Though much of the research on ERVK Env and disease pertains to its association to tumorigenesis, this viral protein is also thought to be implicated in several autoimmune disorders, such as insulin-dependent diabetes mellitus (IDDM), multiple sclerosis (MS), and rheumatoid arthritis (RA) (Sicat et al., 2005; Dickerson et al., 2008; de la Hera et al., 2013; Mason et al., 2014). This evidence concerns the gene ERVW-1 and rheumatoid arthritis.