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Research Interests:
Immunobiology of transplantation
My laboratory is focused upon the immunobiology of transplantation.
There are four basic project areas:
1. Graft-versus-host disease (GVHD). GVHD is a multi-organ
system disorder in which donor T cells recognize host alloantigens
present on antigen-presenting cells and tissues in the context
of an inflammatory response. Studies are directed toward identifying
and modifying signals that drive or inhibit GVHD generation.
These include the analysis of positive costimulatory molecules
and negative regulators of the immune response that counterbalance
positive costimulation. These include cell surface and intracellular
signaling and metabolic pathways along with pro- and anti-inflammatory
cytokines that regulate these responses. We have analyzed
the biochemical events associated with tolerance induction
and have applied these findings to the development of new
approaches to induce tolerance via the use of inhibitors of
signal transduction or cell cycle progression. We have developed
new approaches to propagate and expand CD4+25+ T regulatory
cells that can suppress alloresponses and isolated novel cells
that have more potent regulatory/suppressor cell activity.
We are analyzing the factors that regulate murine and human
CD4+25+ T cell development, expansion and function in vitro
and in vivo. We are also investigating how CD4+25+ T cells
affect hematopoiesis and immune function in mice including
models of human lymphohematopoiesis.The in vivo biological
effects of our immune manipulations are being monitored using
whole-body imaging techniques to track donor effector or regulatory
T cells using transgenic mice expressing green fluorescent
protein and firefly luciferase. In other studies, we have
developed an ex vivo induction of tolerance as a means of
preventing GVHD.
2. Thymopoiesis post-transplant. Because GVHD and the
conditioning regimens used for bone marrow transplantation
induce severe thymic injury, we also are exploring new approaches
to protect the thymic epithelial cells (TEC) against injury
including the use of cytokines that stimulate TEC proliferation/repair
(eg. keratinocyte growth factor), agents that protect against
genotoxic stress (eg. p53 inhibitors), and those that prevent
endogenous hormone induced suppression of thymopoiesis (eg.
sex steroid hormone blockade). The mechanism(s) responsible
for the protective effects of these biological agents are
being explored in wild-type and in transgenic mice with disruptions
of various signaling pathways. Within TECs, we are examining
the thymocyte signals that regulate TEC function and characterizing
the effects of micro-RNA regulation on TEC regeneration and
function. In complimentary studies, we are developing strategies
to induce pluriopotent progenitor cells to differentiate into
TECs, which will be used as a cellular therapy to replace
damaged TEC. We also are analyzing the mature T cell response
to foreign antigens in transplanted mice to better understand
the qualitative defects associated with post-transplant T
cell reconstitution
.
3. Graft-versus-leukemia (GVL). Projects are ongoing
to identify the host mechanisms responsible for tumor-mediated
immune suppression of endogenous T effector cells, focusing
on negative regulators of immune response expressed on the
cell surface or via intracellular pathways. Adoptive T cell
immunotherapy is being tested using new approaches to generate
T effector cells that have superior in vivo cytolytic potential
and/or result in increased persistence of transferred T cells.
T cell immune therapy is used in combination with approaches
that dampen the host immune suppressive response (CD4+25+
regulatory T cells; negative costimulatory molecules; intracellular
metabolic pathways), cause homeostatic expansion of T cells
via the induction of lymphopenia, or target tumor cells (eg
proteosomal inhibitors; histone deacetylase inhibitors; chemotherapy
agents). We have developed new approaches to simultaneously
track green fluorescent cytotoxic lymphocytes that are generated
in vitro against leukemia cells and tumor cells that are red
fluorescent. T cells and tumor cells each are labeled with
distinct luciferase enzymes to permit sequential in vivo quantification
of T cell expansion and residual tumor cells to determine
how our in vitro or in vivo manipulations affect lymphocyte
trafficking to tumor sites and tumor cell metastasis using
sensitive whole body imaging techniques. The immune response
against tumors in distinct sites (eg bone marrow versus liver
or spleen) is being analyzed.
4. Gene therapy/repair. As an alternative to transplantation,
we are using molecular strategies to correct congenital disorders.
