Longitudinal studies performed in Senegal have shown that higher variability in the env V3 region is generally found in patients with faster disease progression to AIDS [23] and that in elite controllers (patients infected for ≈ 10 years with normal CD4+ T cell counts without antiretroviral therapy and with low or undetectable viral load) the rate of env gene diversification may be positively associated with the rate of CD4+ T cell number decrease [24]. The gene discussed is CD4; the disease is AIDS.