Pasteurella haemolytica antigens associated with resistance to pneumonic pasteurellosis

Antigens associated with whole Pasteurella haemolytica biotype A serotype 1, a capsular carbohydrate-protein extract of the organism, and P. haemolytica leukotoxin were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Antigens of the electrophoresed preparations were detected by Western blotting (immunoblotting) with sera from cattle which were either nonvaccinated or vaccinated with live or killed P. haemolytica vaccines and had variable degrees of resistance to experimental pneumonic pasteurellosis. Distinct, easily recognizable antigens of these preparations were identified, and the antibody responses to these antigens were quantified by densitometry. To determine their importance to disease resistance, we then compared antibody responses with experimental lesion scores. Antibody reactivity to surface antigens which were significantly correlated with resistance and present in two or more of the preparations were detected at 86, 66, 51, 49, 34, 31, and 16 kilodaltons (kDa). Of these, antibody responses to antigens at 86, 49, and 31 kDa appeared most important based on their concentration and significance levels. Antibody reactivity to leukotoxin antigens which were significantly correlated with resistance and common with important surface antigens were detected at 86, 66, and 49 kDa. Antibody responses to unique leukotoxin antigens which were significantly correlated with resistance were present at 92 and 58 kDa.