Nanoparticle vaccines based on the receptor binding domain of porcine deltacoronavirus elicit robust protective immune responses in mice.

Background: Porcine deltacoronavirus (PDCoV), a novel swine enteropathogenic coronavirus, challenges the global swine industry. Currently, there are no approaches preventing swine from PDCoV infection. Methods: A new PDCoV strain named JS2211 was isolated. Next, the dimer receptor binding domain of PDCoV spike protein (RBD-dimer) was expressed using the prokaryotic expression system, and a novel nanoparticle containing RBD-dimer and ferritin (SC-Fe) was constructed using the SpyTag/SpyCatcher system. Finally, the immunoprotection of RBD-Fe nanoparticles was evaluated in mice. Results: The novel PDCoV strain was located in the clade of the late Chinese isolate strains and close to the United States strains. The RBD-Fe nanoparticles were successfully established. Immune responses of the homologous prime-boost regime showed that RBD-Fe nanoparticles efficiently elicited specific humoral and cellular immune responses in mice. Notably, high level PDCoV RBD-specific IgG and neutralizing antibody (NA) could be detected, and the histopathological results showed that PDCoV infection was dramatically reduced in mice immunized with RBD-Fe nanoparticles. Conclusion: This study effectively developed a candidate nanoparticle with receptor binding domain of PDCoV spike protein that offers protection against PDCoV infection in mice.

An adenovirus-vectored vaccine based on the N protein of feline coronavirus elicit robust protective immune responses.

Feline coronavirus (FCoV) is an unsegmented, single-stranded RNA virus belonging to the Alphacoronavirus genus. It can cause fatal feline infectious peritonitis (FIP) in cats of any ages. Currently, there are no effective prevention and control measures to against FCoV. In this study, we developed a recombinant adenovirus vaccine, AD5-N, based on the nucleocapsid(N) protein of FCoV. The immunogenicity of AD5-N was evaluated through intramuscular immunization in 6-week-old Balb/c mice and 9-12 months old cats. Compared to the control group, AD5-N specifically induced a significant increase in IgG and SIgA levels in the vaccinated mice. Furthermore, AD5-N not only effectively promoted strong cellular immune responses in cats but also induced high levels of specific SIgA, effectively helping cats resist FCoV infection. Our findings suggest that adenovirus vector vaccines based on the N gene have the potential to become candidate vaccines for the prevention and control of FCoV infection.

Research Progress of Porcine Reproductive and Respiratory Syndrome Virus NSP2 Protein.

Porcine reproductive and respiratory syndrome virus (PRRSV) is globally prevalent and seriously harms the economic efficiency of pig farming. Because of its immunosuppression and high incidence of mutant recombination, PRRSV poses a great challenge for disease prevention and control. Nonstructural protein 2 (NSP2) is the most variable functional protein in the PRRSV genome and can generate NSP2N and NSP2TF variants due to programmed ribosomal frameshifts. These variants are broad and complex in function and play key roles in numerous aspects of viral protein maturation, viral particle assembly, regulation of immunity, autophagy, apoptosis, cell cycle and cell morphology. In this paper, we review the structural composition, programmed ribosomal frameshift and biological properties of NSP2 to facilitate basic research on PRRSV and to provide theoretical support for disease prevention and control and therapeutic drug development.

Identification of Linear Epitopes in the C-Terminal Region of ASFV p72 Protein.

African swine fever, which is induced by the African swine fever virus (ASFV), poses a significant threat to the global pig industry due to its high lethality in domestic pigs and wild boars. Despite the severity of the disease, there is a lack of effective vaccines and drugs against the ASFV. The p72 protein, constituting 31 to 33% of the total virus particle mass, serves as the primary capsid protein of ASFV. It is a crucial antigen for the development of ASF subunit vaccines and serological diagnostic methods. In this investigation, 27 monoclonal antibodies (mAbs) were generated through mouse immunization with the truncated C-terminal p72 protein expressed by Escherichia coli. Among these, six mAbs exhibited binding to the p72 trimer, with their respective recognized epitopes identified as 542VTAHGINLIDKF553, 568GNAIKTP574, and 584FALKPREEY592. All three epitopes were situated within the interval sequences of functional units of the C-terminal jelly-roll barrel of p72. Notably, two epitopes, 568GNAIKTP574 and 584FALKPREEY592, were internal to the p72 trimer, while the epitope 542VTAHGINLIDKF553 was exposed on the surface of the trimer and consistently conserved across all ASFV genotypes. These findings enhance our comprehension of the antigenic function and structure of the p72 protein, facilitating the utilization of p72 in the development of diagnostic techniques for ASFV.

