Martin Guimond - Academia.edu (original) (raw)

Papers by Martin Guimond

Blood Cancer Journal, 2017

Imatinib mesylate (IM) therapy has been shown to induce lower T cell counts in chronic myelogenou... more Imatinib mesylate (IM) therapy has been shown to induce lower T cell counts in chronic myelogenous leukemia (CML) patients and an interference of IM with T cell receptor (TCR) signaling has been invoked to explain this observation. However, IL-7 and TCR signaling are both essential for lymphocyte survival. This study was undertaken to determine whether IM interferes with IL-7 or TCR signaling to explain lower T cell counts in patients. At diagnosis, CML patients have typically lower CD4+ counts in their blood, yet CD8+ counts are normal or even increased in some. Following the initiation of IM treatment, CD4+ counts were further diminished and CD8+ T lymphocytes were dramatically decreased. In vitro studies confirmed IM interference with TCR signaling through the inhibition of ERK phosphorylation and we showed a similar effect on IL-7 signaling and STAT5 phosphorylation (STAT5-p). Importantly however, using an in vivo mouse model, we demonstrated that IM impaired T cell survival thr...

Cell Metabolism, 2013

In stroke and proliferative retinopathy, despite hypoxia driven angiogenesis, delayed revasculari... more In stroke and proliferative retinopathy, despite hypoxia driven angiogenesis, delayed revascularization of ischemic tissue aggravates the loss of neuronal function. What hinders vascular regrowth in the ischemic central nervous system remains largely unknown. Using the ischemic retina as a model of neurovascular interaction in the CNS, we provide evidence that the failure of reparative angiogenesis is temporally and spatially associated with endoplasmic reticulum (ER) stress. The canonical ER stress pathways of protein kinase RNA-like ER kinase (PERK) and inositol-requiring enzyme-1a (IRE1a) are activated within hypoxic/ischemic retinal ganglion neurons, initiating a cascade that results in angiostatic signals. Our findings demonstrate that the endoribonuclease IRE1a degrades the classical guidance cue netrin-1. This neuron-derived cue triggers a critical reparative-angiogenic switch in neural macrophage/microglial cells. Degradation of netrin-1, by persistent neuronal ER stress, thereby hinders vascular regeneration. These data identify a neuronal-immune mechanism that directly regulates reparative angiogenesis.

Encyclopedia of Biomedical Engineering, 2019

This article provides a general overview of immunological responses, with an emphasis on the role... more This article provides a general overview of immunological responses, with an emphasis on the role of the immune system in orthopedics and solid organ transplantation. After an introduction of the immune system, the innate immune system is described, including key cell types, inflammation, and innate immunity in wound repair. We then provide an overview of the adaptive immune response, including how different lymphocyte cell types arise, their specialized functions, antigen presentation, mechanisms of antibody production, antibodies in biomedical research and therapies, and vaccines. The role of major histocompatibility antigens is covered in the context of solid organ transplantation, osteochondral allografts, and allogenic hematopoietic stem cell transplantation. Finally, the immunopathology of several auto-immune diseases including type I diabetes and rheumatoid arthritis is explained. Illustrations are used to complement key concepts including complement activation, macrophage ph...

Blood Cancer Journal

A correction to this paper has been published and can be accessed via a link at the top of the pa... more A correction to this paper has been published and can be accessed via a link at the top of the paper.

Blood

PURPOSE: Chronic myelogenous leukemia (CML) is a disorder affecting early hematopoietic stem cell... more PURPOSE: Chronic myelogenous leukemia (CML) is a disorder affecting early hematopoietic stem cells (HSC) and is characterized by excessive proliferation and accumulation of myeloid progenitors and progeny in the periphery. During the chronic phase of the disease, CML patients are normally at low risk of developing infections but such complications tend to rise during the progression of the disease. Gleevec (imatinib mesylate) is currently administered as first line therapy for patients with Philadelphia chromosome-positive CML. Despite the relative high specificity of tyrosine kinase inhibitor (TKI) treatment towards the BCR-ABL fusion protein, off-target multikinase inhibitory effects occur and can interfere with normal hematopoiesis. This study was conducted to evaluate how myeloid and lymphoid immune homeostasis are affected by Imatinib mesylate. METHODS: Healthy volunteer donors (n=25) and CML patients were recruited during their first visit at our CML clinic. Seven CML patients...

