T Cell Suicide Gene Therapy Prompts Thymic Renewal in Adults After Haploidentical Hematopoietic Stem Cell Transplantation in the Absence of Post-Transplant Immunesuppression

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 1968-1968
Author(s):  
Luca Vago ◽  
Giacomo Oliveira ◽  
Attilio Bondanza ◽  
Maddalena Noviello ◽  
Corrado Soldati ◽  
...  
Keyword(s):  
Clinical Trial ◽  
T Cells ◽  
Stem Cell ◽  
T Cell ◽  
Immune Reconstitution ◽  
Suicide Gene ◽  
Phase Iii ◽  
Hematopoietic Stem ◽  
Donor T Cells

Abstract Abstract 1968 BACKGROUND: The genetic modification of T cells with a suicide gene grants a mechanism of control of Graft-versus-Host Disease (GvHD), allowing safe infusion of donor lymphocytes after partially HLA-incompatible Hematopoietic Stem Cell Transplantation (HSCT). In the TK007 phase I-II clinical trial, which enrolled a total of 54 adults with hematologic malignancies, 22 of the 28 treated patients experienced a rapid and sustained immune recovery after T cell-depleted HSCT and serial infusions of purified donor T cells expressing the Herpes Simplex Virus Tymidine Kinase suicide gene (TK cells; Ciceri and Bonini et al., Lancet Oncology, 2009). In these patients, after a first wave of circulating TK cells, the majority of T cells supporting long-term immune reconstitution did not carry the suicide gene and displayed high numbers of naïve lymphocytes, leading us to hypothesize a thymus-dependent development of T cells, occurring only upon TK cell engraftment. METHODS: Thymic function was investigated in a total of 31 patients enrolled in the TK007 trial (median age 55 years), which were compared to a cohort of adult patients receiving non T cell-depleted haploidentical transplantation (n=31), and to healthy pediatric and adult subjects. T cell subsets and the proportion of CD31+ recent thymic emigrants amongst CD4 naïve T cells were measured by immunophenotypic analysis. Single joint T cell Receptor Excision Circles (sjTREC) were quantified by qPCR. The volume of the biologically active thymus was assessed by chest CT scans. Serum concentration of cytokines was assessed by a multiplex luminex-based assay. Pathogen-specific immunity was quantified by interferon-γ ELISpot. RESULTS: After the infusion of TK cells we documented a significant increase in peripheral blood sjTRECs as compared to the pre-HSCT determination (p = 0.02), suggesting an improved thymic output. Importantly, in line with that, only in TK007 patients almost the totality of CD4 naïve T cells circulating after transplantation were CD31+, thus bona fide recent thymic emigrants (89.54±9.55% at immune reconstitution, 81.84±15.9% at 6 months after HSCT, and 79.55±16.66% at 12 months after HSCT). Accordingly, a substantial expansion of the active thymic tissue was observed at chest tomography scans as compared to the pre-HSCT counterparts (p < 0.0001). A peculiar observation, possibly linked to the renewal of thymic activity and unique to the TK007 patients who achieved immune reconstitution, was the documentation of a peak in the serum level of interleukin-7, reproducibly occurring after each infusion of suicide gene-modified cells and anticipating the appearance of the newly generated T cells. Ultimately, the development of a wide repertoire of T cells in the patient thymus from donor precursors ensured a long-term protective immunity against pathogens, as exemplified by the preservation of a physiological and protective response against viruses both ex vivo and in vivo, even after the elimination of the infused TK cells in case of GvHD. CONCLUSIONS: Our data from TK007 patients show that the infusion of genetically modified donor T cells after transplantation can drive the recovery of thymic activity in adults, leading to long-term immune reconstitution. On the lead of the encouraging biological and clinical results of the phase I-II clinical trial, demonstrating a dramatic decrease in late infectious mortality, a multicenter, phase III clinical trial (TK008 study) to assess the efficacy of TK cells in the context of haploidentical HSCT for leukemia started in 2010 at the San Raffaele Institute, and is currently expanding to multiple centers throughout Europe and US. Main endpoints of this randomized phase III trial are disease free survival and overall survival. The first TK008 patients randomized to receive suicide gene-modified cells showed recovery of thimyc activity and concomitantly achieved a rapid and robust T cell immune reconstitution. Disclosures: Bonini: MolMed SpA: Consultancy.

