Biological activity of syncytial virus rH5/PR8 generated by reverse genetics system for influenza virus.

Objective To investigate the biological activity of the syncytial virus strain rH5/PR8 generated by reverse genetics system for influenza virus,and to provide evidence for the availability and effectiveness of the virus as a vaccine candidate.Methods rH5/PR8,an attenuated influenza strain,was generated by plasmid-based reverse genetics system.The sequences of virus HA were detected to confirm the genetic stability.The proliferative ability was determined by cell experiment,and the pathogenicity was identified by animal experiment.Results The transfectant influenza virus strains of rH5/PR8 were all generated from A/PR/8/34(PR8)except for HA.HA was from highly pathogenic avian influenza virus(HPAIV)H5N1,with a base substitution from G to C at position 1050 which resulted in alteration of arginine at position 344 to threonine and with the removal of bases from position 1054 to 1065 which resulted in the removal of basic amino acid(RKKR)motif in the connecting peptide from 346 to 349.The proliferative ability of the virus reached 109 PFU/ml,and the exogenous gene HA5 was stable,suggesting that it can be used as a vaccine candidate.Inoculation of the live virus induced weak toxicity in chickens.Conclusion The syncytial virus strain rH5/PR8 generated by reverse genetics system for influenza virus has high proliferative activity and genetic stability.Removing the consecutive basic amino acids in HA by gene splicing can reduce the pathogenicity of the virus and induces weak toxicity in chickens.