A Tolerogenic Artificial Antigen-presenting Cell Durably Ameliorates EAE By On-target Depletion Or Modulation Of Myelin-autoreactive T Cells

Background:Biomimetic micro-and nanoparticles（MNPs）have been reported recently as immune-modulators in multiple sclerosis（MS）and experimental autoimmune encephalomyelitis（EAE）by numerous researchers.In these previous studies,most therapeutic strategies were based on the mechanism of encapsulation and controlled release of myelin antigens,peptides,toxins,or cytokines by cellular uptake of particles through phagocytosis and pinocytosis to induce tolerogenic antigen-presenting cells（APCs）and consequent T cell tolerance.But few researches focus on the antigen-specific contacts of MNPs with auto-reactive T cells and the combined use of multiple regulatory molecules for the MS or EAE treatment.Purposes:This study aims to initially develop a tolerogenic artificial antigen-presening cell（TaAPC）to directly and selectively modulating meylin-autoreactive CD4⁺and CD8⁺T cells in the myelin oligodendrocyte glycoprotein（MOG）_35-55 peptide-induced EAE murine model.Methods:The biodegradable and biocompatible PLGA microparticles were generated as a cell-sized scaffold to co-coupling tartget complexes(MOG_40-54/H-2D^b-Ig dimer,MOG_35-55/I-A^b multimer),regulatory molecules（anti-Fas and PD-L1-Fc）and“self-marker”CD47-Fc onto surface,and encapsulating inhibitory cytokine（TGF-β1）inside.Then,the resulting TaAPCs were administered i.v.into the MOG_35-55-induced EAE mice,followed by the investigation of therapeutic effects,in vivo distribution,precise mechanism and side effects.Results:（1）Cell-sized TaAPCs in a diameter around 5.0μm were successfully prepared with the correct phenotypes.Five kinds of immune molecules were co-coupled onto surface and TGF-β1 was encapsulated with a sustained paracrine release;（2）Early four infusions of the TaAPCs after EAE onset markedly and durably decreased the clinical scores of EAE mice during 100 days and reduced the local inflammation,demyelination and T cells infiltration in CNS tissue;（3）The TaAPCs circulated throughout vasculature into peripheral lymphoid tissues and various organs,but not into brain,with a retention time of more than 36 hours;and made plenty of contacts with CD4⁺T cells and CD8⁺T cells,but few co-localiztion with other immune cells;In addition,CD47-Fc minimized the uptake of TaAPCs by phagocytes;（4）Two infusions of the TaAPCs depleted 65-79%of MOG_35-55-specific CD4⁺and 46-62%of MOG_40-54-specific CD8⁺T cells in peripheral blood,spleen and CNS tissues with an elevation of T cell apoptosis,in an antigen-specific manner and regulatory molecule-dependent fashion;inhibited the activation and proliferation of MOG peptide-reactive T cells;reduced MOG peptide-reactive Th1,Th17 and Tc17 cells and induced regulatory T cells.They also inhibited IFN-γ/IL-17A secretion and elevated IL-10/TGF-β1 production in splenocytes,but not in CNS tissue;（5）The TaAPCs treatment did not obviously suppress the overall immune function of host,including the anti-tumor capability and immune reactions in responses to non-cognate myelin peptides and third-party alloantigens.Conclusion:This study provides the first experimental evidence for the capability of TaAPCs bearing 6 kinds of immune molecules to directly modulate autoreactive T cells by surface presentation of multiple ligands and paracrine release of cytokine,thus suggests a novel antigen-specific immunotherapy and immune modulator for the T cell-mediated autoimmune diseases.