We have shown that nanoparticles (NPs) can be used as ligand-multimerization platforms to activate specific cellular receptors in vivo. Nanoparticles coated with autoimmune disease-relevant peptide-major histocompatibility complexes (pMHC) blunted autoimmune responses by triggering the differentiation and expansion of antigen-specific regulatory T cells in vivo. Here, we define the engineering principles impacting biological activity, detail a synthesis process yielding safe and stable compounds, and visualize how these nanomedicines interact with cognate T cells. We find that the triggering properties of pMHC-NPs are a function of pMHC intermolecular distance and involve the sustained assembly of large antigen receptor microclusters on murine and human cognate T cells. These compounds show no off-target toxicity in zebrafish embryos, do not cause haematological, biochemical or histological abnormalities, and are rapidly captured by phagocytes or processed by the hepatobiliary system. This work lays the groundwork for the design of ligand-based NP formulations to re-program in vivo cellular responses using nanotechnology.

Peptide-major histocompatibility complex class II (pMHCII)-based nanomedicines displaying tissue-specific autoantigenic epitopes can blunt specific autoimmune conditions by re-programming cognate antigen-experienced CD4+ T-cells into disease-suppressing T-regulatory type 1 (TR1) cells. Here, we show that single pMHCII-based nanomedicines displaying epitopes from mitochondrial, endoplasmic reticulum or cytoplasmic antigens associated with primary biliary cholangitis (PBC) or autoimmune hepatitis (AIH) can broadly blunt PBC, AIH and Primary Sclerosing Cholangitis in various murine models in an organ- rather than disease-specific manner, without suppressing general or local immunity against infection or metastatic tumors. Therapeutic activity is associated with cognate TR1 cell formation and expansion, TR1 cell recruitment to the liver and draining lymph nodes, local B-regulatory cell formation and profound suppression of the pro-inflammatory capacity of liver and liver-proximal myeloid dendritic cells and Kupffer cells. Thus, autoreactivity against liver-enriched autoantigens in liver autoimmunity is not disease-specific and can be harnessed to treat various liver autoimmune diseases broadly.

T cell-T cell Ag presentation is increasingly attracting attention. We previously showed that the in vitro OVA-pulsed dendritic cell (DCOVA)-activated CD4+ Th cells acquired OVA peptide/MHC (pMHC) class I and costimulatory molecules such as CD54 and CD80 from DCOVA and acted as CD4+ Th-APC capable of stimulating OVA-specific CD8+ CTL responses. In this study, we further applied the OVA-specific TCR-transgenic OT I and OT II mice with deficiency of various cytokines or costimulatory molecule genes useful for studying the molecular mechanisms underlying in Th-APC’s stimulatory effect. We demonstrated that DCOVA-stimulated OT II CD4+ Th-APC also acquired costimulatory molecules such as CD40, OX40L, and 4-1BBL and the functional pMHC II complexes by DCOVA activation. CD4+ Th-APC with acquired pMHC II and I were capable of stimulating CD4+ Th1 and central memory CD8+44+CD62LhighIL-7R+ T cell responses leading to antitumor immunity against OVA-expressing mouse B16 melanoma. Their stimulatory effect on CD8+ CTL responses and antitumor immunity is mediated by IL-2 secretion, CD40L, and CD80 signaling and is specifically targeted to CD8+ T cells in vivo via acquired pMHC I. In addition, CD4+ Th-APC expressing OVA-specific TCR, FasL, and perforin were able to kill DCOVA and neighboring Th-APC expressing endogenous and acquired pMHC II. Taken together, we show that CD4+ Th-APC can modulate immune responses by stimulating CD4+ Th1 and central memory CD8+ T cell responses and eliminating DCOVA and neighboring Th-APC. Therefore, our findings may have great impacts in not only the antitumor immunity, but also the regulatory T cell-dependent immune tolerance in vivo.

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Application of cancer vaccines is limited due to their systemic immunotoxicity and inability to satisfy all the steps, including loading of tumor antigens, draining of antigens to lymph nodes (LNs), internalization of antigens by dendritic cells (DCs), DC maturation, and cross-presentation of antigens for T cell activation. Here, we present a combinatorial therapy, based on a α-cyclodextrin (CD)–based gel system, DOX/ICG/CpG-P-ss-M/CD, fabricated by encapsulating doxorubicin (DOX) and the photothermal agent indocyanine green (ICG). Upon irradiation, the gel system exhibited heat-responsive release of DOX and vaccine-like nanoparticles, CpG-P-ss-M, along with chemotherapy- and phototherapy-generated abundant tumor-specific antigen storage in situ. The released CpG-P-ss-M acted as a carrier adsorbed and delivered antigens to LNs, promoting the uptake of antigens by DCs and DC maturation. Notably, combined with PD-L1 blocking, the therapy effectively inhibited primary tumor growth and induced tumor-specific immune response against tumor recurrence and metastasis.