CD4 and infection: Consistent with the model of direct infection of blood resting T cells, it has been shown that HIV glycoprotein (gp)120 binds to the C-X-C chemokine receptor (CXCR)4 can activate Gαi-dependent signaling, which promotes cofilin activation and actin dynamics to overcome the barrier of actin cytoskeleton in resting CD4+ T cells (10).