After 4 days of co-culture, i) untreated CD4+ T cells and untreated bystander (CTV-labeled) CD4+ T cells were both productively infected with HIV (2.5–3% p24+ cells); ii) treated CD4+ T cells were protected from infection, presenting with significantly lower frequencies of HIV-p24+ cells than untreated CD4+ T cells (i). This evidence concerns the gene CD4 and infection.