Flt3 ligand enhanced the immunogenicity of classical swine fever vectored vaccine based on human adenovirus by fusing to the E2 glycoprotein
Li, HelinLin, ZhiLiang, WulongXu, HanZhang, ChengchengCao, ZhiZhang, Yanming
Background: Classical swine fever (CSF) is a highly contagious disease of domestic pigs and wild boar. CSFV E2 protein is the major target for neutralizing antibodies and the main component of marker vaccine. CSF vaccine based on human adenovirus type 5 (HAdV-5) had achieved an efficient protection in swine. However, the efficacy of rAdV-E2 only expressed the E2 glycoprotein was unstable. As a vaccine adjuvant, FL has been proven to enhance the immune effect, and its extracellular domain retained full biological activity. The adjuvant activity of the porcine Flt3L (the extracellular domain) in CSF vectored vaccine based on HAdV-5 was investigated.Materials, Methods & Results: The FL (the extracellular domain) was linked to the CSFV E2 (N-terminus) by a 10GS (Gly4/Ser) linker. The rAdV-FL-E2 based on HAdV-5 was constructed and the FL-E2 protein expressed in 293 cells infected with rAdV-FL-E2 was confirmed by Western blot with the use of anti-CSFV serum. Twelve CSFV-free cross-bred piglets, which were 6 to 7 weeks old and double confirmed to be free to CSFV specific serum antibodies and antigens using the IDEXX HerdChek* CSFV Antibody Test Kit and real-time RT-PCR, respectively, and were randomly divided into four groups (A, B, C, and D) with three animals in each group. Groups A and B were vaccinated with a dose of 2×106 TCID50 of rAdV-FL-E2, and rAdV-E2 by intramuscular (i.m.) inoculation respectively. All pigs were given a booster immunization at 14 d intervals. Group C was immunized with one-dose CSFV C-strain vaccine and served as the positive control. Group D was injected with DMEM medium. Finally, all animals were challenged with 1×103 TCID50 of CSFV Shimen strain by i.m. injection at 21 d after the second vaccination. CSFV-specific neutralizing antibodies in sera were tested by using the IDEXX HerdChek* CSFV Antibody Test Kit and NPLA.[ ](AU)
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