ERVW-1 and multiple sclerosis: In multiple sclerosis patients, elevated antibody reactivity has also been reported against peptides corresponding to the envelope glycoproteins of HERV-W proviruses (128, 129), including Syncytin-1, encoded by the ERVW-1 provirus on chromosome 7q21.2 (49), and multiple sclerosis–associated retrovirus (MSRV), a speculated but so far elusive virus thought to be related to HERV-W proviruses (130).