The main characteristics of LTNP infections are (i) infection for more than 7 years; (ii) stable CD4+ T cell counts greater than 600 cells/μl; (iii) low/undetectable levels of HIV in the peripheral blood; (iv) no symptoms of HIV-induced disease; (v) apparent control of viral replication through vigorous CD4+ and CD8+ T cell responses against HIV suggesting, but not proving that these cells may be causally related to virus control [1]. This evidence concerns the gene CD4 and infection.