Outer membrane protein of Pasteurella multocida serotype B:2 is immunogenic and antiphagocytic

Outer membrane protein (OMP) from Pasteurella multocida serotype B:2 was extracted and studied for its ability to immunize animals against P. multocida infection and to resist phagocytosis by murine peritoneal macrophage. Inoculation of OMP in rabbits resulted in the production of agglutinating antibodies which passively protected mice against P. multocida challenge and caused lysis of virulent P. multocida cells in vitro. Mice vaccinated with OMP vaccine resisted the challenge showing a satisfactory survival rate (67%) similar to mice given commercial whole cell vaccine (84%). The OMP was also found to be antiphagocytic, interfering with the phagocytosis of opsonized Candida albicans by murine peritoneal cells in vivo. The study suggested the role of OMP in conferring protection in animals against P. multocida infection and enhancing the virulence in infected animals through the anti-phagocytic mechanism.