Characterization of an iron-regulated outer membrane protein of Pasteurella multocida

Pasteurella multocida strain P1059 (serotype 3) expressed an 84 kilodalton (kDa) outer membrane protein (OMP) when grown in brain heart infusion (BHI) broth containing the iron chelator dipyridyl (20 {dollar}mu{dollar}g/ml) but not in BHI alone. The OMP was also expressed by P. multocida strain P1059 when grown in turkey plasma or BHI containing Desferal (20.5 {dollar}mu{dollar}g/ml). The proteinaceous nature of the OMP was confirmed and the OMP was demonstrated to be at the surface of the bacterial cell. Plasma collected from turkeys naturally infected with P. multocida (serotype 3) contained antibodies to the OMP. Polyclonal and monoclonal antibodies specific to the 84 kDa OMP were prepared. It was shown that antigenically related iron-regulated OMPs were expressed by other serotypes of P. multocida. Turkeys passively immunized with the polyclonal antibodies had a greater mean death time and percent survival compared to unimmunized turkeys following challenge with P. multocida. The gene (or part of the gene) was cloned and sequenced in order to determine a function of the protein by comparison with previously sequenced procaryotic genes. A 2033 bp EcoRI DNA fragment was cloned into lambda gt11 which expressed a fusion product that reacted with the polyclonal antibodies specific to the 84 kDa OMP. It was believed that a portion of the gene was cloned corresponding to the carboxy terminal end of the protein. The DNA had some homologies with the Escherichia coli ferric hydroxamate uptake operon suggesting a role in iron acquisition. It was concluded that the 84 kDa OMP might be a suitable candidate for inclusion in an immunizing agent against fowl cholera.