ERVW-1 and myeloid sarcoma: Independent studies have shown that MSRVenv and syncytin-1 proteins share several potentially pathogenic, biological features, as induction of T mediated immunopathology, of pro-inflammatory cytokines and T-cell responses, with polyclonal expansion, as reviewed in [10]–[11], and have been shown to cause neurotoxic effects in vitro and in humanized or transgenic animal models [15], [17]: they may cause neuroinflammation, neurodegeneration, alterations of the immune system and stress responses; both have been suggested as co-factors triggering the immuno-pathogenesis of MS.