A HIGHLY CONSERVED EPITOPE ON THE SPIKE PROTEIN OF INFECTIOUS-BRONCHITIS VIRUS

The predicted amino acid sequence and secondary structures of SI of th e spike protein (S) of infectious bronchitis viral (IBV) strains from Europe, the U.S.A., and Japan were compared. An antigenic determinant that was highly conserved in both the primary amino acid sequence and secondary structure of all strains was identified between amino acid p ositions 240 to 255. A synthesized peptide corresponding to this regio n was found to react with all polyclonal antisera examined from variou s IBV strains and with one monoclonal antibody (MAb), 9B1B6, out of ni ne known to react with the S of Gray. The specificity of the interacti on with MAb 9B1B6 was confirmed by competitive ELISA using bound and u nbound peptide. Interestingly, the previously described epitope for 9B 1B6 had been characterized as cross-reactive with several strains of I BV, as conformation-independent but reacting only with intact whole S, and as associated with the functional integrity of other epitopes, in cluding neutralizing epitopes on the S protein. The apparent critical functional and structural nature of this highly immunogenic determinan t suggests a potential contribution in developing protective, cross-re active subunit vaccines to IBV.