Since the outbreak of corona virus disease 2019 (COVID-19), viral strains have mutated and evolved. Vaccine research is the most direct and effective way to control COVID-19. According to different production mechanisms, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines included inactivated virus vaccine, live attenuated vaccine, mRNA vaccine, DNA vaccine, viral vector vaccine, virus-like particle vaccine and protein subunit vaccine. Among them, viral protein subunit vaccine has a wide application prospect due to its high safety and effectiveness. Viral nucleocapsid protein has high immunogenicity and low variability which could be a new direction for vaccine production. We summarized the current development of vaccine research by reviewing the current progress, vaccine safety and vaccine immune efficiency. It is hoped that the proposed possible development strategies could provide a reference for epidemic prevention work in future.
Humans ; SARS-CoV-2/genetics* ; COVID-19/prevention & control* ; Protein Subunits ; Vaccines, DNA ; Nucleocapsid Proteins

Rice stripe virus (RSV) transmitted by the small brown planthopper causes severe rice yield losses in Asian countries. Although viral nuclear entry promotes viral replication in host cells, whether this phenomenon occurs in vector cells remains unknown. Therefore, in this study, we systematically evaluated the presence and roles of RSV in the nuclei of vector insect cells. We observed that the nucleocapsid protein (NP) and viral genomic RNAs were partially transported into vector cell nuclei by utilizing the importin α nuclear transport system. When blocking NP nuclear localization, cytoplasmic RSV accumulation significantly increased. In the vector cell nuclei, NP bound the transcription factor YY1 and affected its positive regulation to FAIM. Subsequently, decreased FAIM expression triggered an antiviral caspase-dependent apoptotic reaction. Our results reveal that viral nuclear entry induces completely different immune effects in vector and host cells, providing new insights into the balance between viral load and the immunity pressure in vector insects.
Animals ; Cell Nucleus ; Hemiptera/metabolism* ; Insect Vectors/genetics* ; Insecta ; Nucleocapsid Proteins/metabolism* ; Oryza ; Plant Diseases ; Tenuivirus/metabolism* ; Virus Replication

Adolescent ; Adult ; Aged ; COVID-19/virology* ; COVID-19 Nucleic Acid Testing/methods* ; Child ; Coronavirus Nucleocapsid Proteins/genetics* ; Feces/virology* ; Female ; Humans ; Male ; Middle Aged ; Phosphoproteins/genetics* ; RNA, Viral/genetics* ; SARS-CoV-2/isolation & purification* ; Young Adult

Porcine epidemic diarrhea virus (PEDV) is a highly infectious pathogen that can cause severe diseases in pigs and result in enormous economic losses in the worldwide swine industry. Previous studies revealed that PEDV exhibits an obvious capacity for modulating interferon (IFN) signaling or expression. The newly discovered type III IFN, which plays a crucial role in antiviral immunity, has strong antiviral activity against PEDV proliferation in IPEC-J2 cells. In this study, we aimed to investigate the effect of PEDV nucleocapsid (N) protein on type III IFN-λ. We found that the N proteins of ten PEDV strains isolated between 2013 and 2017 from different local farms shared high nucleotide identities, while the N protein of the CV777 vaccine strain formed a monophyletic branch in the phylogenetic tree. The N protein of the epidemic strain could antagonize type III IFN, but not type I or type II IFN expression induced by polyinosinic-polycytidylic acid (poly(I:C)) in IPEC-J2 cells. Subsequently, we demonstrated that the inhibition of poly(I:C)-induced IFN-λ3 production by PEDV N protein was dependent on the blocking of nuclear factor-κB (NF-κB) nuclear translocation. These findings might help increase understanding of the pathogenesis of PEDV and its mechanisms for evading the host immune response.
Active Transport, Cell Nucleus ; Animals ; Coronavirus Infections ; immunology ; veterinary ; virology ; Genes, Viral ; Host-Pathogen Interactions ; immunology ; Interferons ; antagonists & inhibitors ; biosynthesis ; genetics ; Interleukins ; antagonists & inhibitors ; biosynthesis ; genetics ; NF-kappa B ; metabolism ; Nucleocapsid Proteins ; genetics ; immunology ; physiology ; Porcine epidemic diarrhea virus ; genetics ; pathogenicity ; physiology ; Promoter Regions, Genetic ; Swine ; Swine Diseases ; immunology ; virology

