprae cell wall surface

Proteins of the antigen 85 complex in the 30-kDa region secreted by live mycobacteria are important in the immune response against mycobacterial infections and may play an important biological role in the host-parasite interaction. In the present study, we have characterized epitopes of the 30-kDa-region proteins and the antigen 85 complex by using a panel of 13 monoclonal antibodies (MAbs) reacting with these antigens, 6 of which have not been described before. By using five previously characterized related secreted proteins of Mycobacterium tuberculosis, MPT44 (85A), MPT59 (85B), MPT45 (85C), MPT51 (27 kDa), and MPT64 (26 kDa), we have identified at least 10 different MAb-reactive epitopes on the proteins of the antigen 85 complex. A heterogeneous distribution of epitopes was observed within the components of the antigen 85 complex. Two distinct epitopes specific for antigen 85B and two other epitopes restricted to the 85A and 85B components were recognized. Two of them were shared with a previously unidentified 27-kDa protein present in M. tuberculosis culture fluid from which all MPT proteins were derived. The rest of the MAb-reactive epitopes were found to be present mostly in antigens 85A and 85B and to a lesser extent in antigen 85C. None of these MAbs recognized component 85C alone nor did they bind to the related MPT51 and MPT64 proteins. Interestingly, most of the MAbs reacted with purified native proteins of the antigen 85 complex but not to them in their denatured forms. In contrast, reactivity of the MAbs with the cytosol fraction of M. tuberculosis in immunoblotting revealed that they bound to a closely related cytosolic 30-kDa protein(s) even when they were denatured. Heterogeneity of these MAb-reactive epitopes of the antigen 85 complex was further evident as they were found to be distributed in various patterns among 19 different mycobacterial species. By using fusion proteins of the Mycobacterium leprae 30/31-kDa antigen 85 complex, we have localized at least six different epitopes within amino acid residues 55 to 266 of the M. leprae antigen 85 complex. Finally, by immunohistochemical analysis, we have demonstrated the in situ expression of one of the novel MAb-reactive epitopes specific for antigen 85B on the cell wall surface of M. leprae within macrophages in lepromatous leprosy lesions and thus provide direct evidence for the presence of the B component of the antigen 85 complex on the surface of intact M. leprae.

Identification and characterization of epitopes shared between the mycobacterial 65-kilodalton heat shock protein and the actively secreted antigen 85 complex: their in situ expression on the cell wall surface of Mycobacterium leprae

Both mycobacterial hsp65 and the actively secreted antigen 85 complex of 30-kDa region proteins are considered to be major immune targets in mycobacterial diseases. In this study, by using a novel series of monoclonal antibodies (MAbs) directed to these antigens, we identified and partially characterized three unique epitopes (Rb2, Pe12, and A2h11) that are shared between mycobacterial hsp65 and the individual components of the antigen 85 complex. Dot blot assays with native purified proteins revealed that all three MAbs are strongly bound to hsp65 and antigens 85A (MPT44) and 85B (MPT59), while a weak reaction or no reaction was found with antigen 85C (MPT45). Immunoblotting showed that MAb Rb2 reacted strongly with both hsp65 and the antigen 85 complex proteins, whereas MAbs Pe12 and A2h11 reacted strongly with the former but weakly with the latter. Moreover, these MAbs did not react with other closely related MPT51 and MPT64 secreted proteins. Further characterization of these epitopes was performed by using recombinant fusion and truncated proteins of Mycobacterium bovis BCG hsp65 (MbaA) and the M. leprae 30- and 31-kDa antigen 85 complex fusion proteins. In hsp65, Rb2-Pe12- and A2h11-reactive epitopes were found to reside in the C-terminal region of amino acid residues 479 to 540 and 303 to 424, respectively. In the M. leprae 30- and 31-kDa antigen 85 complex, all three epitopes were located in an N-terminal region of amino acid residues 55 to 266, one of the known fibronectin-binding sites of the M. leprae antigen 85 complex. Comparison of these MAb-reactive amino acid sequence regions between mycobacterial hsp65 and the components of the antigen 85 complex revealed that these regions show certain amino acid sequence identities. Furthermore, by immunoperoxidase and immunogold ultracytochemistry, we demonstrated that Rb2-, Pe12-, and A2h11-reactive epitopes are expressed both on the cell wall surface and in the cytosol of M. leprae bacilli within the lesions of lepromatous leprosy patients and in M. leprae-infected armadillo liver tissue.