MiR-7-5p targeted Rb regulating cell cycle is involved in hydroquinone-induced malignant progression in human lymphoblastoid TK6 cells.

MiR-7-5p has been demonstrated to inhibit tumorigenesis by limiting tumor cell proliferation, migration and invasion. However, its role in countering hydroquinone (HQ)-induced malignant phenotype of TK6 cells has remained unclear. The present study aimed to investigate whether miR-7-5p overexpression could restrain the malignant phenotype in TK6 cells exposed to HQ. The results displayed that HQ suppressed the expression of miR-7-5p and promoted cell cycle progression. Further investigations confirmed that miR-7-5p could decelerate the cell cycle progression by targeting Rb after acute HQ exposure. Through the regulation of the Rb/E2F1 signaling pathway, the overexpression of miR-7-5p mitigated HQ-induced malignant phenotype in TK6 cells by impeding cell cycle progression. In conclusion, miR-7-5p overexpression appears to be involved in HQ-induced malignant transformation by suppressing Rb/E2F1 signaling pathway, resulting in a deceleration of the cell cycle progression.

The CD2v protein of African swine fever virus inhibits macrophage migration and inflammatory cytokines expression by downregulating EGR1 expression through dampening ERK1/2 activity.

African swine fever virus (ASFV) is a highly contagious and deadly virus that leads to high mortality rates in domestic swine populations. Although the envelope protein CD2v of ASFV has been implicated in immunomodulation, the molecular mechanisms underlying CD2v-mediated immunoregulation remain unclear. In this study, we generated a stable CD2v-expressing porcine macrophage (PAM-CD2v) line and investigated the CD2v-dependent transcriptomic landscape using RNA-seq. GO terms enrichment analysis and gene set enrichment analysis revealed that CD2v predominantly affected the organization and assembly process of the extracellular matrix. Wound healing and Transwell assays showed that CD2v inhibited swine macrophage migration. Further investigation revealed a significant decrease in the expression of transcription factor early growth response 1 (EGR1) through inhibiting the activity of extracellular signal-regulated kinase 1 and 2 (ERK1/2). Notably, EGR1 knockout in swine macrophages restricted cell migration, whereas EGR1 overexpression in PAM-CD2v restored the ability of macrophage migration, suggesting that CD2v inhibits swine macrophage motility by downregulating EGR1 expression. Furthermore, we performed chromatin immunoprecipitation and sequencing for EGR1 and the histone mark H3K27 acetylation (H3K27ac), and we found that EGR1 co-localized with the activated histone modification H3K27ac neighboring the transcriptional start sites. Further analysis indicated that EGR1 and H3K27ac co-occupy the promoter regions of cell locomotion-related genes. Finally, by treating various derivatives of swine macrophages with lipopolysaccharides, we showed that depletion of EGR1 decreased the expression of inflammatory cytokines including TNFα, IL1α, IL1ß, IL6, and IL8, which play essential roles in inflammation and host immune response. Collectively, our results provide new insights into the immunomodulatory mechanism of ASFV CD2v.

Wetland vegetation cover changes and its response to climate changes across Heilongjiang-Amur River Basin.

