A monoclonal antibody-based antigen capture enzyme-linked immunosorbent assay for identification of infectious bronchitis virus serotypes

An antigen-capture enzyme-linked immunosorbent assay (C-ELISA) was developed for detection and identification of infectious bronchitis virus (IBV) serotypes Arkansas, Connecticut, and Massachusetts using monoclonal antibodies (MAbs) specific to the S1 glycoprotein of the respective serotype. The assay (designed as a double-antibody sandwich assay) gave the best results when the S1-specific MAb, antigen, and chicken serum were of the same serotype. However, when a group-specific (M glycoprotein-specific) MAb was used for antigen capture, a distinctive pattern of cross-reactivity was observed between the antigens and heterologous chicken sera, suggesting a complex distribution of epitopes on the IBV M glycoproteins. Treatment of antigen with NP40 enhanced the ELISA signal only when the M glycoprotein-specific MAb was used for antigen capture. Although C-ELISA was inconsistent in detecting IBV in chicken tissue homogenates, it was highly effective in detecting the virus in allantoic fluid after the homogenates were given one chicken embryo passage.