IgM anti-phenolic glycolipid I and IgG anti-10-kDa heat shock protein antibodies in sera and immune complexes isolated from leprosy patients with or without erythema nodosum leprosum and contacts.

The aim of the present work was to evaluate the levels of anti-PGL-I and anti-10-kDa heat shock protein antibodies in serum and immune complexes isolated from leprosy patients, convivients and controls. Leprosy patients with erythema nodosum leprosum or without it were included and a comparative study was done to investigate intergroup differences. Immune complexes were precipitated from serum by polyethylene glycol 3.5%; antibody levels were measured in sera and in dissociated immune complexes by ELISA. Serum antibody levels were then correlated with immune complex-associated antibody levels. The results showed that the erythema nodosum leprosum group differed from controls, contacts and non-erythema patients in their immune complex levels. IgM anti-PGL-I and IgG anti-10-kDa heat shock protein antibodies were constituents of the immune complexes in patients with erythema nodosum leprosum, who exhibited a significant difference in their immune complex composition compared with controls, contacts and non-erythema patients; while free antibody levels (anti-PGL-I and anti-10-kDa) did not differentiate between erythema and non-erythema patients, the measurement of immune complex-associated antibodies demonstrated a significant difference between the two clinical conditions. Furthermore, the measurement of immune complex-associated anti-PGL-I IgM made it possible to differentiate between contacts and controls. The significance of these results is discussed.

Cross-reactivity of anti-10kD heat shock protein antibodies in leprosy and tuberculosis patients.

The response to recombinant 10-kD heat shock protein (HSP) of Mycobacterium leprae (rML10) was evaluated by indirect ELISA in sera from leprosy patients, household contacts, tuberculosis patients and healthy controls in a leprosy-endemic area in the North East of Argentina. Some technical parameters were analyzed: within-assay and between-assay variability, dose-response curves and detectability indexes (specificity and sensitivity) of ELISA applied to measure anti-10 kDa antibodies. High levels of these antibodies have already been reported in positive bacilloscopy patients; herein we have also demonstrated that tuberculosis patients sera cross-react with this M. leprae antigen. This test seems to have a low sensitivity and specificity for leprosy detection; it confirms that antibodies against highly conserved HSP antigens are important in the polyclonal response against mycobacterial epitopes in leprosy as well as in tuberculosis.

Characterization of circulating immune complexes in leprosy patients and their correlation with specific antibodies against Mycobacterium leprae.

Circulating immune complex (CIC) levels and their antibody and antigenic composition were evaluated in patients with leprosy as well as in any individuals living with them; they were precipitated with 3.5% polyethylene glycol (PEG) and, after affinity chromatography isolation and purification, analysed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblot with monoclonal antibodies (Mabs). The presence of CICs was demonstrated throughout the clinical and immunopathological leprosy spectrum at levels related to bacterial load, and in leprosy patients they showed a positive correlation with specific anti-PGL and anti-65 kDa antibodies. The isolation and analysis, however, failed to identify any Mycobacterium leprae antigenic components; although two specific antibodies anti-PGL-1 and anti-65 kDa were identified as possible CIC constituents and may be potentially useful in the follow-up of leprosy patients, especially to check bacterial load evolution, PGL-1 being an authentic antigen of this mycobacterium. Also, the involvement of 65 kDa in CICs, being homologous with the human heat shock protein (HSP) 60 kDa family, suggests an autoimmune mechanism in leprosy pathogenesis. Furthermore, those results support the inclusion of CIC antibody reactivity studies to enhance the sensitivity of serology.

Immunoglobulin G response against 10-kDa and 65-kDa heat-shock proteins in leprosy patients and their household contacts.

We measured antibody responses to recombinant Mycobacterium leprae 65-kDa (rML65) and 10-kDa (rML10) by indirect ELISA in sera from leprosy patients, household contacts and healthy controls in a leprosy-endemic area in the north east of Argentina. Serum antibody levels to those antigens were correlated with IgM anti-phenolic glycolipid I (PGL-I) levels, with bacterial index and the period of time under chemotherapy. Bacterial index positive (BI+) patients showed higher mean values when compared with BI negatives (BI-). Among lepromatous patients a positive correlation was observed between IgG antibody responses to both recombinant antigens and IgM antibody response to PGL-I. Anti-rML10 test detected a higher percentage of positives/total than anti-rML65 in all leprosy groups and healthy contacts. Bacterial load, leprosy clinical form and the time under chemotherapy were factors which could influence levels of the antibody response. The contribution of these antibody studies for a precise and early diagnosis in leprosy is discussed.