The results of this retrospective analysis of available data on HIV-1 viral load and peripheral blood CD4+ cell counts in the hospital records of a large population of Nigerian patients whose hemoglobin genotype was prospectively determined during the study suggest that, relative to the normal hemoglobin genotype AA, the heterozygous HbAS condition or sickle cell trait does not significantly affect the prevalence nor severity of HIV-1 infection if all the HIV-1 patients who have normal HbAA genotype are compared with all HIV-1 patients who have sickle cell trait (HbAS genotype). The gene discussed is CD4; the disease is HIV-1 infection.