Porcine deltacoronavirus (PDCoV) infection suppresses RIG-I-mediated interferon-β production

Porcine deltacoronavirus (PDCoV), an emerging animal coronavirus causing enteric disease in pigs, belongs to the newly identified Deltacoronavirus genus in the Coronaviridae family. Although extensive studies have been carried out to investigate the regulation of interferon (IFN) responses by alphacoronaviruses, betacoronaviruses, and gammacoronaviruses, little is known about this process during deltacoronavirus infection. In this study, we found that PDCoV infection fails to induce, and even remarkably inhibits, Sendai virus- or poly(I: C)-induced IFN-β production by impeding the activation of transcription factors NF-κB and IRF3. We also found that PDCoV infection significantly suppresses the activation of IFN-β promoter stimulated by IRF3 or its upstream molecules (RIG-I, MDA5, IPS-1, TBK1, IKKε) in the RIG-I signaling pathway, but does not counteract its activation by the constitutively active mutant of IRF3 (IRF3-5D). Taken together, our results demonstrate that PDCoV infection suppresses RIG-I-mediated IFN signaling pathway, providing a better understanding of the PDCoV immune evasion strategy.