To treat enzymatic disorders, non-viral or lentiviral DNA
is delivered in vivo using constructs that the liver for producing
high levels of enzyme that is released systemically or the
brain by taking advantage of receptor mediated uptake of cells
at the blood-brain-barrier. Alternatively, we are using non-hematopoietic
stem cells as vehicles for protein delivery after in vivo
infusion. In a different approach, studies are directed toward
achieving site-directed integration of non-viral DNA delivery
into hematopoietic stem cells. To treat immune deficiency
disorders, studies are being performed to achieve homologous
recombination (e.g short fragment homologous recombination)
or site-directed integration for gene replacement in hematopoietic
stem cells. Recipients are analyzed for molecular and phenotypic
correction. Complimentary studies are developing novel treatments
for congenital disorders characterized by defects in extracellular
matrix proteins (eg. epidermolysis bullosa, collagen VIIa
deficiency).
5. Stem cell homing. Studies are ongoing using a zebrafish
model in which hematopoietic stem cells are fluorescent and
can be visualized in their migration process to the hematopoietic
stem cell niche. Transgenic zebrafish are being generated
to permit visualization of the stem cell niche. The goal of
the project is to identify novel regulators of stem cell homing
and hematopoietic cell engraftment using an adoptive transfer
model in which zebrafish are irradiated and then reconstituted
with fluorescent hematopoietic progenitor cells to permit
visualization and trafficking of stem and progenitor cells,
facilitating identification of stem cell niche factors that
regulate this process.
Selected Recent Publications:
- Kelly RM, Panoskaltsis-Mortari A, Taylor PA, Boyd RL,
Hollander GA, Blazar BR: Keratinocyte growth factor and
androgen blockade work in concert to protect against conditioning
regimen-induced thymic epithelial damage and enhance T cell
reconstitution following murine bone marrow transplantation.
Submitted
- Osborn MJ, McElmurry RT, Tolar J, Blazar BR. Targeting
of Refractory Sites in MPS I Using a Nonviral Transferrin-?-L-Iduronidase
Fusion Gene Product. Submitted
- Chen W, Liang X, Peterson AJ, Mellor AL, Munn DH, Blazar
BR: The indoleamine 2,3-dioxygenase pathway is essential
for human plasmacytoid dendritic cell-induced adaptive
T regulatory cell generation. Submitted
- Vogtenhuber C, O’Shaughnessy MJ, Vignali DA, Blazar
BR. Outgrowth of CD4low/negCD25int T cells with suppressor
function in CD4+CD25+ T cell cultures upon polyclonal stimulation
in vitro. Submitted
- Jasperson LK, Panoskaltsis-Mortari A, Taylor PA, Bucher
C, Mellor AL, Munn DH, Blazar BR. 2007. Indoleamine 2,3-dioxygenase
is a critical regulator of acute graft-versus-host disease
(GVHD) lethality. Blood (in press)
- Guimond M, Leonard WJ, Spolski R, Rossi SW, Veenstra TG,
Hollander GA, Mackall CL, Blazar BR: 2008. The thymopoietic
effect of keratinocyte growth factor (KGF) requires interleukin-7
and not thymic stromal lymphopoietin (TSLP). Blood
111:969-70.
- Taylor PA, Ehrhardt MJ, Lees CJ, Tolar J, Weigel BJ, Panoskaltsis-Mortari
A, Serody JS, Brinkmann V, Blazar BR. 2007. Insights into
the Mechanism of FTY720 and Compatibility with Regulatory
T Cells for the Inhibition of Graft-versus-Host Disease
(GVHD). Blood
110: 3480-88.
- Sharma MD, Baban B, Chandler P, Hou D-Y, Singh N, Yagita
H, Azuma M, Blazar BR, Mellor AL, Munn DH: 2007. Dendritic
cells from tumor-draining lymph nodes directly activate
regulatory T cells via indoleamine 2,3-dioxygenase. J.
Clin. Invest. 117: 2570-82.
- Zayed H, Xia L, Yerich A, Yant SR, Kay MA, Puttaraju M,
Mansfield G, Wiest DL, McIvor RS, Tolar J, Blazar BR. 2--7.
Correction of severe combined immune deficiency in multipotent
adult progenitor cells by spliceosome-mediated RNA trans-splicing
and sleeping beauty transposon delivery. Molec.
Therapy 15:1273-9.
