CD4 and HIV-1 infection: In strong contrast, activation of DCs by lipopolysaccharide (LPS) or interferon (IFN), which are immunomodulatory signals present during HIV-1 infection, diminishes their susceptibility to infection but significantly increases the capture of HIV-1 and enhances the trans-infection of CD4+ T cells (Izquierdo-Useros et al., 2007; Wang et al., 2007).