Recombinant Newcastle disease virus expressing the infectious bronchitis virus S1 gene protects chickens against Newcastle disease virus and infectious bronchitis virus challenge

The recombinant LaSota strain expressing a chimeric IBV S1 gene (rLaSota-S1) was constructed with the S1 gene of the LX4 type IBV ck/CH/LDL/091022. The expression of the S1 protein was detected by an indirect immunofluorescence assay and Western blotting. The rLaSota-S1 strain was slightly attenuated, and its growth dynamics were similar to that of the parental LaSota strain. Vaccination of specific pathogen-free chickens with the rLaSota-S1 strain induced NDV hemagglutination inhibition antibodies, and it protected chickens from challenge with virulent NDV. In addition, vaccination with the rLaSota-S1 strain induced IBV-specific IgG antibodies and cellular immunity; however, a single vaccination provided partial protection with reduced virus shedding. Better protection efficiency was observed after a booster vaccination, which resulted in higher antibody titers, significantly fewer disease symptoms, and reduced virus replication and shedding. Our results suggest that the rLaSota-S1 strain is a bivalent vaccine candidate against both NDV and IBV.