The outer membrane protein P2 (OmpP2) of Haemophilus parasuis induces proinflammatory cytokine mRNA expression in porcine alveolar macrophages

Porins, expressed by Gram-negative bacteria, have several biological effects on host tissues or cells. The outer membrane protein P2 (OmpP2), a member of the porin family, has been identified as a multifunctional protein involved in the pathogenicity of Haemophilus parasuis. In the present study, it was shown that OmpP2 (0.5–10 μg/mL) from H. parasuis Nagasaki strain up-regulated mRNA expression of interleukin (IL)-1α, IL-1β, IL-6 and IL-8 in porcine alveolar macrophages (PAM, 3D4/31) in vitro, in a dose-dependent manner. Moreover, OmpP2 porin induced a more prolonged cytokine response in PAM than that of the lipooligosaccharide (LOS) from this microorganism. The data demonstrate that H. parasuis OmpP2 can stimulate proinflammatory cytokine mRNA expression, suggesting that this particular porin might play an important role in the pathogenesis of disease caused by H. parasuis.