Abstract 4561: Non-integrative lentiviral particles for immunotherapy: RNA delivery to drive tumoral antigen presentation in a safe and efficient way
Authors: Bouillé Pascale , Duthoit Christine , Martin Nicolas , Lamouroux Lucille , Pages Jean-Christophe 
Published: July 2017

Abstract
Safe and efficient cancer therapies using adoptive transfer of engineered cells are very promising but very challenging approaches. Opportunities to improve gene transfer into primary cells involve a better design of the vectors used. Such improvements must lead to an increase of the efficiency of gene expression, the cell phenotype preservation and the increase of the gene number delivered. The use of lentiviral vectors has largely increased in clinical protocols over the past few years but safety concerns have slowed down this progression. Actually, the permanent genetic modification remains a focus of significant regulatory oversight. On another side, mRNA delivery is a versatile, flexible, and safe mean for protein therapies, but existing techniques, such as chemical or electroporation-based transfection protocols, are known to induce cell toxicity and phenotype modifications of the target cells. Here, we present an innovative tool, named LentiFlash, allowing RNA delivery into target cells without any genomic scar. This tool combines RNA delivery, providing the best expression system to get efficient and transient expression, and lentiviral delivery which exhibits the best efficiency of entry into primary and stem cells. The RNA encapsidation is mediated via an RNA/protein interaction using properties of the MS2 bacteriophage. This new vector breaks with all existing systems. The resulting lentiviral particle is able to efficiently deliver non-viral coding or non-coding RNA into the cytoplasm of any cell type. These LentiFlash particles, are able to transduce delicate primary cells, such as dendritic cells, T cells and hematopoietic stem cells. They show an efficient, fast and transient expression of protein and RNA, such as antigenic peptides or genome editing tools, with no cell phenotype modification. Here we show a proof of concept on primary murine dendritic cells transduction with LentiFlash particles, successfully used to deliver several tumoral antigens. As a result, these dendritic cells are able to present the antigens to the immune system which in turn can efficiently fight a tumor development into wild type mice. This new delivery system gives the opportunity for multiple antigens co-expression to enhance immune responses, avoiding tumor relapse. Such multiple co-expressions into immune cells are expected to mimic the innate and adaptive immune responses. This transient RNA delivery mediated by LentiFlash is a powerful tool to induce an efficient gene delivery. The possibility to express multiple genes at once in the target cells is an attractive therapeutic perspective. The absence of any viral sequence avoids any integration event, an important safety consideration for human use. Finally, another advantage of the LentiFlash system is its ability to utilize lentiviral production platforms already validated in clinical settings.
Citation Format: Pascale Bouillé, Christine Duthoit, Nicolas Martin, Lucille Lamouroux, Jean-Christophe Pages. Non-integrative lentiviral particles for immunotherapy: RNA delivery to drive tumoral antigen presentation in a safe and efficient way [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 4561. doi:10.1158/1538-7445.AM2017-4561