Blood Cancer Discovery, Mar 4, 2020

Persistence of drug-resistant quiescent leukemic stem cells (LSC) and impaired natural killer (NK... more Persistence of drug-resistant quiescent leukemic stem cells (LSC) and impaired natural killer (NK) cell immune response account for relapse of chronic myelogenous leukemia (CML). Inactivation of protein phosphatase 2A (PP2A) is essential for CML-quiescent LSC survival and NK cell antitumor activity. Here we show that MIR300 has antiproliferative and PP2A-activating functions that are dose dependently differentially induced by CCND2/CDK6 and SET inhibition, respectively. MIR300 is upregulated in CML LSCs and NK cells by bone marrow microenvironment (BMM) signals to induce quiescence and impair immune response, respectively. Conversely, BCR-ABL1 downregulates MIR300 in CML progenitors to prevent growth arrest and PP2A-mediated apoptosis. Quiescent LSCs escape apoptosis by upregulating TUG1 long noncoding RNA that uncouples and limits MIR300 function to cytostasis. Genetic and pharmacologic MIR300 modulation and/or PP2A-activating drug treatment restore NK cell activity, inhibit BMM-induced growth arrest, and selectively trigger LSC apoptosis in vitro and in patient-derived xenografts; hence, the importance of MIR300 and PP2A activity for CML development and therapy. SIGNIFICANCE: Tumor-naïve microenvironment-induced MIR300 is the only tumor suppressor miRNA that induces CML LSC quiescence while inhibiting NK cell antitumor immune response and CML LSC/ progenitor cell apoptosis through its anti-proliferative and PP2A-activating functions, respectively. Thus, the importance of MIR300 and PP2A-activating drugs for formation/survival and eradication of drug-resistant CML LSCs, respectively.

Blood

BACKGROUND: Allogeneic bone marrow transplant (BMT) is a potent form of immunotherapy against hem... more BACKGROUND: Allogeneic bone marrow transplant (BMT) is a potent form of immunotherapy against hematopoietic and potentially solid tumors, but relapse of malignancy and Graft versus Host Disease (GVHD) remain a major cause of morbidity and mortality. Dendritic cell (DC) vaccines represent a potential strategy to enhance the potency and efficacy of the Graft versus Tumor (GVT) effect without exacerbating GVHD, but little is known regarding the impact of the allogeneic BMT environment on vaccine responses. Previous work in our lab has shown that DC can effectively expand tumor-antigen specific T cells following minor-mismatched allogeneic transplantation, resulting in delay of tumor growth. However, GVHD completely abrogates these responses. We hypothesized that the mechanism behind the loss of DC vaccine responses was through diminished T cell proliferation in the setting of GVHD. METHODS: We established a minor histocompatibility antigen mismatched BMT model by transplanting B6 x C3H...

Blood

The mechanism underlying the robust expansion of natural killer (NK) cells during exogenous admin... more The mechanism underlying the robust expansion of natural killer (NK) cells during exogenous administration of FL is unknown. Endogenous IL-15 had no impact on the in vivo expansion of NK cell precursors during FL administration but was required for the FL-mediated expansion of mature NK cells in the spleen and blood. Studies performed using in vivo BM chimeras showed that cells derived from hematopoietic precursors (HPC), not stromal cells, provided the endogenous IL-15 required for mature NK cell expansion by FL administration. Exogenous administration of FL significantly increased both CD11b(+)CD11c(-) and CD11b(+)CD11c(+) populations but not their relatively abundant expression of IL-15 or IL-15 receptor alpha on a per cell basis. This increase preceded and correlated with NK cell expansion, the latter of which largely resulted from enhanced survival and proliferation of an existing pool of mature NK cells rather than increased de novo production of NK cells from bone marrow prec...

