Construction of a recombinant Newcastle disease virus expressing S gene of infectious bronchitis virus.

The S gene(3 534 bp) encoding the spike protein of infectious bronchitis virus(IBV) Massachusetts 41 strain was amplified by RT-PCR with specific primers and cloned into Newcastle disease virus(NDV) infectious clone of pBRN-FL to construct pBRN-FL-IBVS.The recombinant plasmid was transfected,together with helper plasmid,into the BSR cells that had been pre-infected by recombinant fowl poxvirus expressing T7 polymerase.Recombinant virus rL-IBVS was rescued and insertion of S gene in rL-IBVS was verified by RT-PCR.Expression of S protein in BSR cells infected with rL-IBVS was confirmed by indirect immunofluoresence(IFA).The results of MDT,ICPI and IVPI demonstrated rL-IBVS replicated to a titer similar to that of parental NDV LaSota vaccine strain in chicken embryos and retained low pathogenicity of LaSota strain.The recombinant virus constructed by applying reverse genetic techniques could be further developed as a novel live viral vector vaccine against both infectious bronchitis and Newcastle disease.