Porcine deltacoronavirus nucleocapsid protein antagonizes JAK-STAT signaling pathway by targeting STAT1 through KPNA2 degradation.

Porcine deltacoronavirus (PDCoV) is an enteric pathogenic coronavirus that causes acute and severe watery diarrhea in piglets and has the ability of cross-species transmission, posing a great threat to swine production and public health. The interferon (IFN)-mediated signal transduction represents an important component of virus-host interactions and plays an essential role in regulating viral infection. Previous studies have suggested that multifunctional viral proteins encoded by coronaviruses antagonize the production of IFN via various means. However, the function of these viral proteins in regulating IFN-mediated signaling pathways is largely unknown. In this study, we demonstrated that PDCoV and its encoded nucleocapsid (N) protein antagonize type I IFN-mediated JAK-STAT signaling pathway. We identified that PDCoV infection stimulated but delayed the production of IFN-stimulated genes (ISGs). In addition, PDCoV inhibited JAK-STAT signal transduction by targeting the nuclear translocation of STAT1 and ISGF3 formation. Further evidence showed that PDCoV N is the essential protein involved in the inhibition of type I IFN signaling by targeting STAT1 nuclear translocation via its C-terminal domain. Mechanistically, PDCoV N targets STAT1 by interacting with it and subsequently inhibiting its nuclear translocation. Furthermore, PDCoV N inhibits STAT1 nuclear translocation by specifically targeting KPNA2 degradation through the lysosomal pathway, thereby inhibiting the activation of downstream sensors in the JAK-STAT signaling pathway. Taken together, our results reveal a novel mechanism by which PDCoV N interferes with the host antiviral response.IMPORTANCEPorcine deltacoronavirus (PDCoV) is a novel enteropathogenic coronavirus that receives increased attention and seriously threatens the pig industry and public health. Understanding the underlying mechanism of PDCoV evading the host defense during infection is essential for developing targeted drugs and effective vaccines against PDCoV. This study demonstrated that PDCoV and its encoded nucleocapsid (N) protein antagonize type I interferon signaling by targeting STAT1, which is a crucial signal sensor in the JAK-STAT signaling pathway. Further experiments suggested that PDCoV N-mediated inhibition of the STAT1 nuclear translocation involves the degradation of KPNA2, and the lysosome plays a role in KPNA2 degradation. This study provides new insights into the regulation of PDCoV N in the JAK-STAT signaling pathway and reveals a novel mechanism by which PDCoV evades the host antiviral response. The novel findings may guide us to discover new therapeutic targets and develop live attenuated vaccines for PDCoV infection.

Insights into the response mechanisms of activated sludge system under long-term dexamethasone stress.

Dexamethasone (DEX) is a hormone drug that is often detected in wastewater treatment plants, but its impact on activated sludge systems is unknown. This study explored the long-term effects of DEX on nutrient removal, microbial activities, microbial assembly, and microbial interactions in the activated sludge system. During the 90-day DEX exposure experiment, both chemical oxygen demand and total nitrogen removal efficiencies were initially inhibited and then recovered. Microbial activities, i.e., specific oxygen uptake rate and denitrification, did not differ significantly from that of the control reactor (p > 0.05), possibly due to the secretion of extracellular polymers that act as a protective barrier against excess reactive oxygen species induced by DEX. This barrier protects cell membrane integrity and ensures stable treatment performance. Analysis of microbial assembly identified the drift of stochastic processes (from 92.7 % to 51.8 %) and homogeneous selection of deterministic processes (from 1.6 % to 38.7 %) as the main driving forces of microbial community structure succession under long-term DEX stress. Although long-term exposure to 1000 µg/L DEX did not significantly increase the abundance levels of functional bacteria (Nitrosomonas and 996-1) and key genes (AmoCAB and Hao), the ammonia oxidation capacity of the activated sludge system was enhanced. Analysis of microbial interactions indicated that streamlining of functional subnetworks and increased cooperation were the primary reasons. This is the first study to explore the long-term effects of DEX on activated sludge and provide insights into microbial interaction and assembly. Moreover, the findings of this study broaden our knowledge and lay an experimental foundation for reducing risks associated with hormone drugs.

