ERVW-1 and HIV-1 infection: Compared with the non-ionic surfactant-based virus inactivators, such as N9[36,37] and C31G[38,39], 2DLT protein has much lower cytotoxicity, with an in vitro CC50 (50% cytotoxicity concentration) value greater than 100 μM on the cells susceptible to HIV-1 infection and reproductive tract epithelial cells (data not shown), and better specificity since it specifically interacts with the HIV-1 Env, rather than other components that are also present in host cells[40,41].