Blood

BACKGROUND: PT-100 is an aminoboronic dipeptide that competitively inhibits dipeptidyl peptidases... more BACKGROUND: PT-100 is an aminoboronic dipeptide that competitively inhibits dipeptidyl peptidases. While PT-100 has no direct effect on tumor cells in vitro, it exhibits potent antitumor effects in vivo. We have shown that female C57BL/6 (B6) mice with MB49 tumors, which naturally express the male minor histocompatibility antigen complex (HY), are primed to HY, but the immune response is insufficient to control tumor growth. In this study, we used the well-characterized HY antigen system to examine the immunomodulatory effects of PT-100 during treatment-induced tumor regression. METHODS: B6 female mice were inoculated subcutaneously with MB49 (106 cells) on day 0 and treated daily with PT-100 by gavage. For re-challenge experiments mice received high dose MB49 (3×106 cells) three weeks after complete regression of primary tumors. IFN-g ELISPOT was used to measure HY antigen specific T cell responses in the spleen and lymph nodes (LNs) during tumor growth. For adoptive transfer exper...

Blood

Stable mixed chimerism is likely to be sufficient for clinical benefit when HSCT is undertaken fo... more Stable mixed chimerism is likely to be sufficient for clinical benefit when HSCT is undertaken for benign disease. However, potential short and long term morbidities of current ablative or non-myeloablative conditioning regimens present an unfavorable risk:benefit ratio when HSCT is undertaken in this setting. We sought to develop an entirely non-cytotoxic approach to achieve stable mixed chimerism by modulating accessibility of thymic niches. Previous work identified occupancy of the double negative (DN)3 niche (CD3-4-8-44-25+) as a primary barrier to thymic engraftment based upon evidence that IL-7Rα−/− and γc−/− mice (who have an accessible DN3 niche) are receptive to thymic engraftment, whereas RAG−/− mice (who have a full DN3 niche) are resistant to thymic engraftment. Our results are consistent with this paradigm, since transfer of 5 × 106 TCD BM cells from WT into IL-7Rα−/− mice vs RAG−/− mice showed higher rates of thymic chimerism (mean donor % 83±8 vs 3±3 respectively, p=0...

Blood

Interleukin-7 (IL-7) is the only cytokine demonstrated thus far to directly support the developme... more Interleukin-7 (IL-7) is the only cytokine demonstrated thus far to directly support the development and maintenance of naive T cells. Interleukin-7 is produced mainly by the stroma of lymphoid organs but also to a lesser extent by antigen presenting cells. Dynamic changes in the relative availability of IL-7 during lymphopenia support T cell homeostatic peripheral expansion (HPE). Whereas HPE is very efficient at reconstituting the pool of mature CD8 T lymphocytes, regeneration of CD4 T lymphocytes via HPE is more problematic and deficits in CD4 T lymphocytes persist for years in humans following lymphodepletion. We demonstrate that in mice, CD4+ T cells undergo substantially diminished HPE compared to CD8+ T cells during lymphopenia. We hypothesized that CD4+ T cells uniquely require both MHC Class II plus IL-7 for survival and expansion during lymphopenia and that the availability of these signals are limited by the availability of IL-7 producing APCs. Consistent with this hypothe...

JAIDS Journal of Acquired Immune Deficiency Syndromes

Frontiers in Immunology

• GVHD effect on the thymus. • GVHD effect on the peripheral niche. • Addressing the dysfunction ... more • GVHD effect on the thymus. • GVHD effect on the peripheral niche. • Addressing the dysfunction of the thymus and the peripheral niche to improve T cell regeneration in GVHD patients. inTRODUCTiOn Allogeneic-SCT was developed to treat leukemia and lymphoma as well as congenital or acquired hematologic conditions. Despite important side effects, allogeneic-SCT remains the only curative treatment for several patients with high risk refractory hematologic cancers. Acute graft-versushost disease (aGVHD) is a serious complication of allogeneic-SCT that occurs when donor lymphocytes react to normal host-tissues. Paradoxically, alloreactive T cells can improve survival by eliminating residual leukemia cells that survive SCT; a reaction known as graft-versus-leukemia effect (1). Following SCT, donor hematopoietic stem cells home to the bone marrow (BM) and differentiate into white cells, megakaryocytes and erythrocytes. While the recovery of innate FiGURe 1 | Immune reconstitution after autologous and allogeneic-SCT. (A) Autologous-SCT: chemotherapeutic insults affect the BM and thymopoiesis. During this period, thymopoiesis is inefficient and T cell regeneration occurs primarily through HP of mature T cells contained in the graft. The production of DCs occurs relatively early after autologous SCT and combined with elevated systemic IL-7, produced by stromal cell of primary and secondary lymphoid organs, they induce HP of mature T cells. In younger patients, rapid thymopoiesis recovery contributes to normalize CD4 + T cell counts and T cell receptor diversity. (B) Allogeneic-SCT: the combined GVHD and chemotherapeutic insults to the thymus and the BM induce long-lasting dysfunction of thymopoiesis and the peripheral lymphoid niche. Damages to the BM microenvironment are mediated primarily by alloreactive CD4 + T cells. During GVHD, DC production is reduced and systemic IL-7 is low, which constrain HP of non-alloreactive naïve T cells. Depending on the severity of GVHD and patient's age, the dysfunction of the thymus can persist for several years.

