Oxidative Stress Regulates T Cell Pathogenicity in Gvhd

Allogeneic hematopoietic transplantation (allo-HCT) is a classic immunotherapy for hematologic malignances, but graft-versus-host disease (GVHD) remains a major cause of morbidity and mortality.

Oxidative stress is considered as an unavoidable consequence of allo-HCT and could contribute to GVHD pathogenicity significantly. Owing to the contributions of pre-existing disease conditions and the requirement for conditioning regimens that increases cellular reactive oxygen species (ROS), oxidative stress is elevated in all BMT recipients. Thioredoxin (Trx) is ubiquitously expressed enzymes, counteracts oxidative stress by scavenging ROS and regulating other enzymes metabolizing H₂O₂. In addition, it has been shown that regulatory T cells (Tregs) express and secrete higher levels of Trx than conventional CD4 T cells. Trx-1 is critical for the resilience of Tregs to oxidative stress and sustained expression of surface thiols at a high density. We hypothesis that oxidative stress plays a critical role in the pathology of GVHD development, and thus the maintenance of a redox balance would be an effective strategy to control GVHD after allo-BMT.

To test this hypothesis, we used a strain of mice that express transgenic (Tg) human Trx-1 ubiquitously, refer as Trx-Tg mice. We first verified that Trx-Tg T cells demonstrated significantly reduced ROS accumulation after activation in vitro and in vivo. We next sought to test whether Trx1 affects T cell activation and function. Upon alloantigen stimulation in vitro, Trx-Tg T cells have substantially reduced ability to produce IFN-γ compared with WT counterparts. These results prompted us to evaluate T cell responses in vivo . Upon transfer of T cells into irradiated allogeneic recipients, we observed that the Trx-Tg T cells significantly reduced proliferation and IFN-γ production compared with WT counterparts. Given that Trx-Tg T cells displayed a reduced allogeneic response in vitro and in vivo, we further hypothesized that Trx plays an essential role in regulating allogeneic T cells in GVHD. We performed a MHC-mismatched B6→BALB/c BMT model, and found that recipients of WT T cells developed severe and lethal GVHD, whereas the majority of the recipients of Trx-Tg T cells survived long term and had significantly less weight loss and lower clinical score. Development of GVHD requires donor T cell expansion in lymphoid organs and migration into target organs. Hence, we asked whether TRX-1 is required for T cell infiltration and expansion into target organs. Three weeks after BMT, we observed that recipients of Trx-Tg T cells had significantly fewer pathological injuries in all GVHD target organs, which was consistent with the GVHD outcome. While comparable numbers of Trx-Tg T and WT T cells were found in recipient spleens, a significantly lower number of Trx-Tg T cells were found in recipient livers as compared with that of WT T cells. In addition, T cells that migrated into the liver expressed significantly lower levels of intercellular IFN-γ in the Trx-Tg group. These data suggest that Trx-Tg T cells may reduce expansion and/or migration. For translational purpose, we evaluated therapeutic potential of recombinant human Trx-1 (rhTrx-1), and found that administration of recombinant human Trx-1 significantly reduced ability of T cells to produce IFN-γ compared with control treatment upon alloantigen stimulation in vivo . Furthermore, we performed a MHC-mismatched B6→BALB/c BMT model and found that administration of rhTrx-1had significantly reduced the mortality and mobility of BLAB/c recipients. Theraputic effect of rhTrx-1 in the prevention of GVHD was validated in a haploidentical BMT model (B6→BD2F1). More importantly, administration of rhTrx-1 did not impair the graft-versus-leukemia (GVL) against p815 tumor. Taken together, the current work provides a strong rationale and demonstrates the feasibility to target ROS pathway, which can be readily translated into clinic.