Construction And Protection Of The Classical Swine Fever-vectored Vaccine Based On Human Adenovirus

Classical swine fever(CSF) is a highly contagious disease of swine and wild boar caused by Classical swine fever virus(CSFV) and is listed as a disease by the World Animal Health Organization and the 1st animal disease in China. CSFV E0 and E2 glycoproteins could induce virus-neutralizing antibodies and related to protective immunity; NS3 protein also can induce antibody which didn’t neutralize the virus. However, NS3 protein enhanced specific antibodies of E2 subunit vaccine induced by co-immunizing. Therefore, the three proteins can be used in the study of CSF DIVA vaccine. The CSF DIVA vaccine, which uses HAd V-5 as a viral vector, obtains good immune protective effect in swine. However, the protection of the recombinant adenovirus(r Ad V-E2) which only expressed the glycoprotein E2 was unstable. Some strategies have been adopted to further optimize the efficacy of r Ad V-E2, such as co-expression of E2 and Erns genes, transform vector to chimeric alphavirus replicon to increase the efficiency of adenovirus delivery, or combine with some cytokines that present adjuvant activity.(1)This study is the first to introduce the C terminus of Y. pseudotuberculosis Inv(Inv C) into CSF vectored vaccine and reconstruct a recombinant replication-defective human adenovirus co-expressing E2 and Inv C glycoproteins(r Ad-E2-Inv C). Pigs immunized with r Ad-E2-Inv C were completely protected against lethal challenge. Inv C that acts as an adjuvant could enhance the immunogenicity of r Ad V-E2 and induce high CSFV E2-specific antibody titer and protection level. The r Ad-E2-Inv C could be an alternative to the existing CSF vaccine.(2)This study is the first to introduce the Fms-like tyrosine kinase three-receptor(Flt3) ligand(FL) into CSF vectored vaccine based on HAd V-5(r Ad V-E2-FL) by co-expression with E2 glycoprotein. This work aims to enhance the immunogenicity of the vector vaccine. However, results suggest no significant differences between CSFV E2-specific humoral and cellular immunities in immunization and challenge experiments. Moreover, the protection level between r Ad V-E2 group and r Ad V-E2-FL group(p > 0.05).(3)The three CSF-vectored vaccine based on human adenovirus co-expressing E0, E2, and Inv C; E0, E2, and IL2; E0, E2, and NS3 were constructed and the three genes which expressed respectively were linked by FMDA 2A protein(r Ad V-E0-2A-E2-2A-Inv C, r Ad V-E0-2A-E2-2A-IL2, and r Ad V-E0-2A-E2-2A-NS3). The preliminary results demonstrate that self-cleavage activity of FMDA 2A protein can present and rabbits immunized with these three CSF-vectored vaccines were completely protected against CSFV C strain.In conclusion, the recombinant replication-defective human adenovirus co-expressing E2 and Inv C glycoproteins(r Ad-E2-Inv C) was constructed and its efficacy was evaluated in this present study. The results showed that r Ad-E2-Inv C can induce high CSFV E2-specific antibody titer and protection level in pigs and pigs immunized with r Ad-E2-Inv C were completely protected against lethal challenge. The r Ad-E2-Inv C can be an attractive candidate CSF vaccine. And on this basis, r Ad V-E0-2A-E2-2A-Inv C, r Ad V-E0-2A-E2-2A-IL2, and r Ad V-E0-2A-E2-2A-NS3 were constructed and the three genes expressed by HAd V-5 in each vaccine were linked by FMDV 2A. The results of immunization and challenge in rabbits showed that these three CSF-vectored vaccines were completely protected against CSFV C strain and immune protection experiment of vaccines can be further carried out.