Research Projects

Overview

The Bleakley laboratory focuses on:

  • The development and evaluation of strategies to engineer hematopoietic stem cell grafts to prevent GVHD and augment GVL in order to prevent leukemic relapse,
  • Preclinical development and clinical trials of adoptive T cell immunotherapy to augment GVL and thereby prevent and treat relapse after allogeneic HCT, and
  • Discovery of leukemia-associated minor histocompatibility antigens as targets for future immunotherapy, graft engineering and/or vaccination to manage leukemic relapse after HCT.

The lab has extensive expertise in the isolation, culture, genetic modification, and propagation of antigen-specific T cells, in bioinformatics, genetic and molecular techniques employed for antigen discovery, and in flow cytometry and functional analysis of human T cells for correlative studies of human immunotherapy and HCT clinical trials.

Separating the graft-versus-leukaemia effect from graft-versus-host disease
Separating the graft-versus-leukaemia effect from graft-versus-host disease From: Bleakley & Riddell; Nature Reviews Cancer 4, 371-380; 2004

Antigen Discovery and T cell Immunotherapy to Prevent and Treat Relapse of Leukemia

There is a great need for additional treatment options to prevent or treat relapse of leukemia. We are developing T cell immunotherapy targeting leukemia-associated minor histocompatibility (H) antigens in order to prevent and treat recurrence of leukemia after HCT. The feasibility and efficacy of T cell immunotherapy may be improved by using T cells that have been genetically modified to express a T cell receptor specific for an antigen of interest. We are cloning minor H antigen-specific T cells, isolating the T cell receptors (TCRs) and using viral vectors to express the receptor in third-party T cells and thereby arm the T cells with anti-leukemic activity. We have advanced one TCR into an open clinical trial, testing engineered T cells that target the minor H antigen, HA-1. Read the abstract and learn about clinical trials currently underway

Lab members continue working to discover new minor H antigens and other leukemia-associated antigens. They will create a library of leukemia-antigen specific T cell receptors in order to provide T cell immunotherapy options for patients of all races and HLA types in the future.

Discovery and characterization of mHAg HEATR1: Pretransplantation cells from donor and recipient are used to generate an HLA-B8–restricted hematopoiesis-specific CD8 T-cell clone
Discovery and characterization of mHAg HEATR1: Pretransplantation cells from donor and recipient are used to generate an HLA-B8–restricted hematopoiesis-specific CD8 T-cell clone From: A. John Barrett and J. Joseph Melenhorst, Blood, 115:4630-4631, 2010. High-res version

Method to Manipulate Peripheral Blood Stem Cells

We developed and evaluated a novel 2-step clinically compliant procedure for manipulating peripheral blood stem cells (PBSC) to remove naïve T cells (TN), preserve CD34+ hematopoietic stem cells, and provide for a fixed dose of memory T cells (TM) that includes T cells with specificity for common opportunistic pathogens encountered after HCT. Our studies demonstrate effective and reproducible performance of the immunomagnetic cell selection procedure for depleting TN. Moreover, after cell processing, the CD45RA-depleted PBSC products are enriched for CD4+ and CD8+ TM with a central memory phenotype and contain TM cells that are capable of proliferating and producing effector cytokines in response to opportunistic pathogens. Read the abstract.


HCT Graft Engineering to Prevent Graft-versus-Host Disease (GVHD)

GVHD is a major cause of morbidity, mortality and disability following HCT. GVHD and the immunosuppressive medications required for its management also present a barrier to the implementation of T cell immunotherapy to prevent and manage relapse of leukemia after HCT. Concurrent with our minor H antigen discovery studies, we have developed a new HCT strategy aimed at reducing GVHD, by selective depletion of CD45RA+ TN from allogeneic PBSC grafts. Read the abstract.

This work was informed by 1) studies performed by our collaborators in murine models showing that administration of allogeneic T cell depleted donor bone marrow plus purified TM causes little or no GVHD and allows recovery of immunity to a model antigen and by 2) our in vitro studies showing that human donor CD8+ cytotoxic T cell precursors specific for recipient minor H antigens are found predominantly within the CD45RA+ TN subset. Read the abstract.

We completed a first clinical HCT trial of this novel approach to preventing GVHD and observed that patients with HLA-matched sibling donors who received TN-depleted PBSC grafts experienced a much lower rate of chronic GVHD than is usually observed after HCT with unmanipulated PBSC graft. Moreover, the duration of required immunosuppression after TN-depleted HCT was considerably shorter than with T cell replete HCT, providing a greatly improved platform for immunotherapy. Read the abstract.

We are performing additional clinical trials to confirm these results and extend the application of this new approach to other types of HCT.

Cell collection procedure
Cell selection procedure. The flow diagram depicts the cell processing procedure to deplete TN from G-PBSC, preserve CD34+ stem cells and deliver a fixed dose of TM cells From: M. Bleakley et al, BBMT, 20(5):705-716, 2014