CD4+ T Cell Responses in HIV-Exposed Seronegative Women Are Qualitatively Distinct from Those in HIV-Infected Women

The immune response of human immunodeficiency virus (HIV)–exposed seronegative (ESN) women may be qualitatively different from that in those infected with HIV (HIV+). In a cohort of female commercial sex workers in Nairobi, Kenya, we found significantly lower ( ) levels of CD4+-specific immune activation and apoptosisP .01 in the ESN women compared with those in the HIV+ women. Compared with the HIV+ women, a lower proportion of the ESN women showed p24 peptide pool responses by the short-term, CD4+-specific, interferon (IFN)–g intracellular cytokine staining assay, whereas the proportion showing responses by the long-term, CD8+-depleted T cell proliferation assay was similar. Interestingly, the ESN responders had a 4.5-fold stronger proliferation response ( ) than the HIV+ group. These data suggest that, compared with those in HIV+ women, CD4+P p.002 T cells in ESN women have a much greater ability to proliferate in response to p24 peptides. Those exposed to HIV but remaining persistently se-ronegative have been found in a number of different groups [1, 2], and a variety of mechanisms have been proposed to explain their protection against infection [3, 4]. To further delineate the cellular immune re-sponse in HIV-exposed seronegative (ESN) women, w