ERVW-1 and HIV infectious disease: Although in natural chronic HIV infection, Env-specific CD8+ T-cell responses have been shown to be associated with poor control of viral replication compared to Gag-specific responses [43], non-human primates immunized with DNA plus Ad5 expressing SIV Env as well as Gag were better protected against SIV challenge compared to animals immunized with vaccines expressing only Gag [44].