Making sense of flavivirus non-strctural protein 1 in innate immune evasion and inducing tissue-specific damage.

Flaviviruses include medically important mosquito-borne pathogens, such as Zika virus (ZIKV), Japanese encephalitis virus (JEV), dengue virus (DENV) and West Nile virus (WNV), that cause hundreds of millions of infections each year. Currently, there are no approved effect therapies against mosquito-borne flaviviruses. The flaviviruses encoded nonstructural protein 1 (NS1) is a secreted glycoprotein widely involved in viral replication, immune evasion, and directly causing tissue-specific damage during flaviviruses infection. Upon viral infection of host cell, NS1 can be found in multiple oligomeric forms and include a dimer on the cell surface, and a soluble secreted hexameric lipoparticle. In the recent decade, the detailed crystal structure of several flaviviruses NS1 have been determined and unraveled its broader and deeper functions. Consistent with the potential immune function revealed by its structure, NS1 is involved in the escaping of host signal immune pathway mediated by pattern recognition receptors (PRRs), including RIG-I-like receptors (RLRS) and Toll-like receptors (TLRs). Moreover, the flavivirus NS1 is efficiently secreted by infected cells and circulates in the blood of the host to directly induce specific tissues damage. The NS1 of ZIKV, JEV and WNV changes the permeability of brain microvascular endothelial cell to cause endothelial cell dysfunction and promote virus pathogenesis. DENV NS1 can induce systemic tissues damage in humans through multiple strategies. Mutations of several key amino acids in NS1 can reduce the neurovirulence of the flavivirus. In this article, we provide an overview of the latest research on this fascinating protein in these disparate areas.

Preparation of monoclonal antibody and identification of two novel B cell epitopes to VP1 protein of porcine sapelovirus.

Porcine sapelovirus (PSV) is an important emerging swine pathogen that causes diarrhoea, respiratory distress, severe reproductive system and neurological disorders in pigs, posing huge threat to swine industry. However, there are no effective serological diagnostic products and the epitope characterization of PSV VP1 protein is still largely unknown. In current study, we successfully expressed recombinant His-VP1 protein by prokaryotic expression system and the recombinant VP1 protein had good immunogenicity. BALB/C mice were then selected and immunized with purified recombinant VP1 protein, and two monoclonal antibodies (Mabs) 9F10 and 15E4 against VP1 were successfully prepared by hybrioma technology. The isotype of these two Mabs were identified and showed that Mab 9F10 with the heavy chain subtype was IgG1 and the light chain subtype was kappa. Mab 15E4 was identified as IgG2 for the heavy chain subtype and Kappa for the light chain subtype. The antigen epitopes of prepared two VP1 Mabs were clearly identified. The minimal unit of B cell specific epitope recognized by Mab 15E4 was 203YDGDG207 and conserved in different strain genotypes of PSV, indicating this epitope may be a good target for serological detection of PSV. However, the epitope recognized by Mab 9F10 was 8QAIVNRT14 and varied greatly among different PSV strains. Structural modeling analysis showed that the identified two novel B cell epitopes were located on the surface of VP1. Our study provides useful tool for the establishment the serological detection methods of PSV and may support the study of VP1 protein function.

Co-infection of porcine deltacoronavirus and porcine epidemic diarrhoea virus alters gut microbiota diversity and composition in the colon of piglets.

