Porcine reproductive and respiratory syndrome virus (PRRSV) can predispose pigs to secondary respiratory infection with bacteria such as Haemophilus parasuis. Animals infected with both pathogens develop more severe clinical disease. The immune response of porcine alveolar macrophages (PAMs) to simultaneous infection with PRRSV and H. parasuis was analysed in vitro, describing cytokine production, expression of cell surface molecules, and production of reactive oxygen species (ROS). Concurrent infection with PRRSV and H. parasuis increased gene expression of pro-inflammatory cytokines (TNF-α, IL-1β, IL-8) in PAMs in comparison with PAMs infected with PRRSV or H. parasuis alone. An additive effect of dual infection on IL-1β production was confirmed at the protein level. PAMs infected with PRRSV showed increased production of ROS compared to controls. Conversely, simultaneous infection of PAMs with PRRSV and H. parasuis decreased production of ROS, indicating the presence of an H. parasuis defence mechanism against respiratory burst. Concurrent infection of PAMs with PRRSV and H. parasuis was shown to elicit a pro-inflammatory immune response represented by significant IL-1β production. Severe multifactorial respiratory disease in natural conditions caused by both pathogens could be the consequence of pro-inflammatory mediated immunopathology.

Veterinary Research Institute Hudcova 296 70 62100 Brno Czech Republic

Veterinary Research Institute Hudcova 296 70 62100 Brno Czech Republic; Institute of Experimental Biology Faculty of Science Masaryk University Kotlářská 267 2 61137 Brno Czech Republic

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Dynamics and Differences in Systemic and Local Immune Responses After Vaccination With Inactivated and Live Commercial Vaccines and Subsequent Subclinical Infection With PRRS Virus

Concurrent infection with porcine reproductive and respiratory syndrome virus and Haemophilus parasuis in two types of porcine macrophages: apoptosis, production of ROS and formation of multinucleated giant cells