The Heilongjiang-Amur River Basin is one of the largest and most complex aquatic systems in Asia, comprising diverse wetland resources. The wetland vegetation in mid-high latitude areas has high natural value and is sensitive to climate changes. In this study, we investigated the wetland vegetation cover changes and associated responses to climate change in the Heilongjiang-Amur River Basin from 2000 to 2018 based on the growing season (May to September) climate and LAI data. Our results indicated that the wetland LAI increased at 0.014 m2·m-2/yr across Heilongjiang-Amur River Basin with the regional climate showed wetting and warming trends. On a regional scale, wetland vegetation in China and Russia had positive partial correlation with solar radiation and minimum air temperature, with precipitation showing a slight lag effect. In contrast, wetland vegetation in Mongolia had positive partial correlation with precipitation. These correlations were further investigated at different climate intervals. We found the precipitation is positively correlated with LAI in the warm regions while is negatively correlated with LAI in the wet regions, indicating an increase in precipitation is beneficial for the growth of wetland vegetation in heat sufficient areas, and when precipitation exceeds a certain threshold, it will hinder the growth of wetland vegetation. In the cold regions, we found solar radiation and minimum air temperature are positively correlated with LAI, suggesting SR and minimum air temperature instead of mean air temperature and maximum air temperature play more important roles in affecting the wetland vegetation growth in the heat limited areas. The LAI was found to be negatively correlated with maximum air temperature in the arid areas, indicating excessive temperature would inhibit the wetland vegetation growth when the water is limited. Our investigation can provide a scientific foundation for the trilateral region in wetland ecosystem protection and is beneficial for a more comprehensive understanding of the responses of wetlands in the middle and high latitudes to climate change.

Vegetation-induced asymmetric diurnal land surface temperatures changes across global climate zones.

Unprecedented global vegetation greening during past decades is well known to affect annual and seasonal land surface temperatures (LST). However, the impact of observed vegetation cover change on diurnal LST across global climatic zones is not well understood. Using global climatic time-series datasets, we investigated the long-term growing season daytime and nighttime LST changes globally and explored associated dominant contributors including vegetation and climate factors including air temperature, precipitation, and solar radiation. Results revealed asymmetric growing season mean daytime and nighttime LST warming (0.16 °C/10a and 0.30 °C/10a, respectively) globally from 2003 to 2020, as a result, the diurnal LST range (DLSTR) declined at 0.14 °C/10a. The sensitivity analysis indicated the LST response to changes in LAI, precipitation, and SSRD mainly concentrated during daytime instead of nighttime, however, which showed comparable sensitivities for air temperature. Combining the sensitivities results and the observed LAI and climate trends, we found rising air temperature contributes to 0.24 ± 0.11 °C/10a global daytime LST warming and 0.16 ± 0.07 °C/10a nighttime LST warming, turns to be the dominant contributor to the LST changes. Increased LAI cooled global daytime LST (-0.068 ± 0.096 °C/10a) while warmed nighttime LST (0.064 ± 0.046 °C/10a); hence LAI dominates declines in DLSTR trends (-0.12 ± 0.08 °C/10a), despite some day-night process variations across climate zones. In Boreal regions, reduced DLSTR was due to nighttime warming from LAI increases. In other climatic zones, daytime cooling, and DLSTR decline, was induced by increased LAI. Biophysically, the pathway from air temperature heats the surface through sensible heat and increased downward longwave radiation during day and night, while the pathway from LAI cools the surface by enhancing energy redistribution into latent heat rather than sensible heat during the daytime. These empirical findings of diverse asymmetric responses could help calibrate and improve biophysical models of diurnal surface temperature feedback in response to vegetation cover changes in different climate zones.

PTBP1 suppresses porcine epidemic diarrhea virus replication via inducing protein degradation and IFN production.

