Viral diagnosis by in situ hybridization. Description of a rapid simplified colorimetric method

An improved method of colorimetric in situ hybridization for the diagnosis of viral infections in standard formalin-fixed, paraffin-embedded tissue sections has been developed. This method employs a 2-hour hybridization with biotin-labeled DNA probes followed by direct colorimetric detection with avidin-alkaline phosphatase complexes. Visual results are obtained within 8 h of cutting the tissue section. Specific histologic localization of cytomegalovirus and adenovirus genetic information has been achieved in infected lung tissues from autopsy or biopsy. Simultaneous denaturation of tissue and probe DNA at elevated temperature (100-105 degrees C) resulted in increased signal. It is our suggestion that these denaturing conditions may be required to denature more fully formalin cross-linked tissue DNA and favor penetrance of probe into the tissues. Comparison of the results of hybridization and viral culture for the diagnosis of CMV infections suggest that in clinical situations hybridization will allow specific diagnosis of productive viral infection more rapidly than viral culture with some loss in sensitivity. Colorimetric in situ DNA hybridization offers the surgical pathologist a powerful new technique that provides an alternative to immunocytochemistry and electron microscopy in the diagnosis of viral pathogens.