Evaluation of specific chicken IgY antibody value developing diagnostic capture antibody ELISA kit against Foot and Mouth disease

The most preferred method for the detection of foot-and-mouth disease (FMD) viral antigen and identification of viral serotype is the enzyme-linked immunosorbent assay (ELISA). Diagnostic tests with high sensitivity are necessary both to distinguish infected vaccinated animals and execute disease control programs for the identification of the carrier animals. The current strategies for the detection of FMD virus are mainly based on the capture antibody (sandwich) ELISA test. The usage of laying pullets as an animal bioreactor for the production of specific egg yolk antibodies (IgY) has increased in recent years due to its high yield, affinity, low price, and quick production turnover. The present study aimed to produce a concentrated and purified IgY polyclonal antibody to design a capture antibody ELISA kit against the FMD virus (FMDV) serotype A. At first, laying hens were immunized with inactivated FMDV serotype virus, and then, on days 14, 21, and 28 following vaccination, the eggs and sera were collected. Afterward, the IgY polyclonal antibodies were extracted and purified from the chicken egg yolk using a polyethylene glycol 6000-ethanol precipitation procedure. Extracts were filtered, purified by ion exchange chromatography, and dialyzed. The purified IgY concentration, estimated by Bradford assay, confirmed its presence by SDS-PAGE and Western blot and also its specific immune reaction by Ouchterlony double immunodiffusion and Dot blot tests. Moreover, for achieving the optimum concentration of antigen/antibody (sera) in sandwich ELISA, a checkerboard titration test was set up based on indirect ELISA results. Eventually, 119 previously confirmed samples (including 80 positive and 39 negative) by both real-time polymerase chain reaction (quantitative PCR, qPCR) and a commercial ELISA kit were used for evaluation of the sensitivity and accuracy of our developed Capture antibody ELISA kit. In this manner, the sensitivity and specificity of our designed kit were 100% and 98%, respectively. Accordingly, the present developed capture ELISA kit based on IgY had high sensitivity and specificity for FMD virus detection and it could be used in the future for both commercial detecting and serotyping applications.