Safety And Immunogenicity Of The Recombinant Adenoviruses Expressing GP5 And M Protein Of Porcine Reproductive And Respiratory Syndrome Virus In Piglets

Porcine reproductive and respiratory syndrome virus (PRRSV) has been recognized as one very important swine disease. Now the attenuated vaccine and inactivated vaccine were available, but can not provide vaccinated pigs full protection from heterogenous stains. The attenuated vaccine might revert to virulence, and the inactivated vaccine is of questionable efficacy. So the engineer vaccines are being studied in the world. It is known that the major neutralizing epitopes are located on GP5. One neutralizing epitope is also recognized on the envelope protein M. M protein is the most conserve structural protein of PRRSV between American and European isolates. Furthermore, GP5 and M form heterodimers, which is essential for authentic maturation and post-translational modification of GP5. Also, GP5 and M are targets for CD4 T cell response. Human adenoviruses (Ads) have received increasing attention as potential vectors for recombinant viral vaccines. Two replication-defective human adenovirus type 5 recombinants expressing GP5 (rAd-GP5) and M (rAd-M) were constructed previously in our Lab. rAd-GP5 and rAd-M could elicit PRRSV-specific ELISA and NA antibody in mice as described previously. In this paper, we studyed on their biosecurity, immunogenicity and efficacy in piglets.(i) Twelve 30-day-old post-weaning PRRSV-negative piglets were divided into three groups with 4 pigs per group, and bred separately. One group was mock control. Animals of one group were each vaccinated with cell supernatant of rAd-GP5. Animals of another group were each vaccinated with rAd-M in duplicate. Following inoculation, pigs were monitored for general signs, notably fever. Sera samples, nasal swabs and faecal samples of each pig and dirt in each pen were collected on schedule in 3 months post vaccination, as to detecting recombinant adenoviruses and the parental wild type adenovirus by PCR as to evaluate the biosecurity of recombinant adenovirus to pigs and environment. The results were as following: The piglets vaccinated with rAd-GP5 or rAd-M showed no significant clinical syndrome, and blood, nasal scraping, faecal samples and pen environment were all negative against PRRSV and parental Adenovirus by RT-PCR. The results suggest that...