HIV-specific T helper responses and frequency of exposure among HIV-exposed seronegative female sex workers in Abidjan, Cote d'Ivoire

Background. The characteristics of human immunodeficiency virus (HIV) exposure that determine the induction of HIV-specific T cells and, in particular, T helper cells are not well understood. Methods. HIV-1 Gag- and Env-specific T helper cells were analyzed by use of an interferon (IFN)-gamma enzyme-linked immunosorbent spot (ELISPOT) assay and by use of IFN-gamma secretion flow cytometry. Responses among HIV-exposed seronegative (ESN) female sex workers (FSWs) were compared with responses among HIV-seropositive FSWs and HIV-seronegative female blood donors from Abidjan, Cote d'Ivoire. Results. Low- level ELISPOT responses were detected in 8 (20%) of 40 ESN FSWs. All of 25 HIV-seropositive FSWs had high-level ELISPOT responses. HIV-specific CD4(+) T cells and, occasionally, CD8(+) T cells were detected by secretion flow cytometry in 3 (38%) of 8 ESN FSWs and in 4 (80%) of 5 HIV-seropositive FSWs. ESN FSWs with detectable HIV-specific T helper responses had more clients on the previous working day (P=.02) and more exposures to HIV per month (P=.02) and tended to have a lower total duration of commercial sex work. Conclusions. These findings demonstrate that the presence of HIV-specific T helper cells in ESN FSWs is associated with the frequency, rather than the duration, of exposure to HIV. The data may have important implications for the evaluation of HIV vaccine efficacy.