Several studies have demonstrated the presence of actively replicating human endogenous retroviruses associated with various autoimmune disorders (Perron and Seigneurin, 1999; Portis, 2002), in particular, Sjögrens's syndrome, rheumatoid arthritis, type 1 or insulin-dependent diabetes mellitus, multiple sclerosis, systemic lupus erythematosus, and systemic sclerosis. Serum antibodies specific for human intracisternal A-type particles (HIAP), a human endogenous retrovirus recognized by monoclonal antibody against HIV-1 p24 capsid protein (Garry et al, 1990), have been detected significantly in association with primary biliary cirrhosis (Mason et al, 1998) and systemic sclerosis (La Placa et al, 2004).