A histochemical method for demonstrating papilloma virus infection in paraffin-embedded tissue.

In order to study the location of cells infected with human papilloma virus in paraffin-embedded tissues, the authors developed the following stain. Tissue sections were digested overnight with 0.01% deoxyribonuclease and then stained using the Feulgen stain with a light green counterstain. Cellular DNA was degraded, but viral DNA was not. Thus infected cells retained magneta nuclei, while uninfected cells stained a homogenous green. The stain was positive in 5/5 plantar warts, 7/8 verruca vulgaris, 2/2 laryngeal papilloma, and 18/20 condylomata accuminata. As a comparison, the indirect immunoperoxidase method on the same tissues stained 5/5 plantar warts, 6/8 verruca vulgaris, 0/2 laryngeal warts, and 2/20 condylomata accuminata. The presence of virus was confirmed by electron microscopic examination on one of the sections. Molluscum contageosum infected tissue also stained positively, but tissues infected with cytomegalovirus and herpes simplex virus did not. The only nonviral positive staining occurred with smears of sperm. The reasons for these results are discussed.