DETECTION OF ANTIBODIES TO A RECOMBINANT GAG PROTEIN-DERIVED FROM HUMAN ENDOGENOUS RETROVIRUS CLONE-4-1 IN AUTOIMMUNE-DISEASES

To investigate whether human endogenous retroviruses (HERV) contribute to autoimmune diseases, we prepared a recombinant p30(gag) protein de rived from clone 4-1 of the HERV family, using a baculovirus-vector sy stem. This p30(gag) protein (CA41B) was approximately 30 kDa, as expec ted, and reacted with antibodies for p30(gag) purified from both murin e and feline leukemia virus. This result suggested that the antigenic determinant for p30(gag) was well conserved in CA41B. Analysis of seru m antibodies to p30(gag) in patients with autoimmune diseases was done by Western blotting. CA41B detected anti-pg30(gag) antibodies in 48.3 % of systemic lupus erythematosus (SLE) patients, 35.0% of Sjogren's s yndrome (SS) patients, and 33.3% of mixed connective tissue disease (M CTD) patients, whereas no anti-p30(gag) antibodies were found in healt hy subjects. This suggested that HERV p30(gag) or other retroviral p30 (gag) proteins possessing the same antigenic determinant as CA41B may play a role in these diseases. Although detection of antibodies to HER V p30(gag) in autoimmune diseases is indirect evidence that HERV prote ins are involved, this study showed that patients with autoimmune dise ases have antibodies to HERV p30(gag) using a recombinant HERV protein rather than synthetic peptides based on HERV or retroviral proteins o f other species.