Topology of bovine rotavirus (RF strain) VP6 epitopes by real-time biospecific interaction analysis

An automated biosensor system designed for measuring molecular interactions in real-time (BIAcore) was used to characterize monoclonal antibodies (Mabs) raised against the inner capsid protein (VP6) of the bovine rotavirus (RF strain). Six Mabs, all reactive in Western blot and in indirect immunofluorescence assays, were mapped, using purified recombinant VP6. These Mabs were delineated into several groups of antibodies. Interactions of selected monoclonal antibodies with purified viral particles were studied by the BIAcore methodology. We showed that some Mabs did not react with single-shelled particles. Conversely, several Mabs reacted with single-shelled particles and one antibody reacted with both single-shelled and double-shelled particles. The latter Mab seemed to interact with VP6 through the holes of the outer capsid and its interaction with the double-shelled particles induced a significant decapsidation. These results allowed a better characterization of the epitopes of VP6. The localization of the epitopes in the viral particle is discussed in comparison with a pepscan study that determined the reactivity of Mabs with nested heptapeptides derived from the whole VP6 molecule.