Publications by authors named "Jocelyn A Schroeder"

13 Publications

  • Page 1 of 1

Platelet-targeted hyperfunctional FIX gene therapy for hemophilia B mice even with preexisting anti-FIX immunity.

Blood Adv 2021 Mar;5(5):1224-1238

Blood Research Institute, Versiti Wisconsin, Milwaukee, WI.

Gene therapy may lead to a cure for hemophilia B (HB) if it is successful. Data from clinical trials using adeno-associated virus (AAV)-mediated liver-targeted FIX gene therapy are very encouraging. However, this protocol can be applied only to adults who do not have liver disease or anti-AAV antibodies, which occur in 30% to 50% of individuals. Thus, developing a protocol that can be applied to all HB patients is desired. Our previous studies have demonstrated that lentivirus-mediated platelet-specific FIX (2bF9) gene therapy can rescue bleeding diathesis and induce immune tolerance in FIXnull mice, but FIX expression was only ∼2% to 3% in whole blood. To improve the efficacy, we used a codon-optimized hyperfunctional FIX-Padua (2bCoF9R338L) to replace the 2bF9 cassette, resulting in 70% to 122% (35.08-60.77 mU/108 platelets) activity levels in 2bCoF9R338L-transduced FIXnull mice. Importantly, sustained hyperfunctional platelet-FIX expression was achieved in all 2bCoF9R338L-transduced highly immunized recipients with activity levels of 18.00 ± 9.11 and 9.36 ± 12.23 mU/108 platelets in the groups treated with 11 Gy and 6.6 Gy, respectively. The anti-FIX antibody titers declined with time, and immune tolerance was established after 2bCoF9R338L gene therapy. We found that incorporating the proteasome inhibitor bortezomib into preconditioning can help eliminate anti-FIX antibodies. The bleeding phenotype in 2bCoF9R338L-transduced recipients was completely rescued in a tail bleeding test and a needle-induced knee joint injury model once inhibitors dropped to undetectable. The hemostatic efficacy in 2bCoF9R338L-transduced recipients was further confirmed by ROTEM and thrombin generation assay (TGA). Together, our studies suggest that 2bCoF9R338L gene therapy can be a promising protocol for all HB patients, including patients with inhibitors.
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http://dx.doi.org/10.1182/bloodadvances.2020004071DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7948262PMC
March 2021

Platelet gene therapy induces robust immune tolerance even in a primed model via peripheral clonal deletion of antigen-specific T cells.

Mol Ther Nucleic Acids 2021 Mar 5;23:719-730. Epub 2021 Jan 5.

Blood Research Institute, Versiti Wisconsin, Milwaukee, WI, USA.

While platelet-specific gene therapy is effective in inducing immune tolerance to a targeted protein, how the reactivity of pre-existing immunity affects the efficacy, and whether CD8 T cells were involved in tolerization, is unclear. In this study, ovalbumin (OVA) was used as a surrogate protein. Platelet-OVA expression was introduced by 2bOVA lentivirus transduction of Sca-1 cells from either wild-type (WT)/CD45.2 or OT-II/CD45.2 donors followed by transplantation into OVA-primed WT/CD45.1 recipients preconditioned with 6.6 Gy of irradiation. Sustained platelet-OVA expression was achieved in >85% of OVA-primed recipients but abolished in animals with high-reactive pre-existing immunity. As confirmed by OVA rechallenge and skin graft transplantation, immune tolerance was achieved in 2bOVA-transduced recipients. We found that there is a negative correlation between platelet-OVA expression and the percentage of OVA-specific CD4 T cells and a positive correlation with the OVA-specific regulatory T (Treg) cells. Using the OT-I/WT model, we showed that antigen-specific CD8 T cells were partially deleted in recipients after platelet-targeted gene transfer. Taken together, our studies demonstrate that robust antigen-specific immune tolerance can be achieved through platelet-specific gene therapy via peripheral clonal deletion of antigen-specific CD4 and CD8 T effector cells and induction of antigen-specific Treg cells. There is an antagonistic dynamic process between immune responses and immune tolerance after platelet-targeted gene therapy.
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http://dx.doi.org/10.1016/j.omtn.2020.12.026DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7851450PMC
March 2021

In vivo enrichment of genetically manipulated platelets for murine hemophilia B gene therapy.

J Cell Physiol 2021 Jan 8;236(1):354-365. Epub 2020 Jun 8.

