MAPPING OF EPITOPES ON THE SMD MOLECULE - THE USE OF MULTIPLE ANTIGENPEPTIDES TO MEASURE AUTOANTIBODIES IN SYSTEMIC LUPUS-ERYTHEMATOSUS

Autoantibodies against the ribonucleoproteins B, B' and D are a serolo gical marker of systemic lupus erythematosus (SLE). We mapped the epit opes recognized by autoantibodies on the SmD molecule by means of 7 sy nthetic peptides corresponding to the entire length of the protein. By ELISA assay, 25% of the lupus sera contained IgG antibodies specific for the C-terminal SmD sequence 95-119. This reactivity was confirmed by synthesizing the sequence as a multiple antigen peptide (MAP): anti bodies reactive with the MAP 95-119 were present only in SLE and not i n other connective tissue disorders. Sera containing high titers of an ti-MAP 95-119 antibodies reacted in immunoblot with the SmD protein. T hese results indicate the presence of a dominant epitope in the C-term inal region of SmD, which is highly homologous to the Epstein-Barr vir us induced nuclear protein EBNA I.