Human papillomavirus vaccine development

The greatest successes in combating important viral infections have been achieved using vaccines. A vaccine to prevent genital tract human papillomavirus (HPV) infections, especially those types associated with genital tract malignancy, could significantly reduce morbidity and mortality from cervical and other genital tract cancers. However, several barriers currently stand in the way of HPV vaccine development. The immunological response to natural HPV infection is incompletely understood and there is uncertainty about which viral antigen(s) should be included in a candidate vaccine. It is clear that immunization of several animal species with the L1 major capsid protein (usually in the form of virus-like particles) spurs the production of anti-HPV antibodies that are neutralizing in several assay systems. However, it is not clear if neutralizing antibody will be present in the genital tract in sufficient quantities to block infection. A second problem is the lack of a reliable serological assay for HPV. This is a major problem for clinical trials in which the identification of susceptible individuals, and incident infections, usually relies on serological diagnosis. Finally, there is also interest in the development of a vaccine that is used to treat individuals who are already infected--a therapeutic vaccine. It is likely that a therapeutic vaccine will need to target different or additional antigens to those comprising a prophylactic vaccine.