scholarly journals T-cell suicide gene therapy prompts thymic renewal in adults after hematopoietic stem cell transplantation

Blood ◽  
2012 ◽  
Vol 120 (9) ◽  
pp. 1820-1830 ◽  
Author(s):  
Luca Vago ◽  
Giacomo Oliveira ◽  
Attilio Bondanza ◽  
Maddalena Noviello ◽  
Corrado Soldati ◽  
...  
Keyword(s):  
T Cells ◽  
Stem Cell ◽  
T Cell ◽  
Hematopoietic Stem Cell Transplantation ◽  
Stem Cell Transplantation ◽  
Cell Transplantation ◽  
Immune Reconstitution ◽  
Suicide Gene ◽  
Hematopoietic Stem ◽  
Donor T Cells

Abstract The genetic modification of T cells with a suicide gene grants a mechanism of control of adverse reactions, allowing safe infusion after partially incompatible hematopoietic stem cell transplantation (HSCT). In the TK007 clinical trial, 22 adults with hematologic malignancies experienced a rapid and sustained immune recovery after T cell–depleted HSCT and serial infusions of purified donor T cells expressing the HSV thymidine kinase suicide gene (TK+ cells). After a first wave of circulating TK+ cells, the majority of T cells supporting long-term immune reconstitution did not carry the suicide gene and displayed high numbers of naive lymphocytes, suggesting the thymus-dependent development of T cells, occurring only upon TK+-cell engraftment. Accordingly, after the infusions, we documented an increase in circulating TCR excision circles and CD31+ recent thymic emigrants and a substantial expansion of the active thymic tissue as shown by chest tomography scans. Interestingly, a peak in the serum level of IL-7 was observed after each infusion of TK+ cells, anticipating the appearance of newly generated T cells. The results of the present study show that the infusion of genetically modified donor T cells after HSCT can drive the recovery of thymic activity in adults, leading to immune reconstitution.

Infusion of Ex-Vivo Expanded Donor T Cells To Improve Graft-Derived T-Cell Reconstitution after Allogeneic Hematopoietic Stem Cell Transplantation.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 3261-3261
Author(s):  
Nicolas Montcuquet ◽  
Sylvain Perruche ◽  
Benjamin Shipman ◽  
Aliette Marandin-Decock ◽  
Francis Bonnefoy ◽  
...  
Keyword(s):  
Bone Marrow ◽  
T Cells ◽  
Stem Cell ◽  
T Cell ◽  
Hematopoietic Stem Cell Transplantation ◽  
Immune Reconstitution ◽  
Ex Vivo ◽  
Murine Models ◽  
Hematopoietic Stem ◽  
Donor T Cells

