The envelope proteins of HERV-W (HERV-Wenv) has been detected in serum, in peripheral blood mononuclear cells and within the pancreas of patients with T1D [18,19,20], also, in an in vitro study in transgenic mice, HERV-Wenv repressed internal insulin secretion [22,23]. Here, ERVW-1 is linked to type 1 diabetes mellitus.