Jacques Millan

Demographic, Ethnic, and Geographic Differences between Human T Cell Lymphotropic Virus (HTLV) Type I-Seropositive Carriers and Persons with HTLV-I Gag-Indeterminate Western Blots in Central Africa

Using stringent Western blot (WB) criteria, human T cell lymphotropic virus (HTLV) type I seroprevalence among 3783 persons from representative rural populations of Cameroon averaged 1.1% and was higher in females (1.5%) and in Pygmies (2.0%), increasing with age. Furthermore, an HTLV-I Gag-indeterminate WB profile (HGIP), exhibiting strong reactivities to p19, p26, p28, p32, p36, and pr 53 but lacking both p24 and env reactivity, was observed in 1.6% of the same populations. The prevalence of the HGIP was similar between males and females, did not increase with age, and appeared to cluster in tropical forests of southern Cameroon, especially among Pygmies (reaching 4%). These contrasting epidemiologic features, together with the lack of detection by polymerase chain reaction of HTLV-I sequences in the peripheral blood mononuclear cells of the persons with HGIP, strongly suggest that such a WB profile does not appear to reflect an HTLV-I-related viral infection but possibly an environmental (viral or parasitic) factor endemic in tropical rain forest areas.

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

T cell proliferation and IFN‐γ 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‐γ levels were very low, close to detection limits. In all lepromin positive controls, significant proliferation and IFN‐γ 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‐γ secretion to antigen 85. All tuberculoid (TT) leprosy patients responded to BCG, M. teprae 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 eross‐reactivity between the two species and underlining the biological importance of such secreted antigens.

T-cell stimulation with purified mycobacterial antigens in patients and healthy subjects infected with Mycobacterium leprae: secreted antigen 85 is another immunodominant antigen

Peripheral blood leucocytes from 9 paucibacillary and 12 multibacillary leprosy patients, from 18 healthy controls and from 34 healthy leprosy contacts were stimulated with three mycobacterial heat shock proteins with respective molecular weights of 70,65 and 18 kDa and with the secreted 30–32 kDa protein, also called antigen 85. Antigen 85 was found to be the most powerful T‐cell antigen (as measured by lymphoproliferation and IFN‐γ secretion), eliciting a positive response in all (100%) paucibacillary patients and in all lepromin‐positive controls and contacts. The three heat shock proteins (hsp) were less active T‐cell stimuli. Reactivity to the 70 kDa hsp was found in only 44% of the paucibacillary patients, in 80% of the lepromin‐positive controls and in 60% of the lepromin‐positive leprosy contacts. The 65 kDa hsp stimulated T cells in 89% of the paucibacillary patients and in 80% of the lepromin‐positive controls and contacts. Responsiveness to the 18 kDa hsp, finally, was clearly more frequent in tuberculoid leprosy patients (78%) than in lepromin‐positive controls (40%) or lepromin‐positive leprosy contacts (4%). T‐cell reactivity of 8 lepromin‐negative controls, of 9 lepromin‐negative contacts and of 12 multibacillary leprosy patients was low to all the antigens tested. Although proliferative and IFN‐γ responses were generally closely related, some subjects demonstrated a dissociation of these two immune parameters. Our data confirm previous findings on the powerful T‐cell stimulatory properties of antigen 85 during M. leprae infection and suggest that this antigen is indeed a potentially protective T‐cell immunogen.

Anti-peripheral nerve antibodies in leprosy patients recognize an epitope shared by the M. leprae 65 kDa heat shock protein

Binding of leprosy sera to peripheral nerve from different species (mouse, guinea pig and rabbit) was evaluated by ELISA. A majority of sera, whatever the clinical form of leprosy, bind to these antigens. Absorption with Mycobacterium bovis BCG demonstrated that these antibodies recognize cross-reactive epitopes between peripheral nerve and mycobacteria. In immunoblot analysis, both leprosy patient sera and a monoclonal antibody directed at the 65 kDa heat shock protein of M. leprae were shown to react with a heat-shock 67-68 kDa sciatic nerve protein. Binding of the monoclonal antibody to this sciatic nerve antigen was prevented by incubation with lepromatous patient sera, showing that some peripheral nerve epitopes recognized by patient antibodies are shared by the 65 kDa heat shock protein of M. leprae.