Mycobacterium leprae produces extracellular homologs of the antigen 85 complex

The antigen 85 complex is a set of at least three closely related secreted proteins (85A, 85B, and 85C) of 30 to 32 kDa produced by Mycobacterium tuberculosis and other mycobacteria. Their prominence in Mycobacterium leprae, the one obligate intracellular pathogen of the genus, had been assumed on the basis of immunological evidence and proof of the existence of the gene encoding the 85B protein of the complex. We have now observed the production of this family of proteins by M. leprae through analysis of various fractions by Western blotting (immunoblotting) with monospecific rabbit antisera raised against the individual Mycobacterium bovis BCG 85A, 85B, and 85C proteins. A predominant cross-reactive band with an apparent molecular mass of 30 kDa was detected in extracts of nondisrupted whole M. leprae and in soluble fractions prepared from the tissues of M. leprae-infected armadillos. Further studies of the subcellular distribution of this protein within the bacterium confirmed that it is secreted by the organism, an observation that explains past difficulties in detecting the antigen 85 complex in M. leprae. Confirmation that the M. leprae product is a member of the antigen 85 complex was obtained by comparison of peptide fingerprints with those from the BCG product. The pattern of reactivity of the M. leprae antigen 85 complex with anti-M. bovis BCG 85B serum, as well as two-dimensional electrophoresis, established that the 85B component was the predominant member of the complex in M. leprae. The fibronectin-binding capacity of the M. leprae and BCG 85 complexes was reinvestigated by new approaches and is questioned. Nevertheless, the results obtained with the native proteins reinforce previous reports, derived primarily from the use of homologous proteins, that the antigen 85 complex is one of the dominant protein immunogens of the leprosy bacillus.

Mycobacterial 65,000 MW heat-shock protein shares a carboxy-terminal epitope with human epidermal cytokeratin 1/2

Molecular mimicry between mycobacterial heat-shock protein (hsp) 65 and host tissue antigens have been implicated in the autoimmune pathogenesis of certain idiopathic diseases. Here, we demonstrated that two of our previously characterized monoclonal antibodies (mAb), Ne5 and Nd4 that were directed to a carboxy-terminal epitope on the mycobacterial hsp 65, specifically cross-reacted with suprabasal cytokeratin of the normal human skin. These mAb also showed similar keratin staining of hair follicle epithelia and produced no reaction with other dermal components. Both mAb strongly stained the cytoplasm of the majority of freshly isolated epidermal keratinocytes from the normal human skin. None of these mAb showed staining with human HeLa cells and with human skin fibroblasts. Immunoblotting using total keratin extract prepared from isolated epidermal keratinocytes revealed that mAb Ne5 and Nd4 specifically reacted with a molecular size of 65,000-67,000 MW keratin protein(s) and such reactivity was not observed from cytoskeletal proteins extracted from HeLa cells and skin fibroblasts. Comparison of immunoblotting reactivity with conventional anti-cytokeratin mAb further revealed that mAb Ne5/Nd4 recognized a 65,000-67,000 MW molecular-sized protein corresponding to cytokeratin 1/2 from the same keratinocyte extract as anti-cytokeratin mAb. Preincubation of mAb Ne5/Nd4 with the purified mycobacterial hsp 65 abolished this keratin cross-reactivity in both immunohistochemistry and immunoblotting. Moreover, these mAb showed no keratin staining in lesional psoriatic skin and also reacted weakly with cultured epidermal keratinocytes. Since mAb Ne5/Nd4 specifically recognized a 67,000-65,000 MW molecular-sized protein(s) derived from epidermal keratinocytes and the known characteristics of epidermal cytokeratin 1/2 appeared to be consistent with present results, we concluded that Ne5/Nd4 cross-reactive protein(s) in the human epidermis is suprabasal cytokeratin 1/2. Comparison of the previously mapped Ne5/Nd4 epitope region of amino acid residues 525-540 of the mycobacterial hsp 65 with the entire sequence of human 65,000 MW keratin revealed that a stretch of nine amino acids of the Ne5/Nd4 epitope sequence resembled certain regions of the carboxy-terminus of the human 65,000 MW keratin. This similarity of the mycobacterial hsp 65 probably contributes to the cytokeratin cross-reactive epitope. Our results presented here demonstrate direct evidence of immunological cross-reactivity between mycobacterial hsp 65 and human epidermal cytokeratin 1/2. We speculate that Ne5/Nd4 cross-reactive epitope of epidermal cytokeratins might be an important target for skin diseases.