Biology of Blood and Marrow Transplantation

Chronic graft-versus-host disease (cGVHD) is a major complication, affecting 50% to 80% of long-t... more Chronic graft-versus-host disease (cGVHD) is a major complication, affecting 50% to 80% of long-term survivors of allogeneic hematopoietic stem cell transplantation. Current cGVHD therapies are neither specific nor curative, and patients are typically maintained for several months to years under immunosuppressive regimens that are associated with important side effects and increased susceptibility to life-threatening infections. As a result, continued investigation into the pathology of the disease and the search for novel diagnostic and therapeutic strategies to treat cGVHD remains a high priority. We report that the cellular dynamics of various immune cell subsets are related to cGVHD onset and severity in a cohort of allogeneic hematopoietic stem cell transplantation recipients. We document a decrease in the proportion of CD45RO + CD4 ¡ CD8 ¡ (double-negative [DN]) T cells at the onset of cGVHD, a time at which serum levels of B cell activating factor and B cells are increased. We also find that DN T cell levels are correlated with cGVHD severity. Our present findings are in line with the view that activated DN T cells exhibit their immunoregulatory potential by eliminating B cells in vivo. Taken together, these findings suggest that maintaining elevated DN T cell numbers before the onset of cGVHD may prevent pathological B cell responses.

The Journal of Clinical Investigation, 2006

We previously identified a rearrangement of mixed-lineage leukemia (MLL) gene (also known as ALL-... more We previously identified a rearrangement of mixed-lineage leukemia (MLL) gene (also known as ALL-1, HRX, and HTRX1), consisting of an in-frame partial tandem duplication (PTD) of exons 5 through 11 in the absence of a partner gene, occurring in approximately 4%-7% of patients with acute myeloid leukemia (AML) and normal cytogenetics, and associated with a poor prognosis. The mechanism by which the MLL PTD contributes to aberrant hematopoiesis and/or leukemia is unknown. To examine this, we generated a mouse knockin model in which exons 5 through 11 of the murine Mll gene were targeted to intron 4 of the endogenous Mll locus. Mll PTD/WT mice exhibit an alteration in the boundaries of normal homeobox (Hox) gene expression during embryogenesis, resulting in axial skeletal defects and increased numbers of hematopoietic progenitor cells. Mll PTD/WT mice overexpress Hoxa7, Hoxa9, and Hoxa10 in spleen, BM, and blood. An increase in histone H3/H4 acetylation and histone H3 lysine 4 (Lys4) methylation within the Hoxa7 and Hoxa9 promoters provides an epigenetic mechanism by which this overexpression occurs in vivo and an etiologic role for MLL PTD gain of function in the genesis of AML.

The Journal of Immunology, May 1, 2014

Cytokine, 2016

For numerous patients, allogeneic stem cell transplantation (SCT) is the only therapeutic option ... more For numerous patients, allogeneic stem cell transplantation (SCT) is the only therapeutic option that could potentially cure their disease. Despite significant progress made in clinical management of allogeneic SCT, acute graft-versus-host disease (aGVHD) remains the second cause of death after disease recurrence. aGVHD is highly immunosuppressive and the adverse effect of allogeneic SCT on T cell regeneration is typically more important than the levels of immunosuppression normally seen after autologous SCT. In these patients, immune reconstitution often takes several years to occur and restoring immunocompetence after allogeneic SCT represents an important challenge, principally because clinical options are limited and current methods used to accelerate immune reconstitution are associated with increased GVHD. Interleukin-7 and IL-15 are both under clinical investigation and demonstrate the greatest potential on peripheral T cells regeneration in mice and humans. However, awarenes...

