Hiv-specific Cd8 T-cell activity in uninfected injection drug users is associated with maintenance of seronegativity

Objectives To determine whether HIV-exposed, uninfected subjects (EUs) having HIV-specific effector activity are at a reduced risk for seroconverting compared with EUs with no HIV-specific effector responses. Design Twenty-eight intravenous drug users (IVDU) with documented risk for HIV infection over a 1-year period were screened for the presence of HIV-specific CD8+ effector cell activity. Group I included 18 IVDUs who remained seronegative despite exposure to HIV through needle sharing with partner(s) known to be HIV infected. Group II included 10 IVDUs who seroconverted after similar HIV exposure. Methods The enzyme-linked immunospot (ELIspot; Mabtech AB, Nacka, Sweden) assay was used to measure the frequency of HIV-specific interferon-γ secreting cells. Peripheral blood mononuclear cells (PBMC) were stimulated with a panel of synthetic HIV peptides in a major histocompatibility complex class I antigen-restricted fashion. PBMC from group II were obtained from timepoints 7 months or less before seroconversion. Results Twelve of 18 (66.7%) persistently seronegative subjects versus none of 10 seroconverters exhibited detectable HIV-specific effector responses at the sampling date (P 3000). Conclusion EUs who have developed HIV-specific effector responses are at a reduced risk for seroconversion compared with EUs who do not develop this type of immunity. This observation supports the hypothesis that HIV-specific effector responses are a correlate of immune protection from HIV infection.