Abstract 1478: Human transgenic IL-15 NOG mice reconstituted with human NK cells as a model for NK cell depletion
Authors: Bunin Anna , Rossi Ann Marie , Vidal Christian , Trihn David , Garcia Marco , Woska Joseph , Iben Lawrence , Rastelli Luca , Volden Paul , Alvarez Enrique 
Published: August 2019

Abstract
Natural killer cells (NK cells) are emerging as powerful mediators of anti-tumor effects in many cancer immunotherapy modalities.A multitude of these targeting strategies, however, cannot avoid cross-reactivity and potential NK cell depletion is a result of treatment. Furthermore, some therapies aim to directly engage surface receptors expressed by NK cells, including killer-cell immunoglobulin-like receptors (KIR) or NKG2D, as well as NKp30 and NKp46, to enhance their activity. Thus, NK cell activity modulation is an active area of immune-oncology drug development and there is a need for robust rodent models that can reliably evaluate human NK cell activity without the effort required in non-human primate (NHP) models. In addition, therapeutic intervention can have depletion of NK-like cells as its final goal as in NK- and NK/T lymphomas. To enable monitoring of NK cell response to treatment in vivo, we have established a humanized mouse model in which NK cell depletion can be followed in response to a wide variety of therapeutic interventions. To this end, human IL-15 NOG mice were preconditioned with busulfan, and reconstituted with human NK cells purified from a leukopheresis product. Our model allows for a long-term engraftment of human NK cells. We find that intraperitoneal administration of human NK cells is a route that yields long term robust engraftment of human NK cells in these mice. Peak engraftment of human NK cells in circulation of IL-15 NOG mice occurs at 3 weeks post-engraftment (hu CD45+ cells, 50%±10, SD, n=2). Human NK cells persist in the spleen and bone marrow compartment of IL-15 NOG mice for as long as 6 weeks post-engraftment (huCD45+cells: spleen 47%±3 SD n=3, blood 5%±0.4 SD n=3, bone marrow 0.3%±0.05, n=2). Furthermore, NK cells harvested ex-vivofrom IL-15 NOG mice can mediate a robust ADCC response against RAJI Burkitt’s lymphoma cells in the presence of Rituximab (32% cytotoxicity). These harvested cells also maintain their original expression of CD56+ 99.6%, CD16+ 71%, NKG2D+ 89.7%, NKp46+ 96%. To evaluate the in-vivoresponse of these engrafted human NK cells, we administered Daratumumab as a therapeutic agent to these mice. Daratumumab is an antibody against CD38, which is highly expressed by human NK cells. Our results demonstrate specific, complete depletion of NK cells in treated mice 41% ctrl vs 2.5% (Daratumumab) in the blood, and 24% (ctrl) vs 0% (Daratumumab) in the spleen. We therefore have established a humanized mouse system that can be used to monitor the ability of therapeutic agents to deplete NK cells both as a surrogate and as a direct readout of efficacy. This human NK cell fratricide mouse model can be used in a preclinical drug development setting that looks to augment our understanding of human NK cell depletion.
Citation Format: Anna Bunin, Ann Marie Rossi, Christian Vidal, David Trihn, Marco Garcia, Joseph Woska, Lawrence Iben, Luca Rastelli, Paul Volden, Enrique Alvarez. Human transgenic IL-15 NOG mice reconstituted with human NK cells as a model for NK cell depletion [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1478.