Single cell analysis of antigen-specific T cell responses in HIV-infected individuals.

Antigen-specific and polyclonally induced T cell responses were analyzed in 10 HIV-infected individuals and in 14 controls by enumerating the numbers of tetanus toxoid (TT)-specific and phytohemagglutinin (PHA)-induced IFN-gamma-secreting cells (SC) and IL-4-SC using an enzyme-linked immunospot assay. Whereas the numbers of IFN-gamma-SC in HIV-infected patients were not different from those of the controls in response to an in vitro stimulation with PHA, they were significantly decreased in response to an in vitro stimulation with TT, both before and after a TT booster. Cell depletion experiments indicated that this difference was related to an impairment of CD4(+) T-cell-mediated TT-specific IFN-gamma secretion. Concerning IL-4, the numbers of both polyclonally induced IL-4-SC and TT-specific IL-4-SC were significantly lower in HIV-infected patients than in the controls. It is concluded that secretion of antigen-specific cytokines of both Th1 and Th2 types is depressed in HIV-infected patients.