Cellular localization of cytomegalovirus nucleic acids in guinea pig salivary glands by in situ hybridization

In situ hybridization with guinea pig cytomegalovirus (CMV) DNA probes was used to detect guinea pig CMV nucleic acid sequences in salivary glands during the course of infection. Optimum conditions for detection of guinea pig CMV gene sequences at the cellular level were determined. The technique of nucleic acid hybridization was compared to antigen detection and histologic examination for cellular localization of guinea pig CMV during acute and chronic infection. Tissue sections fixed for 1 h in 4% paraformaldehyde demonstrated darker specific staining and contained significantly larger numbers of cells positive for guinea pig CMV nucleic acids and antigens than sections fixed longer and in other fixatives. The method of in situ hybridization detected more guinea pig CMV infected cells than did routine histological evaluation. Histologically normal salivary gland duct cells as well as cells bearing typical inclusions were found to contain guinea pig CMV nucleic acids. Guinea pig CMV nucleic acids were also detected although less frequently in cells outside of the ducts. These results suggest that in situ hybridization allows for the detection of histologically inapparent guinea pig CMV infections at the cellular level.