Our data show that vector-specific CD4 T cells induced by different HIV vaccine vectors manifest marked difference in their susceptibility to HIV infection; compared to Ad5-specific CD4 T cells in HVTN204 PBMC, the ALVAC-specific CD4 T cells in RV144 PBMC are substantially less susceptible to both R5 and X4 HIV infection in vitro. This evidence concerns the gene CD4 and HIV infectious disease.