High-Expression Porcine FVIII Driven by Erythroid-Specific Promoters for Lentiviral Vector-Mediated Gene Therapy

• Published in: Blood 2008-11, Vol.112 (11), p.3544-3544
• Main Authors: Sutherland, Nadia, Dooriss, Kerry L, McCarty, David A, Doering, Christopher B, Spencer, H. Trent
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood.V112.11.3544.3544

Hemophilia A is an X-linked gene disorder that results in a deficiency of circulating coagulation factor VIII (fVIII) and may be ameliorated by only modest amounts of circulating protein, which makes it a logical candidate for gene therapy. Due to the potential risk of insertional mutagenesis from oncoretroviral-mediated gene therapy, cell-specific expression of transgenes using self-inactivating viral vectors may provide a safer gene therapy approach for use in humans. Therefore, we constructed simian immunodeficiency virus (SIV)-based lentiviral vectors containing a 5′ long-terminal repeat (LTR) and 3′ LTR with self-inactivating U3 deletion, the bovine growth hormone polyA signal, a packaging signal (ψ), and a single internal ankyrin-1 or β-globin promoter, designated SIV-Ank and SIV-Bg, respectively. The minimal 314-bp ankyrin-1 promoter and 180-bp β-globin promoter flanked upstream by enhancing sequences, HS2, HS3, and HS4 (Hanawa et al., Hum Gene Ther, 2002) from the locus control region were cloned into the SIV vector backbone upstream from either enhanced green fluorescent protein (eGFP) or B-domain deleted porcine factor VIII (BDDpfVIII). The erythroid-specificity of each promoter was evaluated in vitro by measurement of either eGFP or fVIII expression following transduction of SIV-Ank and SIV-Bg constructs into both K562 myelogenous leukemic cells and 293T human embryonic kidney cells. GFP expression, as measured by flow cytometry, in transduced cells revealed that the ankyrin-1 and β-globin promoters are more active in K562 cells as compared to 293T cells. The β-globin promoter yielded higher mean fluorescent intensity values for GFP compared to the ankyrin-1 promoter at similar MOIs in K562 cells, suggesting stronger β-globin promoter activity in these cells. Transduction of cells with the SIV vector encoding BDDpfVIII driven by the β-globin promoter resulted in a 14-fold higher number of transcripts per DNA copy number in K562 cells compared to 293T cells, while cells transduced with the ankyrin-l promoter had only a 1.4-fold greater number of transcripts per DNA copy number. In addition, SIV-Bg-fVIII-modified K562 cells produced a 5.2-fold greater number of transcripts per DNA copy number than SIV-Ank- fVIII-modified cells. To evaluate the usefulness of these vectors for in vivo expression of BDDpfVIII, hemophilia A mice (exon 16 knockout) were conditioned with 11 Gy total body irradiation and transplanted with gene-modified Sca-1+ cells trans