Differences in phagocytosis susceptibility in Haemophilus parasuis strainsAlexandre Olvera1, Maria Ballester1, Miquel Nofrarias1, Marina Sibila1 and Virginia Aragon1, 2
1 Centre de Recerca en Sanitat Animal (CReSA), UAB-IRTA, Campus de la Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain
2 Institut de Recerca i Tecnologia Agroalimentaries (IRTA), Barcelona, Spain
Received 31 October 2008; accepted 24 February 2009; published online 26 February 2009
Abstract - Haemophilus parasuis is a colonizer of the upper respiratory tract of healthy pigs, but virulent strains can cause a systemic infection characterized by fibrinous polyserositis, commonly known as Glässer's disease. The variability in virulence that is observed among H. parasuis strains is not completely understood, since the virulence mechanisms of H. parasuis are largely unknown. In the course of infection, H. parasuis has to survive the host pulmonary defences, which include alveolar macrophages, to produce disease. Using strains from different clinical backgrounds, we were able to detect clear differences in susceptibility to phagocytosis. Strains isolated from the nose of healthy animals were efficiently phagocytosed by porcine alveolar macrophages (PAM), while strains isolated from systemic lesions were resistant to this interaction. Phagocytosis of susceptible strains proceeded through mechanisms independent of a specific receptor, which involved actin filaments and microtubules. In all the systemic strains tested in this study, we observed a distinct capsule after interaction with PAM, indicating a role of this surface structure in phagocytosis resistance. However, additional mechanisms of resistance to phagocytosis should be explored, since we detected different effects of microtubule inhibition among systemic strains.
Key words: phagocytosis resistance / Haemophilus parasuis / alveolar macrophages / strain variability
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© INRA, EDP Sciences 2009