Poor correlation of systemic immunological parameters with clinical features in macular leprosy.

On the basis of clinical features and bacteriological status, macular skin lesions of nine cases of leprosy were classified as falling within a spectrum between the tuberculoid at one end and the lepromatous at the other. While histologic correlation was seen in 60% of cases, humoral and cellular systemic immunologic features were found to be uncharacteristic. It is suggested that macular lesions form an early stage in the development of leprosy where the systemic immunological response is yet to set in fully.

Immunological profiles of leprosy patients and healthy family contacts toward M. leprae antigens.

In this study, we measured simultaneously the in vitro and in vivo T lymphocyte reactivities and the antibody responses of leprosy patients and healthy family contacts (HFC) toward Mycobacterium leprae antigens. The in vitro lymphoproliferative response of the HFC to leprosin A was comparable to that of tuberculoid leprosy patients. However, their skin-test reactivity to Dharmendra lepromin was considerably higher compared to the in vitro response to leprosin A. A significant number of HFC failed to respond to M. leprae antigens, both in vitro and in vivo, and the unresponsiveness to either test was not related to the type of leprosy patients in the household. A marginal correlation was observed between the skin-test reactivity of HFC and the age of the individuals. Even though a significant proportion of HFC showed positive anti-PGL-I IgM levels, none showed a positive titer in the serum antibody competition test toward the M. leprae-specific epitope My2. A positive anti-PGL-I IgM response together with a negative lepromin skin-test reactivity showed a clear downward trend from the lepromatous pole toward the tuberculoid pole. A small number of HFC, all contacts of lepromatous patients, were lepromin skin-test negative with positive anti-PGL-I IgM levels, but the majority among them showed T-cell reactivity to mycobacterial antigens in vitro. These results are discussed in relation to immunological correlates of the susceptibility to M. leprae infection.

Antibody response to recombinant 65-kDa, 70-kDa and 18-kDa mycobacterial antigens in leprosy patients and healthy contacts in a leprosy-endemic population.

Antibody responses to recombinant Mycobacterium leprae 65-kDa (rML65) and 18-kDa (rML18), M. bovis BCG 65-kDa (rMB65) and M. tuberculosis 70-kDa (rMT70) antigens were measured by indirect ELISA in sera from leprosy patients and healthy contacts in a leprosy-endemic area in southern India. Antibody responses to M. leprae-specific epitopes on phenolic glycolipid-I (PGL-I) and a 35-kDa protein antigens also were measured simultaneously by PGL-I ELISA and the serum antibody competition test (SACT), respectively. Significantly higher levels of antibodies of the IgG isotype to rML65 and rMB65 were observed in bacterial index (BI)-positive, lepromatous (LBI+) patients but not in other groups of leprosy patients and endemic controls [healthy family contacts (HFC), healthy hospital contacts (HHC), and healthy non-contacts (HNC)]. LBI+ patients could be distinguished from LBI- patients on the basis of their higher levels of IgG antibodies to rML65, rMB65 and rMT70; lower levels of IgM antibodies to these antigens and higher levels of anti-PGL-I IgM levels. In the former group, 84% were SACT positive in contrast to 39% in the latter groups. Among lepromatous patients good positive correlations were observed between IgG antibody responses to rML65 and rMB65 and anti-PGL-I IgM levels, SACT ID50 titers as well as BIs. Among healthy controls, HFC had higher levels of IgG antibodies to rML65, but lower levels to rMB65 than did HNC. Thirty-nine percent of the HFC were seropositive to anti-PGL-I IgM antibodies in contrast to 4% in the HNC. On the basis of these criteria, the immune profile of the HFC appears to be distinctly different from that of the HNC, even though both groups are from the same endemic area. It is therefore possible that antibody response to defined protein antigens of mycobacteria is influenced by the lesional bacterial load in leprosy patients and by exposure to homologous proteins of M. leprae and/or related environmental mycobacteria in the case of healthy contacts and noncontacts. The above results are discussed in relation to T- and B-cell activity toward M. leprae antigens and the immunoregulatory mechanisms of antibody production in leprosy.

Cellular and humoral immune responses to recombinant 65-kD antigen of Mycobacterium leprae in leprosy patients and healthy controls.