Blood Cancer Journal, 2017

Imatinib mesylate (IM) therapy has been shown to induce lower T cell counts in chronic myelogenou... more Imatinib mesylate (IM) therapy has been shown to induce lower T cell counts in chronic myelogenous leukemia (CML) patients and an interference of IM with T cell receptor (TCR) signaling has been invoked to explain this observation. However, IL-7 and TCR signaling are both essential for lymphocyte survival. This study was undertaken to determine whether IM interferes with IL-7 or TCR signaling to explain lower T cell counts in patients. At diagnosis, CML patients have typically lower CD4+ counts in their blood, yet CD8+ counts are normal or even increased in some. Following the initiation of IM treatment, CD4+ counts were further diminished and CD8+ T lymphocytes were dramatically decreased. In vitro studies confirmed IM interference with TCR signaling through the inhibition of ERK phosphorylation and we showed a similar effect on IL-7 signaling and STAT5 phosphorylation (STAT5-p). Importantly however, using an in vivo mouse model, we demonstrated that IM impaired T cell survival thr...

Cell Metabolism, 2013

In stroke and proliferative retinopathy, despite hypoxia driven angiogenesis, delayed revasculari... more In stroke and proliferative retinopathy, despite hypoxia driven angiogenesis, delayed revascularization of ischemic tissue aggravates the loss of neuronal function. What hinders vascular regrowth in the ischemic central nervous system remains largely unknown. Using the ischemic retina as a model of neurovascular interaction in the CNS, we provide evidence that the failure of reparative angiogenesis is temporally and spatially associated with endoplasmic reticulum (ER) stress. The canonical ER stress pathways of protein kinase RNA-like ER kinase (PERK) and inositol-requiring enzyme-1a (IRE1a) are activated within hypoxic/ischemic retinal ganglion neurons, initiating a cascade that results in angiostatic signals. Our findings demonstrate that the endoribonuclease IRE1a degrades the classical guidance cue netrin-1. This neuron-derived cue triggers a critical reparative-angiogenic switch in neural macrophage/microglial cells. Degradation of netrin-1, by persistent neuronal ER stress, thereby hinders vascular regeneration. These data identify a neuronal-immune mechanism that directly regulates reparative angiogenesis.

Encyclopedia of Biomedical Engineering, 2019

This article provides a general overview of immunological responses, with an emphasis on the role... more This article provides a general overview of immunological responses, with an emphasis on the role of the immune system in orthopedics and solid organ transplantation. After an introduction of the immune system, the innate immune system is described, including key cell types, inflammation, and innate immunity in wound repair. We then provide an overview of the adaptive immune response, including how different lymphocyte cell types arise, their specialized functions, antigen presentation, mechanisms of antibody production, antibodies in biomedical research and therapies, and vaccines. The role of major histocompatibility antigens is covered in the context of solid organ transplantation, osteochondral allografts, and allogenic hematopoietic stem cell transplantation. Finally, the immunopathology of several auto-immune diseases including type I diabetes and rheumatoid arthritis is explained. Illustrations are used to complement key concepts including complement activation, macrophage ph...

Blood Cancer Journal

A correction to this paper has been published and can be accessed via a link at the top of the pa... more A correction to this paper has been published and can be accessed via a link at the top of the paper.

Blood

PURPOSE: Chronic myelogenous leukemia (CML) is a disorder affecting early hematopoietic stem cell... more PURPOSE: Chronic myelogenous leukemia (CML) is a disorder affecting early hematopoietic stem cells (HSC) and is characterized by excessive proliferation and accumulation of myeloid progenitors and progeny in the periphery. During the chronic phase of the disease, CML patients are normally at low risk of developing infections but such complications tend to rise during the progression of the disease. Gleevec (imatinib mesylate) is currently administered as first line therapy for patients with Philadelphia chromosome-positive CML. Despite the relative high specificity of tyrosine kinase inhibitor (TKI) treatment towards the BCR-ABL fusion protein, off-target multikinase inhibitory effects occur and can interfere with normal hematopoiesis. This study was conducted to evaluate how myeloid and lymphoid immune homeostasis are affected by Imatinib mesylate. METHODS: Healthy volunteer donors (n=25) and CML patients were recruited during their first visit at our CML clinic. Seven CML patients...

