Cellular, Humoral, and Gamma Interferon Responses toMycobacterium lepraeand BCG Antigens in Healthy Individuals Exposed to Leprosy

Abstract

Protective immunity against mycobacteria is dependent on antigen-specific T cells. The antibodies induced upon immunization with mycobacteria have no apparent role in host protection. Serological techniques have detected some antigens that are also recognized by human T cells but may fail to recognize others. Potentially, there may be differences in the epitopes seen by the T and B cell anti-mycobacterial antigen repertoires. We have screened the different components of sonicated BCG or Mycobacterium leprae that were separated according to their molecular weight (MW) by SDS-PAGE and then electroblotted on nitrocellulose paper. The blots were cut into squares and tested directly in a T cell proliferation assay. Our results indicate that peripheral T cells of healthy leprosy patient contacts respond preferentially to the lower MW (less than 70,000) and not the higher MW fractions of M. leprae and BCG, in contrast to the humoral response of these same individuals. The most important fractions in inducing a lymphoproliferative response were in the regions of 11-16 kDa of BCG and M. leprae and to the 22-26 kDa region of M. leprae. These fractions appeared to represent molecular weight regions that were in some instances clearly distinct from previously defined antigens. It was further shown that lymphoproliferation in response to mycobacterial fractions correlated with the production of gamma interferon, a lymphokine required for macrophage activation and elimination of mycobacteria. These studies allow the direct assessment of antigens involved in protective T cell-mediated immunity, and should be helpful in selecting relevant antigens for skin testing and immunization.

T cell responses to fractionated Mycobacterium leprae antigens in leprosy. The lepromatous nonresponder defect can be overcome in vitro by stimulation with fractionated M. leprae components

“…Such a vaccine seems one of the key strategies for the control of leprosy in the third world since the leprosy bacillus itself cannot be grown in vitro [ 11. Our results indicate that T cells of the majority of tuberculoid patients respond predominantly to BCGnc and Mlepnc antigens in the MI range of 10-40 kDa with most intense reactivity to the 10-25 kDa range. Less pronounced and interindividually more variable T cell responses were found against fractions between 40 and 70 kDa, consistent with our previous results with healthy exposed individuals from the same ethnic background as those in the present study [6]. Perhaps the most interesting result in this study is that M. leprue-non-responder LL patients can be turned into responders when rechallenged with single M. leprae fractions rather than the whole microorganism.…”

“…2 5000 cpm (or A cpm 2 5000 in case of patients 8 and 11 of Table 1) in the 7 BCGnc responders were seen in general against the BCGnc fractions with MI components < 70 kDa, showing a strong similarity to our previously reported results for M. leprae-exposed but disease-free individuals [6]. In the region > 70 kDa, significant responses could occasionally be detected against fractions with MI ranging from 97 to 115 kDa (no.…”

“…In these three individuals a pattern similar to that for BCGnc was observed since T cell responses were almost only seen towards fractions < 70 kDa. The most intense responses were again directed against the 10-25 kDa regions, but in distinction from healthy exposed individuals [6] responses were also seen to regions ranging from 35-50 kDa (peak: 9757 cpm) and 57-71 kDa For a comparison of the cellular and humoral responses to BCGnc-and Mlepnc-fractionated antigens, results from the T cell assay and from the Western blot (probed with autologous serum of the same bleeding date) are shown together in Fig. 1 and will be discussed below in more detail.…”

T cell proliferative responses to molecular fractions of periodontopathic bacteria

“…This finding was not confirmed in the present study, since the stimulation indices in SP patients were comparable with stimulation induced by soluble Veillonella antigen in previous studies (Ivanyi et al, 1981;Ivanyi, 1986). The responsiveness to fractionated antigens in non-responders to whole bacterial extract was also reported by other investigators (Converse et at., 1988;Mendez-Samperio et al, 1989). The interpretation may rest in the abolition of a 'suppressor' constituent by the separation of the wbole antigen extract.…”

Induction of antigen‐specific CD4+ HLA‐DR‐restricted cytotoxic T lymphocytes as well as nonspecific nonrestricted killer cells by the recombinant mycobacterial 65‐kDa heat‐shock protein

“…IFN titers in the SN of cultures were determined as described in [35] using the WISH cell assay.TNF titers were measured using an ELISA as described in' [36] with minor modifications.…”