Department of Pediatrics, Medical College of Wisconsin, Milwaukee, Wisconsin.

Our previous studies have demonstrated that platelet-targeted factor IX (FIX) gene therapy can introduce sustained platelet-FIX expression in hemophilia B (FIX ) mice. In this study, we aimed to enhance platelet-FIX expression in FIX mice with O -methylguanine-DNA-methyltransferase (MGMT)-mediated in vivo drug selection of transduced cells under nonmyeloablative preconditioning. We constructed a novel lentiviral vector (2bF9/MGMT lentivirus vector), which harbors dual genes, the FIX gene driven by the αIIb promoter (2bF9) and the MGMT P140K gene under the murine stem cell virus promoter. Platelet-FIX expression in FIX mice was introduced by 2bF9/MGMT-mediated hematopoietic stem cell transduction and transplantation. The 2bF9/MGMT-transduced cells were effectively enriched after drug selection by O -benzylguanine/1,3-bis-2-chloroethyl-1-nitrosourea. There were a 2.9-fold higher FIX antigen and a 3.7-fold higher FIX activity in platelets, respectively, posttreatment compared with pretreatment. When a 6-hr tail bleeding test was used to grade the bleeding phenotype, the clotting time in treated animals was 2.6 ± 0.5 hr. In contrast, none of the FIX control mice were able to clot within 6 hr. Notably, none of the recipients developed anti-FIX antibodies after gene therapy. One of four recipients developed a low titer of inhibitors when challenged with rhF9 together with adjuvant. In contrast, all FIX controls developed inhibitors after the same challenge. Anti-FIX immunoglobulin G were barely detectable in recipients (1.08 ± 0.54 µg/ml), an 875-fold lower level than in the FIX controls. Our data demonstrate that using the MGMT-mediated drug selection system in 2bF9 gene therapy can significantly enhance therapeutic platelet-FIX expression, resulting in sustained phenotypic correction and immune tolerance in FIX mice.
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http://dx.doi.org/10.1002/jcp.29861DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7722216PMC
January 2021

Induction of activated T follicular helper cells is critical for anti-FVIII inhibitor development in hemophilia A mice.

Blood Adv 2019 10;3(20):3099-3110

Blood Research Institute, Versiti, Milwaukee, WI.

The development of neutralizing anti-FVIII antibodies (inhibitors) is a major complication of FVIII protein replacement therapy in patients with hemophilia A (HA). Although multiple lines of evidence indicate that the immune response against FVIII is CD4 T-cell-dependent and many FVIII-derived CD4 epitopes have already been discovered, the role of T follicular helper (TFH) cells in FVIII inhibitor development is unknown. TFH cells, a newly identified subset of CD4 T cells, are characterized by expression of the B-cell follicle-homing receptor CXCR5 and PD-1. In this study, we show for the first time that IV FVIII immunization induces activation and accumulation and/or expansion of PD-1+CXCR5+ TFH cells in the spleen of FVIII-deficient (FVIIInull) mice. FVIII inhibitor-producing mice showed increased germinal center (GC) formation and increased GC TFH cells in response to FVIII immunization. Emergence of TFH cells correlated with titers of anti-FVIII inhibitors. Rechallenge with FVIII antigen elicited recall responses of TFH cells. In vitro FVIII restimulation resulted in antigen-specific proliferation of splenic CD4+ T cells from FVIII-primed FVIIInull mice, and the proliferating cells expressed the TFH hallmark transcription factor BCL6. CXCR5+/+ TFH-cell-specific deletion impaired anti-FVIII inhibitor production, confirming the essential role of CXCR5+/+ TFH cells for the generation of FVIII-neutralizing antibodies. Together, our results demonstrate that the induction of activated TFH cells in FVIIInull mice is critical for FVIII inhibitor development, suggesting that inhibition of FVIII-specific TFH-cell activation may be a promising strategy for preventing anti-FVIII inhibitor formation in patients with HA.
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http://dx.doi.org/10.1182/bloodadvances.2019000650DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6849959PMC
October 2019

Nongenotoxic antibody-drug conjugate conditioning enables safe and effective platelet gene therapy of hemophilia A mice.

Blood Adv 2019 09;3(18):2700-2711

Blood Research Institute, Versiti Wisconsin, Milwaukee, WI.

