Extracorporeal photopheresis combined with pentostatin in the conditioning regimen for canine hematopoietic cell transplantation does not prevent GVHD

Developments and translational relevance for the canine haematopoietic cell transplantation preclinical model

The development of safe and reliable haematopoietic cell transplantation (HCT) protocols to treat human patients with malignant and non-malignant blood disorders was highly influenced by preclinical studies obtained in random-bred canines. The surmounted barriers included recognizing the crucial importance of histocompatibility matching, establishing long-term donor haematopoietic cell engraftment, preventing graft-vs-host disease and advancing effective conditioning and post-grafting immunosuppression protocols, all of which were evaluated in canines. Recent studies have applied the tolerance inducing potential of HCT to solid organ and vascularized composite tissue transplantation. Several advances in HCT and tolerance induction that were first developed in the canine preclinical model and subsequently applied to human patients are now being recruited into veterinary practice for the treatment of malignant and non-malignant disorders in companion dogs. Here, we review recent HCT advancements attained in the canine model during the past 15 years.

Dendritic polyglycerol sulfate attenuates murine graft-versus-host disease

Graft-versus-host disease (GvHD) is a severe immune reaction commonly occurring after hematopoietic stem cell transplantation. The outcome of patients who do not respond to the currently used immunosuppressive drugs is poor, thus there is an urgent need for the evaluation of new therapies. Heparin has a well-known anti-inflammatory effect and heparin analogues with a low anticoagulant effect are interesting candidates as new anti-inflammatory drugs. We explored the therapeutic potential of dendritic polyglycerol sulfates (dPGS), a novel class of heparin derivatives, on murine acute GvHD in vivo. The therapeutic effect of dPGS on murine GvHD was more intense after intravenous application compared to subcutaneous injection. An increased survival rate and improved clinical scores were observed in mice treated with 5 mg/kg once a week. In these animals, there was a reduction in the percentage of CD4(+) and CD8(+) T cells, which are the main effectors of GvHD. In addition, dPGS treatment decreased the number of tumor necrosis factor alpha (TNFα)-producing T cells. Increasing the dose of dPGS reversed the positive effect on survival as well as the clinical score, which indicates a small therapeutic range. Here, we report for the first time that dPGS have a significant immunosuppressive in vivo effect in a mouse model of severe acute GvHD. Therefore, we propose to study dPGS as promising candidates for the development of potential new drugs in the treatment of steroid-refractory GvHD patients first in larger animals and later in humans.

Extracorporeal photopheresis in prevention and treatment of acute GVHD

Acute graft versus host disease (GVHD), a common complication after allogeneic hematopoietic cell transplantation (HCT), occurs in as many as 70% of recipients of this life saving treatment. Front line therapy for GVHD with corticosteroids will fail in up to 40% of patients, which leads to high morbidity and mortality. Traditional prevention and treatment strategies have focused on reducing alloreactivity, typically with therapy to reduce cytotoxic T-cell function. Emerging evidence exists that promotion of regularly T-cell function, through treatments such as extracorporeal photopheresis, is effective for GVHD treatment and has potential for prevention as well. This review will focus on literature reporting the success of ECP for steroid refractory acute GVHD and the potential for delivery of ECP in the early pre and post-transplant periods that shows promise as a less immunosuppressive strategy to reduce rates of acute GVHD.