Progress in prophylactic and therapeutic vaccines for human papillomavirus infection.

Virus-like particle (VLP) subunit vaccines composed of the major capsid protein L1 of the genital human papillomaviruses (HPVs) are now in Phase III clinical trials. The vaccines are immunogenic and safe and early results indicate efficacy. VLPs induce strong cell-mediated as well as humoral immune responses and chimeric VLPs including an HPV early protein may have therapeutic potential. Polynucleotide and recombinant viral vaccines encoding nonstructural viral proteins show therapeutic and prophylactic efficacy in animal models and are candidate immunotherapies for established low-grade benign genital infections. Vaccines designed to elicit cytotoxic T-lymphocytes specific for the HPV oncoproteins E6 and E7 show immunogenicity and efficacy in transplantable tumor models in rodents. In Phase I and II trials these vaccines are immunogenic and safe but show limited efficacy.