Structure analysis of the nucleoprotein of Newcastle disease virus: An insight towards its multimeric form in solution

The W195 Residue of the Newcastle Disease Virus V Protein Is Critical for Multiple Aspects of Viral Self-Regulation through Interactions between V and Nucleoproteins

The transcription and replication of the Newcastle disease virus (NDV) strictly rely on the viral ribonucleoprotein (RNP) complex, which is composed of viral NP, P, L and RNA. However, it is not known whether other viral non-RNP proteins participate in this process for viral self-regulation. In this study, we used a minigenome (MG) system to identify the regulatory role of the viral non-RNP proteins V, M, W, F and HN. Among them, V significantly reduced MG-encoded reporter activity compared with the other proteins and inhibited the synthesis of viral mRNA and cRNA. Further, V interacted with NP. A mutation in residue W195 of V diminished V-NP interaction and inhibited inclusion body (IB) formation in NP-P-L-cotransfected cells. Furthermore, a reverse-genetics system for the highly virulent strain F48E9 was established. The mutant rF48E9-VW195R increased viral replication and apparently enhanced IB formation. In vivo experiments demonstrated that rF48E9-VW195R decreased virulence and retarded time of death. Overall, the results indicate that the V-NP interaction of the W195 mutant V decreased, which regulated viral RNA synthesis, IB formation, viral replication and pathogenicity. This study provides insight into the self-regulation of non-RNP proteins in paramyxoviruses.

Newcastle disease virus forms inclusion bodies with features of liquid-liquid phase separation

Formation of inclusion bodies (IBs) is a hallmark of infections with negative-strand RNA viruses. Although the Newcastle disease virus (NDV) IBs had been observed in the 1950s, the characteristics of NDV IBs remained largely unknown. Here, we show that NDV infection triggers the formation of IBs that contain newly synthesized viral RNA. The structures of NDV IBs, observed by electron microscopy, were not membrane-bound. Fluorescence recovery after photobleaching a region of NDV IBs occurred rapidly, and IBs were dissolved by 1,6-hexanediol treatment, demonstrating they exhibited properties consistent with liquid-liquid phase separation (LLPS). We find the nucleoprotein (NP) and phosphoprotein (P) are sufficient to generate IB-like puncta, with the N arm domain and N core region of NP and the C terminus of P playing important roles in this process. In summary, our findings suggest that NDV forms IBs containing viral RNA, and provide insights into the formation of NDV IBs.

Polydopamine-based nanomedicines for efficient antiviral and secondary injury protection therapy

Viral infections continue to threaten human health. It remains a major challenge to efficiently inhibit viral infection while avoiding secondary injury. Here, we designed a multifunctional nanoplatform (termed as ODCM), prepared by oseltamivir phosphate (OP)-loaded polydopamine (PDA) nanoparticles camouflaged by the macrophage cell membrane (CM). OP can be efficiently loaded onto the PDA nanoparticles through the π-π stacking and hydrogen bonding interactions with a high drug-loading rate of 37.6%. In particular, the biomimetic nanoparticles can accumulate actively in the damaged lung model of viral infection. At the infection site, PDA nanoparticles can consume excess reactive oxygen species and be simultaneously oxidized and degraded to achieve controlled release of OP. This system exhibits enhanced delivery efficiency, inflammatory storm suppression, and viral replication inhibition. Therefore, the system exerts outstanding therapeutic effects while improving pulmonary edema and protecting lung injury in a mouse model of influenza A virus infection.

Structure of the Newcastle Disease Virus L protein in complex with tetrameric phosphoprotein

Newcastle disease virus (NDV) belongs to Paramyxoviridae, which contains lethal human and animal pathogens. NDV RNA genome is replicated and transcribed by a multifunctional 250 kDa RNA-dependent RNA polymerase (L protein). To date, high-resolution structure of NDV L protein complexed with P protein remains to be elucidated, limiting our understanding of the molecular mechanisms of Paramyxoviridae replication/transcription. Here, we used cryo-EM and enzymatic assays to investigate the structure-function relationship of L-P complex. We found that C-terminal of CD-MTase-CTD module of the atomic-resolution L-P complex conformationally rearranges, and the priming/intrusion loops are likely in RNA elongation conformations different from previous structures. The P protein adopts a unique tetrameric organization and interacts with L protein. Our findings indicate that NDV L-P complex represents elongation state distinct from previous structures. Our work greatly advances the understanding of Paramyxoviridae RNA synthesis, revealing how initiation/elongation alternates, providing clues for identifying therapeutic targets against Paramyxoviridae.

