The nucleocapsid (N) gene of infectious bronchitis virus (IBV) strain X isolated in Chinawas expressed in E. coli and was purified as a recombinant protein. An indirect ELISA assay (N-ELISA) for antibody detection was established using the purified recombinant nucleocapsid protein. Antigen coating conditions and serum dilution for the N-ELISA were optimized. The S/P ratio of the absorbency value was calculated in the N-ELISA to evaluate the antibody level of chicken serum. In an experiment to test field samples for antibody detection, the N-ELISA assay shared 95.7% identity of total positive ratio with the commercial ELISA kit. It indicated that the N-ELISA assay, which was safer and easier to prepare than traditional methods, was a good candidate for evaluation of IB vaccine efficiency and virus exposure.
Recombinant nucleocapsid protein is potentially an inexpensive, effective serodiagnostic reagent for infectious bronchitis virus