The papillomavirus virion: a machine built to hide molecular Achilles' heels.

Papillomaviruses are a diverse group of DNA viruses that infect the skin and mucosal tissues of vertebrates. More than 100 distinct human papillomavirus (HPV) genotypes have so far been identified. A subset of HPVs is known to cause human cancer. Although recently developed vaccines protect vaccinated individuals from the two most carcinogenic HPV types, there is a pressing need for next-generation vaccines that might offer broad-spectrum protection against the full range of cancer-causing HPVs. The ongoing development of such vaccines will be facilitated by a deeper understanding of the mechanics of the assembly of the nonenveloped papillomavirus virion, as well as the machine-like structural changes that occur in the virion during the process of infectious entry into host cells. This chapter reviews the field's current knowledge of these two aspects of papillomavirus biology and speculates about areas where further work is needed.