Detection of virus-specific RNA-dependent RNA polymerase activity in extracts from cells infected with lymphocytic choriomeningitis virus: in vitro synthesis of full-length viral RNA species.

We have developed an in vitro assay for the lymphocytic choriomeningitis virus (LCMV) RNA-dependent RNA polymerase with ribonucleoprotein complexes extracted from acutely infected tissue culture cells. The RNA products synthesized in vitro corresponded in size to the full-length genomic L and S RNAs and subgenomic NP and GP mRNAs normally produced in vivo during acute LCMV infection. In a temporal analysis spanning the first 72 h of acute infection, the in vitro polymerase activity of ribonucleoprotein complexes was maximal at 16 h and declined significantly at later times. In contrast, the intracellular levels of the viral L protein (the putative polymerase protein) appeared to be maximal at 48 to 72 h postinfection. Our results suggest that the accumulation of L protein correlates with reduced viral replication and transcription at later times in acute infection and may be involved in the transition from acute to persistent LCMV infection.