Tonsil conventional dendritic cells are not infected by porcine reproductive and respiratory syndrome virus

Porcine reproductive and respiratory syndrome virus (PRRSV) infects monocyte-derived DCs, and previous reports have shown that PRRSV does not infect conventional DCs (cDCs) in vitro, but the effects on cDCs from lymphoid tissues are unknown. This study analyzed the response and susceptibility of tonsil DEC205 ⁺ cDCs from infected pigs. We confirmed the phenotype and lineage of bona fide tonsil cDCs with the mRNA expression of FLT3 ⁺ and the phenotype MHCII ⁺ CADM1 ^high DEC205 ⁺ (DEC205 ⁺ cDCs). These cells were not infected by PRRSV, whereas CD163 ⁺ tonsil cells were infected. The numbers of tonsil cDCs and CD163 ⁺ cells were not affected by PRRSV, in contrast to the reduction in alveolar macrophage numbers. DEC205 ⁺ cDCs exhibited an increase in the expression of IL-12 at 5 days postinfection, suggesting a proinflammatory response by these cells to the virus. In summary, this study confirms that, in vitro and in vivo, cDCs are not susceptible to PRRSV but can respond against it.