Isolation And Identification Of H3N2 Subtype Swine Influenza Virus And Evaluation Of Immunological Effect Of Its Inactivated Vaccine

Swine influenza?SI?is an acute,heat,and highly contagious respiratory infection caused by influenza A virus.Its clinical symptoms are characterized by sudden onset,cough,sneezing,salivation,difficulty breathing,fever,exhaustion,loss of appetite and slow growth.The disease has a high incidence and is highly contagious.The mortality rate is not high when it is infected alone,but it can affect the whole population in a short period of time,which has an adverse effect on the growth performance of pigs.If mixed infection with other pathogens,it will increase mortality,cause serious economic losses to the pig breeding industry.At present,the prevention and control of swine flu is mainly carried out by immunization,but there are very few types of swine flu vaccines on the market in China,and the cross protection is not strong.In this study,the domestically popular H3N2 subtype swine influenza virus was isolated,optimized for inactivating agents and adjuvants,and prepared into inactivated vaccines.At the same time,the inactivated vaccine was evaluated for immunological efficacy to provide a safe and effective vaccine.The swine flu inactivated vaccine reduces the economic losses caused by the disease to the pig industry.In this study,13 nasal swabs of pigs suspected of swine flu were collected from a pig farm in Heilongjiang Province.After treatment,they were inoculated into SPF chicken embryos of 10-11days old,and a hemagglutinating virus was isolated.The virus was identified by serological identification,molecular biological identification,electron microscopic observation,biological characteristics and physical and chemical properties.The results showed that the agglutination titer of the isolate against chicken red blood cells was 1:256,and it could only be inhibited by H3.The positive result type was identified by RT-PCR is H3 and N2 subtypes.The virions were spherical under the electron microscope and the diameter was about 80-120 nm.There were capsules on the surface,and there were spikes and fibrils on the surface.The half-infection(EID₅₀)dose of embryos was 10^-6.38EID₅₀/0.1mL;the virus was sensitive to heat,chloroform and ether;from the above studies on the characteristics of the virus,the isolated virus was determined to be the H3N2subtype swine influenza virus.The virus solution for seedling production was prepared by using 10 to 11 days old SPF chicken embryos,and the virus was inactivated with a final concentration of 0.2%diethyleneimine?BEI?,which was emulsified to prepare an oil emulsion inactivated vaccine,and evaluated by serologically and immunologically methods.The challenge method was to evaluate the immune efficacy of the vaccine and determine the immunization period of the vaccine.The results showed that the inactivated vaccine had good immunological efficacy.Compared with the commercially available swine influenza inactivated vaccine,the immunization period was the same,and the immune efficacy of the vaccine was somewhat better than the commercial vaccine.It can be seen that the strain can be used as a high-quality alternative strain for seedling production,laying a foundation for the development of swine flu vaccine.