Electronmicroscopic demonstration of HPV in oral warts

Human Papilloma Virus (HPV) has been demonstrated in a series of benign proliferative lesions of the skin and the mucosae. The virus has also been found in verrucous laryngeal carcinoma and carcinomas of the oral cavity and other organs. DNA hybridization techniques have classified, the HPV into 51 types, some of which seem to be associated with specific lesions. In order to study the intracellular distribution of HPV, we performed ultrastructural analysis with the electron microscope on 14 specimens taken from 7 patients by large excisional biopsy, which had been histologically classified as "fibropapilloma". From each patient specimens were taken from both the clinically evident lesion and the clinically normal surrounding mucosa. The specimens were fixed with glutaraldehyde, washed with cacodylate buffer, post-fixed with potassium ferrocyanide reduced-osmium tetroxide, block stained with uranyl acetate and embedded in EPON 812. The tissues underwent to amylase digestion before the electron microscopic examination. We found a large number of viral particles in both nuclei and cytoplasm, without forming crystal array structures as described typically for the virus of the verruca vulgaris (HPV-2). No significant differences were found between the cells derived from the clinical lesion and those derived from the surrounding mucosa. The passage of viral particles from infected to not yet infected cells through the intercellular space was observed. Of particular interest, we found a high intracytoplasmatic presence of the virus and its clear abundance in the cells surrounding the clinical lesion.