CD4 and HIV-1 infection: Pre-treatment with PC liposomes significantly inhibited the luciferase activity in macrophages infected with HIV-1 (Ba-L Env) but not in those infected with HIV-1 (VSV-G) (Figure 3A), indicating that PC liposome-mediated CD4 downregulation reduced HIV-1 infection in type-1 macrophages at entry level.