Current and Next-generation Vaccines against Human Papillomaviruses

Human papillomaviruses (HPVs) infect the squamous epithelium, and cause skin warts, genital warts and cancers, including uterine cervical cancer. Amongst the enormously diverse types of HPVs, HPV16 and HPV18 are most prevalent and responsible for approximately 70% of cervical cancer cases. Current preventive HPV vaccines contain virus-like particles which are composed of L1 major capsid proteins of HPV16 and HPV18. Although bivalent and quadrivalent vaccines exhibit excellent preventive efficacy and safety, they have several limitations. First, since the protection against HPV is type-restricted, the remaining 30% of cervical cancers and warts cannot be prevented. Second, due to the absence of therapeutic activity in the vaccines, people already infected by the HPVs cannot benefit from the current vaccines. Therefore, new preventive and therapeutic vaccines are required for better control of HPV-associated diseases. New developments include a novel nonavalent preventive vaccine that contains five additional cancer-associated HPV types, and it has been tested and approved in 2014. Recently, several groups reported promising clinical results with novel therapeutic HPV vaccines. This review provides an overview of the success of current preventive vaccines and perspectives on the next-generation HPV vaccines.