Preliminary Study on Expression Infectious Bronchitis Virus Level of the S1 Gene of Avian in a Baeulovirus System

The recombinant transfer plasmids pSXIVVI\++X3 S1.Holte and pSXIVVI\++X3/4 S1.Holte containing S1 gene cDNA of avian infectious bronchitis virus and the parent virus (TnNPV SVI -G) DNA were used to co transfect \%Spodotera frugiperda\% (Sf) cells. The recombinant viruses TnNPV (X3)S1.Holte OCC + and TnNPV (X3/4)S1.Holte OCC +, which included the S1 gene and could form polyhedra, were plaque purified. The expression products of S1 gene were detected by SDS PAGE and Western blotting in Tn 5B1 cells infected with the recombinant viruses. The S1 protein with a molecular weight of 100 kD was expressed in the cells infected with TnNPV (X3/4)S1.Holte OCC + at high efficiency, the expression level in Tn 5B1 cells 72 h postinfection being 35.8% by SDS PAGE gel thin layer chromatography. No expression product was detected by SDS PAGE and Western blotting in Tn 5B1 cells infected with TnNPV (X3)S1.Holte OCC +. The expression level depends mainly upon the translational start site of the S1 gene