Comparison of Target Pocket Similarity and Progress into Research on Inhibitors of Picornavirus 3C Proteases.

The 3C protease (3C Pro) plays a significant role in the life cycle of picornaviruses from replication to translation, making it an attractive target for structure-based design of drugs against picornaviruses. The structurally related 3C-like protease (3CL Pro) is an important protein involved in the replication of coronaviruses. With the emergence of COVID-19 and consequent intensive research into 3CL Pro, development of 3CL Pro inhibitors has emerged as a popular topic. This article compares the similarities of the target pockets of various 3C and 3CL Pros from numerous pathogenic viruses. This article also reports several types of 3C Pro inhibitors that are currently undergoing extensive studies and introduces various structural modifications of 3C Pro inhibitors to provide a reference for the development of new and more effective inhibitors of 3C Pro and 3CL Pro.

The TGEV Membrane Protein Interacts with HSC70 To Direct Virus Internalization through Clathrin-Mediated Endocytosis.

Coronavirus membrane protein is a major component of the viral envelope and plays a central role in the viral life cycle. Studies of the coronavirus membrane protein (M) have mainly focused on its role in viral assembly and budding, but whether M protein is involved in the initial stage of viral replication remains unclear. In this study, eight proteins in transmissible gastroenteritis virus (TGEV)-infected cells coimmunoprecipitated with monoclonal antibodies (MAb) against M protein in PK-15 cells, heat shock cognate protein 70 (HSC70), and clathrin were identified by matrix-assisted laser desorption ionization-tandem time of flight mass spectrometry (MALDI-TOF MS). Further studies demonstrated that HSC70 and TGEV M colocalized on the cell surface in early stages of TGEV infection; specifically, HSC70 bound M protein through its substrate-binding domain (SBD) and preincubation of TGEV with anti-M serum to block the interaction of M and HSC70 reduced the internalization of TGEV, thus demonstrating that the M-HSC70 interaction mediates the internalization of TGEV. Remarkably, the process of internalization was dependent on clathrin-mediated endocytosis (CME) in PK-15 cells. Furthermore, inhibition of the ATPase activity of HSC70 reduced the efficiency of CME. Collectively, our results indicated that HSC70 is a newly identified host factor involved in TGEV infection. Taken together, our findings clearly illustrate a novel role for TGEV M protein in the viral life cycle and present a unique strategy used by HSC70 to promote TGEV infection in which the interaction with M protein directs viral internalization. These studies provide new insights into the life cycle of coronaviruses. IMPORTANCE TGEV is the causative agent of porcine diarrhea, a viral disease that economically affects the pig industry in many countries. However, the molecular mechanisms underlying viral replication remain incompletely understood. Here, we provide evidence of a previously undescribed role of M protein in viral replication during early stages. We also identified HSC70 as a new host factor affecting TGEV infection. We demonstrate that the interaction between M and HSC70 directs TGEV internalization in a manner dependent on CME, thus revealing a novel mechanism for TGEV replication. We believe that this study may change our understanding of the first steps of infection of cells with coronavirus. This study should facilitate the development of anti-TGEV therapeutic agents by targeting the host factors and may provide a new strategy for the control of porcine diarrhea.

Innate Immune Evasion of Porcine Epidemic Diarrhea Virus through Degradation of the FBXW7 Protein via the Ubiquitin-Proteasome Pathway.

