Bone Marrow Infiltrating T-Cell Signatures Following Allo-HCT for Adult Acute Lymphoblastic Leukaemia Differentiate between Patients in Continuous CR and Those with Persistent Minimal Residual Disease or Relapse

Allogeneic stem cell transplantation (allo-HCT) has a proven survival benefit in adult acute lymphoblastic leukaemia (ALL) and remains the most commonly applied immunotherapy. The mechanism of graft-versus-leukaemia (GVL) in allo-HCT relies upon donor T cell immunity. After contributing to initial control of ALL, allo-reactive anti-tumour T cells may either persist, thus providing continuing immune surveillance, or undergo deletion/loss of function as a result of both extrinsic regulation and/or exhaustion. Therefore, there is a clear need to identify and track T cells with potential anti-ALL reactivity. UKALL14 (ISRCTN66541317) is an ongoing clinical trial for adults with de novo ALL in the UK in which all patients over 40 years are regarded as ‘high risk’ and are assigned to reduced intensity-conditioned allo-HCT. Minimal residual disease (MRD) monitoring - by immunoglobulin heavy chain/ T cell receptor quantification - of bone marrow and peripheral blood multilineage chimerism are assessed at regular intervals for 2 years post allo-HCT.