Immunoprecipitation of a 50-kDa protein: a candidate receptor component for tomato spotted wilt tospovirus (Bunyaviridae) in its main vector, Frankliniella occidentalis

A 50-kDa protein that binds to viral particles in solid-phase assays and that is recognized by anti-idiotypic antibodies made against anti-viral glycoproteins G1/G2 (anti-Ids) has been proposed as a receptor candidate for tomato spotted wilt tospovirus (TSWV) in its main thrips vector, Frankliniella occidentalis Pergande (Bandla et al., 1998. Phytopathology 88, 98–104). Here we show the immunoprecipitation of the 50-kDa protein by anti-Ids and by an anti-G1/G2-TSWV conjugate — a new immunoprecipitation method. In addition, we show that anti-Ids made against anti-G1 (anti-IdG1) block virus replication in an insect tissue replication assay. The results indicate that (a) the TSWV–50-kDa protein interaction occurs in solution, as it must do in vivo; (b) G1 is a viral attachment protein; and (c) the 50-kDa protein is a candidate host factor essential for TSWV entry. These results provide additional support for the role of the 50-kDa thrips protein as a viral receptor. Additionally these experiments provide the basis for testing saturable binding and represent an important step toward the first cloning and identification of a cellular receptor for a plant virus.