CCR5 and AIDS: Univariate analysis indicated that homozygosity for the H43Y polymorphism, CD4 T cell counts below 500 cells per μl, viral RNA load above 104.5 copies per ml plasma and the presence of X4-variants at 18–30 months after seroconversion were predictive for more rapid progression to AIDS, whereas heterozygosity for the CCR5-Δ32 genotype had a protective effect (Table 3).