Porcine epidemic diarrhea virus (PEDV) causes a porcine disease associated with swine epidemic diarrhea. Different antagonistic strategies have been identified, and the mechanism by which PEDV infection impairs the production of interferon (IFN) and delays the activation of the IFN response to escape host innate immunity has been determined, but the pathogenic mechanisms of PEDV infection remain enigmatic. Our preliminary results revealed that endogenous F-box and WD repeat domain-containing 7 (FBXW7) protein, the substrate recognition component of the SCF-type E3 ubiquitin ligase, is downregulated in PEDV-infected Vero E6 cells, according to the results from an isobaric tags for relative and absolute quantification (iTRAQ) analysis. Overexpression of FBXW7 in target cells makes them more resistant to PEDV infection, whereas ablation of FBXW7 expression by small interfering RNA (siRNA) significantly promotes PEDV infection. In addition, FBXW7 was verified as an innate antiviral factor capable of enhancing the expression of RIG-I and TBK1, and it was found to induce interferon-stimulated genes (ISGs), which led to an elevated antiviral state of the host cells. Moreover, we revealed that PEDV nonstructural protein 2 (nsp2) interacts with FBXW7 and targets FBXW7 for degradation through the K48-linked ubiquitin-proteasome pathway. Consistent with the results proven in vitro, FBXW7 reduction was also confirmed in different intestinal tissues from PEDV-infected specific-pathogen-free (SPF) pigs. Taken together, the data indicated that PEDV has evolved with a distinct antagonistic strategy to circumvent the host antiviral response by targeting the ubiquitin-proteasome-mediated degradation of FBXW7. Our findings provide novel insights into PEDV infection and pathogenesis. IMPORTANCE To counteract the host antiviral defenses, most viruses, including coronaviruses, have evolved with diverse strategies to dampen host IFN-mediated antiviral response, by interfering with or evading specific host regulators at multiple steps of this response. In this study, a novel antagonistic strategy was revealed showing that PEDV infection could circumvent the host innate response by targeted degradation of endogenous FBXW7 in target cells, a process that was verified to be a positive modulator for the host innate immune system. Degradation of FBXW7 hampers host innate antiviral activation and facilitates PEDV replication. Our findings reveal a new mechanism exploited by PEDV to suppress the host antiviral response.

Optimism and friendship quality as mediators between trait emotional intelligence and life satisfaction in Chinese adolescents: A two-wave longitudinal study.

Using a convenience sample of adolescents (N = 1609; 63.5% female; M age = 16.54), this study explored whether EI predicted adolescent life satisfaction and whether friendship quality and optimism mediated this relationship during the COVID-19 pandemic. The structural equation modeling revealed that EI predicted adolescent life satisfaction, friendship quality, and optimism, friendship quality partially mediated the relationship between EI and life satisfaction, and optimism partially mediated the relationship between EI and friendship quality. These findings prove that psychological or educative approaches focused on EI could increase life satisfaction in adolescents during difficult times such as COVID-19, but EI may be linked with life satisfaction via friendship quality only. Training in optimism approaches and friendship quality enhancement programs could also effectively promote life satisfaction.

The value of ROX index in evaluating the efficacy of high-flow nasal cannula oxygen therapy in patients with COVID-19

Objective: To assess the value of the ROX index in evaluating the efficacy of highflow nasal cannula oxygen therapy (HFNC) in patients with coronavirus infected disease (COVID-19).

Molecular characterization and phylogenetic analysis of porcine epidemic diarrhea virus strains circulating in China from 2020 to 2021.

BACKGROUND: Porcine epidemic diarrhea virus (PEDV), an enteric coronavirus, has become the major causative agent of acute gastroenteritis in piglets since 2010 in China. RESULTS: In the current study, 91 complete spike (S) gene sequences were obtained from PEDV positive samples collected from 17 provinces in China from March 2020 to March 2021. A phylogenetic analysis showed that 92.3% (84 out of 91) of the identified strains belonged to GII subtype, while 7.7% (7 out of 91) were categorized as S-INDEL like strains and grouped within GI-c clade. Based on a recombination analysis, six of S-INDEL like strains were recombinant strains originated from S-INDEL strain FR/001/2014 and virulent strain AJ1102. In addition, PEDV variant strains (CH/GDMM/202012, CH/GXDX/202010 et al) carrying novel insertions (360QGRKS364 and 1278VDVF1281) in the S protein were observed. Furthermore, the deduced amino acid sequences for the S protein showed that multiple amino acid substitutions in the antigenic epitopes in comparison with the vaccine strains. CONCLUSIONS: In conclusion, these data provide novel molecular evidence on the epidemiology and molecular diversity of PEDV in 2020-2021. This information may help design a strategy for controlling and preventing the prevalence of PEDV variant strains in China.

SARS-CoV-2 immunity and functional recovery of COVID-19 patients 1-year after infection.

