Virologica Sinica最新文献

African swine fever virus (ASFV) pB318L is an important protein for viral replication that acts as a membrane-bound trans-geranylgeranyl-diphosphate synthase (GGPPS) catalyzing the condensation of isopentenyl diphosphate (IPP) with allylic diphosphates. Recently we solved the crystal structure pB318L lacking N-terminal transmembrane region and performed a preliminary structural analysis. In this study, structure-based mutagenesis study and geranylgeranyl pyrophosphate (GGPP) production assay further revealed the key residues for the GGPPS activity. Structural comparison showed pB318L displays a strong similarity to typical GGPPSs instead of protein prenyltransferases. The phylogenetic analysis indicated pB318L may share a common ancestor with the GGPPSs from Brassicaceae plants rather than from its natural host. The subcellular localization analysis showed pB318L is localized in both nucleus and cytoplasm (including the endoplasmic reticulum membrane and mitochondria outer membrane). A unique N-terminal nuclear localization signal (NLS) following the transmembrane region was discovered in pB318L and the NLS was confirmed to be required for the nuclear import. We further revealed the NLS plays an essential role in the interaction with nuclear transporter karyopherin subunit alpha 1 (KPNA1). Their interaction may suppress signal transducers and activators of transcription 1 (STAT1) translocation and subsequently competitively inhibit nuclear import of IFN-stimulated gene factor 3 (ISGF3) complex. Our biochemical, structural and cellular analyses provide novel insights to pB318L that acts as an essential GGPPS that promotes viral replication and as a nuclear import protein that may be involved in immune evasion of ASFV.

The evolution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has resulted in mutations not only in the spike protein, aiding immune evasion, but also in the NSP3/4/6 proteins, crucial for regulating double-membrane vesicle (DMV) formation. However, the functional consequences of these NSP3/4/6 mutations remain poorly understood. In this study, a systematic analysis was conducted to investigate the evolutionary patterns of NSP3/4/6 mutations and their impact on DMV formation. The findings revealed that the NSP4 T492I mutation, a prevalent mutation found in all Delta and Omicron sub-lineages, notably enhances DMV formation. Mechanistically, the NSP4 T492I mutation enhances its homodimerization, leading to an increase in the size of puncta induced by NSP3/4, and also augments endoplasmic reticulum (ER) membrane curvature, resulting in a higher DMV density per fluorescent puncta. This study underscores the significance of the NSP4 T492I mutation in modulating DMV formation, with potential implications for the transmission dynamics of SARS-CoV-2. It contributes valuable insights into how these mutations impact viral replication and pathogenesis.

The cross-species infection of coronaviruses has resulted in several major epidemics since 2003. Therefore, it is of great importance to explore the host ranges of coronaviruses and their features among different hosts. In this study, the porcine epidemic diarrhea virus (PEDV), with swine as the only natural reservoir, was detected in rat fecal samples collected from pig farms. Further animal tests showed PEDV can cause systemic infections in neonate mice and rats. The brain, lung intestine and spleen were all targets for PEDV in rodents in contrast to the intestine being targeted in pigs. Morbidity and mortality vary via different infection routes. PEDV was also detectable in feces after infection, suggesting that the infected rodents were potential infectious sources. Moreover, the cerebric tropism of PEDV was verified in piglets, which had not been identified before. In conclusion, our findings demonstrate that PEDV can cross the species barrier to infect mice and rats through different routes. Although it is highly devastating to piglets, PEDV changes the target organs and turns to be milder when meeting with new hosts. Based on these findings, more attention should be paid to the cross-species infection of PEDV to avoid the emergence of another zoonosis.

Severe fever with thrombocytopenia syndrome (SFTS) is a novel emerging acute infectious disease caused by severe fever with thrombocytopenia syndrome virus (SFTSV), characterized by high fever and thrombocytopenia. It has been proved that traditional Chinese medicine (TCM) has displayed definite therapeutic effects on viral hemorrhagic fever, indicating its potential to treat SFTS. In this study, SFTS-relative key targets were predicted via Gene ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. Molecular docking was then used to select stable binders. Molecules matched TCMs were identified, and a new prescription, Qingqi Guxue decoction (QQGX), was formulated to clear heat and nourish blood, with a resulting drug composition network. We explored the optimal drug proportion for QQGX. Through an in-depth study of molecular mechanisms, we found that QQGX induces S phase arrest by promoting the degradation of Cyclin A2 (CCNA2) and Cyclin-dependent kinase 2 (CDK2), thereby inhibiting SFTSV replication. Finally, we verified the effectiveness and safety of QQGX based on the mouse liver bile duct organoid model infected with SFTSV. In summary, our study prepared a TCM decoction using the method of network pharmacology. This decoction has a significant inhibitory effect on the replication of SFTSV and provides a new treatment strategy for hemorrhagic fever with TCM.

