Five autopsy cases of cytomegalovirus (CMV) infections were studied. Conventional light microscopy disclosed characteristic cytopathic effects in lungs, kidneys, and brain. In one case, electron microscopy was carried out and revealed typical herpesvirus particles. In situ hybridization was done with biotin-labeled CMV-DNA probes and an avidin-alkaline phosphatase detection system. 4/5 cases were observed to contain hybridizing cells in different organs. Intensity of hybridization was related to the severity of CMV infection, roughly estimated by counting cytomegalic cells. In addition to cytomegalic cells, a high number of normal-looking epithelial and mesenchymal cell types were positive. These latter cells showed nuclear hybridizations in contrast to cytomegalic cells which hybridized both within the nuclei and the cell bodies. This modified in situ hybridization procedure is a rapid and valuable tool for the detection and final demonstration of virus infection, and will be of particular help for the examination of paraffin-embedded specimens.