The long-term immunity and functional recovery after SARS-CoV-2 infection have implications in preventive measures and patient quality of life. Here we analyzed a prospective cohort of 121 recovered COVID-19 patients from Xiangyang, China at 1-year after diagnosis. Among them, chemiluminescence immunoassay-based screening showed 99% (95% CI, 98-100%) seroprevalence 10-12 months after infection, comparing to 0.8% (95% CI, 0.7-0.9%) in the general population. Total anti-receptor-binding domain (RBD) antibodies remained stable since discharge, while anti-RBD IgG and neutralization levels decreased over time. A predictive model estimates 17% (95% CI, 11-24%) and 87% (95% CI, 80-92%) participants were still 50% protected against detectable and severe re-infection of WT SARS-CoV-2, respectively, while neutralization levels against B.1.1.7 and B.1.351 variants were significantly reduced. All non-severe patients showed normal chest CT and 21% reported COVID-19-related symptoms. In contrast, 53% severe patients had abnormal chest CT, decreased pulmonary function or cardiac involvement and 79% were still symptomatic. Our findings suggest long-lasting immune protection after SARS-CoV-2 infection, while also highlight the risk of immune evasive variants and long-term consequences for COVID-19 survivors.

Malnutrition is associated with hyperinflammation and immunosuppression in COVID-19 patients: A prospective observational study.

BACKGROUND: Coronavirus disease 2019 (COVID-19) is spreading globally and has caused many deaths. This study investigated, for the first time, COVID-19 patients' nutrition status and its effects on their inflammatory and immune responses. METHODS: Forty-seven COVID-19 patients were recruited for this prospective study. According to the subjective global assessment at admission, patients were divided into the normal nutrition (NN), risk of malnutrition (RMN), or MN group. Serum cytokines and whole blood T-cell subpopulations were measured to assess the inflammatory and immune responses in COVID-19 patients. Analysis of covariance and χ2 tests were used. RESULTS: On admission, the incidences of MN and the RMN in COVID-19 patients were 17.0% and 38.3%, respectively. The MN group had a higher proportion with severe/critical COVID-19 and a longer hospitalization duration than the NN group. Serum interleukin (IL) 6 concentrations were elevated in 97.9% of the patients and were the highest in malnourished patients. The IL-4 and IL-10 levels were elevated in 46.8% and 48.9% of the patients, respectively. The proportion of CD8+ T cells was significantly lower in the MN group than in the NN group. CONCLUSION: A high proportion of COVID-19 patients are malnourished or at risk of malnuourishment, especially those with severe disease. MN is associated with hyperinflammation and immunosuppression in COVID-19 patients, and it may contribute to disease progression.

Predictive value of the prognostic nutritional index for the severity of coronavirus disease 2019.

OBJECTIVES: Malnutrition plays a critical role in the onset and progress of the coronavirus disease 2019 (COVID-19). The aim of the present study was to explore the association of the prognostic nutritional index (PNI) score with the severity of COVID-19 and its predictive value of the severe form of COVID-19. METHODS: Clinical data were collected from 122 patients infected with COVID-19 and hospitalized at the Sixth People's Hospital of Wenzhou, China, a specialized infectious hospital affiliated with the Wenzhou Central Hospital. PNI score was calculated as serum albumin (g/L) + 5 × total lymphocyte count (/nL). RESULTS: The study population consisted of 105 patients (86.1%) with a common form and 17 patients (13.9%) with a severe form of COVID-19. PNI score significantly decreased from patients with common to severe forms of COVID-19 (P = .029) regardless of sex, age range, and body mass index (BMI). After adjustment for sex, age, indexes of liver and renal function, C-reactive protein, and current smoking status, PNI scores remained independently and inversely associated with the severity of COVID-19 (odd ratio: 0.797; P = .030). A receiver operating characteristic analysis showed that PNI scores had a similar accuracy to predict severe forms of COVID-19 compared with its combination with sex, age, and BMI (P = .402). PNI < 49 was defined as the cutoff value to predict the severe form of COVID-19. CONCLUSIONS: Poorer nutritional status predisposed patients infected with COVID-19 to its severe form. Independently associated with the severity of COVID-19, PNI score could serve as a simple, fast, and effective predictor among patients with different sex, age, and BMI.

Development of a rapid immunochromatographic strip test for the detection of porcine epidemic diarrhea virus specific SIgA in colostrum.

