A single-injection vaccine providing protection against two HPV types†

Prophylactic human papillomavirus (HPV) vaccines against cervical cancer were successfully developed; however, challenges such as high cost and low compliance still remain to be overcome. In addition, because many HPV types can cause cervical cancer, antigens of multiple HPV types are needed to achieve broad protection. In this study, a bivalent single-injection HPV vaccine was designed in which virus-like particles (VLPs) of HPV 16 L1 and HPV 18 L1 were used as antigens. A recently developed drug carrier that uses tannic acid/polyethylene glycol films as the erodible layer was employed to accomplish multiple pulsatile releases of the antigens. Monovalent single-injection vaccines for HPV 16 and HPV 18 were first designed. A bivalent single-injection vaccine was then obtained by simply mixing the two monovalent vaccines. The bivalent vaccine provided protection against both HPV types. More importantly, it elicited both humoral and cellular immune responses as potent as those elicited by the corresponding multiple dose vaccine because of their similar release profile of antigens. Cross-reactivity was observed between HPV 16 and 18 in terms of cellular immune responses, while no cross-reactivity was found in terms of humoral immune responses. Note that other multivalent single-injection vaccines could be designed in the same way. These vaccines are expected to help prevent cervical cancer because of their broad protection, enhanced compliance and lowered vaccination cost.