Bluetongue virus (BTV) usually infects sheep, cattle, deer and other domesticated and wild ruminants through the bite of the vector insects, Culicoide, causing bluetongue (BT). BT in subtropical and even temperate regions poses a serious threat to the development and international trade of the livestock industry. This article introduced the structure and cellular invasion, and summarized the mechanisms of anti-BTV immune response of host cells and antagonism of host cell innate immune response by the non-structural proteins (e.g., NS3 and NS4) and structural proteins (e.g., VP3 and VP4) of BTV. This review provided a basis for understanding the antagonism mechanisms of BTV against the interferon (IFN) immune response in the host cell and the pathogenesis of BTV as well as for developing novel vaccines against this virus.
Bluetongue virus/immunology* ; Animals ; Bluetongue/prevention & control* ; Immunity, Innate ; Interferons/immunology* ; Sheep ; Viral Nonstructural Proteins/immunology* ; Cattle

To screen and identify the key host proteins interacting with the non-structural protein 15 (Nsp15) of porcine epidemic diarrhea virus (PEDV). The IP/pull-down assay and mass spectrometry were employed to screen and identify the host proteins interacting with Nsp15. The interaction between the host protein and Nsp15 was studied by co-immunoprecipitation and laser scanning confocal microscopy. Finally, Western blotting and RT-qPCR were employed to examine the interaction between SLC25a3 and PEDV. The recombinant eukaryotic expression vector pcDNA3.1(+)-Flag-Nsp15 was successfully constructed, and the host protein SLC25a3 interacting with PEDV Nsp15 was screened out. An interaction existed between SLC25a3 and Nsp15, and SLC25a3 significantly inhibited PEDV replication in a dose-dependent manner. SLC25a3 inhibits PEDV replication. The results of this study provide a basis for deciphering the role and mechanism of SLC25a3 in the host immune response to PEDV infection.
Porcine epidemic diarrhea virus/genetics* ; Viral Nonstructural Proteins/metabolism* ; Animals ; Swine ; Virus Replication ; Coronavirus Infections/veterinary* ; Swine Diseases/metabolism*

Porcine deltacoronavirus (PDCoV) is a major pathogen causing fatal diarrhea in suckling piglets, and there is currently a lack of effective vaccines and drugs to prevent and control the virus. The nonstructural protein 13 (NSP13) serves as a virus-coded helicase and is considered to be a crucial target for antiviral drugs, making it imperative to investigate the helicase activity of NSP13. In this study, the NSP13 gene of PDCoV was synthesized and integrated into the prokaryotic expression vector pET-28a to construct the recombinant plasmid pET-28a-NSP13. NSP13 was successfully expressed in BL21 (DE3) and subsequently purified. The study also verified the helicase activity of the purified NSP13 and explored the factors that influence this activity. The results indicated that NSP13 from PDCoV was effectively expressed in the prokaryotic system and exhibited helicase activity, capable of unwinding double-stranded DNA with a tail at the 5' end. Additionally, NSP13 demonstrated an annealing function by promoting the complementary pairing of single-stranded nucleotide chains to form double strands. The helicase activity of NSP13 was affected by metal ions, but Mg²⁺concentrations in the range of 0.5-6.0 mmol/L had no significant effect on helicase activity of NSP13. When the solution pH was in the range of 4-9, there was no difference in helicase activity. ATP concentrations in the range of 0.25-6.00 mmol/L had a weak effect on helicase activity, and NSP13 concentration ≥80 nmol/L inhibited the helicase activity. We obtained the NSP13 of PDCoV and investigated its helicase activity. These findings provided a theoretical foundation for the further research on the regulatory mechanism of NSP13 in PDCoV replication and the development of anti-coronaviral drugs.
Viral Nonstructural Proteins/metabolism* ; Escherichia coli/metabolism* ; Recombinant Proteins/metabolism* ; Swine ; Animals ; DNA Helicases/metabolism* ; Genetic Vectors/metabolism*

The global COVID-19 coronavirus pandemic has infected over 109 million people, leading to over 2 million deaths up to date and still lacking of effective drugs for patient treatment. Here, we screened about 1.8 million small molecules against the main protease (M^pro) and papain like protease (PL^pro), two major proteases in severe acute respiratory syndrome-coronavirus 2 genome, and identified 1851M^pro inhibitors and 205 PL^pro inhibitors with low nmol/l activity of the best hits. Among these inhibitors, eight small molecules showed dual inhibition effects on both M^pro and PL^pro, exhibiting potential as better candidates for COVID-19 treatment. The best inhibitors of each protease were tested in antiviral assay, with over 40% of M^pro inhibitors and over 20% of PL^pro inhibitors showing high potency in viral inhibition with low cytotoxicity. The X-ray crystal structure of SARS-CoV-2 M^pro in complex with its potent inhibitor 4a was determined at 1.8 Å resolution. Together with docking assays, our results provide a comprehensive resource for future research on anti-SARS-CoV-2 drug development.
Humans ; Antiviral Agents/chemistry* ; COVID-19 ; COVID-19 Drug Treatment ; High-Throughput Screening Assays ; Molecular Docking Simulation ; Protease Inhibitors/chemistry* ; SARS-CoV-2/enzymology* ; Viral Nonstructural Proteins

