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Porcine reproductive and respiratory syndrome (PRRS) significantly impacts the global swine industry. Sichuan province, a key pig breeding center in China, has limited data on the molecular epidemiology of PRRS Virus (PRRSV). To address this, 1618 suspected PRRSV samples were collected from 2021 to 2023, with a prevalence rate of 39.74% (643/1618). Phylogenetic analysis showed PRRSV-2 as dominant (95.65%, 615/643), with PRRSV-1 at 4.35% (28/643). PRRSV-2 strains were further classified into NADC30-like (74.18%), NADC34-like (11.98%), C-PRRSV (5.44%), and HP-PRRSV (4.04%). The significant change in the proportions of different lineages indicates genomic divergence. NADC30-like strains exhibited significant amino acid mutations in ORF5, aiding immune evasion. Recombination analysis revealed complex patterns, primarily involving NADC30-like strains. This study highlights the genomic divergence of PRRSV in Sichuan, with NADC30-like strains becoming predominant and emerging strains like NADC34-like showing potential for further spread.

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Chikungunya virus (CHIKV) is responsible for the most endemic alphavirus infections called Chikungunya. The endemicity of Chikungunya has increased over the past two decades, and it is a pathogen with pandemic potential. There is currently no approved direct-acting antiviral to treat the disease. As part of our antiviral drug discovery program focused on alphaviruses and the non-structural protein 2 protease, we discovered that J12 and J13 can inhibit CHIKV nsP2 protease and block the replication of CHIKV in cell cultures. Both compounds are metabolically stable to human liver microsomal and S9 enzymes. J13 has excellent oral bioavailability in pharmacokinetics studies in mice and ameliorated Chikungunya symptoms in preliminary efficacy studies in mice. J13 exhibited an excellent safety profile in in vitro safety pharmacology and off-target screening assays, making J13 and its analogs good candidates for drug development against Chikungunya.

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Rotaviruses (RVs) are classified into nine species, A-D and F-J, with species A being the most studied. In rotavirus of species A (RVA), replication occurs in viroplasms, which are cytosolic globular inclusions composed of main building block proteins NSP5, NSP2, and VP2. The co-expression of NSP5 with either NSP2 or VP2 in uninfected cells leads to the formation of viroplasm-like structures (VLSs). Although morphologically identical to viroplasms, VLSs do not produce viral progeny but serve as excellent tools for studying complex viroplasms. A knowledge gap exists regarding non-RVA viroplasms due to the lack of specific antibodies and suitable cell culture systems. In this study, we explored the ability of NSP5 and NSP2 from non-RVA species to form VLSs. The co-expression of these two proteins led to globular VLSs in RV species A, B, D, F, G, and I, while RVC formed filamentous VLSs. The co-expression of NSP5 and NSP2 of RV species H and J did not result in VLS formation. Interestingly, NSP5 of all RV species self-oligomerizes, with the ordered C-terminal region, termed the tail, being necessary for self-oligomerization of RV species A-C and G-J. Except for NSP5 from RVJ, all NSP5 interacted with their cognate NSP2. We also found that interspecies VLS are formed between closely related RV species B with G and D with F. Additionally, VLS from RVH and RVJ formed when the tail of NSP5 RVH and RVJ was replaced by the tail of NSP5 from RVA and co-expressed with their respective NSP2. IMPORTANCE: Rotaviruses (RVs) are classified into nine species, A-D and F-J, infecting mammals and birds. Due to the lack of research tools, all cumulative knowledge on RV replication is based on RV species A (RVA). The RV replication compartments are globular cytosolic structures named viroplasms, which have only been identified in RV species A. In this study, we examined the formation of viroplasm-like structures (VLSs) by the co-expression of NSP5 with NSP2 across RV species A to J. Globular VLSs formed for RV species A, B, D, F, G, and I, while RV species C formed filamentous structures. The RV species H and J did not form VLS with their cognates NSP5 and NSP2. Similar to RVA, NSP5 self-oligomerizes in all RV species, which is required for VLS formation. This study provides basic knowledge of the non-RVA replication mechanisms, which could help develop strategies to halt virus infection across RV species.

