EVALUATION OF COMMERCIAL INFECTIOUS BRONCHITIS VIRUS ENZYME-LINKED IMMUNOASSAY KITS

In Taiwan, infectious bronchitis virus (IBV) is mainly restricted to two groups Taiwan Group I (TW-I) and Taiwan Group II (TW-II) that are distinct from other countries. To evaluate the reliability of commercial enzyme-linked immunosorbent assay (ELISA) kits, imported commercial test kits (namely, A, B and C) were used to test field samples. The results were further compared with hemagglutination inhibition (HI) test to figure out the consistency. Results showed that the three commercial ELISA kits had only partial consistency with HI results. In fact, testing results of breeders and layers bore resemblance to HI, whereas there were ELISAs negatively detecting results of broilers opposed in HI. The specificities of these ELISA kits were 0.45, 0.86 and 0.77 for kits A, B and C, respectively, and their sensitivities were 0.79, 0.68 and 0.70, respectively. The commercial ELISA kits may not sustainably provide us the whole view of birds infected or vaccinated status. Based on the results of in-house ELISA and western blot, different IBV strains showed different antigen–antibody interaction. Thus, different ELISA coatings with different antigens might result in different antibody titers. Furthermore, according to HI results, 91% (256) and 70% (198) of the 282 tested sera were positive to H120 (as a Massachusetts vaccine) and 3263/04 (as a field strain), respectively. These high positive rates indicate that in spite of popular use of Massachusetts vaccines, the chickens are still commonly infected with field IBVs in Taiwan.