RESUMEN
Porcine deltacoronavirus (PDCoV) is a newly detected porcine coronavirus causing serious vomiting and diarrhea in piglets, especially newborn piglets. There has been an outbreak of PDCoV in worldwide since 2014, causing significant economic losses in the pig industry. The interferon (IFN)-mediated antiviral response is an important component of virus-host interactions and plays an essential role in inhibiting virus infection. However, the mechanism of PDCoV escaping the porcine immune surveillance is unclear. In the present study, we demonstrated that the PDCoV nucleocapsid (N) protein antagonizes porcine IFN-ß production after vesicular stomatitis virus (VSV) infection or poly(I:C) stimulation. PDCoV N protein also suppressed the activation of porcine IFN-ß promoter when it was stimulated by porcine RLR signaling molecules. PDCoV N protein targeted porcine retinoic acid-inducible gene I (pRIG-I) and porcine TNF receptor associated factor 3 (pTRAF3) by directly interacting with them. The N-terminal region (1-246 aa) of PDCoV N protein was important for interacting with pRIG-I and interfere its function. We confirmed that PDCoV N antagonizes IFN-ß production by associating with pRIG-I to impede it from binding double-stranded RNA. Furthermore, porcine Riplet (pRiplet) was an important activator for pRIG-I by mediating the K63-linked polyubiquitination. However, PDCoV N protein restrained the pRiplet binding pRIG-I to inhibit pRIG-I K63-linked polyubiquitination. Taken together, our results revealed a novel mechanism by which PDCoV N protein interferes with the early activation of pRIG-I in the host antiviral response. The novel findings provide a new insight into PDCoV on evading the host innate immune response and may provide new therapeutic targets and more efficacious vaccines strategies for PDCoV infections.
Asunto(s)
Infecciones por Coronavirus/inmunología , Coronavirus/fisiología , Interferón beta/metabolismo , Receptores de Superficie Celular/metabolismo , Animales , Interacciones Huésped-Patógeno , Humanos , Vigilancia Inmunológica , Nucleocápside/metabolismo , Unión Proteica , ARN Bicatenario/metabolismo , Receptores de Superficie Celular/genética , Transducción de Señal , Porcinos , Factor 3 Asociado a Receptor de TNF/metabolismo , UbiquitinaciónRESUMEN
Toll-like receptor 5 (TLR5) is responsible for the recognition of bacterial flagellin in vertebrates. In the present study, the first TLR5 gene in duck was cloned. The open reading frame (ORF) of duck TLR5 (dTLR5) cDNA is 2580 bp and encodes a polypeptide of 859 amino acids. We also cloned partial sequences of myeloid differentiation factor 88, 2'-5'-oligoadenylate synthetase (OAS), and myxovirus resistance (Mx) genes from duck. dTLR5 mRNA was highly expressed in the bursa of Fabricius, spleen, trachea, lung, jejunum, rectum, and skin; moderately expressed in the muscular and glandular tissues, duodenum, ileum, caecum, and pancreas; and minimally expressed in the heart, liver, kidney, and muscle. DF-1 or HeLa cells transfected with DNA constructs encoding dTLR5 can activate NF-kappaB leading to the activation of interleukin-6 (IL-6) promoter. When we challenged ducks with a Herts33 Newcastle disease virus (NDV), mRNA transcription of the antiviral molecules Mx, Double stranded RNA activated protein kinase (PKR), and OAS was up-regulated in the liver, lung, and spleen 1 and 2 days post-inoculation.