Abstract Limitations resulting from the reduced availability of related donors have been solved by the development of haplo-identical transplantation or by the use of cord blood as an alternative source of hematopoietic stem cells (HSC) to the bone marrow or peripheral blood. However, these kinds of transplantation remain associated with an impaired immune reconstitution, leading to an increased risk of infection and require an efficient modulation of post-transplant alloreactivity. In this setting, we and others demonstrated the possibility to control the alloreactivity by suicide gene transfer into donor T cells after ex-vivo T-cell culture. Such ex vivo culture was associated with the acquisition of a memory-like phenotype and with a decreased alloreactivity of gene-modified T cells, leading to an impaired potential of GvHD induction in murine models of allogeneic bone marrow transplantation (BMT). Chen and al. (Blood 2004) showed in an allogeneic BMT murine models that memory T cells were less alloreactive than naive T cells, leading to a less severe GvHD, but improved the immune reconstitution as compared with mice transplanted with bone marrow cells (BMC) only. By analogy with these results, we investigated the potential of ex-vivo expanded T cells (consisting of Con-A-activated splenocytes cultured ex vivo for 12 days in the presence of 500 UI/ml IL-2) to improve immune reconstitution without inducing GvHD. As compared with recipients of T-cell-depleted (TCD) BMC only, the administration of 106ex-vivo-expanded splenocytes (T) from CD45.1 C57Bl/6 mice together with 106 TCD-BMC from CD45.2 C57Bl/6 donors into 8 Gy-irradiated Balb/c allogeneic recipients significantly increased survival of transplanted mice at day 45 (58.3% vs 23.4% for BMC + T vs BMC only; p=0.0012, log rank test). Improved survival was associated with accelerated lymphoid and myeloid reconstitution as evidenced by day 15 lymphocyte and granulocyte blood counts: 212 (median) [range: 15–991]) vs 135 [14–632] lymphocytes/μl (p=0.0220) and 802 [6–5648] vs 114 [5–2411] granulocytes/μl (p=0.0006) for BMC + T (n=61) vs BMC only (n= 55). Importantly, FACS analysis demonstrated that enhanced lymphoid and myeloid reconstitution induced by ex-vivo expanded donor T-cells was due to enhanced donor bone-marrow-derived cells (lymphocyte and granulocyte blood counts: 129 [0–932] vs 11 [0–603] lymphocytes/μl (p=0.0014) and 801 [2–5637] vs 114 [2–2409] granulocytes/μl (p=0.0007) for BMC + T vs BMC only) and not ex-vivo expanded donor cells or residual recipient cells. Within the lymphoid compartment, enhanced reconstitution was observed mainly for CD3+CD8+ cells. Co-infusion of ex-vivo expanded donor T-cells did not induce GvHD (no GvHD-induced mortality or weight loss) while co-infusion of fresh splenocytes from CD45.1 C57Bl/6 mice induced severe GvHD (p<0.001 vs BMC only). Our results establish that ex-vivo expanded donor T-cells have a graft-facilitating effect and that they could be considered as a new cell therapy product allowing improving immune reconstitution after hematopoietic stem cell transplantation. Mechanisms involved in this graft-facilitating effect of ex-vivo expanded donor T cells remain to be elucidated.

scholarly journals The Role of T Cells in Hematopoietic Stem Cell Engraftment

2006 ◽  
Vol 6 ◽  
pp. 246-253 ◽  
Author(s):  
Elizabeth Hexner
Keyword(s):  
Stem Cells ◽  
T Cells ◽  
Stem Cell ◽  
Hematopoietic Stem Cell ◽  
Immune Cells ◽  
Immune Reconstitution ◽  
Host Immune System ◽  
Hematopoietic Stem ◽  
Cell Engraftment ◽  
Donor T Cells

Much attention has focused on the immune recovery of donor T cells following hematopoietic stem cell transplantation (HSCT). Termed immune reconstitution, a better understanding of the dynamics of the functional recovery of immune cells following HSCT has important implications both for fighting infections and, in the allogeneic setting, for providing antitumor activity while controlling graft-vs.-host disease (GVHD). The immune cells involved in immune reconstitution include antigen-presenting cells, B lymphocytes, natural killer cells, and, in particular, T lymphocytes, the immune cell that will be the subject of this review. In addition, T cells can play an important role in the process of engraftment of hematopoietic stem cells. The evidence for a T cell tropic effect on hematopoietic engraftment is both direct and indirect, and comes from the clinic as well as the research lab. Animal models have provided useful clues, but the molecular mechanisms that govern the interaction between donor stem cells, donor T cells, the host immune system, and the stem cell niche remain obscure. This review will describe the current published clinical and basic evidence related to T cells and stem cell engraftment, and will identify future directions for translational research in this area.

