Identification of bluetongue virus type 17 genome segments coding for polypeptides associated with virus neutralization and intergroup reactivity.

Double-stranded (ds) RNA was isolated from either partially purified bluetongue virus (BTV) type 17 or BTV-17 infected cells. The RNA was denatured with either methylmercury hydroxide or dimethyl sulfoxide and translated in a reticulocyte cell-free system. The translation products were found to be similar to BTV-17 specific polypeptides in infected cells when analyzed by polyacrylamide gel electrophoresis and immunoprecipitation with BTV-17 specific polyclonal mouse ascitic fluid. The 10 dsRNA BTV-17 genome segments were resolved by preparative gel electrophoresis and the coding assignment of each segment was determined by translation in a cell-free system. Immunoprecipitation of VP3 from infected cell lysates by a type-specific neutralizing monoclonal antibody identified this polypeptide, which is coded for by genome segment 2, as being involved in virus neutralization. Immunoprecipitation of in vitro translation products directed by total BTV-17 RNA with a monoclonal antibody that reacts with all the serotypes of BTV and some other orbiviruses and precipitates VP7 directly demonstrated that gene segment 8 codes for this intergroup-specific polypeptide.