PROS1 and systemic lupus erythematosus: These and other ERVs provide promoter and enhancer exaptation and non-coding transcripts of viral accessory proteins as regulatory units (Buzdin et al., 2006, 2017; Daskalakis et al., 2018) that might have a pathogenic role in several autoimmune diseases such as rheumatoid arthritis and systemic lupus erythematosus by providing epitopes, superantigens, and/or hypomethylation motifs (Moyes et al., 2007; Balada et al., 2010; Tugnet et al., 2013; Trela et al., 2016).