In vivo administration of lentiviral vectors triggers a type I interferon response that restricts hepatocyte gene transfer and promotes vector clearance

Abstract

Liver gene transfer is a highly sought goal for the treatment of inherited and infectious diseases. Lentiviral vectors (LVs) have many desirable properties for hepatocyte-directed gene delivery, including the ability to integrate into nondividing cells. Unfortunately, upon systemic administration, LV transduces hepatocytes relatively inefficiently compared with nonparenchymal cells, and the duration of transgene expression is often limited by immune responses. Here, we investigated the role of innate antiviral responses in these events. We show that administration of LVs to mice triggers a rapid and transient IFN␣␤ response. This effect was dependent on functional vector particles, and in vitro challenge of antigen-presenting cells suggested that plasmacytoid dendritic cells initiated the response. Remarkably, when LVs were administered to animals that lack the capacity to respond to IFN␣␤, there was a dramatic increase in hepatocyte transduction, and stable transgene expression was achieved. These findings indicate that, even in the setting of acute delivery of replication-defective vectors, IFNs effectively interfere with transduction in a celltype-specific manner. Moreover, because disabling a single component of the innate/immune network was sufficient to establish persistent xenoantigen expression, our results raise the hope that the immunologic barriers to gene therapy are less insurmountable than expected. IntroductionLentiviral vectors (LVs) are a promising candidate system for therapeutic gene transfer. Because of their capacity to transduce nondividing cells and stably integrate a gene expression cassette of relatively large size and complexity, LVs have significant potential for achieving long-term expression of a therapeutic molecule. Several groups, including our own, have carried out studies using LV for in vivo gene delivery in rodents. [1][2][3][4][5] Efficient gene transfer to the liver could be achieved; however, hepatocytes, which were the main target of the therapy, were transduced at a relatively low efficiency compared with nonparenchymal cells. At a low vector dose, this effect was particularly pronounced. While a high frequency of Kupffer cells (KCs) were found to be vector positive, only a small fraction of hepatocytes were transduced.Interestingly, by increasing the concentration of injected vector a threshold is reached in which hepatocyte transduction becomes dose responsive, and improved hepatocyte gene transfer is achieved. This may be due to the requirement for saturating the particleclearance systems of the sinusoid-lining cells in blood-filtering organs. 6 Nonetheless, a better understanding of the rate-limiting factors in transduction would help to improve both the dose-effect relationship and risk-benefit ratio of systemic LV administration.A high incidence of transgene-specific immunity has also been observed in studies using LVs for in vivo gene delivery. [1][2][3][4][5] This response resulted in elimination of transduced cells and/or neutralization of the transgene product,...

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