Ebola virus (EBOV) harbors an RNA genome encapsidated by nucleoprotein (NP) along with other viral proteins to form a nucleocapsid complex. Previous Cryo-eletron tomography and biochemical studies have shown the helical structure of EBOV nucleocapsid at nanometer resolution and the first 450 amino-acid of NP (NPΔ451-739) alone is capable of forming a helical nucleocapsid-like complex (NLC). However, the structural basis for NP-NP interaction and the dynamic procedure of the nucleocapsid assembly is yet poorly understood. In this work, we, by using an E. coli expression system, captured a series of images of NPΔ451-739 conformers at different stages of NLC assembly by negative-stain electron microscopy, which allowed us to picture the dynamic procedure of EBOV nucleocapsid assembly. Along with further biochemical studies, we showed the assembly of NLC is salt-sensitive, and also established an indispensible role of RNA in this process. We propose the diverse modes of NLC elongation might be the key determinants shaping the plasticity of EBOV virions. Our findings provide a new model for characterizing the self-oligomerization of viral nucleoproteins and studying the dynamic assembly process of viral nucleocapsid in vitro.
Ebolavirus ; chemistry ; genetics ; metabolism ; Escherichia coli ; genetics ; metabolism ; Gene Expression ; Nucleocapsid ; chemistry ; genetics ; metabolism ; RNA, Viral ; chemistry ; genetics ; metabolism ; Recombinant Proteins ; chemistry ; genetics ; metabolism ; Virus Assembly

This article aimed to study the antigenicity of nucleocapsid proteins (NPs) in six pathogenic phleboviruses and to provide theoretical evidence for the development of serological diagnostic reagents. NPs of six pathogenic phleboviruses were expressed and purified using a prokaryotic expression system and rabbits were immunized with individual recombinant NPs. Cross-reactions among NPs and rabbit sera were determined by both indirect ELISA and Western blotting analyses, and the sera titer was determined by indirect ELISA. Furthermore, sera from SFTS patients were also detected by each recombinant NP as a coating antigen using indirect ELISA. The cross-reactions and the sera titer were subsequently determined. Both the concentration and purity of recombinant NPs of six pathogenic phleboviruses met the standards for immunization and detection. The results of indirect ELISA and Western blotting showed that each anti-phlebovirus NP rabbit immune serum had potential serological cross-reactivity with the other five virus NP antigens. Furthermore, the sera from SFTS patients also had cross-reactivity with the other five NP antigens to a certain extent. Our preliminary study evaluated the antigenicity and immune reactivity of six pathogenic phleboviruses NPs and laid the foundation for the development of diagnostic reagents.
Animals ; Antibodies, Viral ; immunology ; Antigens, Viral ; genetics ; immunology ; Cross Reactions ; Humans ; Nucleocapsid Proteins ; genetics ; immunology ; Phlebotomus Fever ; diagnosis ; immunology ; virology ; Phlebovirus ; classification ; genetics ; immunology ; isolation & purification ; Rabbits

Adolescent ; Adult ; Animals ; Bites and Stings ; Dog Diseases ; virology ; Dogs ; Female ; Humans ; Male ; Middle Aged ; Nucleocapsid Proteins ; genetics ; Phylogeny ; Post-Exposure Prophylaxis ; Rabies ; prevention & control ; veterinary ; virology ; Rabies Vaccines ; immunology ; Young Adult

