IFNG and infection: In order to identify the individual HIV-1-specific CD8+ T cell epitopes targeted during primary infection, as well as their relative contribution to the entire detectable HIV-1-specific CD8+ T cell response, cryopreserved PBMCs from 104 study participants were tested for responses to peptides corresponding to previously described epitopes for each person's respective HLA class I allotypes [26] using an IFN-γ ELISPOT assay.