Screening And Immunogenicity Analysis Of Avian Reovirus Vaccine Strains

Chicken viral arthritis is an avian infectious disease caused by avian reovirus(ARV).In recent years,it has been on the rise in China,and the variability of strains is large.The traditional vaccine strains are not ideal for protection.Therefore,it has caused great economic losses to the poultry industry in China.This experiment separates the pathogens of suspected reovirus-infected chickens collected from poultry farms in Shandong,Henan,Hebei,Liaoning and other provinces from the first half of 2017 to the first half of 2018 by inoculation of sensitive cells and chicken embryos.RT-PCR,FA,EM and other methods are used to study the biological characteristics of the isolated ARV strains,and explored the hemagglutination of ARV isolates and their pathogenicity to LMH,CEF cells,SPF chicken embryos and chicks.The animal regression test are used to compare the virulence of each isolated strain and the detoxification period after challenge.The protective effect of the traditional vaccine strain on the newly isolated strain was verified by immunoprotection test.The physical and chemical properties of each isolate are verified by physical and chemical tests.The vaccine strains are screened from the isolates by comprehensive test results,and the virus-inactivated vaccines are prepared by proliferating the virus solution through the CEF cells.The selected vaccine strains are compared with the traditional vaccine strains,and SPF chickens were used for the immunological challenge protection test.The immunogenicity of the two viruses are analyzed and evaluated from the antibody level after immunization and the results of the challenge protection test.1 The isolation,identification and biological characteristics of the isolated avian reovirusSix strains of ARV are successfully isolated from the tissue materials.The results shows that all of the strains have no hemagglutination.The EM observation virions ranges from 70 to 80 nm.The isolated strains are specifically recognized by ARV monoclonal antibody and show strong positive signal;the isolated strains can proliferate on LMH and CEF cells,but LMH cells are more sensitive to them;all isolate strains can cause test chicken to appear symptoms after challenge in animal regression test,but the virulence is different.The cloaca swabs were used to detect the detoxification of some isolates after challenge.The results shows that infectious virions can be detected from the feces after 24 hours of challenge and the first week after challenge is the peak of virion detachment.In the second week,the amount of fecal detoxification are significantly reduced,and the detoxification period of some strains can last for more than 2 weeks.The results of physical and chemical tests showed that the strains are not sensitive to chloroform,mildly sensitive to pancreatic enzymes,and have good heat resistance.The treatment at 50℃ for 1 h has no significant effect on the virus titer of each strain,and the physical and chemical characteristics are in accordance with ARV characteristics.The results of immunoprotection test show that the traditional vaccine can not treat 6 strains of ARV.Finished Protection.At the same time,the virulence strains of RPVA1306 and RPVA1307 are significantly different from the control group and the incidence is more serious,which is more valuable than other isolates.The results verify the pathogenicity of the isolates and enriched the ARV strain library,which confirmes that the traditional vaccine can not protect the newly isolated strains and provides a theoretical basis for the development of new ARV vaccines.2 Preparation and immunogenicity analysis of inactivated ARV vaccineA variety of ARV vaccines have been used in the prevention of ARV in domestic and foreign markets,but the incidence of viral arthritis remains high in clinical practice.In this experiment,two strains of virulence strains RPVA1306 and RPVA1307 are screened by measuring the TCID50 and ELD50 of each isolated strain of ARV,combining with the results of animal regression and immunoprotection test,and the oil emulsion inactivated vaccine is prepared by cell proliferation.Compared with traditional vaccine strains,self-made vaccines were used for immune challenge protection test.After immunization,the immunogenicity of the two viruses is analyzed and evaluated from the antibody level and the challenge protection test results.The results shows that the two isolates have the best protective effect on the original strains,and the protection rate of RPVA1306 on both isolates could reach more than 80%,and the immune effect is ideal.