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Mucus secretion is an important feature of asthma that highly correlates with morbidity. Current therapies, including administration of mucolytics and anti-inflammatory drugs, show limited effectiveness and durability, underscoring the need for novel effective and longer lasting therapeutic approaches. Here we show that mucus production in the lungs is regulated by the TNF superfamily member 15 (TL1A) acting through the mucus-inducing cytokine IL-13. TL1A induces IL13 expression by innate lymphoid cells leading to mucus production, in addition to promoting airway inflammation and fibrosis. Reciprocally, neutralization of IL13 signaling through its receptor (IL4Rα), completely reverses TL1A-induced mucus secretion, while maintaining airway inflammation and fibrosis. Importance of TL1A is further demonstrated using a preclinical asthma model induced by chronic house dust mite exposure where TL1A neutralization by genetic deletion or antagonistic blockade of its receptor DR3 protected against mucus production and fibrosis. Thus, TL1A presents a promising therapeutic target that out benefits IL13 in reversing mucus production, airway inflammation and fibrosis, cardinal features of severe asthma in humans., Competing Interests: Authors KS, AM, and RS were employed by Kyowa Kirin Pharmaceutical Research, Inc. The authors declare that this study received funding from Kyowa Kirin Pharmaceutical Research, Inc. Authors KS, AM, and RS of Kyowa Kirin Pharmaceutical Research, Inc participated in discussing results and editing the manuscript. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Steele, Sachen, McKnight, Soloff and Herro.)

Death receptor 3 (DR3) is a tumor necrosis factor receptor superfamily member (TNFRSF25), which is minimally expressed on resting conventional T cells (though readily inducible upon cell activation), yet highly expressed on resting FoxP3 + regulatory T cells (Treg). We recently demonstrated that activation of DR3 with an agonistic antibody (4C12) leads to selective expansion and activation of Treg in healthy mice and suppression of graft-versus-host disease (GVHD) in recipient mice when donor mice are treated. However, given the long antibody half-life and concomitant safety concerns, along with the lack of a humanized agonistic antibody to DR3, both human and murine fusion proteins incorporating the natural DR3 ligand TL1A (TL1A-Ig) have been developed. Herein, we show that DR3 activation with 4C12 or with TL1A-Ig, with or without the addition of low dose IL-2 to the treatment regimen, led to a significant expansion of murine Treg in spleen, lymph nodes, and peripheral blood. Bioluminescent imaging revealed peak Treg expansion around day 7-8, with return to near baseline after 2-3 weeks. In addition to expansion, all DR3 agonist treatment regimens led to increased activation of Tregs, with significant upregulation of the activation markers ICOS, KLRG-1, PD-1, and CD103, and the proliferation marker Ki-67. The near absence of activated Treg populations in control treated spleens was also detected on tSNE analysis of flow cytometry data. Subtly different patterns of splenic Treg activation by the different DR3 agonists were noted in both tSNE analysis of flow cytometry data and RNA-sequencing analysis. However, upregulation of gene transcripts which play important roles in cell proliferation, trafficking, activation, and effector function were observed regardless of the DR3 agonist treatment regimen used. In the major MHC-mismatch model of hematopoietic cell transplantation, DR3 agonist-mediated expansion and activation of Tregs in donor mice led to a significant improvement in GVHD in recipient mice. These data provide important preclinical information regarding the outcome of DR3 activation with an agonistic antibody or natural ligand and provide insight into the therapeutic use of this approach to reduce GVHD in recipients and improve outcomes of hematopoietic cell transplantation.

Death receptor 3 (DR3), a member of the tumor necrosis factor receptor (TNFR) superfamily, has been implicated in regulating T-helper type-1 (T H 1), type-2 (T H 2), and type-17 (T H 17) responses as well as regulatory T cell (T reg ) and innate lymphoid cell (ILC) functions during immune-mediated diseases. However, the role of DR3 in controlling lymphocyte functions in inflammatory bowel disease (IBD) is not fully understood. Recent studies have shown that activation of DR3 signaling modulates T reg expansion suggesting that stimulation of DR3 represents a potential therapeutic target in human inflammatory diseases, including Crohn's disease (CD). In this study, we tested a specific DR3 agonistic antibody (4C12) in SAMP1/YitFc (SAMP) mice with CD-like ileitis. Interestingly, treatment with 4C12 prior to disease manifestation markedly worsened the severity of ileitis in SAMP mice despite an increase in FoxP3 + lymphocytes in mesenteric lymph node (MLN) and small-intestinal lamina propria (LP) cells. Disease exacerbation was dominated by overproduction of both T H 1 and T H 2 cytokines and associated with expansion of dysfunctional CD25 - FoxP3 + and ILC group 1 (ILC1) cells. These effects were accompanied by a reduction in CD25 + FoxP3 + and ILC group 3 (ILC3) cells. By comparison, genetic deletion of DR3 effectively reversed the inflammatory phenotype in SAMP mice by promoting the expansion of CD25 + FoxP3 + over CD25 - FoxP3 + cells and the production of IL-10 protein. Collectively, our data demonstrate that DR3 signaling modulates a multicellular network, encompassing T regs , T effectors, and ILCs, governing disease development and progression in SAMP mice with CD-like ileitis. Manipulating DR3 signaling toward the restoration of the balance between protective and inflammatory lymphocytes may represent a novel and targeted therapeutic modality for patients with CD.