CXCR4 and AIDS: CXCR4 is also known to be the receptor for viral ligands, such as viral Macrophage Inflammatory Protein-II (vMIP-II) encoded by Kaposi’s sarcoma-associated herpes virus [10] and the surface subunit (gp120) of the envelope glycoprotein of X4 strains of HIV-1, the etiologic agent of AIDS [11].