ERVW-1 and HIV-1 infection: Although HIV-1 infection is subject to cellular antiviral responses [27], [53], [54], [55], it is unclear if the expression of HIV-1 Env in the absence of viral replication can lead to activation of PKR or PERK, as previously reported for HCV E1/E2 [56] or the non-structural proteins from West Nile virus [57].