CXCR4 and HIV-1 infection: Importantly, the strong inhibition of HIV-1 infection by SUN1 was also observed when we used a full-length nonpseudotyped CXCR4-tropic HIV-1 GFP reporter virus (NL4.3GFP), indicating that the route of viral entry does not affect the magnitude of SUN1-mediated suppression and suggesting an effect downstream of membrane fusion (Fig. 1D).