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Genome-wide association studies have identified risk loci linked to inflammatory bowel disease (IBD)(1)—a complex chronic inflammatory disorder of the gastrointestinal tract. The increasing prevalence of IBD in industrialized countries and the augmented disease risk observed in migrants who move into areas of higher disease prevalence suggest that environmental factors are also important determinants of IBD susceptibility and severity(2). However, the identification of environmental factors relevant to IBD and the mechanisms by which they influence disease has been hampered by the lack of platforms for their systematic investigation. Here we describe an integrated systems approach, combining publicly available databases, zebrafish chemical screens, machine learning and mouse preclinical models to identify environmental factors that control intestinal inflammation. This approach established that the herbicide propyzamide increases inflammation in the small and large intestine. Moreover, we show that an AHR–NF-κB–C/EBPβ signalling axis operates in T cells and dendritic cells to promote intestinal inflammation, and is targeted by propyzamide. In conclusion, we developed a pipeline for the identification of environmental factors and mechanisms of pathogenesis in IBD and, potentially, other inflammatory diseases.

The complement system plays a major role in humoral innate immunity. Upon activation, complement proteins trigger a cascade of enzymatic events leading to the production of inflammatory mediators and membrane attack complexes. Tight regulation of complement proteins is essential for immune homeostasis due to their potency and abundance in fluid phase. Complement Regulatory Proteins (CRPs) that are membrane-bound (e.g., CD59), or in fluid phase (e.g., Factor H), prevent aberrant activation of complement pathways against self and mitigate autoimmunity. The importance of CRPs is underscored by the finding that genetic variations in the CRPs can lead to autoimmune diseases such as paroxysmal nocturnal hemoglobinuria (PNH) characterized by the lysis of host red blood cells from dysregulated complement system. Systemic complement inhibition via anti-C5 antibody has clinically been shown to benefit some patients with complement-mediated disorders, but the therapy requires a high, frequent dosing scheme and supplemental vaccinations to compensate for systemic immunosuppression. In addition, other diseases such as C3 glomerulopathy affect specific tissues and involve pathways beyond C5, limiting treatment options. To this end, local immunomodulation through targeted delivery of CRPs to specific tissues is an attractive strategy to restore homeostasis in complement-mediated autoimmune diseases while circumventing the need for high dose systemic inhibition of complement factors. Here, we present a proof-of-concept study for the design, generation, and evaluation of tissue-tethering antibodies fused with CRPs. Also, we demonstrate the pharmacokinetics and pharmacodynamics of tissue-targeting CRP fusions in mouse models.

Current treatment approaches for autoimmune conditions comprise primarily of systemic immunosuppressants or cytokine blockade. Concentration of therapeutic molecules to the tissues that are the sites of autoimmune and inflammatory diseases is a promising approach with the potential to induce therapeutic benefit and avert risks associated with systemic immunotherapies. Pandion Therapeutics is developing a bifunctional antibody platform that can drive localized immune modulation. The platform combines a “tether antibody” that targets a tissue of choice and “an effector end” that activates specific regulatory immune pathways to restore immune-homeostasis. Here we report the engineering of a skin-tethered PD-1 agonist and a skin-tethered CD39 that inhibit T cell activation and function and deplete local ATP, respectively, modulating different arms of the immune system in a tissue specific manner. These skin-tethered immune effectors were assessed for drug-like properties in biophysical assays and in vitro and in vivo assays for target binding, cellular activity and tissue specific-localization. Moreover, these bifunctionals were tested in pathway-relevant preclinical models such as Vitiligo and Contact Hypersensitivity. Strikingly, a selective accumulation of the tethered bifunctionals to the skin was observed and correlated with a tether-dependent efficacy compared to a non-tether control. We believe that this therapeutic approach has the potential to drive the resolution of cutaneous inflammation, providing an opportunity for developing new targeted therapies for autoimmune and inflammatory skin diseases.

Regulatory T cells (Treg) play a critical role in maintaining graft tolerance following organ transplantation, and increased numbers of Tregs in solid-tissue grafts such as the kidney are associated with improved graft survival and function. Therapeutic approaches that increase Tregs offer a promising alternative to current standard-of-care treatment consisting of broad-acting immunosuppressants and their attendant side effects. While efforts to expand Tregs ex vivo for infusion into patients have shown promise, they present manufacturing and administration challenges. Low dose (LD) interleukin 2 (IL-2) drives Treg proliferation and function via the heterotrimeric IL-2 receptor expressed on Tregs and has been shown to expand Tregs in vivo, including in the context of transplantation. However, IL-2 can also activate other immune cells including conventional T cells and Natural Killer (NK) cells, which express IL-2Rb/CD122 and IL-2g/CD132, and this could accelerate rejection. We have enhanced IL-2 selectivity for Treg by introducing mutations that increase affinity for CD25 and decrease affinity for CD122/CD132, resulting in Treg specific expansion. Here, we demonstrate that this IL-2 Mutein (IL-2M) can be “tethered” to the kidney via a bifunctional antibody targeting a tubule-specific protein. This kidney-tethered IL-2M maintains Treg selectivity and localizes to the kidney with extended tissue PK. Moreover, in a CD34-NSG mouse model, animals dosed with kidney-tethered IL-2M exhibited prolonged kidney Treg expansion compared to a systemic, non-tethered IL-2M. This approach has the potential to substantially improve kidney graft acceptance while reducing adverse effects and improving patient quality of life.

Astrocytes play complex roles in neuroinflammation. Thus, it is important to characterize the mechanisms regulating astrocyte function, as well as potential targets for the therapeutic modulation of astrocyte activity. Here we report that during the chronic-progressive phase of EAE, astrocytes promote disease pathogenesis by a lipid-dependent signaling pathway. In line with previous studies, depletion of reactive astrocytes during the acute phase of chronic-progressive EAE exacerbated disease. However, depletion of astrocytes in the chronic phase ameliorated the disease. Hence, to understand this dichotomy we compared gene expression profiles of astrocytes from mice in acute and chronic stages of EAE. One gene associated with the chronic stage was B4GALT6, which codes for the β-1,4-galactosyltransferase 6 that catalyzes the synthesis of lactosylceramide (LacCer). We observed that LacCer levels are upregulated in the CNS during chronic EAE, and that LacCer synthesized by the astrocytes acts in an autocrine manner to trigger transcriptional programs that promote the recruitment and activation of infiltrating monocytes and microglia, and neurodegeneration. We also detected increased B4GALT6 expression and LacCer levels in MS lesions. Finally, the inhibition of LacCer synthesis suppressed CNS innate immunity and neurodegeneration, and interfered with the activation of human astrocytes. Thus, B4GALT6 is a potential therapeutic target for MS and neuroinflammatory disorders.