Blood Cancer Discovery, Mar 4, 2020

Persistence of drug-resistant quiescent leukemic stem cells (LSC) and impaired natural killer (NK... more Persistence of drug-resistant quiescent leukemic stem cells (LSC) and impaired natural killer (NK) cell immune response account for relapse of chronic myelogenous leukemia (CML). Inactivation of protein phosphatase 2A (PP2A) is essential for CML-quiescent LSC survival and NK cell antitumor activity. Here we show that MIR300 has antiproliferative and PP2A-activating functions that are dose dependently differentially induced by CCND2/CDK6 and SET inhibition, respectively. MIR300 is upregulated in CML LSCs and NK cells by bone marrow microenvironment (BMM) signals to induce quiescence and impair immune response, respectively. Conversely, BCR-ABL1 downregulates MIR300 in CML progenitors to prevent growth arrest and PP2A-mediated apoptosis. Quiescent LSCs escape apoptosis by upregulating TUG1 long noncoding RNA that uncouples and limits MIR300 function to cytostasis. Genetic and pharmacologic MIR300 modulation and/or PP2A-activating drug treatment restore NK cell activity, inhibit BMM-induced growth arrest, and selectively trigger LSC apoptosis in vitro and in patient-derived xenografts; hence, the importance of MIR300 and PP2A activity for CML development and therapy. SIGNIFICANCE: Tumor-naïve microenvironment-induced MIR300 is the only tumor suppressor miRNA that induces CML LSC quiescence while inhibiting NK cell antitumor immune response and CML LSC/ progenitor cell apoptosis through its anti-proliferative and PP2A-activating functions, respectively. Thus, the importance of MIR300 and PP2A-activating drugs for formation/survival and eradication of drug-resistant CML LSCs, respectively.

Blood

BACKGROUND: Allogeneic bone marrow transplant (BMT) is a potent form of immunotherapy against hem... more BACKGROUND: Allogeneic bone marrow transplant (BMT) is a potent form of immunotherapy against hematopoietic and potentially solid tumors, but relapse of malignancy and Graft versus Host Disease (GVHD) remain a major cause of morbidity and mortality. Dendritic cell (DC) vaccines represent a potential strategy to enhance the potency and efficacy of the Graft versus Tumor (GVT) effect without exacerbating GVHD, but little is known regarding the impact of the allogeneic BMT environment on vaccine responses. Previous work in our lab has shown that DC can effectively expand tumor-antigen specific T cells following minor-mismatched allogeneic transplantation, resulting in delay of tumor growth. However, GVHD completely abrogates these responses. We hypothesized that the mechanism behind the loss of DC vaccine responses was through diminished T cell proliferation in the setting of GVHD. METHODS: We established a minor histocompatibility antigen mismatched BMT model by transplanting B6 x C3H...

Blood

The mechanism underlying the robust expansion of natural killer (NK) cells during exogenous admin... more The mechanism underlying the robust expansion of natural killer (NK) cells during exogenous administration of FL is unknown. Endogenous IL-15 had no impact on the in vivo expansion of NK cell precursors during FL administration but was required for the FL-mediated expansion of mature NK cells in the spleen and blood. Studies performed using in vivo BM chimeras showed that cells derived from hematopoietic precursors (HPC), not stromal cells, provided the endogenous IL-15 required for mature NK cell expansion by FL administration. Exogenous administration of FL significantly increased both CD11b(+)CD11c(-) and CD11b(+)CD11c(+) populations but not their relatively abundant expression of IL-15 or IL-15 receptor alpha on a per cell basis. This increase preceded and correlated with NK cell expansion, the latter of which largely resulted from enhanced survival and proliferation of an existing pool of mature NK cells rather than increased de novo production of NK cells from bone marrow prec...

