Foot-and-mouth disease (FMD) is a highly contagious and economically important disease, which is caused by the FMD virus (FMDV). Although the cell receptor for FMDV has been identified, the specific mechanism of FMDV internalization after infection remains unknown. In this study, we found that kinesin family member 5B (KIF5B) plays a vital role during FMDV internalization. Moreover, we confirmed the interaction between KIF5B and FMDV structural protein VP1 by co-immunoprecipitation (Co-IP) and co-localization in FMDV-infected cells. In particular, the stalk [amino acids (aa) 413-678] domain of KIF5B was indispensable for KIF5B-VP1 interaction. Moreover, overexpression of KIF5B dramatically enhanced FMDV replication; consistently, knockdown or knockout of KIF5B suppressed FMDV replication. Furthermore, we also demonstrated that KIF5B promotes the internalization of FMDV via regulating clathrin uncoating. KIF5B also promotes the transmission of viral particles to early and late endosomes during the early stages of infection. In conclusion, our results demonstrate that KIF5B promotes the internalization of FMDV via regulating clathrin uncoating and intracellular transport. This study may provide a new therapeutic target for developing FMDV antiviral drugs.

Enterovirus G (EV-G) has recently been shown to affect weight gain and cause neurological symptoms in piglets. However, the serological investigation of EV-G is limited. In this study, we developed a novel serological detection method based on the structural protein, VP1 of EV-G. The intra-assay and inter-assay coefficient variations were 3.2-8.9% and 2.6-8.0%, respectively. There was no cross-reaction of the VP1-based enzyme-linked immunosorbent assay (ELISA) with antisera against the other known porcine viruses. In addition, a comparison was made with other methods including the developed indirect ELISAs based on VP2 and VP3 proteins and western blot (WB) analysis, which demonstrated the reliability of the novel method. Using the VP1-based ELISA, we carried out the first seroepidemiological survey of EV-G in China by testing 1041 serum samples collected from different pig farms in Guangxi from 2019 to 2021. Our results showed that 68.78% of the serum samples and 100% of the pig farms were positive for EV-G, with a relatively high incidence of seropositivity in pigs of different ages. This was specifically evident in fattening pigs and sows, which may suggest that the piglets have experienced an infection with EV-G during their growth process. Our data provide the first serological evidence of EV-G infections in pigs from China and reveal the widespread presence of EV-G infections in Guangxi, China.

Sapovirus (SaV) infection is increasing globally. Concurrently, several SaV-outbreaks were observed in children of Zhejiang province, China, in recent years, In this study, the genotypes of Sapovirus from seven outbreaks in the Zhejiang province were analysed.
A total of 105 faecal samples were collected from children aged between 4 and 17 years from the Zhejiang Provincial Center for Disease Control and Prevention between October 2021 and February 2023. Genotypes were processed using reverse transcription polymerase chain reaction and Sanger sequencing, while next-generation sequencing was used to generate a complete viral genome. Deduced amino acid sequences were analysed to detect VP1 gene mutations.
In total, 60 SaV-positive patients were detected at a 57.14% (60/105) positivity rate. Positive rates in the seven outbreaks were: 22.22% (2/9), 15.00% (3/20), 93.10% (27/29), 84.21% (16/19), 28.57% (2/7), 53.33% (8/15) and 33.33% (2/6), respectively. Four genotypes were identified in the seven outbreaks, of which, GI.1 accounted for 14.29% (1/7), GI.2 accounted for 14.29% (1/7), GI.6 and GII.5 accounted for 14.29% (1/7), and GI.6 accounted for 57.14% (4/7). All patients were children and outbreaks predominantly occurred in primary schools and during cold seasons. Additionally, the complete sequence from the GI.6 outbreak strain showed high homology (identity: 99.99%) with few common substitutions (Y300S, N302S and L8M) in VP1 protein.
SaV genotype diversity was observed in the seven outbreaks, with GI.6 being the main SaV genotype in Zhejiang province. It demonstrated high homology and may provide a platform for SaV prevention and control measures.

