Abstract
Lentiviral vectors are attractive tools for liver-directed gene therapy because of their capacity for stable gene expression and the lack of preexisting immunity in most human subjects. However, the use of integrating vectors may raise some concerns about the potential risk of insertional mutagenesis. Here we investigated liver gene transfer by integrase-defective lentiviral vectors (IDLVs) containing an inactivating mutation in the integrase (D64V). Hepatocyte-targeted expression using IDLVs resulted in the sustained and robust induction of immune tolerance to both intracellular and secreted proteins, despite the reduced transgene expression levels in comparison with their integrase-competent vector counterparts. IDLV-mediated and hepatocyte-targeted coagulation factor IX (FIX) expression prevented the induction of neutralizing antibodies to FIX even after antigen rechallenge in hemophilia B mice and accounted for relatively prolonged therapeutic FIX expression levels. Upon the delivery of intracellular model antigens, hepatocyte-targeted IDLVs induced transgene-specific regulatory T cells that contributed to the observed immune tolerance. Deep sequencing of IDLV-transduced livers showed only rare genomic integrations that had no preference for gene coding regions and occurred mostly by a mechanism inconsistent with residual integrase activity. Conclusion: IDLVs provide an attractive platform for the tolerogenic expression of intracellular or secreted proteins in the liver with a substantially reduced risk of insertional mutagenesis. (hepatology 2011;)
Highlights
Lentiviral vectors are attractive tools for liver-directed gene therapy because of their capacity for stable gene expression and the lack of preexisting immunity in most human subjects
We show that IDLV-treated mice after the primary (IDLV) can be used to express transgenes for a window of time in the liver as long as the expression is stringently targeted to hepatocytes with transcriptional and microRNA 142 (miR-142)–mediated regulation
The IDLV expression efficiency is lower than that observed for integrase-competent lentiviral vector (ICLV), the expression levels are sufficient to induce immune tolerance and achieve prolonged therapeutic effects in a clinically relevant disease model
Summary
Lentiviral vectors are attractive tools for liver-directed gene therapy because of their capacity for stable gene expression and the lack of preexisting immunity in most human subjects. Thierry VandenDriessche was supported by PERSIST, the Bayer-Schering Hemophilia Special Project Award, the Fund for Scientific Research (FWO & FWO-Wetenschappelijke Onderzoeksgemeenschap), ‘‘Geconcentreerde Onderzoek Acties’’ GOA-EPIGEN (Free University of Brussels), European Hematology Association (EHA) and Association Francaise contre les Myopathies (AFM) and Stichting tegen Kanker (STK). We obtained long-term coagulation factor IX (FIX) expression in hemophilia B mice, which resulted in immune tolerance to FIX and correction of the disease phenotype.[8]
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