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Chikungunya virus (CHIKV) causes a debilitating fever and joint pain, with no specific antiviral treatment available. Halogenated secondary metabolites from plants are a promising new class of drug candidates against chikungunya, with unique properties that make them effective against the virus. Plants produce these compounds to defend themselves against pests and pathogens, and they are effective against a wide range of viruses, including chikungunya. This study investigated the interactions of halogenated secondary metabolites with nsP2pro, a therapeutic target for CHIKV. A library of sixty-six halogenated plant metabolites screened previously for ADME properties was used. Metabolites without violation of Lipinski's rule were docked with nsP2pro using AutoDock Vina. To find the stability of the pipoxide chlorohydrin-nsP2pro complex, the GROMACS suite was used for MD simulation. The binding free energy of the ligand-protein complex was computed using MMPBSA. Molecular docking studies revealed that halogenated metabolites interact with nsP2pro, suggesting they are possible inhibitors. Pipoxide chlorohydrin showed the greatest affinity to the target. This was further confirmed by the MD simulations, surface accessible area, and MMPBSA studies. Pipoxide chlorohydrin, a halogenated metabolite, was the most potent against nsP2pro in the survey.

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Rotavirus (RV) replicates within viroplasms, membraneless electron-dense globular cytosolic inclusions with liquid-liquid phase properties. In these structures occur the virus transcription, replication, and packaging of the virus genome in newly assembled double-layered particles. The viroplasms are composed of virus proteins (NSP2, NSP5, NSP4, VP1, VP2, VP3, and VP6), single- and double-stranded virus RNAs, and host components such as microtubules, perilipin-1, and chaperonins. The formation, coalescence, maintenance, and perinuclear localization of viroplasms rely on their association with the cytoskeleton. A stabilized microtubule network involving microtubules and kinesin Eg5 and dynein molecular motors is associated with NSP5, NSP2, and VP2, facilitating dynamic processes such as viroplasm coalescence and perinuclear localization. Key post-translation modifications, particularly phosphorylation events of RV proteins NSP5 and NSP2, play pivotal roles in orchestrating these interactions. Actin filaments also contribute, triggering the formation of the viroplasms through the association of soluble cytosolic VP4 with actin and the molecular motor myosin. This review explores the evolving understanding of RV replication, emphasizing the host requirements essential for viroplasm formation and highlighting their dynamic interplay within the host cell.

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Background Sivelestat is a potent and specific neutrophil elastase inhibitor. It is clinically used in treating lung injury and respiratory distress syndrome. This engaged us to undertake the present study in which sivelestat was studied as an anti-inflammatory and anti-viral agent. Methodology The docking study of sivelestat on matrix metalloproteinase-2 (MMP-2), matrix metalloproteinase-9 (MMP-9), chikungunya virus nonstructural protein-2 (CVnsP2) protease, and influenza A (H1N9) virus neuraminidase was assessed using the Chemistry at Harvard Macromolecular Mechanics (CHARMM) Dock (CDOCK) method. Furthermore, molecular physicochemical; bioactivity; absorption, distribution, metabolism, and excretion (ADME); toxicity; and Search Tool for Interacting Chemicals (STITCH) analyses were performed by using the Molinspiration (Molinspiration Cheminformatics, Slovensky Grob, Slovak Republic), SwissADME SwissADME (Swiss Institute of Bioinformatics, Quartier Sorge - Bâtiment Amphipôle, Switzerland), pkCSM (University of Melbourne, Melbourne, Australia), and STITCH-free online tools. Results The molecular physicochemical assessment of the ligand (sivelestat) showed no (zero) violation and agreed with the thumb rule of five, otherwise known as Lipinski's rule of five. ADME prediction of the ligand (sivelestat) is shown to possess a low gastrointestinal absorption (GIA) property. Similarly, toxicity analysis of the ligand (sivelestat) is predicted to have a hepatotoxicity effect. STITCH analysis reveals that the ligand (sivelestat) has exhibited interactions with the three human proteins. Conclusions The present molecular docking studies showed that the ligand (sivelestat) has successfully docked with all four enzymes of interest. Hence, the current finding has provided a good understanding of sivelestat as an effective suppressor activity against all four enzymes: MMP-2, MMP-9, CVnsP2 protease, and influenza neuraminidase.

