Detection of rabies virus genomic RNA and mRNA in mouse and human brains by using in situ hybridization.
Rabies virus RNA was detected in mouse and human brains by in situ hybridization. 3H-labeled single-stranded RNA probes were prepared which were specific for genomic RNA and mRNAs coding for the five rabies virus proteins (N, NS, M, G, and L). Paraffin-embedded brain tissues from human cases of rabies and mice experimentally infected with the challenge virus standard (CVS)-11 strain of rabies virus and street rabies virus were examined. In CVS-infected mice, genomic RNA had a multifocal distribution in the perikarya of infected neurons, perhaps reflecting concentration of genomic RNA in viral factories. The mRNAs were more abundant than genomic RNAs in CVS- and street virus-infected mouse brains and had a diffuse distribution in the perikarya. Similar amounts of signal were present in infected neurons for mRNAs coding for different rabies virus proteins. In brain tissues from human cases of rabies, genomic RNA was much more abundant than the mRNAs in infected neurons. This finding suggests either a relative block at the level of transcription or greater loss of mRNAs than of genomic RNA during the agonal period, postmortem interval, or prior to penetration of fixative during immersion fixation.