Ashley Vanderbeck (Mentor: Ivan Maillard, MD, PhD)

“Notch signaling regulates allo-T cell gut-trafficking by altering integrin pairing dynamics”

Ashley Vanderbeck, Victor Tkachev, Eric T Perkey, Samantha Kelly, Leolene Carrington, Ryan Lee, Anneka Allman, Leslie Kean and Ivan Maillard

Intestinal GVHD is the major life-threatening complication of acute GVHD in allo bone marrow transplant (BMT) recipients. Prophylaxis with systemic Notch ligand anti-DLL4 mAb blockade prevents GI-GVHD and reduces T cell accumulation in the gut of both mice and non-human primates, indicating that this is a conserved feature of Notch inhibition. In order to understand how Notch signaling regulates allo-T cell GI trafficking, we first assessed Notch-deprived allo-T cells for expression of classical gut-homing molecules such as 47 and CCR9. We find that Notch loss-of-function blunted 47 surface expression in Tconv 4 days post-BMT. However, Notch blockade does not appear to regulate overall retinoic acid signaling or gene expression of classical T cell gut-homing molecules, as RNA-seq did not show a reduced retinoic acid signaling or gut-trafficking signature. Interestingly, we find that Notch inhibition leads to increased Itgb1 (integrin subunit 1) in Tconv. Itgb1 overexpression was previously reported to reduce surface 47 in T cells by outcompeting 7 for 4 binding. Thus, we hypothesized that Notch signaling alters allo-T cell GI trafficking by skewing the surface integrin repertoire. We find that allo Tconv cells express higher levels of surface integrin b1, and co-expression of integrin a4 and b1. Moreover, genetic inactivation of Itgb1 in Notch deprived allo-T cells restores surface expression of a4b7, thus suggesting that Notch loss-of-function blunts a4b7 expression via upregulation of Itgb1. Altogether, our data reveal a new potential mechanism of Notch immunomodulation in alloreactive T cell gut trafficking and bring a new perspective to the signaling pathways that underlie gut-homing programs in T cells, as Notch has not previously been implicated in regulating gut-tropism.