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Porcine reproductive and respiratory syndrome (PRRS), an important viral disease of swine caused by PRRS virus (PRRSV) was first confirmed in Nepal in 2013. Since then, the virus has spread throughout the country and has now become endemic affecting the pig production nationally. However, molecular characterization of circulating strains has not been done in Nepal yet. In the present study, serum samples were collected from outbreak areas of different districts of Nepal and samples positive for PRRSV by ELISA were sent to Animal and Plant Health Agency (APHA), United Kingdom for sequence analysis. Out of 35 samples that were sent to APHA, only one sample was found positive by PCR and subjected to sequence analysis based on ORF5, ORF7 and Nsp2. The results from the phylogenetic analysis demonstrated that the PRRSV strain belongs to PRRSV-2 and lineage 8 strain. The sequences from the Nepalese PRRSV strain revealed a high degree of similarity with the strains isolated from India, China and Vietnam, with the closest genetic relatedness to the Indian isolates from 2020 and 2018. This is the first study on molecular characterization of PRRS virus circulating in Nepal. Further studies on strains circulating in Nepal are very essential to understand the virus diversity, its spread and evolution.

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Non-structural protein 2 (nsp2) exists in all coronaviruses (CoVs), while its primary function in viral pathogenicity, is largely unclear. One such enteric CoV, porcine epidemic diarrhea virus (PEDV), causes high mortality in neonatal piglets worldwide. To determine the biological role of nsp2, we generated a PEDV mutant containing a complete nsp2 deletion (rPEDV-Δnsp2) from a highly pathogenic strain by reverse genetics, showing that nsp2 was dispensable for PEDV infection, while its deficiency reduced viral replication in vitro. Intriguingly, rPEDV-Δnsp2 was entirely avirulent in vivo, with significantly increased productions of IFNB (interferon beta) and IFN-stimulated genes (ISGs) in various intestinal tissues of challenged newborn piglets. Notably, nsp2 targets and degrades TBK1 (TANK binding kinase 1), the critical kinase in the innate immune response. Mechanistically, nsp2 induced the macroautophagy/autophagy process and recruited a selective autophagic receptor, NBR1 (NBR1 autophagy cargo receptor). NBR1 subsequently facilitated the K48-linked ubiquitination of TBK1 and delivered it for autophagosome-mediated degradation. Accordingly, the replication of rPEDV-Δnsp2 CoV was restrained by reduced autophagy and excess productions of type I IFNs and ISGs. Our data collectively define enteric CoV nsp2 as a novel virulence determinant, propose a crucial role of nsp2 in diminishing innate antiviral immunity by targeting TBK1 for NBR1-mediated selective autophagy, and pave the way to develop a new type of nsp2-based attenuated PEDV vaccine. The study also provides new insights into the prevention and treatment of other pathogenic CoVs.Abbreviations: 3-MA: 3-methyladenine; Baf A1: bafilomycin A1; CoV: coronavirus; CQ: chloroquine; dpi: days post-inoculation; DMVs: double-membrane vesicles; GABARAP: GABA type A receptor-associated protein; GFP: green fluorescent protein; GIGYF2: GRB10 interacting GYF protein 2; hpi: hours post-infection; IFA: immunofluorescence assay; IFIH1: interferon induced with helicase C domain 1; IFIT2: interferon induced protein with tetratricopeptide repeats 2; IFITM1: interferon induced transmembrane protein 1; IFNB: interferon beta; IRF3: interferon regulatory factor 3; ISGs: interferon-stimulated genes; mAb: monoclonal antibody; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MAVS: mitochondrial antiviral signaling protein; NBR1: NBR1 autophagy cargo receptor; nsp2: non-structural protein 2; OAS1: 2'-5'-oligoadenylate synthetase 1; PEDV: porcine epidemic diarrhea virus; PRRs: pattern recognition receptors; RIGI: RNA sensor RIG-I; RT-qPCR: reverse transcription quantitative polymerase chain reaction; SQSTM1: sequestosome 1; TBK1: TANK binding kinase 1; TCID50: 50% tissue culture infectious doses; VSV: vesicular stomatitis virus.