Infectious bronchitis (IB), a highly contagious acute respiratory disease affecting avian species, poses significant challenges to poultry production. The causative agent, Infectious Bronchitis Virus (IBV), exhibits a high mutation rate, leading to limited cross-protection by existing vaccines. This necessitates the development of novel vaccines. This study, based on preliminary investigations conducted by our research team, identified six potential strains (PYG QX1, ZQF QX2, FQH QX3, LYZ QX4, XXX QX5, and CSL strains) for vaccine development. Previous pathogenicity test and serum cross-neutralization experiments conducted in this study have demonstrated that the FQH QX3 strain exhibited the weakest pathogenicity and the broadest spectrum of serum neutralization, while the CSL strain showed the highest pathogenicity and was the most challenging to neutralize, posing the greatest difficulty in prevention and control. Subsequently, we constructed and rescued recombinant vaccine candidates, H120-FQH QX3, and H120-CSL, expressing the S1 and N proteins of the FQH QX3 and CSL strains, respectively. Immunization protection experiments indicated that the H120-CSL recombinant vaccine candidate exhibited the most effective immune protection, making it a promising candidate for further study and evaluation as a recombinant vaccine. The S1 and N genes of the CSL strain demonstrated strong immunogenicity, making them potential candidate antigen genes for future vaccine development.

Human bocavirus 1 (HBoV1; family: Parvoviridae) causes a wide spectrum of respiratory diseases in children and gastroenteritis in adults. A lack of sensitive cell lines and efficient animal models hinders research on HBoV, including the development of anti-HBoV drugs or vaccines. Although the construction of a wild-type HBoV1 infectious clone has been reported, generating HBoV1 infectious clone carrying foreign reporter genes with suitable insertion sites in its genome while retaining replicative ability remains challenging. Here, HBoV1 infectious clones harboring the 11-amino-acid HiBiT tag at five distinct insertion sites were constructed and evaluated. Only the recombinant HBoV1 carrying the HiBiT tag in the N-terminus of the NS1 protein (HBoV1-HiBiT_NS1) displayed comparable characteristics to wild-type HBoV1 as determined via the analysis of viral DNA copy number, NanoLuc activity, viral protein expression, and the formation of replication intermediates. Notably, the replication kinetics of HBoV1-HiBiT_NS1 could be examined by monitoring NanoLuc activity, which was noted to be correlated with the viral DNA level. Additionally, we successfully applied HiBiT-tagged HBoV1 for the evaluation of antiviral drug activity and identified ivermectin (EC50 = 2.27 μM) as a potent anti-HBoV1 replication drug. Overall, our study demonstrated that the HBoV1-HiBiT_NS1 reporter can serve as a convenient platform for screening candidate drugs targeting HBoV1 replication and may also be useful for investigating the life cycle of the virus.

Naf1 (Nef-associated factor 1) is a host protein that interacts with human immunodeficiency virus type 1 (HIV-1) Nef protein. We and others have previously demonstrated that Naf1 restricts HIV-1 infection of T-lymphocytes. Myeloid cells are targets for HIV infection, but Naf1 expression in myeloid cells and whether it also regulates HIV infection in these cells are not yet identified. In this study, we found that Naf1 had a higher expression in CD14⁺ monocytes than in monocyte-derived dendritic cells (MDDCs), and its expression in both types of cells could be induced by HIV-1 gp120 glycoproteins or viral particles. Importantly, the expression of Naf1 restricted HIV-1 infection in monocytes and MDDCs. Functional investigation showed that both the constitutive and the induced expression of Naf1 inhibited NF-κB signaling in MDDCs and reduced the basal level or LPS (Lipopolysaccharide)-stimulated production of cytokines. Moreover, Naf1 reduced the expression of ICAM-1 (intercellular cell adhesion molecule-1) on MDDCs and compromised their capacity to prime the activation of resting CD4⁺ T cells in co-culture. In light of the essential role of NF-κB signaling for HIV-1 transcription, Naf1-mediated inhibition of NF-κB signaling may hinder a robust viral replication in MDDCs and help maintain viral persistence. Furthermore, virus-induced Naf1 expression in MDDCs may diminish the cross-talk between DC (dendritic cell) and T cells, hence suppressing the activation of antiviral immune responses. Taken together, we identified the new function of Naf1 in myeloid cells. Those findings may facilitate the understanding for the host restriction of HIV-1 infection in myeloid cells.

