Immune response to different sequences of the EBNA I molecule in Epstein- Barr virus-related disorders and in autoimmune diseases

Epstein-Barr virus (EBV) infection is associated with production of autoantibodies. The N-terminal 35-58 sequence of EBNA I, one of the nuclear antigens encoded by EBV, is highly homologous to the C-terminal 95-119 region of the ribonucleoprotein SmD. Autoantibodies specific for SmD are present only in systemic lupus (SLE) sera and are therefore considered a serological marker of SLE. We measured antibodies to the EBNA I 35-58 sequence in EBV- related diseases and in autoimmune disorders. Antibodies to the EBNA I.35- 58 peptide were present in 30% of normal sera, 12% Burkitt lymphoma, 22% infectious mononucleosis, 25% rheumatoid arthritis, 38% SLE and 33% Sjogren’ syndrome. Antibodies to the SmD 95-119 peptide were detectable in 32% of SLE sera, 17% infectious mononucleosis and 12% Burkitt lymphoma. The specificity of anti-EBNA I 35-58 antibodies affinity-purified from nine sera was analysed by means of an inhibition assay. Only anti-EBNA I 35-58 antibodies affinity- purified from SLE sera have a similar affinity for the viral peptide and the SmD C-terminal one; they also bind the recombinant SmD in western blot. The results indicate that antibodies to EBNA I 35-58 are produced in normals, in EBV-related diseases and in autoimmune disorder, but only SLE sera contain anti-viral antibodies cross-reactive with an autoantigen.