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Porcine reproductive and respiratory syndrome virus (PRRSV) remains one of the major threats to swine industry, resulting in huge economic losses worldwide. Currently, PRRSV has diversified into multiple lineages with characteristics of extensive recombination in China. In this research, three virus strains were isolated and four virus whole genome sequences were generated and analyzed from clinical samples collected in Gansu province of China in 2023. The four virus strains were designated GSTS4-2023, GSLX2-2023, GSFEI2-2023 and GSBY4-2023. Phylogenetic analysis based on ORF5 sequences showed that GSTS4-2023, GSLX2-2023, GSFEI2-2023 and GSBY4-2023 shared 91.7, 91.2, 93.2 and 92.9% homology with NADC30 strain respectively, and belonged to lineage 1 of PRRSV-2. In addition, one amino acid deletion was observed at position 33 in ORF5 of GSTS4-2023, GSLX2-2023 and GSFEI2-2023. Moreover, amino acid alignment of the four strains showed a typical discontinuous 131-amino acid (aa) deletion in NSP2 for NADC30-like virus strains. Recombination analysis revealed that all four strains originated from NADC30 (lineage 1), with their minor parents coming from JXA1-like strains (lineage 8), VR-2332-like strains (lineage5) and QYYZ-like strains (lineage3). Finally, the three isolated virus strains, GSTS4-2023, GSLX2-2023 and GSFEI2-2023 showed relatively low levels of replication in cell culture. Our findings provide important implications for the field epidemiology of PRRSV.

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porcine reproductive and respiratory syndrome (PRRS), caused by porcine reproductive and respiratory syndrome virus (PRRSV) infection, is an important swine infectious disease that causes substantial losses worldwide each year. PRRSV is a positive-sense single-stranded RNA virus that is highly susceptible to mutation and recombination, making vaccine and drug research for the disease extremely difficult. In this study, the binding of PRRSV nsp2 to HSP71 protein was detected by using the IP/MS technique. And the inhibitory effect of HSP71 on nsp2 antagonistic activity was validated by measuring NF-kB luciferase reporter. According to stress from inhibitory effects, the amino acid variation profile of PRRSV nsp2 under HSP71 stress was further analyzed using second-generation sequencing. Surprisingly, the results indicated that HSP71 pressure limits the random mutations of PRRSV nsp2 and maintains the dominant PRRSV strain within the population. Mutant strain showed weaker antagonistic activity and replication capability in cell. These results imply the binding of HSP71 with PRRSV nsp2 may lead to maintain the stability of highly virulent strains of PRRSV.

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Porcine reproductive and respiratory syndrome virus (PRRSV) is an RNA virus with constantly emerging recombinant and mutant strains. Because of the high genetic diversity of PRRSV, current vaccines only provide partial protection against the infection of heterologous strains, which makes it a challenge for PRRSV prevention and control. Tubercidin is a naturally extracted compound with potential antiviral properties. However, whether tubercidin has anti-PRRSV ability is unknown. Our study found that tubercidin showed effective antiviral effects on PRRSV replication. In terms of mechanism, tubercidin suppressed PRRSV at the entry, replication, and release steps of the viral life cycle. Additionally, we demonstrated that tubercidin treatment promoted the activation of retinoic acid-inducible gene I and nuclear factor kappa-light-chain-enhancer of activated B cell signaling pathway, thus increasing the type I interferon and inflammatory cytokine expression. Furthermore, tubercidin restrained the viral non-structural protein 2 expression and viral dsRNA synthesis and ultimately inhibited PRRSV replication. Hence, our data showed that tubercidin is promising and has potential antiviral ability against PRRSV replication in vitro. IMPORTANCE: Porcine reproductive and respiratory syndrome (PRRS) is one of the most important swine diseases, which causes huge economic loss worldwide. However, there is no effective therapeutic method for PRRS prevention and control. Here, we found that tubercidin, a naturally extracted adenosine analog, exhibited strong anti-porcine reproductive and respiratory syndrome virus (PRRSV) activity. Mechanically, tubercidin inhibited viral binding, replication, and release. Tubercidin suppressed PRRSV non-structural protein 2 expression, which is important for the formation of replication and transcription complex, leading to the block of viral RNA synthesis and PRRSV replication. Moreover, tubercidin could activate retinoic acid-inducible gene I/nuclear factor kappa-light-chain-enhancer of activated B cell innate immune signaling pathway and increased the expression of interferons and proinflammatory cytokines, which was the other way to inhibit PRRSV replication. Our work evaluated the potential value of tubercidin as an antiviral agent on PRRSV replication and provided a new way to prevent PRRSV replication in vitro.

