A monoclonal antibody blocking ELISA to detect serotype-specific infectious bronchitis virus antibodies.

A monoclonal antibody (Mab) blocking enzyme-linked immunosorbent assay (B-ELISA) was developed and compared to a conventional indirect ELISA (I-ELISA) and a virus-neutralization (VN) test for detection of specific antibodies to avian infectious bronchitis virus (IBV) serotypes. Sera used in this study were derived from chickens experimentally inoculated with the three most prevalent IBV serotypes, Arkansas (Ark), Connecticut (Conn), and Massachusetts (Mass). Overall, there was good correlation between the results of B-ELISA and the VN test. Both detected serotype-specific antibodies in chicken sera during primary and secondary phases of the immune response. Results of both tests indicated that the antibodies produced during the primary response to IBV serotypes are strongly serotype-specific. Those produced during the secondary response react more strongly with the homologous virus, but do exhibit some level of cross-reactivity with heterologous antigens. I-ELISA detected IBV group-specific and not serotype-specific antibodies. The B-ELISA which both offers the convenience of the conventional I-ELISA and the serotype specificity of the VN test, hold excellent promise for field application in IBV diagnosis and evaluation of response to IBV vaccines.