Furthermore, some viral proteins, such as the envelope protein encoded by HERV-W and referred to as multiple sclerosis-associated retrovirus (MSRV), can trigger brain inflammation and autoimmunity [28,29,30], while others, such as the syncytins, exhibit intrinsic immunomodulatory properties [20,21,22,31,32]. Here, ERVW-1 is linked to Autoimmunity.