1). Immunology of CML stem cells: Currently there are no active protocols in CML. 2) NK cells in myeloid malignancies: Dr Kate Stringaris has completed studies of natural killer (NK) cell immune function in acute myelogenous leukemia: Study 1 explored genetic diversity of NK killer immunoglobulin receptor (KIR) genes in 248 patients and their stem cell donors and their impact on outcome after stem cell transplantation (SCT) for haematological malignancy. Individuals with AML receiving SCT from donors inheriting 3 particular B-haplotype KIRs were 4 times less likely to relapse than those with donors without these favourable KIRs. Study 2: explored whether KIR genotype affects the risk of developing AML or the outcome of remission induction chemotherapy in 499 AML patients. Results suggest that activatory KIRs can protect against secondary AML. These studies support a role for NK-mediated immune surveillance in AML. Study 3 In 32 AML patients undergoing remission induction chemotherapy patients were found to have reduced NK activatory receptors, increased NK inhibitory receptors, and reduced cytotoxic function towards leukaemia, compared to healthy donors. These abnormalities corresponded with failure to achieve remission and could be induced in normal NK incubated with AML blasts. These results indicate that KIR genetics have a limited influence on AML development and outcome but that AML can impair NK function, reducing the chance of achieving remission. These findings have implications for NK based immunotherapy for AML. 3) Immune profiling in AML: To explore T cell function in AML we established A collaboration with Dr Stephen Strickland, (Vanderbilt University Hospital, Nashville TN) to study immune profile of patients with AML at presentation, after remission induction, and at relapse. We hypothesize that immune function is compromised by the leukemia through one or more mechanisms that suppress T cell responses. We have analyzed 30 patients. We found an increase in T reg cells at presentation and remission and the occurrence of AML blasts with myeloid-derived suppressor cell function suggesting that immune responses to AML may be blunted by a negative immune milieu. We found that levels of IL-27 are strongly elevated in AML and that patients failing to enter remission had the highest and most persistent elevations in IL-27. These findings suggest that AML blunts the T cell response by an IL27 mediated induction of regulatory T cells and a concomittent exhaustion of effector T cells. We also analyzed the potential of patients with AML in remission to generate LAA specific T cells. In comparison with their HLA identical stem cell transplant donors we found that patients possess a comparable but different repertoire of cytotoxic T cells recognizing a panel of LAA. These findings support the development of LAA-specific T cell in the autologous setting to maintain remission in AML patients. Ultimately these studies should identify protective immune mechanisms in AML that inform rational immunotherapy (vaccination, blocking suppressor cells, cytokine treatment, NK or T cell adoptive therapy). 4) MDS: We have shown in prior reports that patients with MDS have a variety of immune abnormalities associated with a T cell mediated suppression of marrow function. We recently completed a trial of Campath immunosuppression to restore hematological function in early , low grade MDS. We showed a 77% response rate in 22 evaluable MDS intermediate-1 patients and a 57% response rate in 7 evaluable intermediate-2 patients at 3 months. We have now addressed the problem of MDS patients with more advanced disease in transformation to AML. These patients have a poor prognosis. We have initiated a trial exploring the association of low dose clofarabine as chemotherapeutic agent with lenalidomide immune stimulation. This trial has accrued three patients. 5) Large granular lymphoproliferative disease (LGL): Previous studies showed that some patients with LGL respond to CSA. To explore whether more intensive immunosuppression would be more effective at restoring hematopoiesis, patients with LGL were given alemtuzemab (anti CD52 monoclonal). Sixteen of 20 patients responded rapidly. All patients had a sustained and prolonged lymphopenia but without developing opportunistic infection. There was a massive reduction of the LGL clones in responders when evaluated at 3 and 6 months. Relapse was associated with resurgence of the clone. We have confirmed that about 40-50% of LGL patients have mutations in stat-3 . However there appears to be no prognostic relationship between stat-3 mutation or CD52 expression on the LGL cell and treatment outcome. We are now using the stat-3 mutation to probe LGL T cell subsets to identify the earliest clonal progenitor of the LGL. Selected LGL samples whose CD8 T cells are over 95% clonal are being screened against a combinatorial peptide library to identify the cognate peptides and attempt to identify the target protein (collaboration with Dr M Wooldridge, Cardiff, UK). Understanding how the LGL T cell suppresses myelopoiesis and erythropoiesis may shed light on the mechanism of suppression of both normal and leukemic cells by cytotoxic T cell populations.

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Ishii, Kazusa; Barrett, Austin J (2016) Novel immunotherapeutic approaches for the treatment of acute leukemia (myeloid and lymphoblastic). Ther Adv Hematol 7:17-39
Barrett, Gene R; Thibodeaux, Kasey E; Replogle, William H et al. (2015) Body Mass Index as an Indicator of Associated Intra-articular Injuries in Patients With Anterior Cruciate Ligament Tears. J Surg Orthop Adv 24:159-63
Barrett, Austin John (2015) A new checkpoint in the path to GVHD? How bedside-to-bench stem cell transplant studies can inform human GVHD biology. J Leukoc Biol 97:213-5
Ito, Sawa; Barrett, A John; Dutra, Amalia et al. (2015) Long term maintenance of myeloid leukemic stem cells cultured with unrelated human mesenchymal stromal cells. Stem Cell Res 14:95-104
Barrett, Austin John; Bollard, Catherine M (2015) The coming of age of adoptive T-cell therapy for viral infection after stem cell transplantation. Ann Transl Med 3:62
Barrett, Austin J (2015) Tailoring steroid-sensitive virus-specific T cells with TALEN. Blood 126:2767-8
Kerkar, Sid P; Chinnasamy, Dhanalakshmi; Hadi, Neima et al. (2014) Timing and intensity of exposure to interferon-γ critically determines the function of monocyte-derived dendritic cells. Immunology 143:96-108
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Parikh, Ankur R; Olnes, Matthew J; Barrett, A John (2012) Immunomodulatory treatment of myelodysplastic syndromes: antithymocyte globulin, cyclosporine, and alemtuzumab. Semin Hematol 49:304-11
Falkenburg, Willem J J; Melenhorst, J Joseph; van de Meent, Marian et al. (2011) Allogeneic HLA-A*02-restricted WT1-specific T cells from mismatched donors are highly reactive but show off-target promiscuity. J Immunol 187:2824-33

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