Interruption of IFNγR Signaling Results in Altered T Cell Trafficking in Vivo and Abrogation of GvHD While Maintaining a Robust Gvl Response

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 455-455
Author(s):  
Jaebok Choi ◽  
Edward Dela Ziga ◽  
Julie Ritchey ◽  
Lynne Collins ◽  
Julie Prior ◽  
...  
Keyword(s):  
T Cells ◽  
Stem Cell ◽  
T Cell ◽  
Hematopoietic Stem Cell ◽  
Cell Trafficking ◽  
Hematopoietic Stem ◽  
T Cell Trafficking ◽  
Target Organs ◽  
Donor T Cells

Abstract Abstract 455 Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the only curative treatment for patients with relapsed/refractory leukemia, and marrow failure states such as myelodysplasia and aplastic anemia. However, allo-HSCT is complicated by allogeneic donor T cell-mediated graft-versus-host disease (GvHD) which can be life-threatening especially in recipients of unrelated or HLA-mismatched hematopoietic stem cell products. These same alloreactive donor T cells also mediate a beneficial graft-versus-leukemia (GvL) effect. Thus, the clinical goal in allo-HSCT is to minimize GvHD while maintaining GvL. Recent studies have suggested that this might be achieved by infusing regulatory T cells (Tregs) which in some preclinical models suppress GvHD-causing alloreactive donor T cells but have only limited effects on GvL-promoting alloreactive donor T cells. Unfortunately, Tregs exist in low frequency in the peripheral blood, are costly to purify and expand, and after expansion are difficult to isolate due to the lack of cell surface markers, all of which prevent their routine use in the clinic. Thus, alternative therapeutic approaches that do not require Tregs are needed. We have found that interferon gamma receptor deficient (IFNγR−/−) allogeneic donor T cells induce significantly less GvHD in both a MHC fully-mismatched (B6 (H-2b) → Balb/c (H-2d)) and a minor-mismatched (B6 (H-2b) → B6×129(H-2b)) allo-HSCT models compared to WT T cells. In addition, IFNγR−/− donor T cells maintain a beneficial GvL effect, which has been examined in both systemic leukemia and solid tumor models using luciferase-expressing A20 cells derived from Balb/c. We find that IFNγR−/− T cells migrate primarily to the spleen while WT T cells to GI tract and peripheral lymph nodes (LNs) using bioluminescence imaging (BLI), suggesting that altered T cell trafficking of IFNγR−/− T cells to GvHD target organs might be the major reason for the reduced GvHD. We further demonstrate that the IFNγR-mediated signaling in alloreactive donor T cells is required for expression of CXCR3 which has been implicated in trafficking of T cells to areas of inflammation and target organs, commonly known to be the sites of GvHD. Indeed, CXCR3−/− T cells recapitulate the reduced GvHD potential of IFNγR−/− T cells. In addition, forced overexpression of CXCR3 in IFNγR−/− T cells via retroviral transduction partially rescues the GvHD defect observed in IFNγR−/− T cells. We next examine if inhibition of IFNγR signaling using a small molecule inhibitor can recapitulate the anti-GVHD effects seen in IFNγR−/− T cells. We find that INCB018424, an inhibitor of JAK1/JAK2 which are the mediators of IFNγR signaling, blocks CXCR3 expression in vitro. Most importantly, in vivo administration of INCB018424 after allo-HSCT alters T cell trafficking and significantly reduces GvHD. Thus, the IFNγR signaling pathway represents a promising therapeutic target for future efforts to mitigate GvHD while maintaining GvL after allo-HSCT. Moreover, this pathway can be exploited in other diseases besides GvHD such as those from organ transplantation, chronic inflammatory diseases and autoimmune diseases. Disclosures: DiPersio: genzyme: Honoraria.

