๐ ็ธฝ็ฎ้ ๏ฝ ๐ ่ฑๆๅๆ๏ผๆฌ็ฏ๏ผ ๏ฝ ๐ ๅฎๆด็ฟป่ญฏ ๏ฝ โญ ็ฒพ่ฏ็ญ่จ
INTRODUCTION
Papillomaviruses are a large group of DNA viruses that are widely distributed in animals and humans, most commonly inducing benign papillomas or warts. Recurrent skin and anogenital warts may be disfiguring, impose a considerable psychological burden, and are a frequent cause of medical office visits. A subset of human papillomaviruses (HPVs) designated as high-risk types, most often HPV-16 and -18, is now recognized as the primary etiologic agent for: cervical cancer and its precursor lesions; a subset of malignancies at other anogenital sites and in the upper aerodigestive tract; and, rarely, squamous cell cancer (SCC) of the digits. In contrast, infection with the common cutaneous HPV types 1, 2, 4, 27, 57, etc. is not thought to have any oncogenic potential. In immunocompromised patients, HPV infections tend to persist and result in an increased risk of anogenital neoplasias. The high prevalence of genital HPV infection in sexually active young adults is a major concern, as effective antiviral treatments do not exist. More than two decades ago, prophylactic vaccines based on virus-like particles (VLPs) that prevent transmission in animal models of papillomavirus infection were developed. Human vaccine studies subsequently demonstrated safety and nearly complete (>90%) efficacy in preventing vaccine type-restricted genital HPV infection and the development of associated neoplasias.
History
An infectious etiology for human warts had long been suspected, and experimental transmission of common warts with a cell-free extract was demonstrated over 100 years ago. The descriptions of cottontail rabbit papillomavirus (CRPV) in 1933 and the rare genodermatosis epidermodysplasia verruciformis (EV) demonstrated the oncogenic potential of papillomaviruses. Following the cloning of the first papillomavirus genome in the late 1970s, the plurality of human and animal papillomaviruses became evident. Based on genome sequencing, HPV types can be grouped into phylogenetic trees with a remarkable relationship to biologic behavior, e.g. mucosal and cutaneous types, high-risk and low-risk genital HPV, and EV-associated HPV. Today, the genomes of more than 200 HPV types have been fully characterized and additional partial DNA sequences have been obtained, indicating the existence of at least 200 HPV genotypes. In 1976, zur Hausen proposed an association between papillomaviruses and cervical cancer, and subsequent molecular studies led to the recognition of a subset of HPV types in a high proportion of cervical carcinomas. The identification of biologic differences between โhigh-riskโ and โlow-riskโ mucosal HPV confirmed that infection with oncogenic HPV was the main cause of cervical cancer and its precursor lesions.