The study by Farzan’s group, however, did not provide a conclusive explanation for the origin of the synergistic effect of the CD4 and CCR5 moieties on the ability of the mimetics to inhibit HIV-1 infection, and suggested that the reduced capacity of the inhibitors to promote HIV-1 infection results from a competition between the CCR5 moiety and the membrane co-receptor for Env binding [43]. This evidence concerns the gene CD4 and HIV-1 infection.