The JC polyomavirus virus (JCPyV) affects more than 80% of the human population in their early life stage. It mainly affects immunocompromised individuals where virus replication in oligodendrocytes and astrocytes may lead to fatal progressive multifocal encephalopathy (PML). Virus protein 1 (VP1) is one of the major structural proteins of the viral capsid, responsible for keeping the virus alive in the gastrointestinal and urinary tracts. VP1 is often targeted for antiviral drug and vaccine development. Similarly, this study implied immune-informatics and molecular modeling methods to design a multi-epitope subunit vaccine targeting JCPyV. The VP1 protein epitopic sequences, which are highly conserved, were used to build the vaccine. This designed vaccine includes two adjuvants, five HTL epitopes, five CTL epitopes, and two BCL epitopes to stimulate cellular, humoral, and innate immune responses against the JCPyV. Furthermore, molecular dynamics simulation (100 ns) studies were used to examine the interaction and stability of the vaccine protein with TLR4. Trajectory analysis showed that the vaccine and TLR4 receptor form a stable complex. Overall, this study may contribute to the path of vaccine development against JCPyV.

Proanthocyanidins (PC), a natural flavonoid compound, was reported to possess a variety of pharmacological activities such as anti-tumor and anti-viral effects. In this study, the anti-Enterovirus 71 (EV71) activities and mechanisms of PC were investigated both in vitro and in vivo. The results showed that PC possessed anti-EV71 activities in different cell lines with low toxicity. PC can block both the adsorption and entry processes of EV71 via directly binding to virus VP1 protein. PC may competitively interfere with the binding of VP1 to its receptor SCARB2. PC can also regulate three different MAPK signaling pathways to reduce EV71 infection and attenuate virus induced inflammatory responses. Importantly, intramuscular therapy of EV71-infected mice with PC markedly improved their survival and attenuated the severe clinical symptoms. Therefore, the natural compound PC has potential to be developed into a novel anti-EV71 agent targeting viral VP1 protein and MAPK pathways.

OBJECTIVE: The present study aimed to explore if bovine parvovirus (BPV) impacts beta interferon (IFN-β) production and to reveal further molecular mechanism of BPV immune escape.
METHODS: The pCMV-Myc-BPV-VP1 recombinant plasmid was verified with both double-enzyme digestion and sequence. HEK 293 T cells were transfected with this recombinant protein and then infected with the vesicular stomatitis virus (VSV). Expression levels of IFN-β mRNA were detected using qPCR.
RESULTS: The expression level of BPV VP1 mRNA in the pCMV-Myc-BPV-VP1 group was significantly higher than those of the untreated group (UT) and pCMV-Myc vector group. BPV virus copies in bovine turbinate (BT) cells of the BPV-VP1 group were raised (P < 0.05) with an increment of 5.8 × 104. Expression levels of IFN-β mRNA of the BPV VP1 group in HEK 293 T cells were decreased (P < 0.01). Following treatment of TBK1 and IRF3(5D), IFN-β expression levels in HEK 293 T cells were depressed. Additionally, expression levels of TBK1, IRF3(5D), MDA5, and MAVS were less than those of the flag empty vector, respectively.
CONCLUSIONS: pCMV-Myc-BPV-VP1 could heighten transcription levels of VP1 protein in BT cells, promote BPV proliferation, and ascend the production of IFN-β. Overexpression of pCMV-Myc-BPV-VP decreased IFN-β mRNA expression in HEK 293 T cells and inhibited IFN-β production induced by TBK1 and IRF3(5D). Furthermore, BPV VP1 obviously declined expression levels of TBK1, IRF3(5D), MDA5, and MAVS in the RIG-I-like receptor (RLR) pathway. Our findings revealed a novel mechanism evolved by BPV VP1 to inhibit type I IFN production and provided a solid scientific basis into the immunosuppression of BPV.

Porcine sapelovirus (PSV) is an important emerging swine pathogen that causes diarrhoea, respiratory distress, severe reproductive system and neurological disorders in pigs, posing huge threat to swine industry. However, there are no effective serological diagnostic products and the epitope characterization of PSV VP1 protein is still largely unknown. In current study, we successfully expressed recombinant His-VP1 protein by prokaryotic expression system and the recombinant VP1 protein had good immunogenicity. BALB/C mice were then selected and immunized with purified recombinant VP1 protein, and two monoclonal antibodies (Mabs) 9F10 and 15E4 against VP1 were successfully prepared by hybrioma technology. The isotype of these two Mabs were identified and showed that Mab 9F10 with the heavy chain subtype was IgG1 and the light chain subtype was kappa. Mab 15E4 was identified as IgG2 for the heavy chain subtype and Kappa for the light chain subtype. The antigen epitopes of prepared two VP1 Mabs were clearly identified. The minimal unit of B cell specific epitope recognized by Mab 15E4 was 203YDGDG207 and conserved in different strain genotypes of PSV, indicating this epitope may be a good target for serological detection of PSV. However, the epitope recognized by Mab 9F10 was 8QAIVNRT14 and varied greatly among different PSV strains. Structural modeling analysis showed that the identified two novel B cell epitopes were located on the surface of VP1. Our study provides useful tool for the establishment the serological detection methods of PSV and may support the study of VP1 protein function.

