We further identified that HIV infection rate in CCR5-/CXCR4- subset of Ad5-specific CD4 T cells remained higher than that in ALVAC-specific CD4 T cells (Fig 2C), suggesting that factors other than co-receptor expression are also involved in regulating the differential HIV susceptibility of vector-specific CD4 T cells in our system. This evidence concerns the gene CCR5 and HIV infectious disease.