Gene therapy offers the potential to cure hemophilia A (HA). We have shown that hematopoietic stem cell (HSC)-based platelet-specific factor VIII (FVIII) (2bF8) gene therapy can produce therapeutic protein and induce antigen-specific immune tolerance in HA mice, even in the presence of inhibitory antibodies. For HSC-based gene therapy, traditional preconditioning using cytotoxic chemotherapy or total body irradiation (TBI) has been required. The potential toxicity associated with TBI or chemotherapy is a deterrent that may prevent patients with HA, a nonmalignant disease, from agreeing to such a protocol. Here, we describe targeted nongenotoxic preconditioning for 2bF8 gene therapy utilizing a hematopoietic cell-specific antibody-drug conjugate (ADC), which consists of saporin conjugated to CD45.2- and CD117-targeting antibodies. We found that a combination of CD45.2- and CD117-targeting ADC preconditioning was effective for engrafting 2bF8-transduced HSCs and was favorable for platelet lineage reconstitution. Two thirds of HA mice that received 2bF8 lentivirus-transduced HSCs under (CD45.2+CD117)-targeting ADC conditioning maintained sustained therapeutic levels of platelet FVIII expression. When CD8-targeting ADC was supplemented, chimerism and platelet FVIII expression were significantly increased, with long-term sustained platelet FVIII expression in all primary and secondary recipients. Importantly, immune tolerance was induced and hemostasis was restored in a tail-bleeding test, and joint bleeding also was effectively prevented in a needle-induced knee joint injury model in HA mice after 2bF8 gene therapy. In summary, we show for the first time efficient engraftment of gene-modified HSCs without genotoxic conditioning. The combined cocktail ADC-mediated hematopoietic cell-targeted nongenotoxic preconditioning that we developed is highly effective and favorable for platelet-specific gene therapy in HA mice.
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http://dx.doi.org/10.1182/bloodadvances.2019000516DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6759737PMC
September 2019

The impact of GPIbα on platelet-targeted FVIII gene therapy in hemophilia A mice with pre-existing anti-FVIII immunity.

J Thromb Haemost 2019 03 3;17(3):449-459. Epub 2019 Feb 3.

Blood Research Institute, BloodCenter of Wisconsin, Milwaukee, WI, USA.

Essentials Platelet-specific FVIII gene therapy is effective in hemophilia A mice even with inhibitors. The impact of platelet adherence via VWF/GPIbα binding on platelet gene therapy was investigated. GPIbα does not significantly affect platelet gene therapy of hemophilia A with inhibitors. Platelet gene therapy induces immune tolerance in hemophilia A mice with pre-existing immunity. SUMMARY: Background We have previously demonstrated that von Willebrand factor (VWF) is essential in platelet-specific FVIII (2bF8) gene therapy of hemophilia A (HA) with inhibitory antibodies (inhibitors). At the site of injury, platelet adherence is initiated by VWF binding to the platelet GPIb complex. Objective To investigate the impact of GPIbα on platelet gene therapy of HA with inhibitors. Methods Platelet-FVIII expression was introduced by 2bF8 lentivirus (2bF8LV) transduction of hematopoietic stem cells (HSCs) from GPIbα (Ib ) mice or rhF8-primed FVIII (F8 ) mice followed by transplantation into lethally irradiated rhF8-primed F8 recipients. Animals were analyzed by flow cytometry, FVIII assays and the tail bleeding test. Results After transplantation, 99% of platelets were derived from donors. The macrothrombocytopenia phenotype was maintained in F8 mice that received 2bF8LV-transduced Ib HSCs (2bF8-Ib /F8 ). The platelet-FVIII expression level in 2bF8-Ib /F8 recipients was similar to that obtained from F8 mice that received 2bF8LV-transduced F8 HSCs (2bF8-F8 /F8 ). The tail bleeding test showed that the remaining hemoglobin level in the 2bF8-Ib /F8 group was significantly higher than in the F8 control group, but there was no significant difference between the 2bF8-Ib /F8 and 2bF8-F8 /F8 groups. The half-life of inhibitor disappearance time was comparable between the 2bF8-Ib /F8 and 2bF8-F8 /F8 groups. The rhF8 re-challenge did not elicit a memory immune response once inhibitor titers dropped to undetectable levels after 2bF8 gene therapy. Conclusion GPIbα does not significantly impact platelet gene therapy of HA with inhibitors. 2bF8 gene therapy restores hemostasis and promotes immune tolerance in HA mice with pre-existing immunity.
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http://dx.doi.org/10.1111/jth.14379DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6397061PMC
March 2019

Platelet Gene Therapy Promotes Targeted Peripheral Tolerance by Clonal Deletion and Induction of Antigen-Specific Regulatory T Cells.

