ANTIGEN-CAPTURE ENZYME-IMMUNOASSAY FOR DETECTION OF AVIAN INFLUENZA-VIRUS IN TURKEYS

A double-antibody sandwich ELISA (DAS-ELISA) was developed for detecti on of avian influenza virus (AIV) antigen. A monoclonal antibody to th e viral nucleoprotein (NP) was used to coat the ELISA plates. A direct DAS-ELISA and an indirect DAS-ELISA were evaluated. In the direct DAS -ELISA, monoclonal antibody to the AIV NP conjugated with horseradish peroxidase was used. The direct DAS-ELISA was evaluated for its sensit ivity to detect purified NP; this procedure detected as little as 0.1 ng. In the indirect DAS-ELISA, rabbit NP antibody and horseradish pero xidase-conjugated goat anti-rabbit immunoglobin were used as primary a nd secondary antibodies, respectively. The indirect DAS-ELISA WaS eval uated for its ability to detect the AIV antigen in tracheal and cloaca l specimens from turkeys inoculated with AIV. Results of indirect DAS- ELISA were compared with those of conventional virus isolation. Percen tage agreement between indirect DAS-ELISA and virus isolation in AIV-p ositive samples was found to be 76.1% and, in AIV-negative samples, it was found to be 82.1%. These results indicate that the DAS-ELISA migh t bc a viable alternative to virus isolation because of its rapidity, compared with virus isolation.