Abstract
Pasteurella multocida primarily causes hemorrhagic septicemia and pneumonia in poultry and livestock. Identification of the relevant virulence factors is therefore essential for understanding its pathogenicity. Pmorf0222, encoding the PM0222 protein, is located on a specific prophage island of the pathogenic strain C48-1 of P. multocida. Its role in the pathogenesis of P. multocida infection is still unknown. The proinflammatory cytokine plays an important role in P. multocida infection; therefore, murine peritoneal exudate macrophages were treated with the purified recombinant PM0222, which induced the secretion of tumor necrosis factor alpha (TNF-α) and interleukin-1β (IL-1β) via the Toll-like receptor 1/2 (TLR1/2)-nuclear factor kappa B (NF-κB)/mitogen-activated protein kinase (MAPK) signaling and inflammasome activation. Additionally, the mutant strain and complemented strain were evaluated in the mouse model with P. multocida infection, and PM0222 was identified as a virulence factor, which was secreted by outer membrane vesicles of P. multocida. Further results revealed that Pmorf0222 affected the synthesis of the capsule, adhesion, serum sensitivity, and biofilm formation. Thus, we identified Pmorf0222 as a novel virulence factor in the C48-1 strain of P. multocida, explaining the high pathogenicity of this pathogenic strain.