A lyophilizable LNP vaccine enables STING-reinforced postoperational adjuvant immunotherapy

Immune checkpoint blockade therapy (iCBT) has revolutionized cancer treatment, however, there is a low response rate, especially in treating postsurgical reoccurring tumors. Vaccine based immunotherapy can sensitize iCBT, but its development was largely hindered by inefficient delivery and high requirements of storage. In this study, the vaccine loaded with immunostimulant was employed to improve iCBT-based adjuvant postsurgical therapy. A lyophilized, antigen E7 peptide and manganese ion (Mn²⁺) co-delivered tumor vaccine was developed based on lipid nanoparticles (EM@LNP). The vaccination efficacy was examined in both prophylactic and therapeutic schemes in murine subcutaneous models, the synergetic effect of vaccination combined with anti-PD-1 therapy was further investigated in post-operative tumor model. EM@LNP vaccination elicited effective CD8⁺T cell response through modulating tumor immunosuppressive microenvironment and conferring immune memory, demonstrating potent immunization in both preventive and therapeutic schemes. What's more, EM@LNP vaccination orchestrated with iCBT, efficiently repressing tumor recurrence. Further mechanism studies using inhibitor for cells invitro and the investigation using STING^-/- mice confirmed that the cGAS-STING signaling pathway activated by Mn²⁺ is indispensable for LNP vaccination and the coordination with iCBT-based adjuvant immunotherapy. In summary, this study shows a lyophilized LNP vaccine could significantly amplify iCBT efficiency, providing a translational strategy of adjuvant immunotherapy for treating postsurgical tumor recurrence.