Differential detection of viral DNA and RNA in situ in cells infected with human cytomegalovirus

We have analyzed the ability to use in situ cytohybridization to distinguish between human cytomegalovirus (HCMV) DNA and RNA in human cells infected in vitro. Two different viral-specific probes were used, one for an abundantly expressed late gene, and one which includes at least two genes coding for immediate early (IE) proteins. In productively infected cells, hybridization of the late gene probe extended over both the nucleus and cytoplasm and was RNase sensitive, whereas hybridization of the IE probe was restricted to the nucleus and was DNasesensitive. In nonproductively infected cells hybridization of the IE probe was localized to the cytoplasm and was RNase-sensitive. The specific nuclease sensitivities indicate that a cytoplasmic hybridization pattern correlates with detection of viral RNA sequences, whereas a nuclear pattern represents detection of viral DNA. These results demonstrate that in situ cytohybridization can potentially be used to determine the extent of HCMV infection in a particular tissue or cell type by distinguishing between transcription and replication of specific viral genes.