Hematopoietic stem cell dose correlates with the speed of immune reconstitution after stem cell transplantation

Blood ◽  
2004 ◽  
Vol 103 (11) ◽  
pp. 4344-4352 ◽  
Author(s):  
Benny J. Chen ◽  
Xiuyu Cui ◽  
Gregory D. Sempowski ◽  
Jos Domen ◽  
Nelson J. Chao
Keyword(s):  
Stem Cells ◽  
T Cells ◽  
Stem Cell ◽  
T Cell ◽  
B Cells ◽  
Hematopoietic Stem Cells ◽  
Immune Reconstitution ◽  
Hematopoietic Stem ◽  
Time Points ◽  
Cell Dose

Abstract In the current study, we tested whether higher numbers of hematopoietic stem cells correlate with the speed of immune reconstitution in a congenic transplantation model (C57BL/Ka, CD45.1, Thy1.1→C57BL/6, CD45.2, Thy1.2) using purified hematopoietic stem cells (c-Kit+Thy1.1lowLin-/lowSca-1+). There were 3 different doses of stem cells used (400, 1000, and 5000). Phenotypic analyses in peripheral blood and spleen demonstrated that higher numbers of infused stem cells are associated with more rapid regeneration of T cells (CD4+, CD8+, naive CD4+, naive CD8+) and B cells at early time points. The numbers of T and B cells eventually became equivalent between different dose groups at late time points. Production of interleukin-2 and inter-feron-γ per T cell was similar regardless of stem cell dose even when tested at the time when there were significant differences in peripheral T-cell counts. The improved immune recovery was attributed to a more rapid regeneration of donor-type immune cells. Higher numbers of total thymocytes and signal joint T-cell receptor excision circles were observed in the higher dose stem cell recipients, suggesting that accelerated regeneration of T cells was due to enhanced thymopoiesis. (Blood. 2004;103:4344-4352)

Long-term safety and survival outcomes after TK-expressing donor lymphocyte infusion (TK-DLI) in allogeneic hematopoietic stem cell transplantation (HSCT).

2013 ◽  
Vol 31 (15_suppl) ◽  
pp. 7007-7007
Author(s):  
Fabio Ciceri ◽  
Maria Teresa Lupo-Stanghellini ◽  
Giacomo Oliveira ◽  
Raffaella Greco ◽  
Luca Vago ◽  
...  
Keyword(s):  
T Cells ◽  
Low Frequency ◽  
Suicide Gene ◽  
Complete Response ◽  
Donor Lymphocyte Infusion ◽  
Phase Iii ◽  
Hematopoietic Stem ◽  
Disease Response

7007 Background: Suicide gene therapy (SGT) was firstly applied to allogeneic HSCT, addressing the need for modulation of graft vs host disease (GvHD) reactions while preserving graft vs leukemia (GvL) effect of alloreactive T cells. HSV-TK gene insertion in donor T-cells modulates alloreactivity by selectively destroying dividing alloreactive cells involved in GvHD. Methods: Long-term safety and survival was assessed in 128 pts entering worldwide 10 phase I-II trials that used TK-DLI to improve GvL, immune reconstitution (IR) and GvHD control. In all, 57 pts received TK DLI at our Institution: 23 to treat relapse after HLA-identical HSCT (Ciceri, 2007) and 34 to improve IR after haploidentical HSCT (Ciceri, Bonini, 2009). Results: SGT was feasible, safe and effective in promoting a dynamic and specific modulation of alloreactivity. TK-DLI clinical benefit, defined by chimerism, tumor response and/or IR, was achieved by 65 pts (51%). Grade 2 to 4 GvHD (n=28, 22%) was fully controlled by SGT. TK-DLI engrafted in 51 pts (90%) and, being detectable at low frequency up to 14 yrs, no SGT-related adverse events occurred. In HLA-identical setting (n=23; median follow-up, 15 yrs), 11 pts (48%) had disease response and 2 pts (9%) were alive in complete response (CR). In haploidentical setting (n=34; median follow-up, 7 yrs), 25 pts (73%) had IR and 9 pts (26%) were alive in CR. All pts were monitored according to guidelines on long-term survivors (Majhail, 2012). There were no major infections, while 3 pts had a second tumor. Immunity against TK-DLI was reported exclusively after HLA-identical allo-HSCT indicating that TK-DLI is not limited by SGT-specific immunity after haploidentical HSCT. Conclusions: Long-term follow-up confirms the high benefit to risk ratio of TK-DLI. A phase III trial is ongoing in haploidentical HSCT (NCT00914628). Clinical trial information: NCT00423124.

