EPITOPE MAPPING OF HISTONE-5 (H5) WITH SYSTEMIC LUPUS-ERYTHEMATOSUS, PROCAINAMIDE-INDUCED LUPUS AND HYDRALAZINE-INDUCED LUPUS SERA

To define the linear epitopes on H5 that react with systemic lupus ery thematosus (SLE) and drug-induced lupus (DIL) sera, concurrent overlap ping hexameric peptides corresponding to the sequence of H5 were synth esized by stepwise elongation of the polypeptide chains on polyethylen e supports. The hexapeptides were tested for reactivity with 8 SLE and 8 DIL sera using an enzyme linked immunosorbent assay (ELISA). SLE an d hydralazine-induced lupus (HIL) antibodies were most reactive with p eptide 45 (SSRQSI) and patients with procainamide-induced lupus (PIL) were most reactive with peptide 24 (SHPTYS). The epitopes of highest r eactivity were in the globular domain of H5. Low reactivity was observ ed with carboxyl terminal peptides. These findings differ from immunob lotting studies of protease cleaved peptides which have previously sho wn that the H5 determinants are in the carboxyl terminus.