No abstract

Foot-and-mouth disease is a highly contagious viral illness of wild and domestic cloven-hoofed animals. The causative agent, foot-and-mouth disease virus (FMDV), replicates rapidly, efficiently disseminating within the infected host and being passed on to susceptible animals via direct contact or the aerosol route. To survive in the host, FMDV has evolved to block the host interferon (IFN) response. Previously, we and others demonstrated that the leader proteinase (L pro ) of FMDV is an IFN antagonist. Here, we report that another FMDV-encoded proteinase, 3C pro , also inhibits IFN-α/β response and the expression of IFN-stimulated genes. Acting in a proteasome- and caspase-independent manner, the 3C pro of FMDV proteolytically cleaved nuclear transcription factor kappa B (NF-κB) essential modulator (NEMO), a bridging adaptor protein essential for activating both NF-κB and interferon-regulatory factor signaling pathways. 3C pro specifically targeted NEMO at the Gln 383 residue, cleaving off the C-terminal zinc finger domain from the protein. This cleavage impaired the ability of NEMO to activate downstream IFN production and to act as a signaling adaptor of the RIG-I/MDA5 pathway. Mutations specifically disrupting the cysteine protease activity of 3C pro abrogated NEMO cleavage and the inhibition of IFN induction. Collectively, our data identify NEMO as a substrate for FMDV 3C pro and reveal a novel mechanism evolved by a picornavirus to counteract innate immune signaling.

Background: Corona virus disease (COVID-19) is an infectious respiratory disease that has spread rapidly across the world. Many studies have already evaluated the clinical features of COVID-19, but how it compares with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-negative community-acquired pneumonia (SN-CAP) is still unclear. Moreover, COVID-19 mortality is correlated with disease severity, but indicators for severity grading have not been specified. We aimed to analyze the clinical characteristics of COVID-19 in comparison with SN-CAP and find indicators for disease severity in COVID-19. Methods: Patients diagnosed with COVID-19 and SN-CAP were enrolled. Clinical, radiological, and laboratory data were analyzed. Results: The numbers of COVID-19 and SN-CAP patients enrolled were 304 and 138, respectively. The age of the patients was not significantly different between the groups. Compared with SN-CAP, COVID-19 patients had more symptoms of fever and dyspnea; and showed significant difference in blood count results. Computed tomography (CT) imaging of COVID-19 patients showed patchy ground-glass opacities that correlated with disease severity, whereas the CT imaging of SN-CAP patients showed patchy high-density shadows. COVID-19 patients were classified into moderate, severe, and critically severe groups. The severe and critically severe groups had elevated levels of white blood cells (WBC), neutrophils, platelets, C-reaction protein (CRP), lymphocyte ratio (NLR), platelet to lymphocyte ratio (PLR), troponin-I, creatinine, and blood urea nitrogen (BUN). However, they had decreased levels of lymphocytes, lymphocyte ratio, and albumin. Compared with the younger patients, the older COVID-19 individuals had more chronic diseases and significantly elevated levels of WBC, neutrophil, and CRP levels. Conclusion: SN-CAP showed more inflammatory reaction than COVID-19. Old people with chronic diseases are more susceptible to COVID-19 and have a high likelihood of developing severe and critically severe infection. Levels of WBC, lymphocytes, neutrophils, CRP, NLR, PLR, troponin-I, creatinine, and BUN are important indicators for severity grading in COVID-19.

Since its emergence in the late 1980s, porcine reproductive and respiratory syndrome (PRRS) has been devastating the swine industry worldwide. The causative agent is an Arterivirus, referred to as PRRS virus (PRRSV). The pathogenic mechanisms of PRRS are poorly understood, but are believed to correlate with the ability of PRRSV to inhibit immune responses of the host. However, precisely how the virus is capable of doing so remains obscure. In this study, we showed that PRRSV infection led to reduced ubiquitination of cellular proteins. Screening all of the 12 nonstructural proteins (Nsps) encoded by PRRSV revealed that, apart from the Nsp2 which contains the deubiqintinating (DUB) ovarian tumor (OTU) domain, Nsp11, which encodes a unique and conserved endoribonuclease (NendoU) throughout the Nidovirus order, also possesses DUB activity. In vivo assay demonstrated that Nsp11 specifically removed lysine 48 (K48)-linked polyubiquitin chains and the conserved sites C112, H144, D173, K180, and Y219 were critical for its DUB activity. Remarkably, DUB activity was responsible for the capacity of Nsp11 to inhibit nuclear factor κB (NF-κB) activation. Mutations abrogating the DUB activity of Nsp11 toward K48-linked polyubiquitin chains of IκBα nullified the suppressive effect on NF-κB. Our data add Nsp11 to the list of DUBs encoded by PRRSV and uncover a novel mechanism by which PRRSV cripples host innate immune responses.