Blood

BACKGROUND: PT-100 is an aminoboronic dipeptide that competitively inhibits dipeptidyl peptidases... more BACKGROUND: PT-100 is an aminoboronic dipeptide that competitively inhibits dipeptidyl peptidases. While PT-100 has no direct effect on tumor cells in vitro, it exhibits potent antitumor effects in vivo. We have shown that female C57BL/6 (B6) mice with MB49 tumors, which naturally express the male minor histocompatibility antigen complex (HY), are primed to HY, but the immune response is insufficient to control tumor growth. In this study, we used the well-characterized HY antigen system to examine the immunomodulatory effects of PT-100 during treatment-induced tumor regression. METHODS: B6 female mice were inoculated subcutaneously with MB49 (106 cells) on day 0 and treated daily with PT-100 by gavage. For re-challenge experiments mice received high dose MB49 (3×106 cells) three weeks after complete regression of primary tumors. IFN-g ELISPOT was used to measure HY antigen specific T cell responses in the spleen and lymph nodes (LNs) during tumor growth. For adoptive transfer exper...

Blood

Stable mixed chimerism is likely to be sufficient for clinical benefit when HSCT is undertaken fo... more Stable mixed chimerism is likely to be sufficient for clinical benefit when HSCT is undertaken for benign disease. However, potential short and long term morbidities of current ablative or non-myeloablative conditioning regimens present an unfavorable risk:benefit ratio when HSCT is undertaken in this setting. We sought to develop an entirely non-cytotoxic approach to achieve stable mixed chimerism by modulating accessibility of thymic niches. Previous work identified occupancy of the double negative (DN)3 niche (CD3-4-8-44-25+) as a primary barrier to thymic engraftment based upon evidence that IL-7Rα−/− and γc−/− mice (who have an accessible DN3 niche) are receptive to thymic engraftment, whereas RAG−/− mice (who have a full DN3 niche) are resistant to thymic engraftment. Our results are consistent with this paradigm, since transfer of 5 × 106 TCD BM cells from WT into IL-7Rα−/− mice vs RAG−/− mice showed higher rates of thymic chimerism (mean donor % 83±8 vs 3±3 respectively, p=0...

Blood

Interleukin-7 (IL-7) is the only cytokine demonstrated thus far to directly support the developme... more Interleukin-7 (IL-7) is the only cytokine demonstrated thus far to directly support the development and maintenance of naive T cells. Interleukin-7 is produced mainly by the stroma of lymphoid organs but also to a lesser extent by antigen presenting cells. Dynamic changes in the relative availability of IL-7 during lymphopenia support T cell homeostatic peripheral expansion (HPE). Whereas HPE is very efficient at reconstituting the pool of mature CD8 T lymphocytes, regeneration of CD4 T lymphocytes via HPE is more problematic and deficits in CD4 T lymphocytes persist for years in humans following lymphodepletion. We demonstrate that in mice, CD4+ T cells undergo substantially diminished HPE compared to CD8+ T cells during lymphopenia. We hypothesized that CD4+ T cells uniquely require both MHC Class II plus IL-7 for survival and expansion during lymphopenia and that the availability of these signals are limited by the availability of IL-7 producing APCs. Consistent with this hypothe...

JAIDS Journal of Acquired Immune Deficiency Syndromes

Frontiers in Immunology

• GVHD effect on the thymus. • GVHD effect on the peripheral niche. • Addressing the dysfunction ... more • GVHD effect on the thymus. • GVHD effect on the peripheral niche. • Addressing the dysfunction of the thymus and the peripheral niche to improve T cell regeneration in GVHD patients. inTRODUCTiOn Allogeneic-SCT was developed to treat leukemia and lymphoma as well as congenital or acquired hematologic conditions. Despite important side effects, allogeneic-SCT remains the only curative treatment for several patients with high risk refractory hematologic cancers. Acute graft-versushost disease (aGVHD) is a serious complication of allogeneic-SCT that occurs when donor lymphocytes react to normal host-tissues. Paradoxically, alloreactive T cells can improve survival by eliminating residual leukemia cells that survive SCT; a reaction known as graft-versus-leukemia effect (1). Following SCT, donor hematopoietic stem cells home to the bone marrow (BM) and differentiate into white cells, megakaryocytes and erythrocytes. While the recovery of innate FiGURe 1 | Immune reconstitution after autologous and allogeneic-SCT. (A) Autologous-SCT: chemotherapeutic insults affect the BM and thymopoiesis. During this period, thymopoiesis is inefficient and T cell regeneration occurs primarily through HP of mature T cells contained in the graft. The production of DCs occurs relatively early after autologous SCT and combined with elevated systemic IL-7, produced by stromal cell of primary and secondary lymphoid organs, they induce HP of mature T cells. In younger patients, rapid thymopoiesis recovery contributes to normalize CD4 + T cell counts and T cell receptor diversity. (B) Allogeneic-SCT: the combined GVHD and chemotherapeutic insults to the thymus and the BM induce long-lasting dysfunction of thymopoiesis and the peripheral lymphoid niche. Damages to the BM microenvironment are mediated primarily by alloreactive CD4 + T cells. During GVHD, DC production is reduced and systemic IL-7 is low, which constrain HP of non-alloreactive naïve T cells. Depending on the severity of GVHD and patient's age, the dysfunction of the thymus can persist for several years.

