Delayed-type hypersensitivity, in vitro T-cell responsiveness and risk of active coccidioidomycosis among HIV-infected patients living in the coccidioidal endemic area

Abstract

The prognostic importance of specific and general tests of immune function were examined among a cohort of 170 subjects infected with human immunodeficiency virus type-1 (HIV), living in an area endemic for the fungal infection coccidioidomycosis. Using the proportional hazards model and multivariate analysis, lack of expression of coccidioidal delayed-type hypersensitivity (DTH) was found to be dependent on anergy in response to the non-coccidioidal antigens mumps, Trichophyton and Candida (relative hazard 4.2, 95% CI 1.8-9.8, P=0.001). Among subjects with CD4 lymphocyte counts >/=250 microl-1 on entry into the study, the in vitro lymphocyte transformation (LT) response to the coccidioidal antigen toluene spherule lysate was 4967+/-1652 (mean counts per minute (c.p.m.)+/-SEM) in subjects with coccidioidal DTH compared with 136+/-222 in those with negative DTH (P<0.001). However, amongst those whose CD4 count was <250 microl-1, LT responses were low and there was no significant difference based on coccidioidal DTH (P=0.965). Using the proportional hazards model and multivariate analysis, only a CD4 count <250 microl-1 was prognostically associated with the development of either active coccidioidomycosis or AIDS. These data indicate that immunodeficiency, particularly a CD4 lymphocyte count <250 microl-1, is the most important factor in the lack of expression of specific immunity to coccidioidomycosis and in the development of active coccidioidomycosis among HIV-infected individuals living in the coccidioidal endemic area.