Ornithine decarboxylase deficiency in donor T cells preserves strong GVL activity while attenuating acute and preventing steroid-resistant gut GVHD in a recipient tissue PD-L1-dependent manner Free

Graft-versus-leukemia/lymphoma (GVL) activity and graft-versus-host disease (GVHD) are usually mediated by the same alloreactive T cells; and preserving GVL effect while preventing GVHD is the optimal goal of allogeneic hematopoietic cell transplantation (Allo-HCT), but this remains elusive. Severity of acute gut GVHD is associated with the outcome of the Allo-HCT. Metabolic regulation of T cell function has been increasingly recognized in GVHD pathogenesis, but the role of polyamine metabolism in this context remains poorly understood. Using a murine Allo-HCT model with C57BL/6 donors and BALB/c recipients, we evaluated the impact on GVL activity and GVHD by specific deficiency of ornithine decarboxylase (ODC), a crucial enzyme in polyamine synthesis in donor T cells. GVL activity was measured by inoculating Luc⁺/ALL (10x10³/mouse) and in vivo bioluminescent imaging. First, with 1x10⁶ WT or ODC-deficient donor T cells, all recipients died within 8 days with severe GVHD. With 0.8x10⁶ T cells, tumor progression was prevented, but with 0.6x10⁶ T cells, all recipients had tumor progression. With 0.8 and 0.6x10⁶ donor T cells, ODC deficiency notably attenuated the severity of GVHD after day 7, and 0.8x10⁶ T cells allowed all the recipients to survive for more than 100 days without detectable tumor or GVHD. Second, we tested the impact of dexamethasone (DEX) treatment on GVHD and GVL effects of WT and ODC^-/-T cells. A single injection of DEX (5mg/g) on day 3 after HCT attenuated GVHD while preserving GVL effects, thereby enabling long-term (>100 days after HCT) survival in recipients given 1.25x10⁶ and 2.5x10⁶ ODC^-/- T cells, but all recipients given the same numbers of WT T cells died with acute GVHD by day 30. Third, we previously reported that 4 injections of DEX induced steroid-resistant-gut GVHD (SR-Gut-GVHD) with expansion of IL-22⁺ T cells (Song et al: Nature communication 2021). We currently found that SR-Gut-GVHD was associated with the expansion of ODC^hiIL-22⁺ T cells, and ODC^-/-T cells were resistant to the induction of SR-Gut-GVHD, with no expansion of IL-22⁺ T cells. Further mechanistic studies showed that the dissociation of GVHD from GVL effect mediated by ODC^-/- T cells was host-tissue PD-L1-dependent, and DEX-treatment augmented the PD-L1/PD-1 effect. In addition, ODC deficiency enhanced PD-L1/PD-1 mediated inhibition of TCR signaling down-stream PI3-AKT-mTOR pathway, augmented mitochondrial reactive oxygen species (ROS) production and mitochondrial dysfunction, reduced T cell proliferation, augmented activated T cell anergy/exhaustion, and decreased the differentiation of Ly108⁺CD69^- stem-like memory T cells (Tsm) into Ly108^-CD69⁺ tissue-resident effector memory T cells (Trm) that produce GM-CSF, TNF-α, and IFN-g to mediate tissue damage. These findings identify polyamine metabolism as a critical regulator of alloreactive donor T differentiation and function and suggest that targeting this pathway may offer a novel strategy to prevent GVHD while preserving GVL effects (Grant support: R01HL162847 to Zeng).