Biology of Blood and Marrow Transplantation

Chronic graft-versus-host disease (cGVHD) is a major complication, affecting 50% to 80% of long-t... more Chronic graft-versus-host disease (cGVHD) is a major complication, affecting 50% to 80% of long-term survivors of allogeneic hematopoietic stem cell transplantation. Current cGVHD therapies are neither specific nor curative, and patients are typically maintained for several months to years under immunosuppressive regimens that are associated with important side effects and increased susceptibility to life-threatening infections. As a result, continued investigation into the pathology of the disease and the search for novel diagnostic and therapeutic strategies to treat cGVHD remains a high priority. We report that the cellular dynamics of various immune cell subsets are related to cGVHD onset and severity in a cohort of allogeneic hematopoietic stem cell transplantation recipients. We document a decrease in the proportion of CD45RO + CD4 ¡ CD8 ¡ (double-negative [DN]) T cells at the onset of cGVHD, a time at which serum levels of B cell activating factor and B cells are increased. We also find that DN T cell levels are correlated with cGVHD severity. Our present findings are in line with the view that activated DN T cells exhibit their immunoregulatory potential by eliminating B cells in vivo. Taken together, these findings suggest that maintaining elevated DN T cell numbers before the onset of cGVHD may prevent pathological B cell responses.

The Journal of Clinical Investigation, 2006

We previously identified a rearrangement of mixed-lineage leukemia (MLL) gene (also known as ALL-... more We previously identified a rearrangement of mixed-lineage leukemia (MLL) gene (also known as ALL-1, HRX, and HTRX1), consisting of an in-frame partial tandem duplication (PTD) of exons 5 through 11 in the absence of a partner gene, occurring in approximately 4%-7% of patients with acute myeloid leukemia (AML) and normal cytogenetics, and associated with a poor prognosis. The mechanism by which the MLL PTD contributes to aberrant hematopoiesis and/or leukemia is unknown. To examine this, we generated a mouse knockin model in which exons 5 through 11 of the murine Mll gene were targeted to intron 4 of the endogenous Mll locus. Mll PTD/WT mice exhibit an alteration in the boundaries of normal homeobox (Hox) gene expression during embryogenesis, resulting in axial skeletal defects and increased numbers of hematopoietic progenitor cells. Mll PTD/WT mice overexpress Hoxa7, Hoxa9, and Hoxa10 in spleen, BM, and blood. An increase in histone H3/H4 acetylation and histone H3 lysine 4 (Lys4) methylation within the Hoxa7 and Hoxa9 promoters provides an epigenetic mechanism by which this overexpression occurs in vivo and an etiologic role for MLL PTD gain of function in the genesis of AML.

The Journal of Immunology, May 1, 2014

Cytokine, 2016

For numerous patients, allogeneic stem cell transplantation (SCT) is the only therapeutic option ... more For numerous patients, allogeneic stem cell transplantation (SCT) is the only therapeutic option that could potentially cure their disease. Despite significant progress made in clinical management of allogeneic SCT, acute graft-versus-host disease (aGVHD) remains the second cause of death after disease recurrence. aGVHD is highly immunosuppressive and the adverse effect of allogeneic SCT on T cell regeneration is typically more important than the levels of immunosuppression normally seen after autologous SCT. In these patients, immune reconstitution often takes several years to occur and restoring immunocompetence after allogeneic SCT represents an important challenge, principally because clinical options are limited and current methods used to accelerate immune reconstitution are associated with increased GVHD. Interleukin-7 and IL-15 are both under clinical investigation and demonstrate the greatest potential on peripheral T cells regeneration in mice and humans. However, awarenes...