Molecular characterization of Borna virus RNAs

Borna disease virus is cell-associated in infected animals. Antibodies in animals are directed against BDV proteins of 38/39, 24, and 14.5 kD. cDNA clones that encode these proteins hybridize to five mRNAs of 10.5, 3.6, 2.1, 1.4, and 0.85 kb. The 10.5, 3.6, 2.1, and 0.85 kb RNAs are 3' co-terminal; the 1.4 kb RNA is contained within the 10.5, 3.6, and 2.1 kb species but is not 3' co-terminal. A negative strand 10 kb RNA is also present in infected cells. To determine which of the large 10 kb species represents the genomic RNA, strand-specific probes were used for Northern analyses of RNA from infectious particles isolated by Freon extraction of BDV-infected rat brain. RNA purified from these particles contained both positive and negative sense 10 kb species. Treatment of particles with RNaseA before isolation of RNA resulted in detection of only negative strand species, suggesting that BDV is a negative strand RNA virus. However, the genomic organization of BDV is unlike any known negative strand RNA virus.