Identifying the cause of respiratory tract infections is important for reducing the burden of diagnosis and treatment. To assess viral etiologies of hospitalized patients with pulmonary infection (including patients with lower respiratory tract infection, tuberculosis, lung cancer, and pulmonary nodules), bronchoalveolar lavage fluid (BALF) specimens were collected from non-COVID-19 adult patients (n = 333) between November 2020 and November 2021. Multiple common respiratory pathogens were detected using multiplex reverse-transcription polymerase chain reaction. The result showed that at least one virus was identified in 35.44% (118/333) of the cases. Among these, influenza virus was the most commonly identified, followed by the parainfluenza virus, coronavirus, human rhinoviruses, and human respiratory syncytial viruses. The tuberculosis group demonstrated the highest viral detection rate, yet paradoxically exhibited the lowest co-infection rate. In contrast, the highest co-infection frequency was observed in the pulmonary nodules group. Patients with viral infections exhibited more severe clinical symptoms compared to those without detected viral infections. However, this observation was only noted in the lower respiratory tract infection group among the different disease groups. Notably, among patients infected with a specific virus, there were no significant differences in viral load between single and co-infections. Our study identified the major causative agents in hospitalized adult patients with pulmonary infection, offering insights for precise disease diagnosis and the prevention of unnecessary use of antimicrobial drugs.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of novel coronavirus disease 2019, can cause acute respiratory symptoms and even death globally. However, the immune escape mechanism and viral pathogenesis remain poorly understood. Here, we report that the SARS-CoV-2 3C-like (3CL) protease specifically cleaves gasdermin D (GSDMD) at Q29 and Q193, producing two N-terminal fragments, GSDMD_1-29 and GSDMD_1-193. We also found that SARS-CoV-2 infection induced the cleavage of GSDMD. Then, we demonstrated that the ability to cleave GSDMD was dependent on the protease activity of the 3CL protease. Interestingly, unlike the GSDMD_1-275 fragment cleaved by caspase-1, GSDMD_1-29 and GSDMD_1-193 did not trigger pyroptosis or inhibit SARS-CoV-2 replication. Additionally, various RNA viral proteases display different preferences for cleaving GSDMD at Q29 and Q193. Our findings reveal a mechanism by which SARS-CoV-2 and other RNA viruses inhibit pyroptosis, highlighting the critical role of the 3CL protease in immune evasion and viral replication.

Human parainfluenza viruses (HPIV) are common viral pathogens in acute respiratory infection (ARI). We aimed to describe the epidemiological and molecular characteristics of HPIV from ARI patients. This cross-sectional study was conducted using respiratory samples from 9,696 ARI patients between 2016 and 2020 in southern China. All samples were analyzed by quantitative real-time polymerase chain reaction to determine the presence of HPIV and other common respiratory viruses. Descriptive statistics were performed to determine the temporal and population distribution of HPIV. The full-length hemagglutinin-neuraminidase (HN) gene of HPIV3-positive samples was sequenced for phylogenetic analysis. A total of 577 (6.0%) patients tested positive for HPIV, with HPIV3 being the predominant serotype, accounting for 46.8% of cases. Notably, 66.0% of these HPIV-positive cases were children aged 0-2 years. The prevalence of HPIV infections showed a decreased trend and altered peak during 2016-2020. Cough, fever, sputum production, and rhinorrhea were common respiratory symptoms in HPIV-positive patients. The majority of cases had pneumonia (63.4%). Human rhinovirus (HRV) and human coronavirus (HCoV) were the most common coinfection viruses in HPIV-positive cases, with proportions of 20.1% and 14.4%, respectively. Phylogenetic analysis revealed that the predominant lineage of HPIV3 was C3f (86.0%), followed by lineage C3a (8.0%), C3d (4.0%), and C3b (2.0%). These findings help to better understand the epidemiology of HPIV, and improve public health strategies to prevent and control HPIV infections in southern China.