Pathogenicity and alloresponse of T cells confined by thioredoxin-1

Allogeneic hematopoietic cell transplantation (allo-HCT) is an effective therapeutic procedure that activates donor lymphocyte-mediated anti-tumour responses, known as the graft-versus-leukemia (GVL) effect. However, the immune response that contributes to the desired GVL effect, is also responsible to graft-versus-host disease (GvHD). In addition, certain inflammatory cytokines are elevated after allo-HCT, perpetuating GvHD through cytotoxic effects on host tissues. Therefore, novel drug targets need to be evaluated which may attenuate GvHD whilst maintaining the GVL reaction.

Hanief Sofi, from the Department of Microbiology and Immunology, Medical University of South Carolina, Charleston, US, and colleagues explored the role of the human redox-sensing molecule thioredoxin-1, (Trx1) on the development of GvHD in murine and xenograft models. Xenograft models of allogeneic bone marrow transplantation (allo-BMT) and transgenic models of Trx1 (Trx1-Tg) were used for their potential to modify GvHD and GVL effects.

Methods

• C57BL/6, B6.Ly5.1 and BLAB/c mice
• CD4 and CD8 T cells were purified separately and pooled at a ratio of 2:1 (CD4:CD8)
• In vitro:
  • 0.2x10⁶ T cells co-cultured with 0.6x10⁶ T cell depleted splenocytes for 5 days. T cell depleted splenocytes were used as antigen presenting cells (APCs)
• In vivo:
  • 2.0x10⁶ CFSE-labelled purified T cells injected intravenously into irradiated recipient mice and analyzed after four days
  • Long-term GvHD: 0.5x10⁶ injected into irradiated mice
  • Some mice also injected with RTrx1 intraperitoneally at 5ug/mouse/day from day -1 to day 3

Key findings

• Trx1 reduces T cell activation and oxidative stress
  • Trx1-Tg cells stimulated with anti-CD3 and anti-CD28 had significantly reduced NFκB activity and T-bet expression
  • In vitro Trx1-Tg T cells had substantially reduced ability to proliferate and produce IFNy
  • Trx1-Tg T cells had reduced ROS accumulation, CD98 upregulation and glutamine uptake in vitro
  • Trx1-Tg T cells were found to have reduced ROS accumulation in vivo
  • Trx1-Tg cells expressed significantly lower CD98 levels in recipient livers but not recipient spleens
• Txr1 alleviates GvHD after alllo-BMT
  • Trx1-Tg T cells used as donor T cells in murine models of allo-BMT decreased the frequency of CD4⁺CD25⁺Foxp3⁺ (nTregs)
  • Recipients of WT T cells developed severe and lethal GvHD, whilst mice injected with Trx1-Tg T cells survived longer with significantly less weight loss and lower GvHD scores
• RTrx1 treatment led to
  • reduced ROS accumulation, IFNy production and allogenic T cell responses
  • attenuated GvHD severity
  • a 50% reduction in GvHD-related mortality
  • reduced number of donor T cells in recipients, and especially in target organs including the gut and lungs
• Administration of RTrx1 treatment reduces GvHD with little impact on GVL effect
• In a haploidentical 23 B6→BDF1 BMT model with p815 mastocytoma:
  • All recipients of p815 tumor cells without T cell infusion died from leukemia relapse within 20 days after 10 BMT
  • Recipients treated with T-cell infusion and a vehicle control died from GVHD without tumor relapse
  • Recipients treated with RTrx1 survived with mild GVHD and without tumor relapse

Conclusion

Trx1 exerts anti-oxidative and anti-inflammatory effects and down-regulates T cell alloresponses, alleviating GvHD development in both murine and xenograft models while still maintaining a GVL response. The research team anticipate that the effects of RTrx1 treatment can be extended to human T cells, and could have the potential to treat GvHD in patients with hematological malignancies undergoing allo-HSCT.