Soluble-microneedle enhance three T-cell activation signals as efficient tumor vaccines for melanoma prevention and treatment.

Therapeutic tumor vaccines, which activate self-T cells to eliminate tumors, hold tremendous promise in future cancer immunotherapy with high specificity and low side effects. To effectively activate T cell, dendritic cells (DCs) need simultaneously provide three indispensable signals to naive T cells, including MHC-antigen signal, costimulation signal and cytokine stimulation. However, current marketed therapeutic tumor vaccines still suffer from lacking the ability to activate three stimulation signals at the same time, which resulted to the low response rate and unsatisfied therapeutic efficiency. Here, we proposed a soluble microneedle-based tumor vaccines (TR-12@LGMN) which facilitate triple activation of antigen presentation and induce high immune response rate. First, the melanoma-specific antigen tyrosinaserelated protein-2 (Trp2), Resiquimod (R848), and IL-12 mRNA co-loaded liposomes (TR-12@LIPO) was prepared. The TR-12@LIPO ensured triple-activating three essential signals of antigen presentation through enhancing the binding of MHC I-antigen peptides to T cell receptor (TCR), the binding of CD80/86 on DCs to CD28 on T cells, and the release of cytokines for T cells activation. Second, TR-12@LIPO was co-dispersed in polyvinylpyrrolidone-polyvinyl alcohol (PVP-PVA) matrix with granulocyte-macrophage colony stimulating factor (GM-CSF) to prepare TR-12@LGMN by mold method. The TR-12@LGMN was quadrilateral shape with sufficient mechanical strength for skin piercing. After skin insertion, TR-12@LGMN dissolved in the skin interstitial fluid to release GM-CSF and TR-12@LIPO. DCs were recruited by GM-CSF and uptaked TR-12@LIPO. TR-12@LIPO showed enhancement of cross-presentation by antigen cytoplasmic delivery, DCs maturation and IL-12 secretion. In vivo results showed that TR-12@LGMN could efficiently activate CD8+ T cells, induce antigen-specific cytotoxic T cells (CTLs) and memory T cell (Tm). Ultimately, strong anti-tumor immunity and long-term durable tumor control were achieved in the B16F10 tumor prevention and treatment model. Overall, our work proposes a triple-activated antigen presentation strategy and designs a microneedle-based tumor vaccine for skin delivery, revealing a potential promising direction for the development of new therapeutic tumor vaccines methods.