Cellular and humoral immune responses to recombinant 65-kD antigen of Mycobacterium leprae (rML65) were studied in leprosy patients and healthy contacts from a leprosy-endemic population. Peripheral blood mononuclear cells from a considerable proportion of tuberculoid leprosy patients, healthy contacts and non-contacts showed proliferative response to rML65 in vitro. A strong positive correlation was observed between the responses to rML65 and bacille Calmette-Guérin (BCG) or leprosin A. Addition of recombinant IL-2 (rIL-2) enhanced the proportion of responders to rML65 considerably in all groups of leprosy patients, healthy contacts and non-contacts. Among lepromatous patients this enhancement was more pronounced in the bacterial index (BI)-negative group. These results indicate that the 65-kD antigen of Myco. leprae is a dominant T cell immunogen in our study population. Though lepromatous patients showed poor lymphoproliferative response to rML65, their IgG antibody levels to the same antigen were markedly high. Most of the BI-positive lepromatous patients with elevated anti-rML65 IgG levels did not show T cell reactivity even with the addition of rIL-2. On the other hand, tuberculoid leprosy patients, healthy contacts and non-contacts showed good T cell reactivity but low levels of IgG antibodies to rML65, thus indicating the presence of an inverse relationship between cell-mediated and humoral immune responses to a defined protein antigen of Myco. leprae in humans. A significant proportion of individuals among tuberculoid leprosy patients, healthy contacts and non-contacts showed neither T cell reactivity nor elevated levels of IgG antibody to rML65. However, in most of these subjects, a T cell response to rML65 was demonstrable with the addition of rIL-2. These results are discussed with reference to the immunoregulatory mechanisms occurring during Myco. leprae infection on the basis of differential activation of Th1 and Th2 subsets.

T lymphocyte reactivity of leprosy patients and healthy contacts from a leprosy-endemic population to delipidified cell components of Mycobacterium leprae.

In this study, we measured in vitro proliferative responses of peripheral blood mononuclear cells from both leprosy patients across the clinical spectrum and also healthy contacts from a leprosy-endemic population to delipidified cell components of Mycobacterium leprae (DCC) and Dharmendra lepromin. Dharmendra lepromin was poor in inducing in vitro T cell proliferation in all the study groups, even though it elicited marked in vivo skin test reaction in tuberculoid leprosy patients and healthy contacts. In contrast, Dharmendra preparation of BCG induced marked T-cell response in tuberculoid as well as bacterial index negative lepromatous patients. DCC induced a significantly higher lymphoproliferative response than Dharmendra lepromin in all study groups. A significant positive correlation was observed between the lymphoproliferative responses to DCC and BCG. The present study, based on a large number of leprosy patients and healthy contacts, clearly demonstrates that DCC, depleted of glycolipids and lipopolysaccharides, is a good antigenic preparation for evaluating T-cell reactivity to M. leprae.

Flow cytometric analysis of CD2 modulation on human peripheral blood T lymphocytes by Dharmendra preparation of Mycobacterium leprae.

It has been reported previously that Mycobacterium leprae modulated CD2 on human peripheral blood T lymphocytes and that this modulation was accompanied by a marked reduction in the proliferative response of these cells to mitogens and antigens. In this study, we report that treatment of peripheral blood mononuclear cells from healthy individuals with Dharmendra preparation of M. leprae inhibited their ability to form rosettes with sheep red blood cells. Flow cytometric analysis of Dharmendra lepromin-treated cells showed that, in addition to CD2, CD4 and CD8 were modulated while the surface expression of CD3 was not affected. The specificity of CD2 modulation was confirmed by similar effects of Dharmendra lepromin on thymocytes and lymph node cells from human CD2 transgenic mice. The modulatory effect of Dharmendra lepromin was not observed at lower temperatures. Dharmendra lepromin treatment of activated T cells resulted in reduced binding of monoclonal antibodies to IL-2R and D66 epitope of CD2. The modulatory effects were not observed with Dharmendra preparation of BCG or other preparations of M. leprae. Our results indicate that certain M. leprae factor(s) specifically modulate(s) CD2, CD4, CD8 and IL-2R but not CD3 on T lymphocytes. The suppressive effect of Dharmendra lepromin on the T-cell proliferative response reported earlier may be explained by its modulatory effect on a number of T-cell surface molecules.