Front Immunol 2018 6;9:1950. Epub 2018 Sep 6.

Blood Research Institute, BloodCenter of Wisconsin, Milwaukee, WI, United States.

Delivery of gene therapy as well as of biologic therapeutics is often hampered by the immune response of the subject receiving the therapy. We have reported that effective gene therapy for hemophilia utilizing platelets as a delivery vehicle engenders profound tolerance to the therapeutic product. In this study, we investigated whether this strategy can be applied to induce immune tolerance to a non-coagulant protein and explored the fundamental mechanism of immune tolerance induced by platelet-targeted gene delivery. We used ovalbumin (OVA) as a surrogate non-coagulant protein and constructed a lentiviral vector in which OVA is driven by the platelet-specific αIIb promoter. Platelet-specific OVA expression was introduced by bone marrow transduction and transplantation. Greater than 95% of OVA was stored in platelet α-granules. Control mice immunized with OVA generated OVA-specific IgG antibodies; however, mice expressing OVA in platelets did not. Furthermore, OVA expression in platelets was sufficient to prevent the rejection of skin grafts from CAG-OVA mice, demonstrating that immune tolerance developed in platelet-specific OVA-transduced recipients. To assess the mechanism(s) involved in this tolerance we used OTII mice that express CD4 effector T cells specific for an OVA-derived peptide. After platelet-specific OVA gene transfer, these mice showed normal thymic maturation of the T cells ruling against central tolerance. In the periphery, tolerance involved elimination of OVA-specific CD4 effector T cells by apoptosis and expansion of an OVA-specific regulatory T cell population. These experiments reveal the existence of natural peripheral tolerance processes to platelet granule contents which can be co-opted to deliver therapeutically important products.
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http://dx.doi.org/10.3389/fimmu.2018.01950DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6136275PMC
September 2019

The impact of von Willebrand factor on factor VIII memory immune responses.

Blood Adv 2017 Aug 18;1(19):1565-1574. Epub 2017 Aug 18.

Blood Research Institute, BloodCenter of Wisconsin, Milwaukee, WI.

Immune tolerance induction (ITI) with aggressive infusion of factor VIII (FVIII) is the current strategy used to eradicate FVIII inhibitors and restore normal FVIII pharmacokinetics in inhibitor patients. Whether the use of FVIII products containing von Willebrand factor (VWF) will affect the efficacy of ITI is still controversial. In this study, we explored the impact of VWF on FVIII memory immune responses in hemophilia A (HA) mice. A T-cell proliferation assay and cytokine profile analysis were used to study FVIII-primed CD4 T cells. When CD4 T cells from primed FVIII mice were restimulated with recombinant human FVIII (rhF8) plus recombinant human VWF (rhVWF) in vitro, the percentages of daughter CD4 T cells were significantly decreased compared with the groups cultured with rhF8 only. Levels of interferon-γ and interleukin 10 were significantly lower in the rhF8 plus rhVWF groups than in the rhF8 groups. When memory B-cell pools from primed FVIII mice were cultured with rhF8 with or without rhVWF to induce differentiation of memory B cells into antibody-secreting cells (ASCs), the number of ASCs was significantly lower in the rhF8 plus VWF group than in the rhF8 group. When memory B-cell pools were transferred into NSGF8KO mice followed by rhF8 immunization with or without rhVWF, the titers of anti-F8 inhibitors and total immunoglobulin G were significantly higher in the rhF8 group than in the rhF8 plus rhVWF group, with an average difference of 2.23- and 2.04-fold. Together, our data demonstrate that VWF attenuates FVIII memory immune responses in HA mice.
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http://dx.doi.org/10.1182/bloodadvances.2017009209DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5600162PMC
August 2017

TGF-β1 along with other platelet contents augments Treg cells to suppress anti-FVIII immune responses in hemophilia A mice.

Blood Adv 2016 Dec;1(2):139-151

Department of Pediatrics, Medical College of Wisconsin, Milwaukee, WI; Children's Research Institute, Children's Hospital of Wisconsin, Milwaukee, WI; Midwest Athletes Against Childhood Cancer Fund Research Center, Milwaukee, WI; Blood Research Institute, BloodCenter of Wisconsin, Milwaukee, WI.