The main protease (Mpro) of SARS-CoV-2 is a highly conserved and mutation-resistant coronaviral enzyme, which plays a pivotal role in viral replication, making it an ideal target for the development of novel broad-spectrum anti-coronaviral drugs. In this study, a codon-optimized Mpro gene was cloned into pET-21a and pET-28a expression vectors. The recombinant plasmids were transformed into E. coli Rosetta(DE3) competent cells and the expression conditions were optimized. The highly expressed recombinant proteins, Mpro and Mpro-28, were purified by HisTrapTM chelating column and its proteolytic activity was determined by a fluorescence resonance energy transfer (FRET) assay. The FRET assay showed that Mpro exhibits a desirable proteolytic activity (25 000 U/mg), with Km and kcat values of 11.68 μmol/L and 0.037/s, respectively. The specific activity of Mpro is 25 times that of Mpro-28, a fusion protein carrying a polyhistidine tag at the N and C termini, indicating additional residues at the N terminus of Mpro, but not at the C terminus, are detrimental to its proteolytic activity. The preparation of active SARS-CoV-2 Mpro through codon-optimization strategy might facilitate the development of the rapid screening assays for the discovery of broad-spectrum anti-coronaviral drugs targeting Mpro.
COVID-19 ; Codon/genetics* ; Cysteine Endopeptidases/genetics* ; Escherichia coli/genetics* ; Humans ; Peptide Hydrolases ; SARS-CoV-2 ; Viral Nonstructural Proteins/genetics*

Bluetongue virus (BTV) causes Bluetongue (BT) of ruminants vectored by culicoides midges. It is also a classic model for studying the release mechanism of non-enveloped virus. This review begins with the infection and assembly of BTV, then summarizes the advances of different ways of releasing BTV. This includes BTV-induced autophagy and the release as extracellular vesicles via multivesicular bodies, BTV-induced apoptosis and the lytic release, as well as different pathways of release through budding via plasma membrane. The regulatory mechanisms of NS3 which is a key non-structural protein during the release of BTV are also discussed, providing a basis for further understanding the molecular mechanisms underpinning the infection, proliferation and release of BTV.
Animals ; Bluetongue ; Bluetongue virus ; Ceratopogonidae ; Sheep ; Viral Nonstructural Proteins

Dengue virus (DENV) is the most widely transmitted arbovirus in the world. Due to the lack of diagnostic technology to quickly identify the virus serotypes in patients, severe dengue hemorrhagic fever cases caused by repeated infections remain high. To realize the rapid differential diagnosis of different serotypes of DENV infection by immunological methods, in this study, four DENV serotype NS1 proteins were expressed and purified in mammalian cells. Monoclonal antibodies (MAbs) against NS1 protein were obtained by hybridoma technology after immunizing BALB/c mice. Enzyme-linked immunosorbent assay, indirect immunofluorescence assay, dot blotting, and Western blotting were used to confirm the reactivity of MAbs to viral native NS1 and recombinant NS1 protein. These MAbs include not only the universal antibodies that recognize all DENV 1-4 serotype NS1, but also serotype-specific antibodies against DENV-1, DENV-2 and DENV-4. Double antibody sandwich ELISA was established based on these antibodies, which can be used to achieve rapid differential diagnosis of serotypes of DENV infection. Preparation of DENV serotype-specific MAbs and establishment of an ELISA technology for identifying DENV serotypes has laid the foundation for the rapid diagnosis of DENV clinical infection.
Animals ; Antibodies, Monoclonal ; Antibodies, Viral/metabolism* ; Dengue/diagnosis* ; Dengue Virus/immunology* ; Enzyme-Linked Immunosorbent Assay ; Humans ; Mice ; Mice, Inbred BALB C ; Sensitivity and Specificity ; Serogroup ; Viral Nonstructural Proteins/immunology*

Antigenic purity is important for quality control of the foot-and-mouth (FMD) whole virus inactivated vaccine. The recommended method for evaluation the antigenic purity of FMD vaccine is to check the serum conversion to non-structural protein (NSP) 3AB antibody after 2 to 3 times inoculation of animals with inactivated vaccine. In this study, we developed a quantitative ELISA to detect the amount of residual 3AB in vaccine antigen, to provide a reference to evaluate the antigenic purity of FMD vaccine. Monoclonal antibody (Mab) of NSP 3A and HRP-conjugated Mab of NSP 3B were used to establish a sandwich ELISA to quantify the NSP 3AB in vaccine antigen of FMD. Purified NSP 3AB expressed in Escherichia coli was serially diluted and detected to draw the standard curve. The detectable limit was determined to be the lowest concentration of standard where the ratio of its OD value to OD blank well was not less than 2.0. Results: The OD value was linearly corelated with the concentration of 3AB protein within the range between 4.7 and 600 ng/mL. The correlation coefficient R² is greater than 0.99, and the lowest detectable limit is 4.7 ng/mL. The amount of 3AB protein in non-purified inactivated virus antigen was detected between 9.3 and 200 ng/mL depending on the 12 different virus strains, whereas the amount of 3AB in purified virus antigen was below the lowest detectable limit. The amount of 3AB in 9 batches of commercial FMD vaccine antigens was between 9.0 and 74 ng/mL, whereas it was below the detectable limit in other 24 batches of commercial vaccine antigens. Conclusion: the sandwich ELISA established in this study is specific and sensitive to detect the content of 3AB protein in vaccine antigen of FMD, which will be a useful method for evaluation of the antigenic purity and quality control of FMD inactivated vaccine.
Animals ; Antibodies, Viral ; Enzyme-Linked Immunosorbent Assay ; Foot-and-Mouth Disease/prevention & control* ; Foot-and-Mouth Disease Virus ; Viral Nonstructural Proteins/genetics* ; Viral Vaccines

