Abstract:The recombinant transfer plasmids pSXIVVI +X3 S1.Holte and pSXIVVI +X3/4 S1.Holte and pAcGHLT C S1.Holte were constructed by insertion of the cDNA of the S1 gene of avian infectious bronchitis virus (IBV) into transfer vector plasmids pSXIVVI +X3 and pSXIVVI +X3/4 and pAcGHLT C.