Study On The Protection Efficacy Of Based On Baculovirus Expression System H7 Influenza Vaccine

Since the first outbreak of the novel H7N9 avian influenza virus?H7N9 AIV?,H7N9 posed a tremendous threat to the poultry industry and public health.However,H7N9 epidemic is more serious in poultry industry at September 2016,some reports demonstrated that some H7N9 viruses were lethal to chicken.As a live viral vector for antigen delivery,baculovir us not only could simultaneous induce both an innate immune response and specific immune response by mediating expression of foreign protein,but also satisfied the demand of extensive production in a short time.In this study,two HA gene of H7N9?A/CK/GD/2013?were cloned into downstream of the C MV-IE promote?C MV?in the baculovirus transfer vector to generate pFast-?CHA?₂.Recombinant baculovirus?BV-?CHA?₂?were subsequently generated according to the manufacturer's manual in the Bac-to-Bac?system.Indirect immunofluorescent assay showed that this recombinant baculovirus BV-?CHA?₂ could express HA protein in DF-1 cells.In order to evaluate the Immunogenicity of BV-?CHA?₂,SPF chickens were immunized intramuscularly?i.m.?with 0.5 mL?10⁹ pfu/mL?BV-?CHA?₂,while these in negative control,immunized with wild type baculovirus or PBS via the same route.HA specific antibodies can be detected in the chiekens immunized with BV-?CHA?₂,at 3 weeks following the second immunization.Moreover all chickens in each group were intranasally challenged with 100ul 10⁶ EID₅₀ of A/CK/GD/2013?G1,H7N9?after three weeks following a second immunization.O ropharyngeal and cloacal swabs were taken for detected virus at 3,5,7,9,11 day post infection?dpi?.In BV-?CHA?₂ group,viral shedding was detectable in two of ten chickens and one of ten chickens at 3 and 5 dpi,respectively,while no virus was recovered from the oropharyngeal or cloacal swabs of chickens on day 7 after viral challenge.In the BV-WT group,virus could be recovered from oropharyngeal or cloacal within 9 dpi.However,virus shedding could be detected within 11 dpi in the PBS group.Notably,the viral tier of oropharyngeal or cloacal swabs were significantly lower in C hickens of BV-?CHA?₂ group,when compared to these in BV-WT or PBS group.Therefore,our results suggested that recombinant vaccine,namely BV-?CHA?₂,could prevent systemic replication of the H7N9 AIV,but not completely inhibit virus replication in chickens.To sum up,BV-?CHA?₂ can effectively control viral infection and replication,and induce HI antibody and HA specific antibody in chickens.Thus,the recombinant baculovirus BV-?CHA?₂ might be selected as a candidate vaccine for the control of avian influenza H7N9 virus in poultry.