CCR5 and AIDS: The most notable polymorphism in the CCR5-Δ32 blocks HIV-1 infection (Dean et al. 1996; Carrington et al. 1999), but HIV-1 susceptibility and time to progression to AIDS have been associated with other CCR5 polymorphisms, many of them located in the 5′ cis-regulatory region of the gene (Carrington et al. 1997; Mummidi et al. 1997; Martin et al. 1998).