Most recent CD4+ T cell count [>500 vs. ≤200 cells/mm3: adjusted rate ratio 0.24 (0.16–0.34)] and CD4+:CD8+ T cell ratio [>0.8 vs. <0.2: 0.33 (0.21–0.52)] were independently associated with a new AIDS event. This evidence concerns the gene CD4 and AIDS.