Long-Term T Cell Immune Reconstitution in Patients Surviving 10 or More Years after Allogeneic Stem Cell Transplantation for Hematologic Malignancies

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 1173-1173
Author(s):  
Quan Le ◽  
J. Joseph Melenhorst ◽  
Bipin N. Savani ◽  
Brenna Hill ◽  
Sarfraz Memon ◽  
...  
Keyword(s):  
T Cells ◽  
Stem Cell ◽  
T Cell ◽  
Stem Cell Transplantation ◽  
T Cell Receptor ◽  
Allogeneic Stem Cell Transplantation ◽  
Immune Reconstitution ◽  
Cell Receptor ◽  
Myelogenous Leukemia

Abstract After allogeneic stem cell transplantation (SCT), there is a prolonged immune deficiency and delayed T cell reconstitutions results in significant morbidity and mortality. However limited data are available on immune reconstitution in patients surviving beyond a decade following SCT. Four hundred sixty two patients with hematological malignancies received SCT from an HLA identical sibling in our institute between 1993–2004. Of these, 110 patients 3 or more years post-transplantation, prospectively enrolled in a long-term evaluation protocol. Twenty one of these survived more than 10 years post SCT (median follow-up 11.8 y range 10–14.75y). Diagnoses included chronic myelogenous leukemia (17), acute myelogenous leukemia and myelodysplastic syndrome (3), and multiple myeloma (1). We studied T cell reconstitution in these patients and compared it to samples from their stem cell donors cryopreserved at time of transplant. There was no difference of age at SCT in patients (median age 35.5, range 13–56y) and in the donors (median age 34, range 14–58y). All patients received cyclophosphamide and 13.6 Gy total body irradiation. Patients received T cell depleted bone marrow (n=15) or peripheral blood SCT (n=6) with cyclosporine GVHD prophylaxis and delayed add-back of donor lymphocytes 30–90 days post transplant. Six (29%) developed acute GVHD (grade II–IV) and 18 (86%) chronic GVHD (13 limited, 5 extensive). Six (29%) patients received immunosuppressive therapy (IST) for cGVHD beyond 3 years from SCT but all were off immunosuppressive treatment at the time of study. In the 21 patients there were no significant difference in the absolute lymphocyte, neutrophil or monocyte count, compared with the donor pre-transplant absolute counts of circulating NK and T cell subsets, and B cells were measured using multicolor flow cytometric analysis in 9 patient-donor pairs. Patients had fewer naïve CD4 (p = 0.049) and naïve CD8 (p = 0.004) T cells, fewer CD4 central memory T cells (p = 0.03), fewer CD56 [int] CD16-NKG2A+2D+ NK cells (p = 0.02); and more effector CD8+ T cells (p = 0.04) in patients compared to their donors. ALC and FoxP3+ regulatory T cells were not significantly different between the patients and their donors. The T cell receptor excision circles (TRECs) and T cell receptor repertoire analyses to evaluate thymic function and T cell regeneration is ongoing. In conclusion, patients surviving 10 or more years after allogeneic SCT still show a deficit in the naïve and central memory post-thymic compartment. However these abnormalities appear to be compatible with good health. Figure Figure

Interruption of the IFN γR/CXCR3 Axis Results in Altered T Cell Trafficking In Vivo and Abrogation of GvHD While Maintaining a Robust Gvl Response