Porcine epidemic diarrhea virus (PEDV) causes very high mortality in newborn piglets. The mucosal immune system in the gut must eliminate potential pathogens while maintaining a mutually beneficial relationship with the commensal microbiota. Antibodies derived from the secretory immunoglobulin A (SIgA) class, act as the first line of antigen-specific immunity in the gut by recognizing both pathogens and commensals. Therefore, the measurement of SIgA levels is an important index in evaluating PEDV infections and immune status. A simple and rapid method for the detection of PEDV-specific SIgA using an immunochromatographic test strip has been developed; incorporating a colloidal gold-labeled anti-SIgA secretory component (SC) mAb probe for the detection of anti-PEDV-specific SIgA in swine. On the strip, a gold-labeled anti-SIgA SC mAb was applied to a conjugate pad; purified PEDV particles and goat anti-mouse antibodies were blotted onto a nitrocellulose membrane to form the test and control lines, respectively. Results showed that the immunochromatographic test strip had high sensitivity and specificity. When compared with enzyme-linked immunosorbent assay, kappa value suggesting that the strip could be used to detect PEDV specific SIgA in colostrum samples. Furthermore, the strip assay is rapid and easy to perform with no requirement for professional-level skills or equipment. We found that the immunochromatographic test strip was a rapid, sensitive, and reliable method for the identification of PEDV specific SIgA, indicating its suitability for epidemiological surveillance as well as vaccine immunity when studying PEDV.

Radiomics-based model for accurately distinguishing between severe acute respiratory syndrome associated coronavirus 2 (SARS-CoV-2) and influenza A infected pneumonia.

Clinicians have been faced with the challenge of differentiating between severe acute respiratory syndrome associated coronavirus 2 (SARS-CoV-2) infected pneumonia (NCP) and influenza A infected pneumonia (IAP), a seasonal disease that coincided with the outbreak. We aim to develop a machine-learning algorithm based on radiomics to distinguish NCP from IAP by texture analysis based on computed tomography (CT) imaging. Forty-one NCP and 37 IAP patients admitted from January to February 6, 2019 admitted to two hospitals in Wenzhou, China. All patients had undergone chest CT examination and blood routine tests prior to receiving medical treatment. NCP was diagnosed by real-time RT-PCR assays. Eight of 56 radiomic features extracted by LIFEx were selected by least absolute shrinkage and selection operator regression to develop a radiomics score and subsequently constructed into a nomogram to predict NCP with area under the operating characteristics curve of 0.87 (95% confidence interval: 0.77-0.93). The nomogram also showed excellent calibration with Hosmer-Lemeshow test yielding a nonsignificant statistic (P = .904). The novel nomogram may efficiently distinguish between NCP and IAP patients. The nomogram may be incorporated to existing diagnostic algorithm to effectively stratify suspected patients for SARS-CoV-2 pneumonia.

Metabolic-associated fatty liver disease is associated with severity of COVID-19.

The Corona Virus Disease 2019 (COVID-19) pandemic has attracted increasing worldwide attention. While metabolic-associated fatty liver disease (MAFLD) affects a quarter of world population, its impact on COVID-19 severity has not been characterized. We identified 55 MAFLD patients with COVID-19, who were 1:1 matched by age, sex and obesity status to non-aged severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-infected patients without MAFLD. Our results demonstrate that in patients aged less than 60 years with COVID-19, MAFLD is associated with an approximately fourfold increase (adjusted odds ratio 4.07, 95% confidence interval 1.20-13.79, P = .02) in the probability for severe disease, after adjusting for confounders. Healthcare professionals caring for patients with COVID-19 need to be aware that there is a positive association between MAFLD and severe illness with COVID-19.

The absence of coronavirus in expressed prostatic secretion in COVID-19 patients in Wuhan city.