Association of the mycobacterial 30-kDa region proteins with the cutaneous infiltrates of leprosy lesions. Evidence for the involvement of the major mycobacterial secreted proteins in the local immune response of leprosy

The granulomatous skin lesions of human leprosy are known to be due to the cutaneous immune reaction to various mycobacterial antigens. In the present study, by immunohistochemical analysis using a previously characterized monoclonal antibody (MoAb) 3A8 we have demonstrated a selective expression of the 3A8 epitope of mycobacterial 30-kDa proteins, the major secreted proteins of mycobacteria, in various forms of leprosy lesions across the clinical spectrum. The localization of MoAb 3A8 staining is confined to the areas of cellular infiltrates of the lesions. In tuberculoid lesions the intense 3A8 staining was seen mostly in association with the membrane of the dermal cellular infiltrates whereas in highly bacilliferous lepromatous lesions the staining seems to be diffused with granular appearance but not in the form of bacteria. In patients with reversal reaction the staining was specifically extended to cells infiltrating the epidermis. MoAb 3A8 did not show any reactivity with inflammatory skin lesions of patients other than those with leprosy. Since the 3A8 epitope of 30-kDa proteins has been shown to be present in all cellular compartments of the mycobacteria and in the actively secreted BCG 85 antigen complex, MoAb 3A8 reactive protein(s) in leprosy lesions may be derived either from degraded somatic mycobacterial products or from antigens actively secreted by live bacilli. The latter could be true in the cases of untreated lepromatous lesions with high bacterial load since live M. leprae has also been considered to secrete corresponding 30-kDa proteins similar to other closely related mycobacteria. By double immunoenzyme staining we clearly demonstrate the expression of 3A8 epitope on CD68+ macrophages in the granulomas of tuberculoid leprosy, whereas in highly bacilliferous lepromatous lesions most of the double staining was seen in a diffuse pattern within the interstitial space of the cellular infiltrate as well as in the cytoplasm of CD68+ macrophages. In lesions from reversal reaction the 3A8 epitope is more strongly expressed on CDla+ dendritic Langerhans cells (LC) both in the epidermis and in the dermis as compared with other types of leprosy. This provides evidence for the involvement of LC in handling of mycobacterial antigenic epitopes in leprosy lesions. Further, immunoenzyme double staining revealed that the expression of this mycobacterial 3A8 epitope on antigen presenting cells such as CD68+ macrophages and CDla+ LC is present in juxtaposition with CD3+ T cells including the alpha beta and gamma delta receptor-bearing T cells in the granuloma.(ABSTRACT TRUNCATED AT 400 WORDS)

Humoral responses against the 85A and 85B antigens of Mycobacterium bovis BCG in patients with leprosy and tuberculosis

Immunoglobulin G antibodies against the 85A and 85B components of the Mycobacterium bovis BCG antigen 85 complex separated by isoelectric focusing were investigated in serum samples from 129 patients representing the major forms of leprosy, 111 tuberculous patients, and 153 healthy subjects. For both of the antigens, a higher degree of staining was observed for lepromatous leprosy patients and patients with active tuberculosis than for the other groups. Because sera from some healthy subjects recognized the 85A antigen, we suggest that antigen 85B is the most useful component of the antigen 85 complex for the serodiagnosis of the multibacillary forms of leprosy or of the active forms of tuberculosis.

