Nucleic acid-based tolerogenic immunotherapies can induce long-lasting, autoantigen-specific immune tolerance in autoimmune diseases. Developing these therapeutics requires a deep understanding of the immunobiology governing induction and maintenance of peripheral tolerance. Here, we utilized the uridine-modified mRNA lipoplex (modRNA-LPX) platform (Krienke et al, 2021 Science) to assess cellular and soluble determinants of successful MHC-II restricted, autoantigen-specific tolerogenic immunotherapy in mouse models.
First, we showed that despite the wide cellular biodistribution of intravenously administered LPX nanoparticles, splenic conventional dendritic cells (cDCs), but not macrophages or B cells, are the main drivers of MHC-II antigen presentation and tolerance induction. Significant upregulation of interleukin 10 (IL-10) was observed in splenic cDCs and antigen-specific Foxp3- and Foxp3+ T cells, suggesting that IL-10 is a key factor at the site of tolerance induction. To test its direct effect on splenic cDCs, we treated mice with IL-10 encoding modRNA-LPX and found that IL-10 could counteract dose-dependent cDC activation caused by LPX, thus pushing the cDCs towards a tolerogenic state.
We then treated Experimental Autoimmune Encephalomyelitis (EAE) mice with modRNA-LPX coding for MHC-II restricted autoantigen and IL-10. While we did not observe enhanced therapeutic benefit, IL-10 could suppress LPX-driven systemic inflammation via upregulating interleukin 1 receptor antagonist (IL-1ra), which is an interferon (IFN)-inducible anti-inflammatory cytokine and a key regulator of nanoparticle-induced inflammation (Tahtinen et al, Nat Imm 2022). scRNAseq analysis of DCs revealed that in the absence of pre-existing inflammation, IL-10 mRNA activated a pro-inflammatory IFN response and drove proliferation of effector T cells over Tregs. Conversely, under inflammatory conditions, IL-10 suppressed DC maturation and T cell activation pathways and further amplified the IFN response. These results demonstrate that pleiotropic IL-10 drives opposing and/or mixed cellular programs in DCs depending on the inflammatory context, tilting the delicate balance between tolerance and immunity.