To better understand the relative contribution of co-receptor expression to the overall HIV susceptibility of vector-induced CD4 T cells in our system, we further analyzed HIV infection in co-receptor+ and co-receptor- (CCR5+/- and CXCR4+/-) subsets of Ad5-specific CD4 T cells as compared to that in ALVAC-specific CD4 T cells. Here, CXCR4 is linked to HIV infectious disease.