ERVW-1 and myeloid sarcoma: Further correlation of HERV-W expression with MS: Sequential studies have demonstrated that HERV-W env protein was recognized in the serum sample of 73% of the MS patients [50], and also HERV-W/HERV-W env and pol RNAs were significantly expressed in peripheral blood mononuclear cells (PBMCs) and autopsied brain tissue from MS patients versus controls.