Assess The Specific Immune Response Induced By NA Antigen Vaccination After Influenza Virus Infection

Influenza outbreaks every year seriously threaten global health security,causing serious economic losses and casualties.Influenza vaccination is still the most effective way to prevent influenza virus infection.Clinical studies have shown that vaccination with traditional inactivated influenza virus vaccine induces weaker neuraminidase specific antibody response.However,the level of neuraminidase inhibitory antibody induced by influenza virus infection is closely related to the clinical immune protection efficacy.One of the main research directions of this group is the development of a broad-spectrum influenza vaccine based on influenza A virus neuraminidase.In order to optimize the immune program for the induction of broad-spectrum antibodies to neuraminidase,this project tried to study the effect of influenza A virus infection in the early stage on the broad-spectrum immune response induced by influenza A virus neuraminidase immunogen in the later stage through in vivo experiments.The trial protocol was designed to inoculate a small amount of A/Hong Kong/1/1968(H3N2)intranasally before inoculation with recombinant protein,determine the serum specific lg G titer and infect 8×LD 50 A/Guizhou/54/1989(H3N2)after the second protein immunization hetero geneous influenza A virus,daily observation and recording of changes in body weight and survival.This research work aims to analyze how the previous influenza A virus infection affects the intensity and broad spectrum of the immune response induced by ne uraminidase immunogen in the later stage.We successfully constructed p Fastbac Dual-N2 and p Fastbac Dual-N9 recombinant plasmids,and successfully expressed N2 and N9 recombinant proteins through the insect expression system,and successfully amplified A/ Hong Kong/1/1968(H3N2)and A/Guizhou/54/1989(H3N2)by the chicken embryo amplifying method.Two influenza A viruses were tested for LD 50 virulence through animal experiments.The experimental results show that the previous influenza virus infection can enhance the specific antibody titer and cross-reactivity induced by the recombinant neuraminidase protein.The lethal dose of H3N2 mice challenge experiment results show that the early influenza A virus infection has a protective effect on the later infection of mice with A/Guizhou/54/1989(H3N2)influenza virus,which not only improves the survival rate of mice,but also effectively slows down the weight loss of mice.