HIV This Week

Jones NG, Decamp A, Gilbert P, Peterson ML, Gurwith M, Cao H. AIDSVAX immunization induces HIV-specific CD8+ T-cell responses in high-risk, HIV-negative volunteers who subsequently acquire HIV infection. Vaccine . 2009;27(7):1136-40.

Correlates of immune protection from HIV vaccines remain undefined. The first HIV vaccine efficacy trial in the US and Europe VAX004, was designed to assess whether rgp120 envelope subunits (AIDSVAX B/B, VaxGen) can induce partial or complete protection from HIV-1 infection. No effectiveness in the reduction of either the acquisition of infection or levels of plasma viraemia after HIV infection was noted. Jones and colleagues found evidence of vaccine-specific CD8+ T cells in volunteers who received the vaccine, regardless of behavioural risk. Surprisingly, the CD8-response is significantly higher in participants who would go on to contract HIV infection. These results suggest that AIDSVAX immunization may boost pre-existing immune responses-due to pre-infection exposure, and a vaccine-induced immune profile may serve as a biological marker for HIV susceptibility.

Editors’ note: It is not clear how the presence of a CD8+ T cell response, which is historically associated with the clearance of virus-infected cells, would be associated with the risk of subsequent HIV infection. These results from the 2003 AIDS VAX trial come after those of the recent STEP vaccine study that suggested that vaccine-mediated T cell responses may have enhanced infection in uncircumcised vaccinees with prior immunity to adenoviruses. We are missing parts of the immunological puzzle. Vaccination before sexual debut would avoid pre-exposure to HIV but would it make a difference? Are genetic profiles conferring differential susceptibility? There is no dearth of questions in HIV vaccinology.