Oral Presentation ANZBMS-MEPSA-ANZORS 2022

The ATP-P2X7 signalling axis in graft-versus-host disease: Recent insights from humanised mouse studies (#64)

Peter Cuthbertson 1 2 , Amal Elhage 1 2 , Amy Button 1 2 , Chloe Sligar 1 2 , Nicholas J Geraghty 1 2 , Sam R Adhikary 1 2 , Ellen M Reilly 1 2 , Nicolas R Tomasiello 1 2 , Katrina Bird 1 2 , Kara L Vine-Perrow 1 2 , Debbie Watson 1 2 , Ronald Sluyter 1 2
  1. University of Wollongong, Wollongong, NSW, Australia
  2. Illawarra Health and Medical Research Institute, Wollongong, NSW, Australia

Allogeneic blood stem cell transplantation is used for the treatment of leukaemia through the generation of life-saving graft-versus-tumour (GVT) immunity. However, this treatment can also result in graft-versus-host disease (GVHD), an often fatal inflammatory response mediated by donor T cells targeting tissues of recipients. Studies in allogeneic mouse models of GVHD indicate a role for the ATP-P2X7 signalling axis in the development of this disease. In this model, ATP is released from damaged tissues to activate P2X7 on host antigen presenting cells to drive T cell-mediated GVHD. However the relevance of this signalling axis to human GVHD and the role of P2X7 donor immune cells remains to be fully elucidated. To address these and other questions, our groups study a humanised mouse model of GVHD, in which NOD-scid IL2Rgnull (NSG) mice are injected with human peripheral blood mononuclear cells (PBMCs) and develop lethal GVHD from 3 weeks. Injection of the human/mouse P2X7 antagonist, Brilliant Blue G (BBG; 50 mg/kg, Days 0-10), into humanised mice reduced clinical and liver GVHD. This effect was associated with a reduction in circulating human IFNg and an increase in human T regulatory cells (Tregs). Injection of a human-specific neutralising anti-P2X7 monoclonal antibody (mAb; 0.1 mg/mouse, Days 0,2,4,6,8,) into humanised mice reduced also clinical and liver GVHD, which was similarly associated with an increase in human Tregs. Use of either inhibitor in cultures of serum-starved human PBMCs prevented the loss Tregs, suggesting that BBG and the anti-P2X7 mAb can prevent the ATP-induced death of these cells, providing a possible mechanism of action of these treatments in mice to reduce GVHD development. Notably, use of BBG (as above) with the clinical treatment post-transplant cyclophosphamide (PtCy; 33 mg/kg, Days 3,4) in humanised mice also reduced clinical and liver GVHD and increased human CD39+ Tregs but did not reduce GVT immunity to human THP-1 myeloid leukaemia cells. Collectively, this data indicates a role for P2X7 activation on donor Tregs and the subsequent loss of these cells in the development of GVHD. Moreover, inhibition of P2X7 does not compromise GVT immunity.