[Study on the specificity of a monoclonal antibody against recombinant envelope proteins of a human endogenous retrovirus, ERV3].

Human endogenous retroviruses (HERVs) and its related sequences have been known to occupy about 1% on human genome, and the expression of messenger RNA has been demonstrated by many investigators including our laboratory. However, only few papers have been indicated they are translated in proteins. Either physiological roles in man or pathogenic roles in diseases are still unknown at present. In this study, to investigate the protein expression of one copy type HERV, ERV3 and its pathogenicity, a recombinant protein to ERV3 env region was produced using E. coli expression system, and a monoclonal antibody to the recombinant protein was prepared. The monoclonal antibody evidenced the translation of ERV3, and 170 and 180 kilodaltons of proteins were detected in normal placentas and adrenal glands by Western blot. Natural antibodies to the products of ERV3 env region with high reactivities were detected in sera from some patients with systemic lupus erythematosus (SLE) compared with normal population and patients with rheumatoid arthritis (RA). The result suggests that ERV3 products may play as one of autoantigens in patients with SLE. The recombinant protein and monoclonal antibody described here may be useful to study the role of ERV3 in vivo and the etiologic relation of HERVs to autoimmune diseases.