Efficacy Of Bartha-K61 Vaccine And A GE~-/gI~-/TK~-Prototype Vaccine Of Variant Porcine Pseudorabies Virus (vPRV) Strain XJ5 For Piglets Against A Sublethal Challenge With VPRV Strain XJ5

Pseudorabies(PR)is a widely-distributed acute infectious disease in livestocK and wild animals caused by Pseudorabies virus(PRV),characterized by fever and itchy(except pigs)in diseased animals.Respiratory and neurological signs are the also common features of PR,and pregnant sows are prone to abortion or stillbirth.So far,there are no effective drugs for treating PR,so one of the effective measures to prevent and control the disease is vaccination intervention.However,vaccination is not an omnipotent strategy.Since 2011,PR has been reemergent in many vaccinated pig populations of China.The reemergent PR has been confirmed to be caused by a Kind of variant PRV(vPRV).with pathogenicity to pigs of all ages.It implied that the partial commercial PR vaccines seem not to protect pigs from vPRV infection,posing a potential threat to the pig industry in China.1.Isolation and identification of a pseudorabies virus isolate and analysis of its selected genesIn early of 2019,an outbreaK of PR befell a pig farm located in Jiangsu province.A vPRV strain,namely vPRV XJ9,was isolated and identified.Five glycoprotein coding genes gE,gC,gI,gD,gB and a virulence gene TK of the strain were amplified and sequenced,the results showed that the tested genes of strain vPRV XJ9 exhibited a minute evolution compared with the vPRV XJ5 strain,which isolated from the same farm in 2014 by our laboratory.It is of significance to trace the vPRV evolution in one pig farm under both field and immune pressure conditions.2.Bartha-K61 vaccine and rPRV-gI-/gE-/TK-vaccine protect pigs from vPRV strain XJ5 sublethal challengeA number of studies have proved that the PR reemergence since the late of 2011 in China is due to the highly pathogenic,antigenic variant PRV(vPRV)strains,and how to prevent and control the recurrence of the disease in China has been put on the agenda.In a previous study,we have proved that a commercial Bartha-K61 vaccine protects growing pigs against lethal challenge with an emerging vPRV strain XJ5.In this study,Bartha-K61 vaccine with different doses(50%tissue culture infectious dose,TCID50),and a prototype rPRY-gI-/gE-/TK-vaccine strain derived from vPRV strain XJ5 constructed in the laboratory were used to evaluate the immune protection effect in growing pigs against a sublethal challenge with the vPRV strain XJ5.Humoral immunity response,clinical signs,body weight,virus shedding and pathology were assessed in commercial pigs.The results showed that the low-doses(103,104 TCID50 per animal)Bartha-K61 vaccine could not effectively against vPRV strain XJ5 sublethal challenge,while the high-dose(105 TCID50 per animal)of either Bartha-K61 vaccine or rPRV-gI-/gE-/TK-prototype vaccine administered pigs could effectively against vPRV strain XJ5-sublethal challenge.In addition,pigs vaccinated with the high-dose of either Bartha-K61 vaccine or rPRV-gI-/gE-/TK-prototype vaccine showed no difference between each other in humoral immune response,clinical symptoms,weight gain,virus shedding and gross or histological lesions after the sublethal challenge with vPRV strain XJ5.Therefore,we can draw a conclusion that the either Bartha-K61 vaccine or rPRV-gI-/gE-/TK-prototype vaccine with a dose of 105 TCID50 exerted a promising protection to pigs against a sublethal challenge with the vPRV strain XJ5,while low doses,e.g.103,104 TCID50 per animal,of Bartha-K61 vaccine were not able to protect pigs against a sublethal challenge with the vPRV strain XJ5.The results of this study provide helpful information in vaccination intervention and ultimate eradication of Pseudorabies caused by the emerging vPRV strains originated in China.