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Rotavirus (RV) NSP2 is a multifunctional RNA chaperone that exhibits numerous activities that are essential for replication and viral genome packaging. We performed an in silico analysis that highlighted a distant relationship of NSP2 from rotavirus B (RVB) to proteins from other human RVs. We solved a cryo-electron microscopy structure of RVB NSP2 that shows structural differences with corresponding proteins from other human RVs. Based on the structure, we identified amino acid residues that are involved in RNA interactions. Anisotropy titration experiments showed that these residues are important for nucleic acid binding. We also identified structural motifs that are conserved in all RV species. Collectively, our data complete the structural characterization of rotaviral NSP2 protein and demonstrate its structural diversity among RV species.IMPORTANCERotavirus B (RVB), also known as adult diarrhea rotavirus, has caused epidemics of severe diarrhea in China, India, and Bangladesh. Thousands of people are infected in a single RVB epidemic. However, information on this group of rotaviruses remains limited. As NSP2 is an essential protein in the viral life cycle, including its role in the formation of replication factories, it may be a target for future antiviral strategy against viruses with similar mechanisms.

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Macroautophagy/autophagy is a cellular degradation and recycling process that maintains the homeostasis of organisms. A growing number of studies have reported that autophagy participates in infection by a variety of viruses. Porcine reproductive and respiratory syndrome virus (PRRSV) causes severe financial losses to the global swine industry. Although much research has shown that PRRSV triggers autophagy for its own benefits, the exact molecular mechanisms involved in PRRSV-triggered autophagy remain to be fully elucidated. In the current study, we demonstrated that PRRSV infection significantly induced Golgi apparatus (GA) fragmentation, which promoted autophagy to facilitate viral self-replication. Mechanistically, PRRSV nonstructural protein 2 was identified to interact with and degrade the Golgi reassembly and stacking protein 65 dependent on its papain-like cysteine protease 2 activity, resulting in GA fragmentation. Upon GA fragmentation, GA-resident Ras-like protein in brain 2 was disassociated from Golgi matrix protein 130 and subsequently bound to unc-51 like autophagy activating kinase 1 (ULK1), which enhanced phosphorylation of ULK1 and promoted autophagy. Taken together, all these results expand the knowledge of PRRSV-triggered autophagy as well as PRRSV pathogenesis to support novel potential avenues for prevention and control of the virus. More importantly, these results provide the detailed mechanism of GA fragmentation-mediated autophagy, deepening the understanding of autophagic processes.IMPORTANCEPorcine reproductive and respiratory syndrome virus (PRRSV) infection results in a serious swine disease affecting pig farming worldwide. Despite that numerous studies have shown that PRRSV triggers autophagy for its self-replication, how PRRSV induces autophagy is incompletely understood. Here, we identify that PRRSV Nsp2 degrades GRASP65 to induce GA fragmentation, which dissociates RAB2 from GM130 and activates RAB2-ULK1-mediated autophagy to enhance viral replication. This work expands our understanding of PRRSV-induced autophagy and PRRSV replication, which is beneficial for anti-viral drug development.

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Vanadium (V) pollution potentially threatens human health. Here, it is found that nsp1 and nsp2, Rhizobium symbiosis defective mutants of Medicago truncatula, are sensitive to V. Concentrations of phosphorus (P), iron (Fe), and sulfur (S) with V are negatively correlated in the shoots of wild-type R108, but not in mutant nsp1 and nsp2 shoots. Mutations in the P transporter PHT1, PHO1, and VPT families, Fe transporter IRT1, and S transporter SULTR1/3/4 family confer varying degrees of V tolerance on plants. Among these gene families, MtPT1, MtZIP6, MtZIP9, and MtSULTR1; 1 in R108 roots are significantly inhibited by V stress, while MtPHO1; 2, MtVPT2, and MtVPT3 are significantly induced. Overexpression of Arabidopsis thaliana VPT1 or M. truncatula MtVPT3 increases plant V tolerance. However, the response of these genes to V is weakened in nsp1 or nsp2 and influenced by soil microorganisms. Mutations in NSPs reduce rhizobacterial diversity under V stress and simplify the V-responsive operational taxonomic unit modules in co-occurrence networks. Furthermore, R108 recruits more beneficial rhizobacteria related to V, P, Fe, and S than does nsp1 or nsp2. Thus, NSPs can modulate the accumulation and tolerance of legumes to V through P, Fe, and S transporters, ion homeostasis, and rhizobacterial community responses.