Porcine deltacoronavirus (PDCoV) and porcine epidemic diarrhoea virus (PEDV) are the main porcine enteric coronaviruses that cause severe diarrhoea in piglets, posing huge threat to the swine industry. Our previous study verified that the co-infection of PDCoV and PEDV is common in natural swine infections and obviously enhances the disease severity in piglets. However, the effects of co-infection of PDCoV and PEDV on intestinal microbial community are unknown. In current study, the microbial composition and diversity in the colon of piglets were analyzed. Our results showed that both of PDCoV and PEDV were mainly distributed in the small intestines and caused severe damage of ileum but not colon in the co-inoculated piglets. Furthermore, we observed that PDCoV and PEDV co-infection alters the gut microbiota composition at the phylum, family and genus levels. The abundance of Mitsuokella and Collinsella at genus level were significantly increased in PDCoV-PEDV co-infection piglets. Spearman's correlation analysis further suggested that there existed strong positive correlation between Mitsuokella and TNF-α, IL-6 and IL-8 secretion, these two factors may together aggravating the small intestine pathological lesions. These results proved there existed obvious correlation between the disease severity caused by PDCoV-PEDV co-infection and intestinal microbial community.

Co-infection of porcine epidemic diarrhoea virus and porcine deltacoronavirus enhances the disease severity in piglets.

Porcine epidemic diarrhoea virus (PEDV) and porcine deltacoronavirus (PDCoV) are the main enteric coronaviruses that cause acute diarrhoea and dehydration in pigs. The co-infection of PDCoV and PEDV is common in natural swine infections, but the clinical outcomes of the interaction between the co-circulating PDCoV and PEDV are unknown. In current study, we established a co-infection model by inoculating the cell culture-adapted PDCoV HNZK-02 strain and PEDV CV777 simultaneously or sequentially using 4-day-old piglets. The weight loss, clinical scores, viral load and titre, histopathological changes and serum cytokines expression were compared with piglets challenged by either virus. Our results indicated the piglets co-inoculated with PDCoV and PEDV showed more serious diarrhoeal symptoms, mainly characterized by longer diarrhoeal period when compared to those of the mono-infection piglets. Furthermore, we observed that PEDV could promote PDCoV replication in the co-inoculated piglets with evidence of prolonged faecal viral shedding, high viral titres in faeces and intestine tissues. Histological analysis indicated the co-infected piglets showed more extensive and serious pathological lesions in small intestine tissues than the mono-infection piglets. Our data also suggested that the co-infection of PDCoV and PEDV caused the excessive expression of pro-inflammatory cytokines (IL-6, IL-8 and TNF-α) in serum. These results proved there existed obvious synergistic pathogenic effects between PDCoV and PEDV co-infection, which provided new insights into the synergistic pathogenic mechanism caused by these two porcine coronaviruses.

Decrease of both river flow and quality aggravates water crisis in North China: a typical example of the upper Yongding River watershed.

Due to unevenly distributed water resources, semi-arid regions are particularly prone to severe water shortage and quality degradation. In this study, based on long-term hydrological database (1935-2015), and the latest available water quality data sets (2011-2016), we analyzed the water crisis and its driving forces in the upper Yongding River watershed, a typical water shortage area in North China. The results showed that human induced excessive water consumption is responsible for the significantly decreased river flow over the past eight decades. Although the capacity of the watershed wastewater treatment has improved, current water quality does not meet the requirements of the national water management goals, because of the excessive nitrogen and CODCr (chemical oxygen demand), which mainly come from the wastewater and feedlots discharge. Due to the decreased river flow, current Yongding River is unable to dilute and assimilate pollutions. The analysis of river pollutant load illustrated that more than 60 % of the nitrogen in the river water system is diverted for reservoir storage, and more than 50 % of the CODCr and TP are diverted for irrigation, thereby, increasing the risk of reservoirs eutrophication and threatening food safety. Besides, the high Cl- (388.2 ± 322.5 mg/L) and SO42- (470.6 ± 357.7 mg/L) imply that the upper river water are not suitable for drinking and irrigation purposes, and a potential risk of salinization if the river flow continues to decrease. We conclude that water resources over extraction and quality degradation are the main driving factors of the Yongding River water crisis.