Molecular and immunological analysis of a fibronectin-binding protein antigen secreted by Mycobacterium leprae

By screening a Mycobacterium leprae lambda gt11 genomic DNA library with leprosy-patient sera we have previously identified 50 recombinant clones that expressed novel M. leprae antigens (Sathish et al., 1990). In this study, we show by DNA sequencing and immunoblot analysis that three of these clones express a M. leprae homologue of the fibronectin-binding antigen 85 complex of mycobacteria. The complete gene was characterized and it encodes a 327-amino-acid polypeptide, consisting of a consensus signal sequence of 38 amino acids followed by a mature protein of 289 amino acids. This is the first sequence of a member of the M. leprae antigen 85 complex, and Southern blotting analysis indicated the presence of multiple genes of the 85 complex in the genome of M. leprae. The amino acid sequence displays 75-85% sequence identity with components of the antigen 85 complex from M. tuberculosis, M. bovis BCG and M. kansasii. Furthermore, antibodies to the antigen 85 complex of M. tuberculosis and M. bovis BCG reacted with two fusion proteins containing the amino acid regions 55-266 and 266-327 of the M. leprae protein. The M. leprae 30/31 kDa protein induces strong humoral and cellular responses, as judged by Western blot analysis with patient sera and proliferation of T cells derived from healthy individuals and leprosy patients. Amino acid regions 55-266 and 265-327 both were shown to bind to fibronectin, indicating the presence of at least two fibronectin-binding sites on the M. leprae protein. These data indicate that this 30/31 kDa protein is not only important in the immune response against M. leprae, but may also have a biological role in the interaction of this bacillus with the human host.

An isoelectric focusing method for the study of the humoral response against the antigen 85 complex of Mycobacterium bovis BCG in the different forms of leprosy

Isoelectric focusing was used to separate the three components of the antigen 85 complex of Mycobacterium bovis BCG. Antibody responses of leprosy patients against each Mycobacterium bovis BCG. Antibody responses of leprosy patients against each component were quantitated by densitometric analysis of immunoblot assays. The 85A component was recognized by 40% (8/20) of the lepromin positive and negative healthy subjects, by 76% (19/25) of the tuberculoid and by 96% (24/25) of the lepromatous leprosy sera. In contrast, the 85B component was not stained by the control sera, nor by the tuberculoid leprosy sera but by 64% (16/25) of the lepromatous leprosy sera. The results suggest that antigen 85B contains one or several epitopes that are specifically recognized by sera of lepromatous leprosy patients only.

T cell response to purified filtrate antigen 85 from Mycobacterium bovis Bacilli Calmette-Guérin (BCG) in leprosy patients

T cell proliferation and IFN-gamma production of peripheral blood mononuclear cells from 25 healthy controls and 39 leprosy patients were tested against BCG-bacilli and culture filtrate. Mycobacterium leprae and purified antigen 85 (the major secreted 30-32 kD protein antigen) from M. bovis strain BCG. In lepromin negative healthy controls, blastogenesis was low to M. leprae and completely negative to antigen 85. IFN-gamma levels were very low, close to detection limits. In all lepromin positive controls, significant proliferation and IFN-gamma secretion was found in response to M. leprae and antigen 85. In the group of lepromatous leprosy (LL) patients, 25/29 of patients (with either positive (13) or negative (12) lymphoproliferative response to BCG) were unreactive to M. leprae or to antigen 85. Four LL patients with positive T cell response to BCG responded with detectable lymphoproliferative response and IFN-gamma secretion to antigen 85. All tuberculoid (TT) leprosy patients responded to BCG, M. leprae and antigen 85. Hence, T cells from leprosy patients and controls demonstrate a marked parallelism of responsiveness towards whole M. leprae and purified antigen 85 from M. bovis BCG, suggesting strong cross-reactivity between the two species and underlining the biological importance of such secreted antigens.

Serology and leprosy: immunoassays comparing immunoglobulin G antibody responses to 28- and 30-kilodalton proteins purified from Mycobacterium bovis BCG