Severe fever with thrombocytopenia syndrome virus (SFTSV), a member of the Phlebovirus genus from the Bunyaviridae family endemic to China, is the causative agent of life-threatening severe fever with thrombocytopenia syndrome (SFTS), which features high fever and hemorrhage. Similar to other negative-sense RNA viruses, SFTSV encodes a nucleocapsid protein (NP) that is essential for viral replication. NP facilitates viral RNA encapsidation and is responsible for the formation of ribonucleoprotein complex. However, recent studies have indicated that NP from Phlebovirus members behaves in inhomogeneous oligomerization states. In the present study, we report the crystal structure of SFTSV NP at 2.8 Å resolution and demonstrate the mechanism by which it processes a ringshaped hexameric form to accomplish RNA encapsidation. Key residues essential for oligomerization are identified through mutational analysis and identified to have a significant impact on RNA binding, which suggests that correct formation of highly ordered oligomers is a critical step in RNA encapsidation. The findings of this work provide new insights into the discovery of new antiviral reagents for Phlebovirus infection.
Binding Sites ; Crystallography, X-Ray ; Mutation ; Nucleocapsid Proteins ; chemistry ; genetics ; metabolism ; Phlebovirus ; metabolism ; Protein Binding ; Protein Multimerization ; Protein Structure, Quaternary ; RNA, Viral ; metabolism ; Recombinant Proteins ; biosynthesis ; chemistry ; genetics

To clarify the pathogenesis of Duck enteritis virus (DEV), the cDNA library of duck's liver infected by DEV and a bait plasmid containing DEV nucleocapsid protein (NP) gene were constructed, then the receptor was screened from the cDNA library plasmid by the yeast two-hybrid system and verified by GST pull-down test. The results showed that the capacity of the primary cDNA library was 1 x 106 CFU with insertion size from 0.5 to 1 kb, and the bait plasmid of pGBKT7-NP showed no self-activation. The receptor reacting with DEV NP in duck liver was initially confirmed as the protein kinase C inhibitor (PKCI). These results provide new clues for further investigation on pathogenesis of DEV.
Alphaherpesvirinae ; pathogenicity ; Animals ; Ducks ; virology ; Gene Library ; Liver ; virology ; Nucleocapsid Proteins ; genetics ; Plasmids ; Receptors, Virus ; analysis ; Two-Hybrid System Techniques

To evaluate the effectiveness of rabies vaccination, we developed the SPA-ELISA method to detect the antibodies against rabies virus (RV) using the main antigenic determinant of nucleoprotein (RV N1) as antigen. The complete Nucleoprotein (N) gene and the partial N1 gene (1 000-1 353 bp) of RV Flury LEP strain were amplified using RT-PCR and PCR approaches. The two fragments were inserted into pGEX-6P-1 respectively. Then we transformed the recombinant plasmids into Escherichia coli BL21(DE3) strain and expressed them by adding 1 mmol/L of IPTG (isopropyl-beta-D-thiogalactopyranoside). SDS-PAGE analysis showed that both of the two recombinant proteins were presented as inclusion bodies. Compared with the complete nucleoprotein, the partial protein (RV N1) was expressed at a much higher level in E. coli BL21(DE3). The antigenic specificity of the partial N1 protein was confirmed by Western blotting. By coating the plates with purified RV N1 as an antigen, an SPA-ELISA method for the detection of the antibodies against RV was established. By optimizing this method, the optimal concentration of RV N1 coating the ELISA plate was 2 mg/L. The optimal concentration of serum samples and SPA-HRP was 1:100 and 1:4 000 respectively. Compared with a commercially available ELISA kit coating RV as antigen, the coincidence rate of SPA-ELISA was 94.1%. Our results show that the developed SPA-ELISA based on the RV N1 was useful for the detection of the antibodies against RV in the sera of dogs.
Animals ; Antibodies, Viral ; analysis ; immunology ; Dogs ; Enzyme-Linked Immunosorbent Assay ; methods ; Epitopes ; immunology ; Escherichia coli ; genetics ; Genetic Vectors ; genetics ; Nucleocapsid Proteins ; immunology ; Rabies virus ; immunology ; Recombinant Proteins ; biosynthesis ; genetics ; immunology ; Staphylococcal Protein A