%0 Journal Article %A Lainson, F. A. %A Murray, J. %A Davies, R. C. %A Donachie, W. %T Characterization of epitopes involved in the neutralization of Pasteurella haemolytica serotype A1 leukotoxin %D 1996 %J Microbiology, %V 142 %N 9 %P 2499-2507 %@ 1465-2080 %R https://doi.org/10.1099/00221287-142-9-2499 %K epitope %K Pasteurella haemolytica %K leukotoxin A %K RTX toxin %I Microbiology Society, %X Defined segments of the leukotoxin A gene (lktA) from an A1 serotype of Pasteurella haemolytica were cloned into a plasmid vector and expressed as LacZα fusion proteins. These fusion proteins were electrophoresed in SDS-PAGE gels and their immunoblotting reactivities with several monoclonal antibodies characterized. The epitope recognized by a strongly neutralizing monoclonal antibody was localized to a 32 amino acid region near the C terminus of the leukotoxin A (LktA) molecule. The epitope recognized by a non-neutralizing antibody was localized to a 33 amino acid region immediately adjacent. Smaller recombinant peptides containing these epitopes were not antigenic, but a polypeptide encompassing 229 amino acids at the C terminus evoked neutralizing antibodies when used to immunize specific-pathogen-free lambs. The distributions of linear epitopes recognized by this antiserum and by antisera raised to full-length recombinant LktA and to native LktA produced by P. haemolytica serotype A1 were determined by their reactivities with a set of overlapping 10 amino acid synthetic peptides. This revealed a complex distribution of linear epitopes at the C-terminal end of LktA. Toxin-neutralizing antibodies in convalescent sheep serum were shown to be directed against conformational epitopes by selective absorption of antibodies directed against linear epitopes. %U https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-142-9-2499