ERVW-1 and Epstein-Barr virus infection: Some Envs show immunomodulatory activity, such as Env derived from HERV-W induces proinflammatory cytokine expression in monocytes through the engagement of TLR4 receptor [13], and Env derived from HERV-K acts as a superantigen (SAg) to stimulate T cell-mediated B cell proliferation during EBV infection [14].