Platelets are a rich source of many cytokines and chemokines including transforming growth factor β 1 (TGF-β1). TGF-β1 is required to convert conventional CD4 T (Tconv) cells into induced regulatory T (iTreg) cells that express the transcription factor Foxp3. Whether platelet contents will affect Treg cell properties has not been explored. In this study, we show that unfractionated platelet lysates (pltLys) containing TGF-β1 efficiently induced Foxp3 expression in Tconv cells. The common Treg cell surface phenotype and in vitro suppressive activity of unfractionated pltLys-iTreg cells were similar to those of iTreg cells generated using purified TGF-β1 (purTGFβ-iTreg) cells. However, there were substantial differences in gene expression between pltLys-iTreg and purTGFβ-iTreg cells, especially in granzyme B, interferon γ, and interleukin-2 (a 30.99-, 29.18-, and 17.94-fold difference, respectively) as determined by gene microarray analysis. In line with these gene signatures, we found that pltLys-iTreg cells improved cell recovery after transfer and immune suppressive function compared with purTGFβ-iTreg cells in factor VIII (FVIII)-deficient (F8, hemophilia A model) mice after recombinant human FVIII (rhF8) infusion. Acute antibody-mediated platelet destruction in F8 mice followed by rhF8 infusion increased the number of Treg cells and suppressed the antibody response to rhF8. Consistent with these data, ex vivo proliferation of F8-specific Treg cells from platelet-depleted animals increased when restimulated with rhF8. Together, our data suggest that pltLys-iTreg cells may have advantages in emerging clinical applications and that platelet contents impact the properties of iTreg cells induced by TGF-β1.
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http://dx.doi.org/10.1182/bloodadvances.2016001453DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5288643PMC
December 2016

The immunogenicity of platelet-derived FVIII in hemophilia A mice with or without preexisting anti-FVIII immunity.

Blood 2016 Mar 14;127(10):1346-54. Epub 2015 Dec 14.

Blood Research Institute, BloodCenter of Wisconsin, Milwaukee, WI; Department of Pediatrics, Medical College of Wisconsin, Milwaukee, WI; Children's Research Institute, Children's Hospital of Wisconsin, Milwaukee, WI; and Midwest Athletes Against Childhood Cancer Research Center, Milwaukee, WI.

Evidence shows that factor VIII (FVIII) ectopically expressed in platelets (2bF8) is therapeutic in FVIII(null) mice even with anti-FVIII inhibitory antibodies (inhibitors). If current efforts to generate platelets in vitro succeed, genetically manipulated platelets containing FVIII may be used therapeutically in hemophilia A patients with inhibitors. One important concern is the immunogenicity of platelet-derived FVIII. To address this concern, we infused 2bF8 transgenic (2bF8(Tg)) platelets into naïve FVIII(null) mice weekly for 8 weeks. No anti-FVIII antibodies were detected in the infused animals during the study course. We then explored whether platelet-derived FVIII is immunogenic in FVIII(null) mice with inhibitors. The 2bF8(Tg) platelets were transfused into rhF8-primed FVIII(null) mice, resulting in no augmentation of anti-FVIII antibodies. To investigate whether preconditioning affects the immune response, animals were sublethally irradiated and subsequently transfused with 2bF8(Tg) platelets. No anti-FVIII antibodies were detected in the recipients after platelet infusions. Following further challenge with rhF8, the inhibitor titer in this group was significantly lower than in naïve FVIII(null) mice utilizing the same immunization protocol. Thus, our data demonstrate that infusion of platelets containing FVIII triggers neither primary nor memory anti-FVIII immune response in FVIII(null) mice and that sublethal irradiation plus 2bF8(Tg) platelet infusion suppresses anti-FVIII immune response in FVIII(null) mice.
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http://dx.doi.org/10.1182/blood-2015-08-662916DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4786841PMC
March 2016

Platelet gene therapy corrects the hemophilic phenotype in immunocompromised hemophilia A mice transplanted with genetically manipulated human cord blood stem cells.

Blood 2014 Jan 22;123(3):395-403. Epub 2013 Nov 22.

Department of Pediatrics, Medical College of Wisconsin.

