Nox2-deficient Tregs improve heart transplant outcomes via their increased graft recruitment and enhanced potency.

Silvia C Trevelin,Robert I Lechler,Anna Zampetaki,Greta Sawyer,Ajay M Shah,Giovanna Lombardi,Lesley Ann Smyth,Aleksandar Ivetic,Robert Köchl,Federica Marelli-Berg,Alison C Brewer

doi:10.1172/jci.insight.149301

Abstract

Nox2 is a ROS-generating enzyme, deficiency of which increases suppression by Tregs in vitro and in an in vivo model of cardiac remodeling. As Tregs have emerged as a candidate therapy in autoimmunity and transplantation, we hypothesized that Nox2 deficiency in Tregs in recipient mice may improve outcomes in a heart transplant model. We generated a potentially novel B6129 mouse model with Treg-targeted Nox2 deletion (Nox2fl/flFoxP3Cre+ mice) and transplanted with hearts from CB6F1 donors. As compared with those of littermate controls, Nox2fl/flFoxP3Cre+ mice had lower plasma levels of alloantibodies and troponin-I, reduced levels of IFN-γ in heart allograft homogenates, and diminished cardiomyocyte necrosis and allograft fibrosis. Single-cell analyses of allografts revealed higher absolute numbers of Tregs and lower CD8+ T cell infiltration in Nox2-deficient recipients compared with Nox2-replete mice. Mechanistically, in addition to a greater suppression of CD8+CD25– T effector cell proliferation and IFN-γ production, Nox2-deficient Tregs expressed higher levels of CCR4 and CCR8, driving cell migration to allografts; this was associated with increased expression of miR-214-3p. These data indicate that Nox2 deletion in Tregs enhances their suppressive ability and migration to heart allografts. Therefore, Nox2 inhibition in Tregs may be a useful approach to improve their therapeutic efficacy.

Highlights

Cardiac transplantation remains the only available “curative” therapy for end-stage heart failure
Our results indicate that Nox2 deficiency in Tregs improves heart allograft outcomes due to a greater suppression of CD8+ T effector cell (Teff) proliferation and IFN-γ production
The development of improved methods to suppress allograft rejection is a major goal to enhance the effectiveness of the life-saving cardiac transplant therapy

Summary

Introduction

Cardiac transplantation remains the only available “curative” therapy for end-stage heart failure. The average survival after surgery is fewer than 10 years due to immune-mediated allograft rejection and side effects of immunosuppressive drugs [1]. This provides the impetus to manipulate the immune system to achieve heart allograft tolerance [2]. Tregs are currently under intensive investigation as an adoptive cell–based therapy to prevent transplant rejection and treat autoimmune diseases [6]. Polyclonal Treg-based cell therapy approaches yielded promising early results for the prevention of graft-versus-host disease [7] and for curing type 1 diabetes [8, 9]. We have completed 2 phase I/ II clinical trials, the ONE Study UK Treg Trial (NCT02129881) [10] and the Safety of Regulatory T Cell Therapy in Liver Transplant Patients (NCT02166177) [11], which assessed the safety and feasibility of adoptive transfer of ex vivo expanded polyclonal Tregs in renal and liver transplant patients [12,13,14]

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Results

Conclusion