Immunological characteristics of syncytial virus strain rH5/PR8 generated by reverse genetics system for influenza virus.

Objective To study the immunological characteristics of the syncytial virus strain rH5/PR8 generated by plasmid-based reverse genetics system for influenza virus,and to provide evidence for the immunity,effectiveness,stability,and persistence of the virus as a vaccine candidate.Methods rH5/PR8,an attenuated influenza virus strain,was generated by plasmid-based reverse genetics system.Animal experiment was performed to confirm the immunity,stability,and immune defense of the virus.Results The transfectant influenza virus strains of rH5/PR8 were all generated from A/PR/8/34(PR8)except for HA,which was from highly pathogenic avian influenza virus(HPAIV)H5N1 with the removal of basic amino acid(RKKR)motif in the connecting peptide from 346 to 349.The mean HI titer of antibody from chickens immunized with inactivated rH5/PR8 was over 29 and lasted for 2 months.The immunogen was kept for 2 to 4 months and used in repeated experiments.In repeated experiments,the antibody level was similar,and the effective antibody level lasted for over 7 months after immunized,which indicated that HA5 antigen of rH5/PR8 virus was stable.The immune defense showed that the mortality of the chickens reached 60% in non-immune group,while none died in immune group,suggesting that the immune defense was effective.Conlusion The exogenous gene HA5 from influenza virus rH5/PR8 generated by plasmid-based reverse genetics system has reliable immunogenicity and stable antigenicity.The antibody level can last for a long time,indicating an effective immune defense.