Obtaining and identifying a mutated and passage-attenuated strain JS18-150 of porcine pseudorabies virus
Pseudorabies is an acute infectious disease of pigs,which is caused by the infection of pseu-dorabies virus(PRV).Pseudorabies is mainly prevented by vaccine,and PRV gene-deleted vaccine is the most widely used and effective.Since 2011,a new outbreak has occurred in many pig farms vaccinated with the Bartha-K61 vaccine and has spread to farms in most parts of the country,causing enormous economic losses to the development of our farms.The study found that the new outbreak was caused by PRV variants and showed that the commercially vaccine did not provide complete protection.Therefore,it is urgent to de-velop a new and efficient PRV vaccine.The prevalent strain JS18 of porcine pseudorabies virus was passaged with chicken embryo fibroblast(CEF)cells to obtain the attenuated vaccine with good safety and high im-munogenicity for mutated strain of porcine pseudorabies virus.JS18-150 strain was obtained.Preliminary studies were conducted on the in vitro growth characteristics,safety,and immunogenicity of JS18-150 strain through PCR identification,sequencing,pathogenicity testing,and immunogenicity testing.The re-sults showed that the gI,gE,and US9 genes of JS18 strain were deleted and the virulence of JS18-150 strain obtained was weakened after continuous passage on CEF.The adaptability on CEF of JS18-150 strain obtained was significantly improved.The growth kinetics of JS18-150 strain obtained was similar to that of the original JS18 strain.No clinical symptoms were observed in all piglets inoculated with 107.0 TCID50 JS18-150 strain obtained,and the rectal temperature did not exceed 40.5℃.Inoculation with 106.0 TCID50 JS18-150 strain obtained effectively protected piglets from the attacks of JS18 strain and HB-ZL05 strain.It is indicated that JS18-150 strain obtained has good safety for piglets and can be used as a candidate strain for the development of attenuated PRV vaccines.
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