Sequence analysis of Pasteurella multocida major outer membrane protein (OmpH) and application of synthetic peptides in vaccination of chickens against homologous strain challenge

Pasteurella multocida major outer membrane protein (OmpH) has been previous ly characterized as a porin. The native OmpH from strain X-73 (serotype 1) but not recombinant protein from Escherichia coli induced homologous protec tion in chickens. In this study OmpH sequences from 15 P. multocida serotyp es as well as the CU vaccine strain were compared by sequence alignment and revealed high homology, with major variations confined to two discrete reg ions which were correspondingly predicted as two largest external loops. Se condary structures of OmpHs were predicted by sequence alignment of OmpHs w ith well defined porins and analyses of amphiphilicity, hydrophobic moment and antigenic index plots. Several synthetic peptides derived from predicte d loop 2 and loop 5 of X-73 OmpH were synthesized as vaccine candidates. Va ccination studies in chickens showed that the cyclic synthetic peptide (Cyc lic-L2) mimicking the predicted loop 2 induced 70% protection in chickens a gainst strain X-73 challenge, This is the first report that a synthetic pep tide mimicking the conformational epitopes of a native protein provide prac tical protection in target animal against bacterial infection. (C) 1999 Els evier Science Ltd. All rights reserved.