Due to the cellular entry of the novel coronavirus (SARS-CoV-2) modulated by angiotensin converting enzyme 2 (ACE2), the ACE2 bearing prostate is therefore hypothesized as a susceptible organ to COVID-19. To delineate whether the pathogenic SARS-CoV-2 of the coronavirus disease (COVID-19) could be detected in the expressed prostatic secretion (EPS), a total of ten male patients with confirmed COVID-19 were recruited. All patients were stratified into two groups: one group with positive nasopharyngeal swabbing SARS-CoV-2 within 3 days of the EPS taken day (PNS group, n = 3) and the other group with previously positive nasopharyngeal swabbing SARS-CoV-2 but turned negative before the taken day (PNNS group, n = 7). The COVID-19 patients showed elevated inflammatory indictors, i.e. C-reaction protein (3.28 (1.14, 33.33) mg/L), erythrocyte sedimentation rate (22.50 (8.00, 78.50) mm/h), and interleukin-6 (6.49 (4.96, 21.09) pg/ml). Serum IgM against SARS-CoV-2 was only positive in the PNS group, whereas serum IgG was positive for all patients. Furthermore, our data showed for the first time that none of the COVID-19 patients had positive SARS-CoV-2 RNA in EPS. To this end, this study found the negativity of SARS-CoV-2 in EPS and possibly exclude the sexual transmission of COVID-19.

Swine acute diarrhea syndrome coronavirus-induced apoptosis is caspase- and cyclophilin D- dependent.

Swine acute diarrhea syndrome coronavirus (SADS-CoV), a newly discovered enteric coronavirus, is the aetiological agent that causes severe clinical diarrhea and intestinal pathological damage in piglets. To understand the effect of SADS-CoV on host cells, we characterized the apoptotic pathways and elucidated mechanisms underlying the process of apoptotic cell death after SADS-CoV infection. SADS-CoV-infected cells showed evidence of apoptosis in vitro and in vivo. The use of a pan-caspase inhibitor resulted in the inhibition of SADS-CoV-induced apoptosis and reduction in SADS-CoV replication, suggestive of the association of a caspase-dependent pathway. Furthermore, SADS-CoV infection activated the initiators caspase-8 and -9 and upregulated FasL and Bid cleavage, demonstrating a crosstalk between the extrinsic and intrinsic pathways. However, the proapoptotic proteins Bax and Cytochrome c (Cyt c) relocalized to the mitochondria and cytoplasm, respectively, after infection by SADS-CoV. Moreover, Vero E6 and IPI-2I cells treated with cyclosporin A (CsA), an inhibitor of mitochondrial permeability transition pore (MPTP) opening, were completely protected from SADS-CoV-induced apoptosis and viral replication, suggesting the involvement of cyclophilin D (CypD) in these processes. Altogether, our results indicate that caspase-dependent FasL (extrinsic)- and mitochondria (intrinsic)- mediated apoptotic pathways play a central role in SADS-CoV-induced apoptosis that facilitates viral replication. In summary, these findings demonstrate mechanisms by which SADS-CoV induces apoptosis and improve our understanding of SADS-CoV pathogenesis.

Development of an indirect ELISA for detecting porcine deltacoronavirus IgA antibodies.

Porcine deltacoronavirus (PDCoV) is a novel coronavirus that can cause vomiting and watery diarrhea in pigs and death in piglets. Since PDCoV was first detected in 2009 in Hong Kong, the prevalence of PDCoV has increased in recent years, resulting in serious economic losses to the swine industry. The coronavirus spike (S) protein is an antigen that has been demonstrated to contain epitopes that induce neutralizing antibodies. The presence of serum and milk IgA antibodies against pathogens that replicate primarily on mucosal surfaces is important for mucosal immunity. Here, an indirect anti-PDCoV IgA antibody enzyme-linked immunosorbent assay (PDCoV S1 IgA ELISA) using the purified S1 portion of S protein as the coating antigen was developed to detect PDCoV IgA antibodies in serum and sow's milk. A receiver operating characteristic (ROC) curve analysis showed high specificity and sensitivity of the PDCoV-S1-IgA-ELISA based on samples confirmed by IFA. Anti-PDCoV IgA antibodies in 152 serum samples and 65 milk samples collected from six farms that had experienced diarrhea outbreaks within previous last two years were detected by this assay, and 62.5% of the serum samples and 100% of the milk samples were positive for PDCoV. The indirect ELISA method established in this study will provide a convenient tool for measurement of serum and milk IgA levels against PDCoV in pig herds, rapid detection of PDCoV infection in pigs, and evaluation of the immunogenicity of vaccines.