The matrix protein of Newcastle disease virus inhibits inflammatory response through IRAK4/TRAF6/TAK1/NF-κB signaling pathway

The matrix (M) protein of several cytoplasmic RNA viruses has been reported to be an NF-κB pathway antagonist. However, the function and mechanism of NDV M protein antagonizing NF-κB activation remain largely unknown. In this study, we found that the expression levels of IRAK4, TRAF6, TAK1, and RELA/p65 were obviously reduced late in NDV infection. In addition, the cytoplasmic M protein rather than other viral proteins decreased the expression of these proteins in a dose-dependent manner. Further indepth analysis showed that the N-terminal 180 amino acids of M protein were not only responsible for the reduced expression of these proteins, but also responsible for the inhibition of NF-κB activation and nuclear translocation of RELA/p65, as well as the production of inflammatory cytokines. Moreover, small interference RNA-mediated knockdown of IRAK4 or overexpression of IRAK4 markedly enhanced or reduced NDV replication by decreasing or increasing inflammatory cytokines production through the IRAK4/TRAF6/TAK1/NF-κB signaling pathway. Strangely, there were no interactions detected between NDV M protein and IRAK4, TRAF6, TAK1 or RELA/p65. Our findings described here contribute to a better understanding of the innate immune antagonism function of M protein and the molecular mechanism underlying the replication and pathogenesis of NDV.

Expression and characterization of hemagglutinin-neuraminidase protein from Newcastle disease virus in Bacillus subtilis WB800

Background

Newcastle disease virus (NDV) belongs to the genus Avaluvirus and Paramyxoviridae family, and it can cause acute, highly contagious Newcastle disease in poultry. The two proteins, haemagglutinin neuraminidase (HN) and Fusion (F), are the main virulence factor of the virus and play an essential role in immunogenicity against the virus. In most paramyxoviruses, the F protein requires HN protein to fuse the membrane, and HN proteins substantially enhance the viruses’ fusion activity.

Results

The present study describes the successful cloning and expression of HN protein from NDV in Bacillus subtilis WB800 using the modified shuttle vector pHT43. HN coding sequence was cloned into the pGet II vector. It was then subcloned into the PHT43 shuttle vector and transferred to Escherichia coli for replication. The recombinant plasmid was extracted from E. coli and used to transform B. subtilis by electroporation. After induction of recombinant B. subtilis by IPTG, total cell protein and the protein secreted into the media were analysed through a time course using SDS-PAGE. The expressed HN protein was purified using cation exchange chromatography followed by metal affinity chromatography, using the 6× His epitope introduced at the carboxyl terminus of the recombinant protein. The accuracy of the PHT43-HN construct was confirmed by sequencing and enzymatic digestion. SDS-PAGE results showed that the recombinant HN protein was successfully expressed and secreted into the medium. Moreover, the purified HN protein showed neuraminidase activity with characteristics similar to the indigenous HN NDV protein. B. subtilis is a free endotoxin host that could be a favourite prokaryotic platform for producing the recombinant HN protein.

Conclusion

The establishment of this expression and purification system has allowed us to explore further the biochemical characteristics of HN protein and obtain material that could be suitable for a new production of NDV candidate vaccine with high immunogenicity.

Molecular Mechanisms of Anti-Neoplastic and Immune Stimulatory Properties of Oncolytic Newcastle Disease Virus

Oncolytic viruses represent interesting anti-cancer agents with high tumor selectivity and immune stimulatory potential. The present review provides an update of the molecular mechanisms of the anti-neoplastic and immune stimulatory properties of the avian paramyxovirus, Newcastle Disease Virus (NDV). The anti-neoplastic activities of NDV include (i) the endocytic targeting of the GTPase Rac1 in Ras-transformed human tumorigenic cells; (ii) the switch from cellular protein to viral protein synthesis and the induction of autophagy mediated by viral nucleoprotein NP; (iii) the virus replication mediated by viral RNA polymerase (large protein (L), associated with phosphoprotein (P)); (iv) the facilitation of NDV spread in tumors via the membrane budding of the virus progeny with the help of matrix protein (M) and fusion protein (F); and (v) the oncolysis via apoptosis, necroptosis, pyroptosis, or ferroptosis associated with immunogenic cell death. A special property of this oncolytic virus consists of its potential for breaking therapy resistance in human cancer cells. Eight examples of this important property are presented and explained. In healthy human cells, NDV infection activates the RIG-MAVs immune signaling pathway and establishes an anti-viral state based on a strong and uninhibited interferon α,ß response. The review also describes the molecular determinants and mechanisms of the NDV-mediated immune stimulatory effects, in which the viral hemagglutinin-neuraminidase (HN) protein plays a prominent role. The six viral proteins provide oncolytic NDV with a special profile in the treatment of cancer.