HPV16 L1 capsid protein expressed from viable adenovirus recombinants elicits neutralizing antibody in mice

Immunization against human papillomavirus (HPV) infection promises to reduce the worldwide burden of cervical cancer. To evaluate the potential of live recombinant adenoviruses for induction of HPV infection-blocking immunity, we prepared viable adenovirus recombinants that express the HPV16 L1 gene from the adenovirus major late transcriptional unit. Adenovirus-produced HPV16 L1 assembles into virus-like particles (VLPs) in infected cells in culture. Purified HPV16 VLPs are recognized by HPV16 neutralizing antibodies and induce high neutralizing titers when injected intraperitoneally into mice. Canine oral papillomavirus VLPs derived from previously described recombinants also induce strong antibody responses in mice. These data support our suggestion that viable adenovirus recombinants will be able to induce protective immunity to papillomavirus infection during replication in human vaccinees.