Porcine epidemic diarrhea virus (PEDV) causes severe morbidity and mortality among newborn piglets. It significantly threatens the porcine industry in China and around the globe. To accelerate the developmental pace of drugs or vaccines against PEDV, a deeper understanding of the interaction between viral proteins and host factors is crucial. The RNA-binding protein, polypyrimidine tract-binding protein 1 (PTBP1), is crucial for controlling RNA metabolism and biological processes. The present work focused on exploring the effect of PTBP1 on PEDV replication. PTBP1 was upregulated during PEDV infection. The PEDV nucleocapsid (N) protein was degraded through the autophagic and proteasomal degradation pathways. Moreover, PTBP1 recruits MARCH8 (an E3 ubiquitin ligase) and NDP52 (a cargo receptor) for N protein catalysis and degradation through selective autophagy. Furthermore, PTBP1 induces the host innate antiviral response via upregulating the expression of MyD88, which then regulates TNF receptor-associated factor 3/ TNF receptor-associated factor 6 expression and induces the phosphorylation of TBK1 and IFN regulatory factor 3. These processes activate the type Ⅰ IFN signaling pathway to antagonize PEDV replication. Collectively, this work illustrates a new mechanism related to PTBP1-induced viral restriction, where PTBP1 degrades the viral N protein and induces type Ⅰ IFN production to suppress PEDV replication.

JNK1 activated pRb/E2F1 and inhibited p53/p21 signaling pathway is involved in hydroquinone-induced pathway malignant transformation of TK6 cells by accelerating the cell cycle progression.

Hydroquinone (HQ) is an important metabolites of benzene in the body, and it has been found to result in cellular DNA damage, mutation, cell cycle imbalance, and malignant transformation. The JNK1 signaling pathway plays an important role in DNA damage repair. In this study, we focused on whether the JNK1 signaling pathway is involved in the HQ-induced cell cycle abnormalities and the underlying mechanism. The results showed that HQ induced abnormal progression of the cell cycle and initiated the JNK1 signaling pathway. We further confirmed that JNK1 suppression decelerated the cell cycle progression through inhibiting pRb/E2F1 signaling pathway and triggering p53/p21 pathway. Therefore, we concluded that JNK1 might be involved in HQ-induced malignant transformation associated with activating pRb/E2F1 and inhibiting p53/p21 signaling pathway which resulting in accelerating the cell cycle progression.

Screening and identification of the dominant antigens of the African swine fever virus.

African swine fever is a highly lethal contagious disease of pigs for which there is no vaccine. Its causative agent African swine fever virus (ASFV) is a highly complex enveloped DNA virus encoding more than 150 open reading frames. The antigenicity of ASFV is still unclear at present. In this study, 35 proteins of ASFV were expressed by Escherichia coli, and ELISA was developed for the detection of antibodies against these proteins. p30, p54, and p22 were presented as the major antigens of ASFV, positively reacting with all five clinical ASFV-positive pig sera, and 10 pig sera experimentally infected by ASFV. Five proteins (pB475L, pC129R, pE199L, pE184L, and pK145R) reacted well with ASFV-positive sera. The p30 induced a rapid and strong antibody immune response during ASFV infection. These results will promote the development of subunit vaccines and serum diagnostic methods against ASFV.

The rPRRSV-E2 strain exhibited a low level of potential risk for virulence reversion.

Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) and Classical Swine Fever Virus (CSFV) are two important pathogens, which cause serious impact on swine industry worldwide. In our previous research, rPRRSV-E2, the recombinant PRRSV expressing CSFV E2 protein, could provide sufficient protection against the lethal challenge of highly pathogenic PRRSV and CSFV, and could maintained genetically stable in vitro. Here, to evaluate the virulence reversion potential risk, rPRRSV-E2 had been continuously passaged in vivo, the stability of E2 expression and virulence of the passage viruses were analyzed. The results showed that no clinical symptoms or pathological changes could be found in the inoculated groups, and there were no significant differences of viraemia among the test groups. Sequencing and IFA analysis showed that the coding gene of exogenous CSFV E2 protein existed in the passaged viruses without any sequence mutations, deletions or insertions, and could expressed steadily. It could be concluded that the foreign CSFV E2 gene in the genome of rPRRSV-E2 could be maintained genetically stable in vivo, and rPRRSV-E2 strain had relatively low level of potential risk for virulence reversion.

Nrf2 affects hydroquinone-induces cell cycle arrest through the p16/pRb signaling pathway and antioxidant enzymes.

