ABSTRACTWe previously identifiedMannheimia haemolyticaouter membrane proteins (OMPs) that may be important immunogens by using immunoproteomic analyses. Genes for serotype 1-specific antigen (SSA-1), OmpA, OmpP2, and OmpD15 were cloned and expressed, and recombinant proteins were purified. Objective 1 of this study was to demonstrate immunogenicity of the four recombinant OMPs in mice and cattle. Objective 2 was to determine if the addition of individual recombinant OMPs or combinations of them would modify immune responsiveness of mice to the recombinant chimeric protein SAC89, containing the main epitope fromM. haemolyticaouter membrane lipoprotein PlpE and the neutralizing epitope ofM. haemolyticaleukotoxin. Mice vaccinated with recombinant OmpA (rOmpA), rSSA-1, rOmpD15, and rOmpP2 developed significant antibody responses toM. haemolyticaouter membranes and to the homologous recombinant OMP. Cattle vaccinated with rOmpA and rSSA-1 developed significant antibodies toM. haemolyticaouter membranes by day 28, whereas cattle vaccinated with rOmpD15 and rOmpP2 developed only minimal responses. Sera from cattle vaccinated with each of the recombinant proteins stimulated complement-mediated killing of the bacterium. Concurrent vaccination with SAC89 plus any of the four rOMPs singly resulted in increased endpoint anti-SAC89 titers, and for the SAC89/rSSA-1 vaccinees, the response was increased significantly. In contrast, the SAC89/P2/SSA-1 and SAC89/OmpA/P2/D15/SSA-1 combination vaccines resulted in significant decreases in anti-SAC89 antibodies compared to SAC89 vaccination alone. In conclusion, under the conditions of these experiments, vaccination of mice and cattle with rOmpA and rSSA-1 stimulated high antibody responses and may have protective vaccine potential.
Effect of Pasteurella haemolytica outer membrane proteins on bovine neutrophils