ERVW-1 and myeloid sarcoma: Its envelope protein, first called “MSRV-ENV” and now named pathogenic envelope “pHERV-W ENV”, was shown to reproduce the hallmarks of MS pathogenesis in studies with in vitro and in vivo models of MS, in parallel with brain immunohistology observations (Perron et al.2012; Perron et al.2013; Kremer et al.2013; Kremer et al.2019a; van Horssen et al.2016).