Hydroquinone (HQ), a well-known carcinogenic agent, induces oxidative stress, cell cycle arrest, apoptosis, and malignant transformation. As an antioxidant actor, the nuclear factor erythroid 2-related factor 2 (Nrf2) drives adaptive cellular protection in response to oxidative stress. The human lymphoblastoid cell line (TK6 cells) is widely used as a model for leukemia researches. In the present study, we focused on exploring whether Nrf2 regulatory cell cycle in TK6 cells upon HQ treatment and the underlying mechanisms. The results showed that the cell cycle arrest in TK6 cells induced by hydroquinone was accompanied by activation of the Nrf2 signaling pathway. We further clarified that Nrf2 loss accelerated cell cycle progression from G0/G1 to S and G2/M phases and promoted ROS production by downregulating the expression of SOD and GSH. Western blotting analysis indicated that Nrf2 regulated cell cycle progression via p16/pRb signaling pathways. Therefore, we conclude that Nrf2 is engaged in HQ-induced cell cycle arrest as well through p16/pRb and antioxidant enzymes.

Nonstructural Protein 2 Is Critical to Infection Efficiency of Highly Pathogenic Porcine Reproductive and Respiratory Syndrome Virus on PAMs and Influence Virulence In Vivo.

Porcine reproductive and respiratory syndrome (PRRS) is an important viral disease, causing significant economic losses to the swine industry worldwide. Atypical cases caused by highly pathogenic PRRS virus (HP-PRRSV) emerged in 2006 in China. The vaccine strain HuN4-F112 has been developed from the wild-type HP-PRRSV HuN4 through repeated passages on MARC-145 cells. However, the mechanisms of attenuation have yet to be defined. Previous studies have shown that the vaccine strain HuN4-F112 could not effectively replicate in porcine alveolar macrophages (PAMs). In the present study, a series of chimeric and mutant PRRSVs were constructed to investigate regions associated with the virus attenuation. Firstly, the corresponding genome regions (ORF1a, ORF1b and ORFs 2-7) were exchanged between two infectious clones of HuN4 and HuN4-F112, and then the influence of small regions in ORF1a and ORF2-7 was evaluated, then influence of specific amino acids on NSP2 was tested. NSP2 was determined to be the key gene that regulated infection efficiency on PAMs, and amino acids at 893 and 979 of NSP2 were the key amino acids. The results of in vivo study indicated that NSP2 was not only important for infection efficiency in vitro, but also influenced the virulence, which was indicated by the results of survival rate, temperature, viremia, lung score and tissue score.

Identification and Characterization of Cell Lines HepG2, Hep3B217 and SNU387 as Models for Porcine Epidemic Diarrhea Coronavirus Infection.

Porcine epidemic diarrhea virus (PEDV), a member of the genera alphacoronavirus, causes acute watery diarrhea and dehydration in suckling piglets and results in enormous economic losses in the swine industry worldwide. Identification and characterization of different cell lines are not only invaluable for PEDV entry and replication studies but also important for the development of various types of biological pharmaceuticals against PEDV. In this study, we present an approach to identify suitable permissive cell lines for PEDV research. Human cell lines were screened for a high correlation coefficient with the established PEDV infection model Huh7 based on RNA-seq data from the Cancer Cell Line Encyclopedia (CCLE). Experimentally testing permissiveness towards PEDV infection, three highly permissive human cell lines, HepG2, Hep3B217, and SNU387 were identified. The replication kinetics of PEDV in HepG2, Hep3B217, and SNU387 cells were similar to that in Vero and Huh7 cells. Additionally, the transcriptomes analysis showed robust induction of transcripts associated with the innate immune in response to PEDV infection in all three cell lines, including hundreds of inflammatory cytokine and interferon genes. Moreover, the expression of inflammatory cytokines and interferons were confirmed by qPCR assay. Our findings indicate that HepG2, Hep3B217, and SNU387 are suitable cell lines for PEDV replication and innate immune response studies.

hnRNP K Degrades Viral Nucleocapsid Protein and Induces Type I IFN Production to Inhibit Porcine Epidemic Diarrhea Virus Replication.

