Phenotypic and functional modulation of bone marrow-derived dendritic cells by porcine reproductive and respiratory syndrome virus.

It is well documented that there is a delay in the development of effective immunity to porcine reproductive and respiratory syndrome virus (PRRSV) in infected and vaccinated pigs. This suggests that PRRSV might possess some inherent properties to evade host defense mechanisms during the early stage of infection. Dendritic cells (DCs) play a crucial role in the activation and control of T-cells in response to viral antigens. In this study, we investigated the phenotypic and functional property changes of bone marrow-derived immature DCs (BM-imDCs) that take place after infection by PRRSV. Results showed that BM-imDCs were permissive to PRRSV infection, as productive replication took place in these cells. A down-regulated expression of MHC I molecules along with an up-regulated expression of CD80/86 is observed at 48 h following infection. Also at 48h following PRRSV infection, a significant increase of IL-10 secretion by BM-imDCs was noticed. Results suggest that the inhibited expression of MHC I and the enhanced secretion of IL-10 by BM-imDCs after PRRSV infection might be among the strategies used by the virus to evade the host immune defenses.