Effects of the major Pasteurella multocida porin on bovine neutrophils

OBJECTIVE: To evaluate in vitro effect of the major fraction of outer membrane proteins of Pasteurella multocida with porin-like activities on some biological functions of bovine neutrophils. ANIMALS: Neutrophils from 5 adult cattle. PROCEDURE: Variations in such biological processes as actin polymerization and chemotaxis and evaluation of hydrogen peroxide attributable to variable concentrations of P multocida were recorded and compared. Data were obtained, using the porin and lipopolysaccharide (LPS) isolated from a strain of P multocida cultivated in brain-heart infusion (BHI) broth. Various concentrations of porin and LPS were analyzed to evaluate changes in functional activation and microbicidal activity of bovine neutrophils. RESULTS: The 37.5-kd major polypeptide of the outer membrane of P multocida was isolated. Presence of this porin was significantly correlated with variations of some biological functions of bovine neutrophils. These immunocompetent cells had a concentration-dependent increase in actin polymerization and chemotactic activity. A concentration-dependent variation in the oxidative burst also was observed. CONCLUSIONS: The porins of gram-negative bacteria affect several biological functions of cells involved in the immune response as well as in inflammation. Significant correlation of results of in vitro experiments also was identified between porin and LPS effect. Pretreatment of bovine neutrophils with various concentrations of porin always caused a concentration-dependent increase in examined biological activities.