OBJECTIVE: Lung-toxin Dispelling Formula No. 1, referred to as Respiratory Detox Shot (RDS), was developed based on a classical prescription of traditional Chinese medicine (TCM) and the theoretical understanding of herbal properties within TCM. Therapeutic benefits of using RDS for both disease control and prevention, in the effort to contain the coronavirus disease 2019 (COVID-19), have been shown. However, the biochemically active constituents of RDS and their mechanisms of action are still unclear. The goal of the present study is to clarify the material foundation and action mechanism of RDS. METHODS: To conduct an analysis of RDS, an integrative analytical platform was constructed, including target prediction, protein-protein interaction (PPI) network, and cluster analysis; further, the hub genes involved in the disease-related pathways were identified, and the their corresponding compounds were used for in vitro validation of molecular docking predictions. The presence of these validated compounds was also measured in samples of the RDS formula to quantify the abundance of the biochemically active constituents. In our network pharmacological study, a total of 26 bioinformatic programs and databases were used, and six networks, covering the entire Zang-fu viscera, were constructed to comprehensively analyze the intricate connections among the compounds-targets-disease pathways-meridians of RDS. RESULTS: For all 1071 known chemical constituents of the nine ingredients in RDS, identified from established TCM databases, 157 passed drug-likeness screening and led to 339 predicted targets in the constituent-target network. Forty-two hub genes with core regulatory effects were extracted from the PPI network, and 134 compounds and 29 crucial disease pathways were implicated in the target-constituent-disease network. Twelve disease pathways attributed to the Lung-Large Intestine meridians, with six and five attributed to the Kidney-Urinary Bladder and Stomach-Spleen meridians, respectively. One-hundred and eighteen candidate constituents showed a high binding affinity with SARS-coronavirus-2 3-chymotrypsin-like protease (3CL), as indicated by molecular docking using computational pattern recognition. The in vitro activity of 22 chemical constituents of RDS was validated using the 3CL inhibition assay. Finally, using liquid chromatography mass spectrometry in data-independent analysis mode, the presence of seven out of these 22 constituents was confirmed and validated in an aqueous decoction of RDS, using reference standards in both non-targeted and targeted approaches. CONCLUSION RDS acts primarily in the Lung-Large Intestine, Kidney-Urinary Bladder and Stomach-Spleen meridians, with other Zang-fu viscera strategically covered by all nine ingredients. In the context of TCM meridian theory, the multiple components and targets of RDS contribute to RDS's dual effects of health-strengthening and pathogen-eliminating. This results in general therapeutic effects for early COVID-19 control and prevention.
Antiviral Agents ; chemistry ; therapeutic use ; Betacoronavirus ; chemistry ; enzymology ; Coronavirus Infections ; drug therapy ; prevention & control ; virology ; Cysteine Endopeptidases ; chemistry ; Drugs, Chinese Herbal ; chemistry ; therapeutic use ; Humans ; Mass Spectrometry ; Medicine, Chinese Traditional ; Molecular Docking Simulation ; Pandemics ; prevention & control ; Pneumonia, Viral ; drug therapy ; prevention & control ; virology ; Protein Interaction Maps ; Viral Nonstructural Proteins ; chemistry

Human bocavirus 1 (HBoV1) non-structural protein NS1 is a multifunctional protein important for virus replication and induction of apoptosis in host cell. To better understand the function of the NS1 protein, it is urgent to address reducing the toxicity of NS1 to host cells. In the present study, we established a stable cell line that regulates expression of NS1 of HBoV1. The recombinant lentivirus plasmid containing a regulatable promoter fused with ns1 gene was constructed and transfected into HEK 293T cells using transfection reagent. The HEK 293T cell lines stably expressing NS1-100 and NS1-70 proteins were established by screening resistant cells with puromycin and inducing NS1 expression with doxycycline. The expression of NS1 protein was determined by fluorescent labeling protein and Western blotting. HBoV1 promoter was transfected into stably expressing NS1 cell line and its trans-transcriptional activity was analyzed. The results showed that NS1 protein was expressed stably in the established cell lines and had a strong activation activity on the HBoV1 promoter driving luciferase gene. Taken together, this study provides a solid basis for further research on the function of NS1 and the pathogenesis of human bocavirus.
Human bocavirus ; Promoter Regions, Genetic ; Transcriptional Activation ; Viral Nonstructural Proteins ; Virus Replication