A TLR- and non-TLR-mediated innate response to lentiviruses restricts hepatocyte entry and can be ameliorated by pharmacological blockade

Lentiviral vector (LV)-mediated gene transfer is a promising method of gene therapy. We previously reported that systemic injection of LV triggers a transient inflammatory response. Here, we carried out studies to better characterize this response, and to develop a strategy to overcome the effects of interferon (IFN) on LV-mediated gene transfer. We profiled gene expression in the liver after LV administration using deep-sequencing, and identified several innate response pathways. We examined the response to LV in MyD88-TRIF knock-out mice, which are incapable of toll-like receptor (TLR) signaling. The IFN response to LV was not reduced in the liver, indicating that a non-TLR pathway can recognize LV in this tissue. Indeed, blocking reverse-transcription with AZT reduced the IFN response only in the liver, suggesting that proviral DNA can be a trigger. To block the inflammatory response, we pre-treated mice with a short-course of dexamethasone. At 4 hours post-treatment, all of the IFN-induced genes were normalized. By blocking the inflammatory response, hepatocyte transduction was dramatically increased, which doubled the level of human factor-IX produced by a hepatocyte-specific LV. Our studies uncover new insights into LV-induced immune responses in the liver, and provide a means to increase the safety and efficiency of LV-mediated gene transfer. mRNA profiles from livers of untreated and LV-treated mice were generated by deep-sequencing in Illumina HiSeq 2000.