Foot-and-mouth disease (FMD) is an acute and highly contagious disease in livestock, such as cattle, sheep, and pigs, leading to a lot of economic losses. The current FMD vaccines formulated by inactivated whole-virus and adjuvant successfully reduce disease outbreaks in many regions of the world. Immunological studies on FMD viruses revealed that the dominant epitope in arising neutral antibody response is amino acid residues constructing the G-H loop, constituting a surface loop of the structural protein, termed VP1. Liposomes as one of the most well-known vehicles are considered an important carrier in vaccine development, and their function is used to encapsulate purified VP1 protein based on their size, charge, and lipid content. Accordingly, the VP1 protein was isolated from the FMD virus. This study aimed to compare four methods of VP1 protein encapsulation in the liposome and the extruding effect, as follows: 1) VP1 protein was dissolved in dimethyl sulfoxide and added to the lipid film hydrated by ethanol, 2) the lipid film was hydrated by VP1 protein with 7M urea, 3) the lipid film was hydrated by VP1 protein and freeze-thawed, and 4) the lipid film was hydrated by VP1 protein. The highest encapsulation efficiency was 91% in the second method which purified protein-containing urea. The VP1 protein in the prepared liposome (1, 2-dimyristoyl-sn-glycero-3-phosphocholine: 1, 2-dimyristoyl-sn-glycero-3-phosphocholine: cholesterol) released more than 90% of protein content after 240 h.

The porcine circovirus-like virus P1, a member of the circovirus family, causes post-weaning multisystemic wasting syndrome (PMWS) in weaned piglets with progressive wasting as the main clinical symptom. The pancreatic secretion pathway induces pancreatic acinar cells to secrete various digestive enzymes and as such is an important signaling pathway for the digestive system and somatic growth. This study examined the effects and mechanism of P1 virus infection on the pancreatic secretion pathway. The experiment was conducted by transfecting double-copy plasmid P1 into PK-15 and 3D4 cells and by infecting cells with the P1 virus. Samples were collected at various times after transfection or infection. The pathway\'s transcription and translation levels of CHRM3, Gq, PLC-β2, PRKCA, Rab3D, RhoA, Rac1, and amyA proteins were detected by real-time PCR and Western blots; these analyses confirmed that the P1 virus infection could upregulate the expression level of key pancreatic secretion signaling molecules. Then, we confirmed that the VP1 protein of the P1 virus could interact with the pathway initiation protein CHRM3 using Co-IP, pull-downs, and confocal fluorescence microscopy. Finally, we demonstrated that the VP1 protein activates the pancreatic secretory pathway through the CHRM3 protein. In conclusion, this study demonstrated that the P1 virus can interact with the CHRM3 receptor protein to activate the pancreatic secretion pathway and promote the secretion of various digestive enzymes downstream of the pathway, thereby providing a basis for P1 virus pathogenesis.

Noroviruses have been identified as major causative agents of acute nonbacterial gastroenteritis in humans. Histo-blood group antigens (HBGAs) are thought to play a major role among the host cellular factors influencing norovirus infection. Genogroup I, genotype 9 (GI.9) is the most recently identified genotype within genogroup I, whose representative strain is the Vancouver 730 norovirus. However, the molecular interactions between host antigens and the GI.9 capsid protein have not been investigated in detail. In this study, we demonstrate that the GI.9 norovirus preferentially binds Lewis antigens over blood group A, B, and H antigens, as revealed by an HBGA binding assay using virus-like particles. We determined the crystal structures of the protruding domain of the GI.9 capsid protein in the presence or absence of Lewis antigens. Our analysis demonstrated that Lewis fucose (α1-3/4 fucose) represents a key moiety for the GI.9 protein-HBGA interaction, thus suggesting that Lewis antigens might play a critical role during norovirus infection. In addition to previously reported findings, our observations may support the future design of antiviral agents and vaccines against noroviruses.