The human papillomaviruses.

The human papillomaviruses (HPVs) have long been recognized as the etiologic agents of a variety of benign cutaneous and mucosal proliferative entities. Currently, 11 distinct HPVs have been described, and each seems preferentially associated with a distinct clinical entity. In animal species, some papillomaviruses (PVs) are associated with lesions that can become malignant. What role specific HPVs may play in cutaneous or mucosal malignant squamous cell neoplasms is under investigation in a number of different laboratories. There is a subgroup of PVs that can malignantly transform fibroblasts of heterologous species. This system provides a model for studying the malignant potential of the PVs and for determining the cellular and viral events associated with PV-induced malignant transformation. A unique characteristic of this system is that the HPV genome exists exclusively nonintegrated as a DNA plasmid in transformed cells.