Genetic variations on 31 and 450 residues of influenza A nucleoprotein affect viral replication and translation

Abstract

Background: Influenza A viruses cause epidemics/severe pandemics that pose a great global health threat. Among eight viral RNA segments, the multiple functions of nucleoprotein (NP) play important roles in viral replication and transcription. Methods: To understand how NP contributes to the virus evolution, we analyzed the NP gene of H3N2 viruses in Taiwan and 14,220 NP sequences collected from Influenza Research Database. The identified genetic variations were further analyzed by mini-genome assay, virus growth assay, viral RNA and protein expression as well as ferret model to analyze their impacts on viral replication properties.Results: The NP genetic analysis by Taiwan and global sequences showed similar evolution pattern that the NP backbones changed through time accompanied with specific residue substitutions from 1999 to 2018. Other than the conserved residues, fifteen sporadic substitutions were observed in which the 31R, 377G and 450S showed higher frequency. We found 31R and 450S decreased polymerase activity while the dominant residues (31 K and 450G) had higher activity. The 31 K and 450G showed better viral translation and replication in vitro and in vivo.Conclusions: These findings indicated variations identified in evolution have roles in modulating viral replication in vitro and in vivo. This study demonstrates that the interaction between variations of NP during virus evolution deserves future attention.

Genetic insertion of mouse Myxovirus-resistance gene 1 increases innate resistance against both high and low pathogenic avian influenza virus by significantly decreasing replication in chicken DF1 cell line

“…Another difference was at position 450 in NP, the 2.3.4.4b viruses contained a serine (S), while the other viruses contained an asparagine (N). Position 450 is considered variable among IAV strains, avian isolates typically contain a S or N, whereas human/mammalian strains contain a glycine (G) [39, 40]. Unexpectedly, there were no differences in the PB2 protein.…”

Impact of patient characteristics on innate immune responses and inflammasome activation in ex vivo human lung tissues infected with influenza A virus

“…CD, cluster of differentiation; EpCAM, epithelial cell adhesion molecule; HLA-DR, human leukocyte antigen-DR; IFN-g, interferon-gamma; IL, interleukin; NP, nucleoprotein; PD-1, programmed death 1; PD-L1, programmed death-ligand 1; TLR, toll-like receptor; TNF-a, tumor necrosis factor-alpha. Hung et al, 2020), we strategically chose to employ flow cytometry for the identification of IAV NP, PD-L1, and TLR1-3 in this research. However, the implementation of Western blotting or quantitative PCR is indispensable for the accurate quantification of protein and mRNA levels of NP, PD-L1, and TLR1-3 in T-cells, macrophages, and epithelial cells, facilitating a more comprehensive understanding of host responses (Zhang Q. et al, 2020).…”

Improvement of PR8-Derived Recombinant Clade 2.3.4.4c H5N6 Vaccine Strains by Optimization of Internal Genes and H103Y Mutation of Hemagglutinin

“…As we were not able to compare the cellular immunity induced by the rH5N6-310PB2 and rH5N6-IG vaccinations, we will confirm the roles of the predicted CD8+ T cell epitopes for NP and the induction of specific CD8+ T cells in further studies. Due to the complicated interactions of NP with PB1 and PB2 and of M1 with viral ribonucleoprotein and viral transmembrane proteins (HA, NA and M2), optimal NP and M genes need to be selected for better viral fitness of vaccine strains [ 34 , 35 , 36 , 37 ]. For this reason, we have not been able to optimize M genes to match CD8+ T cell epitopes in M1 or a B cell epitope in M2e at this time.…”