Combination Of Lentinan And Multipotent Artificial Antigen-presenting Cell Induces Anti-tumor Active Immune Responses

Artificial antigen-presenting cells（aAPCs）play a vital role in facilitating T cells proliferation and tumor immunotherapy.There are two classes of aAPCs according to the carrier materials:cellular aAPCs and cell-free aAPCs.The in vivo observational studies reported by us and other researchers have demonstrated that the static and solid acellular aAPCs have the potent ability to activate and proliferate tumor antigen specific T cells in an antigen-specific manner with the infitring prospects for clinical uses.However,these previous cell-free aAPCs reported only present two or three kinds of surface molecules in design;furthermore,their scaffold materials,such as magnetic beads and polystyrene microspheres etc.,are not biodegradable and are not suitable for clinical application.Based on the previous works,this study aims to further optimize and improve the cell-free aAPCs system in design.Objective:To investigate the capability of biodegradable and multipotent aAPCs to induce anti-tumor active immune responses and the synergistic effects of APCs combined use with lentinan in the treatment of tumor in mice.Methods:The aAPCs with surface presentation and paracrine delivery were generated using polylactic-co-glycolic acid microparticles（PLGA-MPs）as a biodegradable scaffold.Both IL-2 and anti-CTLA-4 were co-encapsulated into the cell-sized PLGA-MPs to concurrently present a third signal and anti-inhibitory signal on T cells by paracrine delivery,while H-2K^b/TRP2_180-188-Ig dimer and anti-CD28 were co-coupled on the surface acted as the first and second signals.The aAPCs were injected into melanoma-bearing mice via tail vein and followed by the investigation of therapeutic effects and immune responses.Futher more,the aAPCs were administered along with lentinan,a traditional Chinese medicine and classical immune modulator,and followed by observation of tumor growth and evaluation of immune response.Results:（1）The multipotent aAPCs carrying four kinds of immune molecules were successfully generated,with the correct phenotypes and sustained paracrine release.（2）aAPCs distributed at various organs through circulation system with a retention time of around 24 hours;powerfully expanded the TRP2_180-188-specific CD8⁺T cells in vivo;increased the the local infiltration of TRP2_180–188-specific CD8⁺T cells in tumor tissue,and enhanced the cytotoxicity of their CTLs against tumor cells;thus markedly inhibited the tumor growth and prolonged the survival of tumor-bearing mice.（3）The multipotent aAPCs possess much stronger capability to induce anti-tumor immune responses and inhibit tumor growth than the conventional two-signal aAPCs;and the co-paracrine of IL-2 and anti-CTLA-4 from aAPCs displayed obvious synergistic effects on inducing anti-tumor immune responses and inhibiting tumor growth.（4）The combination therapy of aAPCs along with lentinan obviously inhibited the tumor growth in a mouse melanoma model and prolonged the medium survival time of tumor-bearing mice.The combined administration of aAPCs and lentinan markedly expanded the T cells and TRP2_180-188-specific CD8⁺T cells in the peripheral blood,spleen and tumor tissue;obviously enhanced the cytotoxicity of NK cells;and effectively decreased the frequency of Treg cells.（5）As compared with the aAPCs injection group and lentinan injection group,the combination therapy of aAPCs with lentinan led to the significant synergistic effects in expanding tumor antigen-specific T cells and inhibiting tumor growth.Conclusion:This study demonstrates that the multipotent aAPCs with surface presentation and paracrine delivery is a novel strategy for the antigen-specific active immunotherapy of tumor;and this study,for the first time,indicates the synergistic effects of aAPCs and lentinan in the treatment of tumor.