LOCALIZATION OF IMMUNODOMINANT SITE IN THE HEPATITIS-DELTA VIRUS-ANTIGEN WITH THE USE OF SYNTHETIC PEPTIDES

A set of 8 peptides from the immunodominant region (65-80 aa) of delta-antigen was prepared by solid-phase synthesis. Peptide 71-80 was synthesized in two variants-with different amino acid residues in positions 73, 74 and 76. Free peptides and their conjugates with bovine serum albumine were tested for antigenicity in ELISA. The correlation between the peptide chain's length and its antigenic activity was noted. Peptides 65-80 and 69-80 displayed a positive reaction with all individual sera and pools of sera from HDV chronic patients. Both variants of the peptide 71-80 reacted with 100% of sera pools but only with 83% of individual sera. Smaller peptides from the same 65-80 region (73-80, 69-78, 71-78, 71-76) did not bind to any anti-delta positive serum. All synthesized peptides reacted strongly with rabbit antisera raised to the conjugate of peptide 65-80 with bovine albumine. These findings suggest that delta-antigen contains multiple highly immunogenic epitopes associated with the single immunodominant site between 69 and 80 amino acid residues.