Association of bluetongue virus with the cytoskeleton.

Analysis of the distribution of [35S]methionine-labeled virus proteins following lysis of bluetongue virus (BTV)-infected cells with nonionic detergents showed that a major proportion of the virus-specific proteins was located in the insoluble nuclear-cytoskeletal fraction. Neither the proportion nor the species of virus protein associated with the cytoskeleton was altered following treatment of infected cells with microtubule or microfilament disrupting drugs (colchicine and cytochalasin B, respectively). Electron microscopic examination of BTV-infected cells revealed cytoplasmic virus-specified tubules, viral inclusion bodies (VIB), and progeny virus particles. Whole-mount transmission electron microscopy of nonionic detergent-extracted cells demonstrated the association of VIB, virus particles, and tubules with the cytoskeleton. The identity of virus particles was confirmed with an immunogold labeling technique using a neutralizing monoclonal antibody to BTV protein VP2. Several lines of evidence indicate that virus particles, VIB, and tubules bind to intermediate filaments in BTV-infected cells. These structures remained cytoskeleton associated in infected cells treated with colchicine or cytochalasin B. Linear arrays of filament-associated virus particles were formed around VIB following colchicine-induced juxtanuclear aggregation of intermediate filaments. Virus particles were associated with filaments approximately 10 nm in diameter. Filaments associated with virus particles reacted with an anti-vimentin monoclonal antibody in an immunogold labeling procedure.