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 2971-2971
Author(s):  
Jaebok Choi ◽  
Edward Dela Ziga ◽  
Julie Ritchey ◽  
Julie Prior ◽  
Lynne Collins ◽  
...  
Keyword(s):  
T Cells ◽  
Stem Cell ◽  
T Cell ◽  
Hematopoietic Stem Cell ◽  
Neutralizing Antibodies ◽  
Conflicts Of Interest ◽  
Hematopoietic Stem ◽  
Target Organs ◽  
Donor T Cells

Abstract Abstract 2971 Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the only curative treatment for patients with relapsed/refractory leukemia, and marrow failure states such as myelodysplasia and aplastic anemia. However, allo-HSCT is complicated by allogeneic donor T cell-mediated graft-versus-host disease (GvHD) which can be life-threatening especially in recipients of unrelated or HLA-mismatched hematopoietic stem cell products. These same alloreactive donor T cells also mediate a beneficial graft-versus-leukemia (GvL) effect. Thus, the clinical goal in allo-HSCT is to minimize GvHD while maintaining GvL. Recent studies have suggested that this might be achieved by infusing regulatory T cells (Tregs) which in some preclinical models suppress GvHD-causing alloreactive donor T cells but have only limited effects on GvL-promoting alloreactive donor T cells. Unfortunately, Tregs exist in low frequency in the peripheral blood, are costly to purify and expand, and after expansion are difficult to isolate due to the lack of cell surface markers, all of which prevent their routine use in the clinic. Thus, alternative therapeutic approaches that do not require Tregs are needed. Using a MHC-mismatched GvHD model, B6 (H-2b) → Balb/c (H-2d), we demonstrated that infusion of IFN γR deficient allogeneic donor T cells induce significantly less GvHD, compared to WT T cells, determined by survival (74% vs. 0 % in overall survival; p =0.0004), weight and percentages of B220+ B cells (12.4% vs. 3.8%; p =0.0205), CD3+ T cells (14.3% vs. 4.3%; p =0.0025) in blood. Of note was that the IFN γR deficient donor T cells maintained a beneficial GvL effect, which was examined in both a systemic leukemia and a solid tumor model using luciferase-expressing A20 cells derived from Balb/c. We found that IFN γR deficient donor T cells responded normally to allogeneic antigens as measured by in vitro mixed lymphocyte reaction analyses, and express similar levels of granzyme B, compared to WT T cells. However, IFN γR deficient T cells trafficked predominantly to the spleen while WT T cells trafficked to gastrointestinal tract and peripheral lymph nodes, which are major GvHD target organs, based on in vivo bioluminescence imaging. All of these findings suggest that the reduced GvHD was not due to reduced function, altered subsets or relative deficiency of allogeneic donor T cells but from modification of in vivo trafficking of IFN γR deficient donor T cells compared to WT T cells. We further demonstrated that the IFN γR-mediated signaling in alloreactive donor T cells was required for expression of CXCR3 which has been implicated in trafficking of T cells to areas of inflammation and target organs, commonly known to be the sites of GvHD. CXCR3−/− T cells demonstrated a reduction in GvHD while maintenance of the same robust GvL effect using the same MHC mismatched transplant model. Thus, the IFN γR-CXCR3 axis represents a promising therapeutic target for future efforts to mitigate GvHD while maintaining GvL after allo-HSCT. Current studies are focused on 1) whether forced expression of CXCR3 rescues the GvHD-inducing potential of IFN γR deficient donor T cells and 2) if inhibition of IFN γR signaling (IFN γR, JAK1 and/or JAK2, CXCR3 and STAT1) using both neutralizing antibodies and small molecule inhibitors can recapitulate the anti-GvHD and pro-GvL effects seen in IFN γR−/− and CXCR3−/− T cells. Disclosures: No relevant conflicts of interest to declare.

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