Porcine epidemic diarrhea virus (PEDV) is a re-emerging enteric coronavirus currently spreading in several nations and inflicting substantial financial damages on the swine industry. The currently available coronavirus vaccines do not provide adequate protection against the newly emerging viral strains. It is essential to study the relationship between host antiviral factors and the virus and to investigate the mechanisms underlying host immune response against PEDV infection. This study shows that heterogeneous nuclear ribonucleoprotein K (hnRNP K), the host protein determined by the transcription factor KLF15, inhibits the replication of PEDV by degrading the nucleocapsid (N) protein of PEDV in accordance with selective autophagy. hnRNP K was found to be capable of recruiting the E3 ubiquitin ligase, MARCH8, aiming to ubiquitinate N protein. Then, it was found that the ubiquitinated N protein could be delivered into autolysosomes for degradation by the cargo receptor NDP52, thereby inhibiting PEDV proliferation. Moreover, based on the enhanced MyD88 expression, we found that hnRNP K activated the interferon 1 (IFN-1) signaling pathway. Overall, the data obtained revealed a new mechanism of hnRNP K-mediated virus restriction wherein hnRNP K suppressed PEDV replication by degradation of viral N protein using the autophagic degradation pathway and by induction of IFN-1 production based on upregulation of MyD88 expression. IMPORTANCE The spread of the highly virulent PEDV in many countries is still leading to several epidemic and endemic outbreaks. To elucidate effective antiviral mechanisms, it is important to study the relationship between host antiviral factors and the virus and to investigate the mechanisms underlying host immune response against PEDV infection. In the work, we detected hnRNP K as a new host restriction factor which can hinder PEDV replication through degrading the nucleocapsid protein based on E3 ubiquitin ligase MARCH8 and the cargo receptor NDP52. In addition, via the upregulation of MyD88 expression, hnRNP K could also activate the interferon (IFN) signaling pathway. This study describes a previously unknown antiviral function of hnRNP K and offers a new vision toward host antiviral factors that regulate innate immune response as well as a protein degradation pathway against PEDV infection.

KLF16 inhibits PEDV replication by activating the type I IFN signaling pathway.

KLF16, a member of KLFs (Krüppel-like factors), contributes to the progression of a variety of cancer types. There is, however, still uncertain regarding the role of KLF16 in viral replication and the signaling mechanism of type I IFN. It was discovered that KLF16 inhibited the replication of porcine epidemic diarrhea virus (PEDV) through the type I IFN signaling pathway. Besides, it can also be found that the expression of KLF16 was down-regulated after PEDV infection of LLC-PK1 cells. Furthermore, overexpression of KLF16 inhibited the replication of PEDV in Vero cells as well as LLC-PK1 cells, whereas the replication of PEDV was promoted by the knockdown of KLF16. KLF16 up-regulated the expression of interferons (IFNs) via the TRAF6-pTBK1-pIRF3 pathway with the aim of promoting the host antiviral innate immune response. In addition, the obtained findings proved that KLF16 plays a novel role in antiviral action, thereby offering novel possibilities for preventing and controlling PEDV.

ATG4B hinders porcine epidemic diarrhea virus replication through interacting with TRAF3 and activating type-I IFN signaling.

Autophagy-related 4B (ATG4B) is found to exert a vital function in viral replication, although the mechanism through which ATG4B activates type-I IFN signaling to hinder viral replication remains to be explained, so far. The current work revealed that ATG4B was downregulated in porcine epidemic diarrhea virus (PEDV)-infected LLC-PK1 cells. In addition, ATG4B overexpression inhibited PEDV replication in both Vero cells and LLC-PK1 cells. On the contrary, ATG4B knockdown facilitated PEDV replication. Moreover, ATG4B was observed to hinder PEDV replication by activating type-I IFN signaling. Further detailed analysis revealed that the ATG4B protein targeted and upregulated the TRAF3 protein to induce IFN expression via the TRAF3-pTBK1-pIRF3 pathway. The above data revealed a novel mechanism underlying the ATG4B-mediated viral restriction, thereby providing novel possibilities for preventing and controlling PEDV.

