| Abstract
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Pasteurella multocida is the causative agent of avian pasteurellosis, which is a highly contagious disease affecting avian species. The objectives of this research are to identify and characterize the cross-protection factor (CPF) immunogen(s) from type A P. multocida. In the first section, lipopolysaccharides from P. multocida were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blots. We found that: (1) the LPS did not contain the O-side chain suggesting that the somatic type-specificity might be located in the core-oligosaccharide region of the molecule, (2) the SDS-PAGE profiles of LPSs from in vivo and in vitro grown P. multocida were identical, (3) iron concentration in the growth medium did not change the LPS patterns in SDS-PAGE, and (4) in Western blots, convalescent-phase sera or bacterin antisera reacted weakly only with the fast moving band. In the second section, the SDS-PAGE was used to compare the outer membrane protein (OMP) profiles of P. multocida. We found that: (1) the live avirulent vaccine strains CU and M9 expressed strain-specific OMP markers of 48 kDa and 45 kDa respectively, and (2) in vivo grown serotype A:3 (but not in vitro grown bacteria), expressed several novel high molecular weight OMPs which reacted intensely with antibodies present in convalescent-phase sera by Western blots. In the third paper, the relationship between the iron regulated outer membrane proteins (IROMPs) and the OMPs of in vivo grown P. multocida serotype A:3 was examined. The results showed that: (1) three IROMPs with molecular masses 76 kDa, 84 kDa, and 94 kDa were expressed by bacteria grown under iron-restricted and in vivo conditions, (2) in Western blots, convalescent-phase sera contained antibodies that reacted intensely with the three IROMPs which indicated that these proteins were expressed in vivo, and (3) all three IROMPs contained epitopes that bound to Fe-multocidin complex. We speculate that the IROMPs and CPF immunogen(s) may be the same molecules. Finally, a dot immunobinding assay (DIA) was used to detect antibodies against P. multocida in turkey sera. We found that DIA was more specific and less sensitive than the enzyme-linked immunosorbent assay (ELISA).
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