Butyrate increases type-A and type-R virus-like particles in BKV-transformed hamster spleen cells

A cell line derived from hamster spleen transformed by human papovavirus BK was adapted to grow in 5 mM butyrate. Ultrastructurally, the butyrate-adapted cells were found to contain large numbers of type-R and intracytoplasmic type-A virus-like particles (VLP). In contrast, the unadapted cells contained only rare VLP. Treatment of the unadapted cells with nontoxic and toxic concentrations of butyrate for 24 and 48 hr failed to induce VLP, indicating the importance of butyrate adaptation in the induction of VLP. The increase in type-R VLP was stable after removal of the adapted cells from butyrate; however, the increase in type-A VLP was not.