CXCR4 and infection: It is thought that the envelope glycoprotein 120 (gp120) of HIV-1 binds the host cell’s primary receptor CD4 and undergoes conformation changes which expose its third variable loop (V3 loop) to interact with coreceptor CXCR4 or CCR5, triggering further molecular events that lead to virus–cell membrane fusion and infection [11,12].