Porcine reproductive and respiratory syndrome virus (PRRSV) predisposes pigs to secondary bacterial infection caused by Haemophilus parasuis. The aim of the present study was to analyse the immune response of monocyte-derived macrophages (MDMs), serving as a model of macrophages accumulating at the site of inflammation. The second part of the study was focused on the role of IFNα in the production of inflammatory cytokines in co-infected MDMs. Concurrent infection with PRRSV and H. parasuis decreased gene expression of pro-inflammatory cytokines (IL-1β, IL-8) in MDMs in comparison with MDMs infected with PRRSV or H. parasuis alone. Our data showed that MDMs express IFNα after PRRSV infection. Thereafter, we exposed cells to the experimental addition of IFNα and a subsequent infection with H. parasuis, and detected a decreased expression/production of pro-inflammatory cytokines. Thus, we assume that IFNα, produced after PRRSV infection, could affect the immune response of monocyte-derived macrophages. Down-regulation of pro-inflammatory cytokine expression in inflammatory macrophages may allow the development of secondary bacterial infections in pigs.

Veterinary Research Institute Hudcova 296 70 62100 Brno Czech Republic

Veterinary Research Institute Hudcova 296 70 62100 Brno Czech Republic; University of Veterinary and Pharmaceutical Sciences Brno Palackého třída 1946 1 612 42 Brno Czech Republic

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Characterization of Porcine Monocyte-Derived Macrophages Cultured in Serum-Reduced Medium

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