Post-transplant cyclophosphamide prevents xenogeneic graft-versus-host disease while depleting proliferating regulatory T cells

Caroline Ritacco; Murat Cem Köse; Justine Courtois; Lorenzo Canti; Charline Beguin; Sophie Dubois; Benoît Vandenhove; Sophie Servais; Jo Caers; Yves Beguin; Grégory Ehx; Frédéric Baron

doi:10.1016/j.isci.2023.106085

Post-transplant cyclophosphamide prevents xenogeneic graft-versus-host disease while depleting proliferating regulatory T cells

iScience. 2023 Jan 31;26(3):106085. doi: 10.1016/j.isci.2023.106085. eCollection 2023 Mar 17.

Authors

Caroline Ritacco¹, Murat Cem Köse¹, Justine Courtois¹, Lorenzo Canti¹, Charline Beguin¹, Sophie Dubois¹, Benoît Vandenhove¹, Sophie Servais^{1

2}, Jo Caers^{1

2}, Yves Beguin^{1

2}, Grégory Ehx¹, Frédéric Baron^{1

2}

Affiliations

¹ Hematology Research Unit, Groupe Interdisciplinaire de Génoprotéomique Appliquée (GIGA)-I³, University of Liège, Liège 4000, Belgium.
² Department of Medicine, Division of Hematology, CHU of Liège, Liège 4000, Belgium.

Abstract

Graft-versus-host disease (GVHD) remains a serious limitation of allogeneic hematopoietic cell transplantation (allo-HCT). While post-transplant administration of cyclophosphamide (PTCy) is increasingly used as GVHD prophylaxis, its precise mechanisms of action and its impact on graft-versus-leukemia effects have remained debated. Here, we studied the mechanisms of xenogeneic GVHD (xGVHD) prevention by PTCy in different humanized mouse models. We observed that PTCy attenuated xGVHD. Using flow cytometry and single-cell RNA-sequencing, we demonstrated that PTCy depleted proliferative CD8⁺ and conventional CD4⁺ T cells but also proliferative regulatory T cells (Treg). Further, T-cell receptor β variable region sequencing (TCRVB) analyses demonstrated that highly xenoreactive T-cell clones were depleted by PTCy. Although Treg frequencies were significantly higher in PTCy-treated than in control mice on day 21, xGVHD attenuation by PTCy was not abrogated by Treg depletion. Finally, we observed that PTCy did not abrogate graft-versus-leukemia effects.

Keywords: Immunology; Medicine; Molecular biology.