CD4 and HIV infectious disease: In addition to directly acting on early HIV infection, some in vitro studies have also documented that the interaction of a recombinant gp120 and CD4/co-receptors led to activation of cellular pathways including cell adhesion, proliferation and actin modulation7, 17, 18, and the elevated expression of cytokines and chemokines18; Other studies also suggest that gp120 could interfere with CD4 costimulatory functions and induces apoptosis19.