In order to determine whether CD4+ T cells from patient 169 were resistant to infection, we purified primary CD4+ T cells from 169 and five HIV-1 seronegative donors and infected them directly ex vivo by spinoculation with CCR5 (Ba-L) and CXCR4 (NL4-3) tropic isolates as previously described. This evidence concerns the gene CD4 and infection.