ERVW-1 and infection: To corroborate our findings that showed the important role of antibodies in FV control after MCMV.env immunization and to confirm the absence of protective CD8+ T cells after MCMV.env immunization, we performed transfer experiments using CD8+ T cells isolated from MCMV.env immunized mice either before or after FV challenge infection, or using plasma isolated from control MCMV or MCMV.env immunized mice 14 days after FV challenge infection.