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The non-structural protein 2 (NSP2) is an RNA-binding protein involved in coronavirus genome replication, and it often decreases human immune response to promote viral invasion and development. It is believed that the NSP2 associates itself with polyamines and heat shock proteins inside the host cell to proceed with viral development. This study aimed to investigate how the SARS-CoV-2 virus' key non-structural proteins (NSP2) utilize polyamines and heat shock proteins using a molecular docking approach and molecular dynamics (MD). ClusPro and HADDOCK servers were used for the docking and Discovery Studio, chimera, and PyMOL were used for analysis. Docking of the heat shock proteins 40 (HSP40), 70 (HSP70), and 90 (HSP90) with SARS-CoV-2 NSP2 resulted in 32, 28, and 19 interactions, respectively. Molecular dynamics revealed Arg458, Asn508, Met297, Arg301, and Trp417 as active residues, and pharmacophore modeling indicated ZINC395648, ZINC01150525, and ZINC85324008 from the zinc database as possible inhibitors for this NSP2.

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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.

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Getah virus (GETV) was becoming more serious and posing a potential threat to animal safety and public health. Currently, there is limited comprehension regarding the pathogenesis and immune evasion mechanisms employed by GETV. Our study reveals that GETV infection exhibits the capacity for interferon antagonism. Specifically, the nonstructural protein nsP2 of GETV plays a crucial role in evading the host immune response. GETV nsP2 effectively inhibits the induction of IFN-ß by blocking the phosphorylation and nuclear translocation of IRF3. Additionally, GETV nsP2 hinders the phosphorylation of STAT1 and its nuclear accumulation, leading to significantly impaired JAK-STAT signaling. Furthermore, the amino acids K648 and R649, situated in the C-terminal region of GETV nsP2, play a crucial role in facilitating nuclear localization. Not only do they affect the interference of nsP2 with the innate immune response, but they also exert an influence on the pathogenicity of GETV in mice. In summary, our study reveals novel mechanisms by which GETV evades the immune system, thereby offering a foundation for comprehending the pathogenic nature of GETV. Video Abstract.

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Introduction: Mutation in the genome of SARS-CoV-2 may play a role in immune evasion, pathogenicity, and speed of its transmission. Our investigation aimed to evaluate the mutations that exist in the NSP2. Materials and Method: RNA was extracted from nasopharyngeal swabs from 100 COVID-19 patients. RT-PCR was performed on all samples using NSP2-specific primers. Following gel electrophoresis, the bands were cut, purified, and sequenced using the Sanger method. After sequencing, 90 sequences could be used for further analysis. Bioinformatics analysis was conducted to investigate the effect of mutations on protein structure, stability, prediction of homology models, and phylogeny tree. Results: The patients' mean age was 51.08. The results revealed that 8 of the 17 NSP2 mutations (R207C, T224I, G262V, T265I, K337D, N348S, G392D, and I431M) were missense. One deletion was also found in NSP2. Among NSP2 missense mutations studied, K337D and G392D increased structural stability while the others decreased it. The homology-designed models demonstrated that the homologies were comparable to the sequences of the Wuhan-HU-1 virus. Conclusion: Our study suggested that the mutations K337D and G392D modulate the stability of NSP2, and tracking viral evolution should be implemented and vaccine development updated.

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IMPORTANCE: Our study highlights the mechanisms behind the cell's resistance to stress granule (SG) formation after infection with Old World alphaviruses. Shortly after infection, the replication of these viruses hinders the cell's ability to form SGs, even when exposed to chemical inducers such as sodium arsenite. This resistance is primarily attributed to virus-induced transcriptional and translational shutoffs, rather than interactions between the viral nsP3 and the key components of SGs, G3BP1/2, or the ADP-ribosylhydrolase activity of nsP3 macro domain. While interactions between G3BPs and nsP3 are essential for the formation of viral replication complexes, their role in regulating SG development appears to be small, if any. Cells harboring replicating viruses or replicons with lower abilities to inhibit transcription and/or translation, but expressing wild-type nsP3, retain the ability for SG development. Understanding these mechanisms of regulation of SG formation contributes to our knowledge of viral replication and the intricate relationships between alphaviruses and host cells.

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