- O’Shaughnessy MJ, Chen Z-M, Gramaglia I, Taylor
PA, Panoskaltsis-Mortari,
Vogtenhuber C, Palmer E, Grader-Beck T, Boussiotis VA, Blazar
BR .2007. Elevation of Intracellular cyclic AMP in alloreactive
CD4+ T cells during a primary MLR can induce
long term alloantigen-specific tolerance that is sufficient
to prevent GVHD lethality in
vivo. Biol.
Blood and Marrow Transplant 13: 530-42.
- Rossi S, Jeker L, Ueno T, Kuse S, Keller M, Zuklys S,
Gudkov A, Takahama Y, Krenger W, Blazar BR, Holländer
G. 2007. Keratinocyte growth factor (KGF) enhances postnatal
T cell development via improvement in proliferation and
function of thymic epithelial cells. Blood
109: 3803-11.
- Serafini M, Dylla SJ, Oki M, Heremans Y, Tolar J, Jiang
J, Buckley SM, Pelacho B, Burns TC, Frommer S, Rossi DJ,
Bryder D, Panoskaltsis-Mortari A, O’Shaughnessy MJ,
Nelson-Holte M, Fine GC, Weissman IL, Blazar BR, Verfaillie
CM. 2007. Hematopoietic Reconstitution by Multipotent Adult
Progenitor Cells: Precursors to Long-Term Hematopoietic
Stem Cells that can be Expanded In Vitro. J.
Exp. Med. 204:129-39.
- Tolar J, O’Shaughnessy MJ, Panoskaltsis-Mortari
A, McElmurry RT, Bell S, Riddle M,
McIvor RS, Yant SR, Kay MA, Krause D, Verfaillie CM, Blazar
BR. 2006. Host Factors that Impact the Biodistribution and
Persistence of Multipotent Adult Progenitor Cells. Blood
107:4182-8.
- Osborn MJ, Panoskaltsis-Mortari A, McElmurry RT, Bell
SK, Vignali DAA, Ryan MD,
Wilber A, McIvor RS, Tolar J, Blazar BR. 2005. A Picornaviral
‘2A-like’ Sequence Based Tricistronic Vector
Allowing for High Level Therapeutic Gene Expression Coupled
to a Dual Reporter System. Molec.
Therapy 12:569-74.
- Taylor PA, Panoskaltsis-Mortari A, Freeman GJ, Sharpe
AH, Noelle RJ, Rudensky AY,
Mak TW, Serody JS, Blazar BR: 2005. Targeting of Inducible
Costimulator (ICOS) Expressed on Alloreactive T cells Downregulates
Graft-versus-Host Disease (GVHD) and Facilitates Engraftment
of Allogeneic Bone Marrow (BM). Blood
105:3372-80.
- Taylor PA, Panoskaltsis-Mortari A, Swedin JM, Lucas PJ,
Gress RE, Levine BL, June CH, Serody JS,Blazar BR: 2004.
L-Selectin(hi) but not the L-selectin(lo) CD4+25+ T-regulatory
cells are potent inhibitors of GVHD and BM graft rejection.
Blood
104:3804-12.
- Moseman EA, Dawson AJ, Liang X, Panoskaltsis-Mortari A,
Krieg AM, Liu YJ,
Blazar BR, Chen W: 2004. Human plasmacytoid dendritic cells
activated by CpG
oligodeoxynucleotides induce the generation of CD4+CD25+
regulatory T cells.
J
Immunol. 173:4433-42.
- Sauer MG, Ericson ME, Weigel BJ, Herron MJ, Panoskaltsis-Mortari
A, Kren BT,
Levine BL, Serody JS, June CH, Taylor PA, Blazar BR: 2004.
A novel system for
simultaneous in vivo tracking and biological assessment
of leukemia cells and ex vivo
generated leukemia-reactive cytotoxic T cells (CTLs). Canc.
Res. 64:3914-3921.
- Panoskaltsis-Mortari A, Price A, Hermanson JB, Taras E,
Lees C, Serody JS, Blazar BR: 2004. In vivo imaging of graft-versus-host
disease (GVHD) in mice. Blood
103:3590-8.
- Taylor PA, Lees CJ, Fournier S, Allison JP, Sharpe AH,
Blazar BR: 2004. B7 expression on T Cells downregulates
immune responses through CTLA-4 ligation via T-T interactions.
J.
Immunology 172:34-39.
Last modified on: February 21, 2008
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