The IFN-γ enzyme-linked immunospot (ELI-Spot) assay is often used to map HIV-specific CD8 T-cell responses. We compared overlapping 15-mer pools with optimized CD8 epitopes to screen ELISpot responses in HIV-infected individuals. The 15-mer pools detected responses to previously undefined epitopes, but often missed low-level responses to predefined epitopes, particularly when the epitope was central in the 15-mer, rather than at the N-terminus or C-terminus. These factors should be considered in the monitoring of HIV vaccine trials.

HIV-specific CD8 T lymphocytes are important in the host control of HIV replication. There is a clear temporal relationship between the development of HIV-specific CD8 T cells and viral control during acute HIV infection [1], and between experimental CD8 T-cell depletion and increases in viral load [2]. In addition, epitope-specific CD8 T cells place considerable evolutionary pressure on the virus in both primates and humans [3–8]. Various HIV-specific immune responses have been described in highly exposed, persistently seronegative (HEPS) populations [8, 9], most commonly HIV-specific CD8 cells [10]. Moreover, the loss of peripheral HIV-specific CD8 effector responses in the absence of HIV exposure has been associated with the seroconversion of HEPS individuals [11]. These findings, among others, have led to the development of HIV vaccines that are designed to induce a virus-specific cellular immune response [12, 13].