Selective depletion of allo-reactive T-cells to improve anti-viral and anti-leukaemic responses post haplo-identical ste

Lead Research Organisation: University College London
Department Name: Unlisted

Abstract

Leukaemia and genetic diseases are often curable by stem cell transplantation. However, many patients who would benefit from this procedure cannot be transplanted because they do not have a matched donor. On the other hand, almost all patients have a half matched (‘haplo-identical‘) parent/sibling and recent advances have made it possible to transplant such patients from haplo-identical donors. When such transplants are done, we have to remove almost all of the immune T-cells from the graft to prevent a complication called graft-versus-host disease (GVHD), which occurs when ‘allo-reactive‘ T-cells from the donor attack the patient. However, if we do this, patients have very little immunity and there is thus a high rate of virus infections and relapse, which are the major problems with haplo-identical stem cell transplantation. Our group and others have investigated trying to improve immunity post-transplant by giving back T-cells from the donor, having specifically removed many of the cells that cause GVHD, whilst leaving the ones that fight viruses and leukaemia. Our studies so far are encouraging, but we still get some GVHD even when quite low doses of T-cells are given back. We want to study the biology of the allo-reactive T-cells that cause GVHD and use the knowledge we gain to design better ways of removing these cells, so that we can give back enough T-cells to prevent virus infections and relapse, without causing GVHD. If successful, these studies may make haplo-identical transplants safer and more effective, so that many more patients with leukaemia and other disorders who do not have a matched donor could benefit from this procedure.

Technical Summary

The rigorous T-cell depletion used to avoid graft-versus-host disease (GVHD) after stem cell transplantation (SCT) from haplo-identical donors results in a high mortality from viral infections and relapse, due to the loss of cell-mediated anti-viral and anti-leukaemic immunity. There is thus a pressing clinical need for a means of infusing donor T-cells to restore these desirable immune responses, having selectively eliminated allo-reactive donor T-cells that cause GVHD. We have investigated the strategy of eliminating donor T-cells that express the activation marker CD25 in response to host stimulators, using an immunotoxin (CD25IT). However, early results from clinical studies suggest this approach is not sufficient to prevent GVHD. It is therefore critical to enhance the level of depletion of allo-reactive T-cells, so that sufficient donor T-cells can be adoptively transferred to give protective anti-viral and anti-leukaemic activity without causing GVHD.
Several potential strategies exist to enhance the degree of depletion of allo-reactive T-cells. To determine which of these is optimal, in the first phase of the study we will functionally characterise allo-reactive T-cells isolated on the basis of dilution of the dye CFSE. We will analyse the cytokine secretion profile, activation marker and effector molecule expression of CFSEdim allo-reactive cells, as well as the relation between these phenotypes, in FACS assays. To gain insight into the phenotype of allo-reactive T-cells that resist CD25-directed destruction, we will perform similar experiments on donor T-cells allo-depleted using CD25 IT. These studies will, for the first time, enable functional characterisation of allo-reactive cells and enable us to design rational approaches to delete residual alloreactivity.
In the next phase of our research, we will determine the efficiency and specificity of allo-depletion strategies chosen based on these studies. For example, our previous data suggest that targeting cells donor T-cells secreting IFN- in response to host stimulators may enable further depletion of allo-reactive T-cells. We will investigate if sequential allo-depletion using the novel approach of -capture, followed by CD25 IT enhances the degree of allo-depletion achievable with anti-CD25 IT alone, using secondary MLR and ELISPOT assays. Similar approaches are possible with other cytokines. ELISPOT and HLA tetramer assays will be used to determine how well anti-viral responses are preserved. Similarly, using tetramer and real-time PCR assays, we will study if responses to candidate tumour antigens in myeloid leukaemias are retained. We anticipate that if a further 1 log depletion of host-reactive donor T-cells is achieved, this may enable sufficient donor T-cells to be infused in the clinical setting to restore anti-viral immunity without causing GVHD. If this approach does not enhance selective depletion of allo-reactive cells, we will use data from our functional studies above to target other phenotypic markers of residual allo-reactive cells, eg the activation marker CD69. If our studies are successful, I will spend a period in our collaborator Prof. Brenner‘s laboratory in Houston to establish conditions for the large scale generation of allo-depleted donor T-cells under Good Tissue Practice conditions for subsequent clinical studies. These studies will provide me with an excellent training in cellular immunology and, if successful, may represent a major advance in improving immune reconstitution after haplo-identical SCT.
 
Description Children with Leukaemia Translational Research Grant
Amount £348,792 (GBP)
Organisation Children with Cancer UK 
Sector Charity/Non Profit
Country United Kingdom
Start 01/2008 
End 01/2011
 
Description Infusion of Depleted T Cells Following Unrelated Donor Stem Cell Transplant (ICAT) NCT01827579 
Organisation University College London
Department UCL Cancer Institute
Country United Kingdom 
Sector Academic/University 
PI Contribution collaboration on future clinical trial and technical collaboration
Collaborator Contribution The purpose of this study is to evaluate whether the administration of allodepleted donor T cells to patients with haematological malignancies after stem cell transplant can improve the recovery of the patients immune system. The study opened in 2014 at UCH and will enrol adults
Impact Phase 1/2 clinical study which will be published.
Start Year 2013
 
Description Infusion of Depleted T Cells Following Unrelated Donor Stem Cell Transplant (ICAT) NCT01827579 
Organisation University of Pavia
Department Department of Haematology
Country Italy 
Sector Academic/University 
PI Contribution collaboration on future clinical trial and technical collaboration
Collaborator Contribution The purpose of this study is to evaluate whether the administration of allodepleted donor T cells to patients with haematological malignancies after stem cell transplant can improve the recovery of the patients immune system. The study opened in 2014 at UCH and will enrol adults
Impact Phase 1/2 clinical study which will be published.
Start Year 2013
 
Description technical 
Organisation Baylor College of Medicine
Department Centre for Cell and Gene Therapy
Country United States 
Sector Academic/University 
PI Contribution Colloaborations on technical areas- learning how to do techniques
Collaborator Contribution supplying antibodies/ experise in technical areasWas shwon by this team how to do intracellular cytokine staining by flow cytometry
Impact Publications as described
Start Year 2006
 
Description technical 
Organisation Imperial College Healthcare NHS Trust
Department Respiratory Medicine
Country United Kingdom 
Sector Hospitals 
PI Contribution Colloaborations on technical areas- learning how to do techniques
Collaborator Contribution supplying antibodies/ experise in technical areasWas shwon by this team how to do intracellular cytokine staining by flow cytometry
Impact Publications as described
Start Year 2006
 
Description VIA iNSTITUTE OF CHILD HEALTH WEBSITE 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Postgraduate students
Results and Impact Brief description of work that I was doing

N/A
Year(s) Of Engagement Activity 2007,2008