Two single mutations in the fusion protein of Newcastle disease virus confer hemagglutinin-neuraminidase independent fusion promotion and attenuate the pathogenicity in chickens

Authors: JI, YANHONG - Chinese Academy Of Agricultural Sciences; LIU, TAO - Chinese Academy Of Agricultural Sciences; LIU, BIN - Chinese Academy Of Agricultural Sciences; Yu, Qingzhong; CUI, XIAOLE - Chinese Academy Of Agricultural Sciences; GUO, FENGFENG - Chinese Academy Of Agricultural Sciences; CHANG, HUIYUN - Chinese Academy Of Agricultural Sciences; ZHU, QIYUN - Chinese Academy Of Agricultural Sciences

Submitted to: Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/15/2017
Publication Date: 6/21/2017
Citation: Ji, Y., Liu, T., Liu, B., Yu, Q., Cui, X., Guo, F., Chang, H., Zhu, Q. 2017. Two single mutations in the fusion protein of Newcastle disease virus confer hemagglutinin-neuraminidase independent fusion promotion and attenuate the pathogenicity in chickens. Virology. 509:146-151. https://doi.org/10.1016/j.virol.2017.06.021.
DOI: https://doi.org/10.1016/j.virol.2017.06.021

Interpretive Summary: Virulent strains of Newcastle disease virus (NDV) are the causative agents of Newcastle disease (ND), affecting a wide variety of birds and causing significant economic losses to the poultry industry worldwide. The fusion (F) protein of NDV plays an important role in viral infection and virulence by mediating membrane fusion between the virion and host cells. The fusion event usually requires a support from another viral protein, the hemagglutinin-neuraminidase (HN), to be occurred. In this study, we identified two single amino acid mutations (T458D and G459D) in the F protein of a virulent NDV mutant that increased the fusion activity of the virus with or without the help of HN, and reduced the virulence of the virus in chickens. These findings will be useful for understanding of the role of membrane fusion in virulence of NDV, and for developing more efficacious vaccines to control of the disease.

Technical Abstract: The fusion (F) protein of Newcastle disease virus (NDV) plays an important role in viral infection and pathogenicity through mediating membrane fusion between the virion and host cells in the presence of the hemagglutinin-neuraminidase (HN). Previously, we obtained a velogenic NDV genotype VII mutant with highly increased fusogenic activity. Sequence analysis identified two mutations (T458D and G459D) in the F protein of the virus. In this study, we generated the F protein expression clones and recombinant viruses bearing one of these two mutations using reverse genetic technology to investigate whether the mutations in F affect the fusogenicity of the virus. Syncytium formation assays showed that T458D or G459D mutation increased the F protein cleavage activity and significantly enhanced cell fusion with or without the presence of HN protein in either avian or mammalian cell lines. The T458D or G459D mutation in the rescued NDV mutants resulted in a decrease in virus replication or release from BHK-21F cells. The animal study showed that the pathogenicity of the mutated NDVs was attenuated in chickens. These results indicate that these two single mutations in the F protein of NDV altered or diminished the requirement of HN for promoting membrane fusion. The highly increased fusogenic activity resulted from the F mutations may disrupt the cellular machinery and consequently decrease the virus replication and pathogenicity in chickens.