Abstract 5092: ZVex® lentiviral vector strongly activates pro-inflammatory, antigen processing, and anti-viral defense response pathways in monocyte-derived dendritic cells

Background: Dendritic cells (DCs) are professional antigen presenting cells that effectively bridge the innate and adaptive immune responses and require activation for successful priming of naive T-cells. We have developed ZVex, an integration deficient, hybrid lentiviral vector engineered to target DC-SIGN expressed on immature myeloid DCs for genetic immunization against tumor antigens. As lentiviruses normally don9t efficiently infect DCs, little is known about the functional effect of LV transduction of conventional DCs. Here, the effect of DC transduction with ZVex vectors was studied by gene expression profiling. Material and Methods: Human moDCs from multiple donors were prepared by 5-day stimulation with IL-4 and GM-CSF and transduced with ZVex-GFP or control vectors, such as a ZVex with nonfunctional reverse transcriptase (RT-dead), ZVex particles generated to contain no vector genome (empty ZVex), and a heat-inactivated ZVex preparation. Cellular RNA was isolated at different time points from transduced DC cultures and used for gene expression profiling with Nanostring’s human pan cancer immune panel (770 genes). Results: DCs transduced with ZVex vectors displayed statistically significant up-regulation of genes involved in pro-inflammatory, antigen processing, and anti-viral defense pathways. Noteworthy among the up-regulated genes were classical anti-viral response genes like OAS3, MX1, and interferon stimulated genes like ISG15 and ISG20. Incubation with the RT-dead mutant vector also led to up-regulation of these genes, albeit to a much lower extent, suggesting that LV-RNA itself can result in the activation of these pathways in DCs, though reverse transcription appears to further potentiate the response. Of note, cells transduced with empty ZVex, which consists of an intact virion particle but lacks encapsulated LV RNA, also mediated a low magnitude and breadth of DC transcriptional activation, possibly via signaling through DC-SIGN. Conclusions: ZVex incorporates several elements capable of inducing a potent innate immune activation in DCs. DCs are relatively insensitive to lentiviral infection, but the use of accessory proteins in ZVex makes DCs conducive to ZVex transduction and results in the induction of a Type-1 IFN response that seems to be largely dependent on reverse transcription. In addition, other engineered vector particle components such as non-reverse transcribed viral RNA, viral structural proteins, and/or engagement of the DC-SIGN receptor, also contribute to DC activation. Citation Format: Anshika Bajaj, Lisa Y. Ngo, Peter Berglund, Jan ter Meulen. ZVex® lentiviral vector strongly activates pro-inflammatory, antigen processing, and anti-viral defense response pathways in monocyte-derived dendritic cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5092. doi:10.1158/1538-7445.AM2017-5092