ELUCIDATION OF LINEAR EPITOPES OF PERTUSSIS TOXIN USING OVERLAPPING SYNTHETIC DECAPEPTIDES - IDENTIFICATION OF A HUMAN B-CELL DETERMINANT IN THE S1 SUBUNIT INDICATIVE OF ACUTE INFECTIONS

To identify relevant linear epitopes within the immunodominant ADP-rib osyl transferase (S1 subunit) of pertussis toxin (PT), its complete am ino acid sequence was synthesized as consecutive, overlapping decapept ides on solid phase and probed for seroreactivity with pertussis speci fic human antisera in ''peptide scans''. Comparison of the resulting a ntigenic profiles revealed two distinct types of hu man antisera, thou gh amino acids 140-200 could not be assessed as the corresponding pept ides reacted non-specifically with the detection system. Human anti-pe rtussis sera predominantly recognized linear immunodominant epitopes l ocated in three separated segments spanning amino acids 3-16, 21-30, a nd 211-222. Antisera originating from infants with acute B. pertussis infections (type I) identified determinants in all three segments, whi le type-it antisera from convalescent patients only recognized epitope s in the N-terminal regions. The binding of pertussis specific antiser a-both type I and type II-to the holotoxin was inhibited by preincubat ion of antibodies with synthetic peptides corresponding to two linear determinants located at the N-terminus of S1: R 3-16 and R 21-30. Howe ver, competitive binding of antibodies to PT and to synthetic peptides equivalent to the third epitope (R 211-222) was only observed with ty pe I antisera. Thus, the linear immunogenic determinant identified at the C-terminus of the A-protomer represents a human epitope which is a pparently specific for antisera from pertussis patients with acute inf ections. The possible application of this determinant in serologic dia gnosis will be a valuable tool to detect and distinguish acute Bordete lla pertussis infections.