Factor VIII ectopically targeted to platelets is therapeutic in hemophilia A with high-titer inhibitory antibodies
Qizhen Shi, … , Jack Gorski, Robert R. Montgomery
Qizhen Shi, … , Jack Gorski, Robert R. Montgomery
Published July 3, 2006
Citation Information: J Clin Invest. 2006;116(7):1974-1982. https://doi.org/10.1172/JCI28416.
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Research Article Hematology

Factor VIII ectopically targeted to platelets is therapeutic in hemophilia A with high-titer inhibitory antibodies

Abstract

Inhibitory immune response to exogenously infused factor VIII (FVIII) is a major complication in the treatment of hemophilia A. Generation of such inhibitors has the potential to disrupt gene therapy for hemophilia A. We explore what we believe to be a novel approach to overcome this shortcoming. Human B-domain–deleted FVIII (hBDDFVIII) was expressed under the control of the platelet-specific αIIb promoter in platelets of hemophilic (FVIIInull) mice to create 2bF8trans mice. The FVIII transgene product was stored in platelets and released at the site of platelet activation. In spite of the lack of FVIII in the plasma of 2bF8trans mice, the bleeding phenotype of FVIIInull mice was corrected. More importantly, the bleeding phenotype was corrected in the presence of high inhibitory antibody titers introduced into the mice by infusion or by spleen cell transfer from recombinant hBDDFVIII–immunized mice. Our results demonstrate that this approach to the targeted expression of FVIII in platelets has the potential to correct hemophilia A, even in the presence of inhibitory immune responses to infused FVIII.

Authors

Qizhen Shi, David A. Wilcox, Scot A. Fahs, Hartmut Weiler, Clive W. Wells, Brian C. Cooley, Drashti Desai, Patricia A. Morateck, Jack Gorski, Robert R. Montgomery

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Figure 1

Construct of the 2bF8 transgene as well as genetic and integration site analysis.

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Construct of the 2bF8 transgene as well as genetic and integration site ...
(A) Schematic diagram of transgene construct and insertion location. Construct of the 2bF8 cassette (from 5′ to 3′): the human GPIIb gene promoter (αIIbpr), chimeric intron, hBDDFVIII, SV40 poly A, and neomycin resistance. Insertion of 2bF8 transgene was in the B1 band of chromosome 18. (B) PCR analysis showed that 2bF8 transgene was detected in 2bF8trans and FVIIInull mice after receiving BMT from 2bF8trans mouse and 3 weeks’ reconstitution. Lane 1, DNA marker; lane 2, WT; lane 3, FVIIInull; lane 4, 2bF8trans; lane 5, FVIIInull following BMT (recipient); lane 6, H2O; lane 7, 2bF8 vector. DNA was purified from peripheral blood, and transgene was amplified with primers P1 and P2 (left panel; see Table 1). Mouse FVIII exon 4 (mFVIII), which is not disrupted in FVIIInull mice, was amplified as an internal control (right panel).