Porcine epidemic diarrhea virus (PEDV) ORF3 protein inhibits cellular type I interferon signaling through down-regulating proteins expression in RLRs-mediated pathway.

Porcine epidemic diarrhea virus (PEDV) is an entero-pathogenic coronavirus, which belongs to the genus Alphacoronavirus in the family Coronaviridae, causing lethal watery diarrhea in piglets. Previous studies have shown that PEDV has developed an antagonistic mechanism by which it evades the antiviral activities of interferon (IFN), such as the sole accessory protein open reading frame 3 (ORF3) being found to inhibit IFN-ß promoter activities, but how this mechanism used by PEDV ORF3 inhibits activation of the type I signaling pathway remains not fully understood. Thus, in this present study, we showed that PEDV ORF3 inhibited both polyinosine-polycytidylic acid (poly(I:C))- and IFNα2b-stimulated transcription of IFN-ß and interferon-stimulated genes (ISGs) mRNAs. The expression levels of antiviral proteins in the retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs)-mediated pathway was down-regulated in cells with over-expression of PEDV ORF3 protein, but global protein translation remained unchanged and the association of ORF3 with RLRs-related antiviral proteins was not detected, implying that ORF3 only specifically suppressed the expression of these signaling molecules. At the same time, we also found that the PEDV ORF3 protein inhibited interferon regulatory factor 3 (IRF3) phosphorylation and poly(I:C)-induced nuclear translocation of IRF3, which further supported the evidence that type I IFN production was abrogated by PEDV ORF3 through interfering with RLRs signaling. Furthermore, PEDV ORF3 counteracted transcription of IFN-ß and ISGs mRNAs, which were triggered by over-expression of signal proteins in the RLRs-mediated pathway. However, to our surprise, PEDV ORF3 initially induced, but subsequently reduced the transcription of IFN-ß and ISGs mRNAs to normal levels. Additionally, mRNA transcriptional levels of signaling molecules located at IFN-ß upstream were not inhibited, but elevated by PEDV ORF3 protein. Collectively, these results demonstrate that inhibition of type I interferon signaling by PEDV ORF3 can be realized through down-regulating the expression of signal molecules in the RLRs-mediated pathway, but not via inhibiting their mRNAs transcription. This study points to a new mechanism evolved by PEDV through blockage of the RLRs-mediated pathway by ORF3 protein to circumvent the host's antiviral immunity.

Porcine epidemic diarrhea virus E protein inhibits type I interferon production through endoplasmic reticulum stress response (ERS)-mediated suppression of antiviral proteins translation.

Porcine epidemic diarrhea virus (PEDV) envelope protein (E) is recognized as a viroporin that plays important functions in virus budding, assembly and virulence. Our previous study found that PEDV E protein induces endoplasmic reticulum stress (ERS), as well as suppresses the type I interferon (IFN) response, but their link and underlying mechanism remain obscure. To better understand this relationship, we investigated the roles of PEDV E protein-induced ERS in regulating cellular type I IFN production. Our results showed that PEDV E protein localized in the ER and triggered ERS through activation of PERK/eIF2α branch, as revealed by the up-regulated phosphorylation of PERK and eIF2α. PEDV E protein also significantly inhibited both poly(I:C)-induced and RIG-I signaling-mediated type I interferon production. The PERK/eIF2α branch of ERS activated by PEDV E protein led to the translation attenuation of RIG-I signaling-associated antiviral proteins, resulting in the suppression of type I IFN production. However, PEDV E protein had no effect on the mRNA transcription of RIG-I-associated molecules. Moreover, suppression of ERS with 4-PBA, a widely used ERS inhibitor, restored the expression of RIG-I-signaling-associated antiviral proteins and mRNA transcription of IFN-ß and ISGs genes to their normal levels, suggesting that PEDV E protein blocks the production of type I IFN through inhibiting expression of antiviral proteins caused by ERS-mediated translation attenuation. This study elucidates the mechanism by which PEDV E protein specifically modulates the ERS to inhibit type I IFN production, which will augment our understanding of PEDV E protein-mediated virus evasion of host innate immunity.

Social distancing is a social dilemma game played by every individual against his/her population.

Since the outbreak of the global COVID-19 pandemic, social distancing has been known to everyone and recommended almost everywhere everyday. Social distancing has been and will be one of the most effective measures and sometimes, the only available one for fighting epidemics and saving lives. However, it has not been so clear how social distancing should be practiced or managed, especially when it comes to regulating everyone's otherwise normal social activities. The debate on how to implement social distancing often leads to a heated political argument, while research on the subject is lacking. This paper is to provide a theoretical basis for the understanding of the scientific nature of social distancing by considering it as a social dilemma game played by every individual against his/her population. From this perspective, every individual needs to make a decision on how to engage in social distancing, or risk being trapped into a dilemma either exposing to deadly diseases or getting no access to necessary social activities. As the players of the game, the individual's decisions depend on the population's actions and vice versa, and an optimal strategy can be found when the game reaches an equilibrium. The paper shows how an optimal strategy can be determined for a population with either closely related or completely separated social activities and with either single or multiple social groups, and how the collective behaviors of social distancing can be simulated by following every individual's actions as the distancing game progresses. The simulation results for populations of varying sizes and complexities are presented, which not only justify the choices of the strategies based on the theoretical analysis, but also demonstrate the convergence of the individual actions to an optimal distancing strategy in silico and possibly in natura as well, if every individual makes rational distancing decisions.

More Significant Impacts From New Particle Formation on Haze Formation During COVID-19 Lockdown.

During the COVID-19 lockdown in 2020, large-scale industrial and transportation emissions were reduced, but high PM2.5 concentration still occurred. This study investigated the variation of particle number size distribution during the lockdown, and analyzed the characteristics of new particle formation (NPF) events and its potential impact on haze formation. Through measurement conducted in urban Beijing during the first 3 months of 2020, and comparison with year-over-year data, the decrease of primary Aitken-mode particles was observed. However, frequencies, formation rates and growth rates of NPF events remained stable between 2020 and 2019 in the same period. As a result, >25 nm particles produced by NPF events, would play a more important role in serving as the haze formation "seeds" compared to those produced by primary emissions. This finding emphasizes the significance on the understanding of NPF mechanisms when making pollution mitigation policy in the future.