Cervical cancer arises from lesions caused by
infection with high-risk types of human papillomavirus (HPV). Therefore, vaccination against HPV could prevent
carcinogenesis by preventing
HPV infection or inducing lesion regression. HPV E2
protein is an attractive candidate for
vaccine development because it is required for
papilloma formation, is involved in all stages of the virus life cycle, and is expressed in all premalignant lesions as well as some
cancers. This study reports vaccination against E2
protein using a rabbit model of
papillomavirus infection. A recombinant adenovirus (Ad) vector expressing the E2
protein of cottontail rabbit papillomavirus (CRPV) was tested for therapeutic efficacy in CRPV-infected rabbits. Primary immunization with the Ad-E2
vaccine, compared to immunization with a control Ad vector, reduced the number of
papilloma-forming sites from 17 of 45 to 4 of 45. After booster immunization, vaccinated rabbits formed no new
papillomas versus an additional 23
papillomas in rabbits that received the control vector.
Papillomas in the Ad-E2 vaccinees were significantly smaller than those in the control rabbits, and all four
papillomas in the Ad-E2 vaccinated rabbits regressed. No CRPV
DNA was detected either in the regression sites or in sites that did not form
papillomas, indicating that the vaccination led to clearance of CRPV from all infected sites.