Human Tregs with 'direct' allospecificity can prevent rejection of human hepatocytes in a humanised mouse model.
Lead Research Organisation:
King's College London
Department Name: Immunology Infection and Inflam Diseases
Abstract
Liver transplantation is a successful treatment for patients with severe liver disease. Despite this, the majority of patients are maintained on immunosuppressants (IS) life long with associated side effects, affecting long term outcome. The goal of this study is, therefore, to devise protocols to enable the patient to accept their graft without the need for long term use of IS. Interestingly, populations of immune cells in the recipient, called regulatory T cells, have been shown to regulate the patient‘s immune system and prevent against organ rejection. The aim of our research is to develop new treatments that involve increasing the number of these cells in the recipient. We will a. isolate these cells from the recipient, expand them and ensure they are stable in culture. b. we will ensure they have a ‘specific‘ inhibitory role on the immune system i.e. they prevent liver rejection, but do not cause general/total immunosuppression c. We will use animal models of liver transplantation to show the safety and efficacy of these cells before re-introduction into the patient. This work will pave the way towards the development of protocols to induce tolerance, leading to more individualized treatment and minimize the complications of long term immunosuppression.
Technical Summary
Liver transplantation (LT) is a successful treatment for end-stage liver disease. Despite this, long-term survival remains suboptimal because of the morbidity and mortality associated with long term use of immunosuppression (IS). There is, therefore, a pressing need to devise protocols that induce a sustained state of ‘specific‘ tolerance to donor liver alloantigens in order to minimise or completely withdraw IS.
CD4+CD25+FOXP3+T cells (Tregs) play an important role in the induction and maintenance of immune tolerance and promote transplantation tolerance in animal models. Clinical protocols, using ‘polyclonal‘ Tregs has been shown to inhibit graft versus host disease (GvHD) after haematopoietic stem cell transplantation. Based on our prior work with mouse Tregs we hypothesise that the use of donor alloantigen-specific Tregs will confer the additional advantage that their immunomodulatory function would be concentrated at the site of the transplant with avoidance of pan-suppression.
Of importance, alloantigens can be recognised by T cells either as intact HLA molecules presented by donor-derived antigen presenting cells (APCs) (‘direct‘ pathway) or after processing of allogeneic HLA molecules to produce allopeptides that can be presented by recipient HLA molecules expressed by recipient APCs (‘indirect‘ pathway). We aim to generate Tregs with ‘direct‘ allospecificity to promote the induction of ‘specific‘ tolerance characterised by prevention of rejection in a humanised mouse model of hepatocyte transplantation. We will address this in three ways:
First, polyclonal Tregs will be isolated and expanded from peripheral blood of healthy volunteers. Rapamycin and all-trans retinoic acid will be used to promote the stability of these cells in vitro and to optimise the expression of CXCR3, a chemokine receptor involved in T cell migration to the liver.
Second, Tregs with ‘direct‘ allospecificity will be generated by co-culturing Tregs with the best allogeneic APC (dendritic cells vs B cells); alloactivate Tregs will then be enriched by bead separation after addition of antibodies specific for activation antigens and expanded. The antigen specific suppressive function of these cells will be evaluated.
Third, a humanised mouse model of hepatocyte transplantation will be used to assess the migratory ability, suppressive function and stability of antigen specific Tregs in vivo.
This research program will address the current challenges facing LT, namely the shortage of donor organs and the complications of IS. It focuses on the therapeutic application of Tregs in the context of LT. The clinical translation of this work will lead to the generation of tolerance promoting protocols used to increase the pool of ‘operationally‘ tolerant LT recipients.
CD4+CD25+FOXP3+T cells (Tregs) play an important role in the induction and maintenance of immune tolerance and promote transplantation tolerance in animal models. Clinical protocols, using ‘polyclonal‘ Tregs has been shown to inhibit graft versus host disease (GvHD) after haematopoietic stem cell transplantation. Based on our prior work with mouse Tregs we hypothesise that the use of donor alloantigen-specific Tregs will confer the additional advantage that their immunomodulatory function would be concentrated at the site of the transplant with avoidance of pan-suppression.
Of importance, alloantigens can be recognised by T cells either as intact HLA molecules presented by donor-derived antigen presenting cells (APCs) (‘direct‘ pathway) or after processing of allogeneic HLA molecules to produce allopeptides that can be presented by recipient HLA molecules expressed by recipient APCs (‘indirect‘ pathway). We aim to generate Tregs with ‘direct‘ allospecificity to promote the induction of ‘specific‘ tolerance characterised by prevention of rejection in a humanised mouse model of hepatocyte transplantation. We will address this in three ways:
First, polyclonal Tregs will be isolated and expanded from peripheral blood of healthy volunteers. Rapamycin and all-trans retinoic acid will be used to promote the stability of these cells in vitro and to optimise the expression of CXCR3, a chemokine receptor involved in T cell migration to the liver.
Second, Tregs with ‘direct‘ allospecificity will be generated by co-culturing Tregs with the best allogeneic APC (dendritic cells vs B cells); alloactivate Tregs will then be enriched by bead separation after addition of antibodies specific for activation antigens and expanded. The antigen specific suppressive function of these cells will be evaluated.
Third, a humanised mouse model of hepatocyte transplantation will be used to assess the migratory ability, suppressive function and stability of antigen specific Tregs in vivo.
This research program will address the current challenges facing LT, namely the shortage of donor organs and the complications of IS. It focuses on the therapeutic application of Tregs in the context of LT. The clinical translation of this work will lead to the generation of tolerance promoting protocols used to increase the pool of ‘operationally‘ tolerant LT recipients.