A new vaccine targeting RANKL, prepared by incorporation of an unnatural Amino acid into RANKL, prevents OVX-induced bone loss in mice.

Bone homeostasis is maintained by a dynamic balance between osteoblastic bone formation and osteoclastic bone resorption. The receptor activator of nuclear-κB ligand (RANKL) is essential for the function of the bone-resorbing osteoclasts, and targeting RANKL has been proved highly successful in osteoporosis patients. This study aimed to design a novel vaccine targeting RANKL and evaluate its therapeutic effects in OVX-induced bone loss model. Anti-RANKL vaccine was generated by incorporating the unnatural amino acid p-nitrophenylalanine (pNOPhe) into selected sites in the murine RANKL (mRANKL) molecule. Specifically, mutation of a single tyrosine residue Tyr (Y234) or Tyr (Y240) of mRANKL to pNOPhe (thereafter named as YpNOPhe or YpNOPhe) induced a high titer antibody response in mice, whereas no significant antibody response was observed for the wild type mRANKL (WT mRANKL). The antiserum induced by YpNOPhe or YpNOPhe could efficiently prevent osteoclastogenesis in vitro. Moreover, immunization with YpNOPhe or YpNOPhe could also prevent OVX-induced bone loss in mice, suggesting that selected pNOPhe-substituted mRANKL may pave the way for creating a novel vaccine to treat osteoporosis.