CHARACTERIZATION OF TOSCANA VIRUS DEFECTIVE INTERFERING PARTICLES GENERATED IN-VIVO

Toscana (TOS) virus stocks strongly interfering with standard virus re plication were obtained by sequential passages of virus in suckling mo use brain. Characterization of viral RNAs in these stocks showed the p resence of a heterogeneous population of defective RNA molecules deriv ed from the L genomic segment, in both nucleocapsid (NC) and messenger RNAs, suggesting that these molecules could be replicated, assembled, and transcribed. Subgenomic RNAs from the L segment but not from the S or M segments were found in cells infected with these stocks. Defect ive RNA molecules interfered with virus replication and retained 5' an d 3' genomic termini. Nucleotide sequence analysis of some cloned defe ctive interfering (DI) RNAs revealed they contained one or more intern al deletions reducing their length to 7-13% of the full-length L segme nt. An identical sequence motif, of variable length, was found at both terminal sites of the RNA junction on standard L sequences. This moti f was retained only in one copy in the subgenomic RNA. These results a re consistent with the generation of TOS virus DI particles in vivo an d suggest that the defective genomic RNAs could be generated by polyme rase jumping from a sequence to an identical one spatially closed beca use of the RNA structure. (C) 1998 Academic Press.