Porcine epidemic diarrhea virus strain FJzz1 infection induces type I/III IFNs production through RLRs and TLRs-mediated signaling.

Interferons (IFNs) including type I/III IFNs are the major components of the host innate immune response against porcine epidemic diarrhea virus (PEDV) infection, and several viral proteins have been identified to antagonize type I/III IFNs productions through diverse strategies. However, the modulation of PEDV infection upon the activation of the host's innate immune response has not been fully characterized. In this study, we observed that various IFN-stimulated genes (ISGs) were upregulated significantly in a time- and dose-dependent manner in LLC-PK1 cells infected with the PEDV G2 strain FJzz1. The transcriptions of IRF9 and STAT1 were increased markedly in the late stage of FJzz1 infection and the promotion of the phosphorylation and nuclear translocation of STAT1, implicating the activation of the JAK-STAT signaling pathway during FJzz1 infection. In addition, abundant type I/III IFNs were produced after FJzz1 infection. However, type I/III IFNs and ISGs decreased greatly in FJzz1-infected LLC-PK1 cells following the silencing of the RIG-I-like receptors (RLRs), including RIG-I and MDA5, and the Toll-like receptors (TLRs) adaptors, MyD88 and TRIF. Altogether, FJzz1 infection induces the production of type-I/III IFNs in LLC-PK1 cells, in which RLRs and TLRs signaling pathways are involved, followed by the activation of the JAK-STAT signaling cascade, triggering the production of numerous ISGs to exert antiviral effects of innate immunity.

FUBP3 Degrades the Porcine Epidemic Diarrhea Virus Nucleocapsid Protein and Induces the Production of Type I Interferon.

Porcine epidemic diarrhea virus (PEDV) is the globally distributed alphacoronavirus that can cause lethal watery diarrhea in piglets, causing substantial economic damage. However, the current commercial vaccines cannot effectively the existing diseases. Thus, it is of great necessity to identify the host antiviral factors and the mechanism by which the host immune system responds against PEDV infection required to be explored. The current work demonstrated that the host protein, the far upstream element-binding protein 3 (FUBP3), could be controlled by the transcription factor TCFL5, which could suppress PEDV replication through targeting and degrading the nucleocapsid (N) protein of the virus based on selective autophagy. For the ubiquitination of the N protein, FUBP3 was found to recruit the E3 ubiquitin ligase MARCH8/MARCHF8, which was then identified, transported to, and degraded in autolysosomes via NDP52/CALCOCO2 (cargo receptors), resulting in impaired viral proliferation. Additionally, FUBP3 was found to positively regulate type-I interferon (IFN-I) signaling and activate the IFN-I signaling pathway by interacting and increasing the expression of tumor necrosis factor (TNF) receptor-associated factor 3 (TRAF3). Collectively, this study showed a novel mechanism of FUBP3-mediated virus restriction, where FUBP3 was found to degrade the viral N protein and induce IFN-I production, aiming to hinder the replication of PEDV. IMPORTANCE PEDV refers to the alphacoronavirus that is found globally and has re-emerged recently, causing severe financial losses. In PEDV infection, the host activates various host restriction factors to maintain innate antiviral responses to suppress virus replication. Here, FUBP3 was detected as a new host restriction factor. FUBP3 was found to suppress PEDV replication via the degradation of the PEDV-encoded nucleocapsid (N) protein via E3 ubiquitin ligase MARCH8 as well as the cargo receptor NDP52/CALCOCO2. Additionally, FUBP3 upregulated the IFN-I signaling pathway by interacting with and increasing tumor necrosis factor (TNF) receptor-associated factor 3 (TRAF3) expression. This study further demonstrated that another layer of complexity could be added to the selective autophagy and innate immune response against PEDV infection are complicated.