Infection with either the primate or the feline lentiviruses requires a subsequent interaction with a member of the seven transmembrane domain (7TM) superfamily molecules; for the human immunodeficiency virus (HIV) the major co-receptors are CXCR4 and CCR5 [6-10], while FIV uses CXCR4 as a sole co-receptor [11,12]. This evidence concerns the gene CXCR4 and infection.