Electron microscopy in assessment of the biological behavior of human papillomavirus infections in the uterine cervix.

To asses the natural history of human papillomavirus (HPV) infections in uterine cervix, currently implicated in etiology of cervical cancer, a prospective follow-up study has been conducted for 418 women at our clinic since 1981. The present communication summarized the current follow-up data of these patients, with special emphasis on detection of the virus in cervical punch biopsies, as correlated with other characteristics pertinent to the clinical behavior of cervical HPV infections. On each attendance, the patients are subjected to colposcopy accompanied either by Papanicolaou (PAP) smears or punch biopsies. The latter are analyzed for the cytopathic changes of HPV, for concomitant cervical intraepithelial neoplasia (CIN), for HPV structural proteins with IP-PAP technique as well as on transmission electron microscopy (TEM) for the presence of HPV particles. The local immunocompetent cell (ICC) infiltrates are analyzed using ANAE technique to define B cells, MPS cells and T cells and monoclonal antibodies (McAb) for T cell subsets, NK (natural killer) cells and Langerhans cells. HPV particles were disclosed with equal frequency (approx. 65%) in all three types of HPV lesions. Surprisingly, HPV particles were present in 70% of the biopsies derived from the regressed lesions (e. g. in those without histological evidence of HPV lesions), suggesting a possibility of a latent HPV infection. Presence of viral particles did not bear any direct correlations with the expression of HPV antigens, intensity or cellular composition of the ICC infiltrate, defined by ANAE or using McAb. Presence of HPV particles was not a major prognostic determinant, whereas the clinical course was most significantly influenced by the grade of HPV-associated CIN, to which regression was inversely and progression directly related. The results clearly confirm that cervical HPV infections are capable of progressing into carcinoma in situ and thus present with a natural history equivalent to that of classical CIN.