Two major proteins from Mycobacterium bovis BCG culture filtrates with molecular masses of 28 kDa (P28) and 30 kDa (P30), identified as components of the BCG 85 complex, were purified and used in enzyme-linked immunosorbent assays (ELISAs) for the determination of specific immunoglobulin G (IgG) levels in patients with leprosy or tuberculosis or with exposure to these diseases. High reactivity to both antigens was observed with sera from lepromatous leprosy patients, whereas antibody levels in sera from paucibacillary leprosy patients were not significantly different from those in sera from healthy individuals from an area in which leprosy is endemic. High IgG responses were also found in some contacts of lepromatous leprosy patients. A comparison of the levels of anti-P28 and anti-P30 within the multibacillary leprosy patient group showed much higher IgG reactivity to P28 than to P30, suggesting that the antibody response of lepromatous patients is directed predominantly against the 28-kDa protein. A high degree of correlation in values of ELISAs based on P28 and on the phenolic glycolipid of Mycobacterium leprae was observed in all groups analyzed. The potential use of an assay based on the 28-kDa protein to selectively distinguish individuals destined to develop multibacillary leprosy is discussed, as also is the likelihood that the 28-kDa-30-kDa complex, part of the fibronectin-binding family, is an important component of M. leprae.

Subcellular distribution of monoclonal antibody defined epitopes on immunodominant Mycobacterium tuberculosis proteins in the 30-kDa region: identification and localization of 29/33-kDa doublet proteins on mycobacterial cell wall

Two different groups of monoclonal antibodies (MAbs) directed to different epitopes on 30-kDa region proteins of Mycobacterium tuberculosis were isolated; MAbs 5F9, 5D5 and 5D2 reacted with a single 33-kDa protein band, whereas MAb 3A8 reacted with a distinct 29/33-kDa doublet when analysed by immunoblotting. The present paper describes the distribution of MAbs defined epitopes in the 29-33-kDa region proteins in well-characterized subcellular fractions: cytosol, plasma membrane, cell wall as well as culture filtrate of M. tuberculosis. MAbs 5F9, 5D5 and 5D2 reactive epitopes were found in cytosol, whereas 3A8 epitope is distributed in all cellular compartments of the mycobacterium as well as in the culture filtrate. Localization of these epitopes by indirect immunofluorescence and immunogold-labelling demonstrated that only 3A8 epitope is present on the cell surface of the mycobacterium. Both immunoblotting and ELISA showed that only MAb 3A8, and not 5F9, 5D5 and 5D2, reacted with secreted BCG 85 antigen complex of Mycobacterium bovis BCG. Furthermore, using an MAb 3A8-coupled affinity column, we purified antigen 3A8 from the cytosol fraction of M. tuberculosis. All these MAbs reacted with antigen 3A8 with varying degrees of intensity, thus suggesting that they are directed to a single protein. Absence of 5F9, 5D5 and 5D2 epitopes in the cell wall, culture filtrate and to a single protein. Absence of 5F9, 5D5 and 5D2 epitopes in the cell wall, culture filtrate and BCG-85 complex suggests that these epitopes might have been lost during the processing of the same 33-kDa protein on its way out from cytosol to the cell wall or when the protein is secreted out into the culture filtrate. Our results demonstrate, for the first time, direct evidence of the presence of a 30-kDa region protein not only in secreted antigens but also in the cell wall and on the cell surface of the mycobacterium.

Identification of a novel B-cell epitope of restricted specificity on the hsp 65-kDa protein of Mycobacterium tuberculosis

A B-cell epitope on the carboxy-terminal region of the mycobacterial 65-kDa heat shock protein that distinguishes Mycobacterium tuberculosis/Mycobacterium bovis BCG from Mycobacterium leprae was identified by two novel monoclonal antibodies (mAbs), Ne5 and Nd4. These mAbs also showed a limited cross reactivity with mycobacterial species belonging to M. tuberculosis complex and Mycobacterium avium complex with the exception of Mycobacterium vaccae. Characterization of the epitope recognized by these mAbs was done with M. bovis BCG 65-kDa fusion proteins expressed in Escherichia coli encoding various segments of the 65-kDa protein. Our results together with those reported in literature indicated that this epitope resides in the highly divergent region of amino acid residues 525 to 540. This B-cell epitope on the 65-kDa protein of M. tuberculosis/M. bovis BCG has not been recognized by previously reported mAbs, although the analogous epitope sequence of M. leprae 65-kDa has been identified by a known mAb (IIIC8) reported in the literature. Therefore Ne5/Nd4 epitope could be considered important in studying the differential immune response of the host against infections with M. tuberculosis complex/M. avium complex and M. leprae.