Development of a latex agglutination test for detecting antibodies against avian influenza virus based on matrix 1 protein expressed in vitro.

The matrix 1 (M1) gene, present in all subtypes of avian influenza virus (AIV), was cloned and expressed in Escherichia coli. Reactivity of the expressed protein was confirmed by western blot. Subsequently, the M1 gene expression product was purified and used as the antigen to develop a latex agglutination test (LAT) for detecting antibodies against these conventional subtypes of AIV including AIV H3, H5, H7, and H9 from chicken sera. The LAT is specific for AIV, and no cross-reaction was shown with chicken antisera against other avian viruses. Compared with the hemagglutination inhibition test, the corresponding specificity, sensitivity, and correlation were 95.7%, 88.7%, and 89.0%, respectively, in detecting 491 serum samples from vaccinated chickens.