ISG15 and HIV-1 infection: These results provide a mechanism whereby CD4+ T cells from subjects immunized with the RV144 vaccine will mount an Env specific type II interferon (interferon γ) response that could, in turn, trigger the expression of these antiviral genes (e.g., XCL1, IFITM3, ISG15, MX2, TRIM26), thereby rendering these cells and bystander cells resistant to HIV-1 infection.