Conformationally dependent epitopes of bluetongue virus neutralizing antigen.

The neutralizing epitopes of Bluetongue virus serotype 17 (BTV 17) were evaluated by virus neutralization assay, flow cytometry, radioimmuno-precipitation, and Western blot. We showed that neutralizing monoclonal antibodies (MABs) raised to BTV 17 bound to viral proteins on intact virus when examined by virus neutralization and by an indirect binding assay analyzed by flow cytometry. In contrast, when the viral proteins were solubilized, a loss in reactivity with some of the neutralizing MABs was observed. Additionally, when the viral proteins were subjected to denaturing conditions, none of the neutralizing MABs reacted with the viral proteins. The results indicate that these neutralizing MABs bind conformationally dependent epitopes.