Human immunodeficiency virus (HIV) and related virus require coreceptors, in addition to CD4, to infect target cells. Some G protein-coupled receptors including CCR5, CXCR4, CCR3, CCR2b and CCR8 in the chemokine receptor family, and four new human molecules GPR15, STRL33, GPR1 and V28 were recently identified as HIV coreceptors. Among them, CCR5 (CC-CKR-5) is a principal coreceptor for macrophage- and dual-tropic HIV-1 strains fusion and entry of human white blood cells. CCR5 is required for the infection by HIV-1, HIV-2, and SIV. The beta-chemokines RANTES, MIP-alpha and MIP-beta are the ligands for CCR5 and prevent infection by M-tropic HIV-1. CXC5 associates with the surface CD4-gp120 of HIV complex and leads to membrane fusion and virus entry of target cells. The amino-terminal domain and the extracellular loops of CCR5 serve as HIV biding sites. CCR5 messenger RNA is expressed in lymphoid organs and monocytes.