Our previous studies have demonstrated that platelet FVIII (2bF8) gene therapy can improve hemostasis in hemophilia A mice, even in the presence of inhibitory antibodies, but none of our studies has targeted human cells. Here, we evaluated the feasibility for lentivirus (LV)-mediated human platelet gene therapy of hemophilia A. Human platelet FVIII expression was introduced by 2bF8LV-mediated transduction of human cord blood (hCB) CD34(+) cells followed by xenotransplantation into immunocompromised NSG mice or NSG mice in an FVIII(null) background (NSGF8KO). Platelet FVIII was detected in all recipients that received 2bF8LV-transduced hCB cells as long as human platelet chimerism persisted. All NSGF8KO recipients (n = 7) that received 2bF8LV-transduced hCB cells survived tail clipping if animals had greater than 2% of platelets derived from 2bF8LV-transduced hCB cells, whereas 5 of 7 survived when human platelets were 0.3% to 2%. Whole blood clotting time analysis confirmed that hemostasis was improved in NSGF8KO mice that received 2bF8LV-transduced hCB cells. We demonstrate, for the first time, the feasibility of 2bF8LV gene delivery to human hematopoietic stem cells to introduce FVIII expression in human platelets and that human platelet-derived FVIII can improve hemostasis in hemophilia A.
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http://dx.doi.org/10.1182/blood-2013-08-520478DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3894495PMC
January 2014

Platelet gene therapy by lentiviral gene delivery to hematopoietic stem cells restores hemostasis and induces humoral immune tolerance in FIX(null) mice.

Mol Ther 2014 Jan 23;22(1):169-77. Epub 2013 Aug 23.

1] Blood Research Institute, BloodCenter of Wisconsin, Milwaukee, Wisconsin, USA [2] Department of Pediatrics, Medical College of Wisconsin, Milwaukee, Wisconsin, USA [3] Children's Research Institute, Children's Hospital of Wisconsin, Milwaukee, Wisconsin, USA [4] MACC Fund Research Center, Milwaukee, Wisconsin, USA.

Here, we developed a clinically translatable platelet gene therapy approach for hemophilia B. Platelet-targeted FIX (2bF9) expression was introduced by transplantation of hematopoietic stem cells (HSCs) transduced with 2bF9 lentivirus (LV). Sustained therapeutic levels of platelet-FIX expression were obtained in FIX(null) mice that received 2bF9 LV-transduced HSCs. Approximately 6-39% of the platelets expressed FIX in the transduced recipients, which was sufficient to rescue the bleeding diathesis in FIX(null) mice in tail clipping models. Sequential bone marrow transplantation demonstrated that platelet-FIX expression in the secondary recipients was sustained, leading to phenotypic correction. Notably, none of the transduced recipients developed anti-FIX antibodies after platelet gene therapy. Only one of the nine recipients developed a low titer of inhibitory antibodies (1.6 BU/ml) after challenge with rhFIX. These data suggest that platelet gene therapy can not only restore hemostasis but also induce immune tolerance in hemophilia B mice, indicating that this approach may be a promising strategy for gene therapy of hemophilia B in humans.
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http://dx.doi.org/10.1038/mt.2013.197DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3978792PMC
January 2014

Correction of murine Bernard-Soulier syndrome by lentivirus-mediated gene therapy.

Mol Ther 2012 Mar 1;20(3):625-32. Epub 2011 Nov 1.

Blood Research Institute, Blood Center of Wisconsin, Milwaukee, Wisconsin 53226, USA.

Bernard-Soulier syndrome (BSS) is an inherited bleeding disorder caused by a defect in the platelet glycoprotein (GP) Ib-IX-V complex. The main treatment for BSS is platelet transfusion but it is often limited to severe bleeding episodes or surgical interventions due to the risk of alloimmunization. We have previously reported successful expression of human GPIbα (hGPIbα) in human megakaryocytes using a lentiviral vector (LV) encoding human GP1BA under control of the platelet-specific integrin αIIb promoter (2bIbα). In this study, we examined the efficacy of this strategy for the gene therapy of BSS using GPIbα(null) as a murine model of BSS. GPIbα(null) hematopoietic stem cells (HSC) transduced with 2bIbα LV were transplanted into lethally irradiated GPIbα(null) littermates. Therapeutic levels of hGPIbα expression were achieved that corrected the tail bleeding time and improved the macrothrombocytopenia. Sequential bone marrow (BM) transplants showed sustained expression of hGPIbα with similar phenotypic correction. Antibody response to hGPIbα was documented in 1 of 17 total recipient mice but was tolerated without any further treatment. These results demonstrate that lentivirus-mediated gene transfer can provide sustained phenotypic correction of murine BSS, indicating that this approach may be a promising strategy for gene therapy of BSS patients.
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http://dx.doi.org/10.1038/mt.2011.231DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3293608PMC
March 2012