Human papillomaviruses: pediatric perspectives on a family of multifaceted tumorigenic pathogens.
As summarized here human papillomaviruses are associated with a wide spectrum of epithelial lesions, ranging from benign warts to invasive carcinomas. They have been difficult to study in part because they have not yet been propagated in tissue culture. Fortunately advances in molecular biology have allowed characterization of HPV genomes and identification of some HPV gene functions. In addition to their clinical importance HPVs represent an important tool for exploring virus-cell interactions, gene expression, cellular differentiation and cancer. HPV infections are not only common but also difficult to treat and prevent. Depending on the HPV type and location, the modes of HPV transmission may involve casual physical contact, sexual contact and perinatal vertical transmission. HPV DNA genomes replicate at a low copy number in basal cells and, as most clinicians know, are difficult to eradicate. There is often a long latent period and subclinical infections, and HPV DNA can be found in normal tissue adjacent to lesions. HPVs can cause widely disseminated lesions, especially in the immunocompromised host and in epidermodysplasia verruciformis. Aside from the rare carcinomas, the most serious life-threatening HPV-induced illness in children is recurrent respiratory papillomatosis. Somewhat surprisingly in malignant lesions HPV DNA is also found as fragments incorporated into the cellular genome. Unlike retroviruses such as human immunodeficiency virus which integrate into the cellular genome as part of their life cycle, HPV integration is a terminal event for viral replication. Such integration may be critical, however, for viral-induced abnormal cell growth. Perhaps the most important implication of the finding that some anogenital cancers are in part sexually transmitted infectious diseases is that they may be preventable. The data overwhelmingly suggest that avoidance of exposure to HPV via abstinence or monogamy in both partners markedly reduces the risk of cervical cancer. A more realistic goal, however is prevention of HPV transmission by the use of barrier method contraceptives, which may be protective against development of cervical carcinoma. The America Association of Pediatrics Committee on Adolescents has outlined the obligation of pediatricians to be actively involved in adolescent education on sexually transmitted diseases. Certainly a fundamental knowledge of HPV epidemiology, the risks of HPV-related sequelae and prevention of HPV infection are important considerations for adolescent sexuality. Although helpful, such awareness alone falls far short of making an impact on sexual behaviors. A significant reduction in HPV infection rates could be achieved only by inundating adolescents at an early age with a highly visible society-wide campaign directed at these issues.
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Department of Pediatrics, University of Iowa College of Medicine, Iowa City 52242.
D002294:Carcinoma, Squamous Cell / Q000209:etiology; D002648:Child; D003218:Condylomata Acuminata / Q000382:microbiology; D004819:Epidermodysplasia Verruciformis / Q000382:microbiology; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007822:Laryngeal Neoplasms / Q000382:microbiology; D010212:Papilloma / Q000382:microbiology; D027383:Papillomaviridae / Q000235:genetics*; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000382:microbiology; D014412:Tumor Virus Infections / Q000382:microbiology* / Q000635:transmission; D002583:Uterine Cervical Neoplasms / Q000209:etiology; D014611:Vaccination; D014860:Warts / Q000382:microbiology