The natural ligands of CCR5 (RANTES, MIP-1α, MIP-1β) [8] and their derivatives [9,10], as well as some specific monoclonal antibodies against certain epitopes of CCR5 [11] possess anti-HIV-1 activity, and homozygous individuals with a 32-base pair deletion in the gene encoding CCR5 do not express the functional receptor and are ultimately resistant to R5-tropic HIV-1 infection [12]. Here, CCR5 is linked to HIV-1 infection.