The properties of two recent isolates of cytoplasmic polyhedrosis viruses.

Cytoplasmic polyhedrosis viruses (CPVs) were isolated from laboratory cultures of Bombyx mori and Spodoptera exempta. The electrophoretic profile of the RNA segments of both viruses showed similarities with that of type 1 CPV. However, whereas the virus isolate from B. mori appeared identical to type 1 CPV (as assessed by serology, as well as the comparative mobilities of RNA segments and structural polypeptides), the isolate from S. exempta was distinct. Three of the ten viral RNA segments did not co-run with type 1 RNA, and the structural polypeptides of polyhedra had different molecular weights. It is proposed that the S. exempta isolate be included as a new 'type' (type 12) in a classification of these viruses.