Studying On Bioreactor Preparation And Establish A Mouse Model Of Recombinant Adenovirus Vaccines Against EU-type PRRSV

Procine reproductive and respiratory syndrome(PRRS)was first reported in China in the 1990 s,and its pathogen was confirmed be NA-type PRRSV.Up to now,it is still one of the major diseases affecting China’s pig breeding industry.The highly pathogenicNA-type PRRSV and its variants have taken a large proportion in Chinasince the outbreak.In recent years,the EU-type PRRSVhas been isolated from thePRRS in placeslike Beijing,Hong Kong and Inner Mongolia as it is no longer restricted by region,resulting in the increasing difficulty inChina’s prevention and treatment of PRRS.Currently,there is no vaccine specifically developed for the EU-type PRRS in China.In this study,the European-type PRRS recombinant adenovirus vaccine constructedin our laboratory was tested,and the candidate vaccines for EU-type PRRS recombinant adenovirus were amplified by bioreactor microcarrier culture system.The efficacy of the candidate vaccines were tested by animal substitutemodel and serology substitute experiment.The construction of EU-typePRRSrecombinant adenovirusrAd-E35-IL-18 was proved to be correctusingWestern blot,PCR,indirect immunofluorescence and electron microscopy.Bioreactor was applied to the culture of HEK293 cells and amplify the EU-type PRRS recombinant adenovirusrAd-E35-IL-18,so as to verify the optimal parameters.HEK293 cells were growing at a higher speed during 36-60 h.In order to accelerate its growth,DMEMculture solution was refreshedat 36 h.The cells almost covered the surface of microcarrier after 84 h,and then the growth showed a downtrend.Virus titer was performed at virus solution sampled at 12 h,24h,36 h,48h,60 h and 72 h,the results of which indicated a high virus titerat 60 h.The recombinant adenovirus candidate vaccine rAd-ORF3-ORF5-IL-18 was used to perform immunogenicity test,challenge test,as well as viral load test on mice and pigs,which primarily proved that mice could be used as a substitute model for pigs.On the basis of the mice substitute model,mice and pigs were subjected to recombinant adenovirus gradient inoculation to detect the level of cytokines and neutralizing antibodies in immunized animals.Challenge test was performed in the immunized animals to further verify the feasibility of using mice as the animal substitute model for thecandidate vaccineof recombinant adenovirus.Specific antibody was obtained to determine theimmune response potency of vaccine orresponding to each gradient.Mice could be preliminary used as the standard for vaccine test when the level of PRRSV antibody reached over 1: 682.7.