Gene therapy for hemophilia

2019

Cellular Immunology

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After two decades of research, in vivo gene transfer with adeno-associated viral (AAV) vectors has now resulted in successful treatments and even cures for several human diseases. However, the potential for immune responses against the therapeutic gene products remains one of the concerns as this approach is broadened to more patients, diverse diseases, and target organs. Immune responses following gene transfer of coagulation factor IX (FIX) for the treatment of the bleeding disorder hemophilia B has been extensively investigated in multiple animal models. Findings from these studies have not only influenced clinical trial design but have broader implications for other diseases. The impact of vector design and dose, as well as target organ/route of administration on humoral and cellular immune responses are reviewed. Furthermore, the potential for tolerance induction by hepatic gene transfer or combination with immune modulation is discussed.

Section: Antibody Formation Against Secreted Gene Products Such Asmentioning

confidence: 99%

“…FVIII and FIX are normally synthesized in the liver by endothelial cells and hepatocytes, respectively [14]. However, other cell types are capable of producing biologically active FVIII and FIX molecules, providing a wide range of potential target cells and tissues for gene therapy.…”

Section: Antibody Formation Against Secreted Gene Products Such Asmentioning

confidence: 99%

Complexity of immune responses to AAV transgene products – Example of factor IX

2019

Cellular Immunology

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“…Because FIX is normally produced by hepatocytes and FIX activity levels as low as 5% of normal can significantly reduce bleeding events, gene therapy was considered a promising means of restoring FIX expression. Positive outcomes in preclinical studies evaluating liver-directed AAV vectors expressing the coagulation FIX protein, in small and large animal models,2, 3, 4 prompted the first clinical trial of an AAV2 vector (expressing FIX from a hepatocyte-specific enhancer/promoter combination, AAV2-ApoE-hAAT- F9 ) delivered to human hepatocytes 5 . A patient receiving a vector dose of 2 × 10 12 vector genome (vg)/kg had transient therapeutic FIX expression levels that returned to baseline accompanied with a self-resolving transaminitis 5 .…”

Section: Introductionmentioning

confidence: 99%

An Immune-Competent Murine Model to Study Elimination of AAV-Transduced Hepatocytes by Capsid-Specific CD8+ T Cells

Palaschak

Marsic

Molecular Therapy - Methods & Clinical Development

et al. 2017

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Multiple independent adeno-associated virus (AAV) gene therapy clinical trials for hemophilia B, utilizing different AAV serotypes, have reported a vector dose-dependent loss of circulating factor IX (FIX) protein associated with capsid-specific CD8+ T cell (Cap-CD8) elimination of transduced hepatocytes. Hemophilia B patients who develop transient transaminitis and loss of FIX protein may be stabilized with the immune-suppressive (IS) drug prednisolone, but do not all recover lost FIX expression, whereas some patients fail to respond to IS. We developed the first animal model demonstrating Cap-CD8 infiltration and elimination of AAV-transduced hepatocytes of immune-deficient mice. Here, we extend this model to an immune-competent host where Cap-CD8 transfer to AAV2-F9-treated mice significantly reduced circulating and hepatocyte FIX expression. Further, we studied two high-expressing liver tropic AAV2 variants, AAV2-LiA and AAV2-LiC, obtained from a rationally designed capsid library. Unlike AAV2, Cap-CD8 did not initially reduce circulating FIX levels for either variant. However, FIX levels were significantly reduced in AAV2-LiC-F9-treated, but not AAV2-LiA-F9-treated, mice at the study endpoint. Going forward, the immune-competent model may provide an opportunity to induce immunological memory directed against a surrogate AAV capsid antigen and study recall responses following AAV gene transfer.

“…In its severe form (<1% FIX activity), it can result in frequent bleeding, reduced quality of life, and early death if left untreated 1 . Currently, treatment is based on intravenous (IV) administration of plasma-derived or recombinant FIX concentrate.…”

Section: Introductionmentioning

confidence: 99%

Immune Modulatory Cell Therapy for Hemophilia B Based on CD20-Targeted Lentiviral Gene Transfer to Primary B Cells

Wang

Molecular Therapy - Methods & Clinical Development

Byrne

et al. 2017

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Gene-modified B cells expressing immunoglobulin G (IgG) fusion proteins have been shown to induce tolerance in several autoimmune and other disease models. However, lack of a vector suitable for gene transfer to human B cells has been an obstacle for translation of this approach. To overcome this hurdle, we developed an IgG-human factor IX (hFIX) lentiviral fusion construct that was targeted to specifically transduce cells expressing human CD20 (hCD20). Receptor-specific retargeting by mutating envelope glycoproteins of measles virus (MV)-lentiviral vector (LV) and addition of a single-chain variable fragment specific for hCD20 resulted in gene delivery into primary human and transgenic hCD20 mouse B cells with high specificity. Notably, this protocol neither required nor induced activation of the B cells, as confirmed by minimal activation of inflammatory cytokines. Using this strategy, we were able to demonstrate induction of humoral tolerance, resulting in suppression of antibody formation against hFIX in a mouse model of hemophilia B (HB). In conclusion, transduction of receptor-specific retargeted LV into resting B cells is a promising method to develop B cell therapies for antigen-specific tolerance induction in human disease.