Evolutionarily conserved effects of Notch signaling drive intestinal graft-versus-host disease in mice and non-human primates

Notch signaling promotes T-cell pathogenicity and graft-versus-host disease (GVHD) after allogeneic hematopoietic cell transplantation (allo-HCT) in mice, with a dominant role for the Delta-like ligand DLL4. To assess if Notch’s effects are evolutionarily conserved and identify key mechanisms, we studied antibody-mediated DLL4 blockade in a non-human primate model similar to human allo-HCT. Short-term DLL4 blockade improved post-transplant survival with striking, durable protection from gastrointestinal GVHD, out of proportion to other disease sites. Unlike prior immunosuppressive strategies, anti-DLL4 interfered with a T-cell transcriptional program associated with intestinal infiltration. In cross-species investigations, Notch inhibition decreased surface abundance of the gut-homing integrin a4b7 in conventional T-cells via b1 competition for a4 binding, while preserving a4b7 in regulatory T-cells. Thereby, DLL4/Notch blockade decreased effector T-cell infiltration into the gut, with increased regulatory to conventional T-cell ratios early after allo-HCT. Our results identify a conserved, biologically unique and targetable role of DLL4/Notch signaling in GVHD. One Sentence Summary Notch signaling promotes pathogenic effector T cell infiltration of the intestine during acute graft-versus-host disease. ### Competing Interest Statement D.G.A. is currently employed by GlaxoSmithKline. G.C., O.H., F.K. and G.T. are employed by Regeneron, while S.C. is a former employee. B.R.B. has received remuneration as an advisor to Magenta Therapeutics and BlueRock Therapeutics; research funding from BlueRock Therapeutics, Rheos Medicines, Carisma Therapeutics, Inc., and he is a co-founder of Tmunity Therapeutics. L.S.K is on the scientific advisory board for HiFiBio. She reports research funding from Magenta Therapeutics, BlueBird Bio, Novartis, EMD-Serono, and Regeneron Pharmaceuticals. She reports consulting fees from Vertex, grants and personal fees from Bristol Myers Squibb. L.S.K. conflict-of-interest with Bristol Myers Squibb is managed under an agreement with Harvard Medical School. In addition, L.S.K. has a patent Method to prevent relapse after transplant which is pending, and a patent Method to prevent GVHD after transplant with royalties paid. I.M. has received research funding from Regeneron and Genentech, and he is a member of Garuda Therapeutics scientific advisory board.