Abstract 3902: Increased sensitivity for detecting cytokine release syndrome with cancer immunotherapy using a PBMC humanized NSG-SGM3 mouse model
Authors: Ye Chunting , Brehm Michael , Cheng Mingshan , Shultz Leonard , Greiner Dale , Keck James 
Published: August 2019

Abstract
We have described a novel humanized NSG (NOD-scid IL2Rgammanull, NOD-scidIL2Rgnull; JAX stock number 005557) mouse model to measure cytokine release syndrome (CRS) after treatment with immunotherapeutic monoclonal antibodies (mAb). This humanized mouse model is based on PBMC engraftment of NSG mice and provides a rapid, robust and sensitive platform to assess CRS. Exposure of PBMC-engrafted NSG mice to mAb therapeutics was characterized by clinical readouts of cytokine production and decreases in body temperature. Moreover this model enabled the evaluation of differential responses between individual donors and allowed a more comprehensive evaluation of CRS than in vitro assays. However, human immune system engraftment in NSG mice injected with PBMC is dominated by human CD3+ T and NK cell in early time point. To expand the application of our model to additional human immune cell types, we explored the NSG-SGM3 (NOD-scid IL2Rgnull-3/GM/SF; JAX stock number 013062) strain as a model to assess CRS. The NSG-SGM3 mouse expresses human KITLG, CSF2 and IL-3 as transgenes and supports increased development of human myeloid and Treg populations following engraftment with umbilical cord CD34+ hematopoietic stem cells as compared to NSG mice. We hypothesized that PBMC-engraftment of NSG-SGM3 mice would augment human myeloid and T cell functionality in vivo. We compared NSG and NSG-SGM3 that were humanized with PBMC from identical donors and evaluated both the human immune cell engraftment profile by flow cytometry and CRS induction with single mAb agent and combination therapy. For PBMC engraftment, six weeks old female NSG and SGM3 mice were irradiated and then injected with human PBMC. Five days after PBMC injection, levels of total human cells (CD45+), and human immune cell subsets including CD3+ T cells, CD33+ myeloid cells, CD14+ monocytes, CD19+ B cells, and CD56+ NK cells, were measured by flow cytometry. Overall no significant differences were observed in the levels of human immune cells between PBMC-injected NSG and NSG-SGM3 mice. Six days after PBMC injection, mice were treated with mAb therapeutics including anti-CD28, pembrolizumab, Anti-thymocyte globulin and Lenalidomide as single agents or in combination. While rapid production of human cytokines (IFN-γ, IL-6, IL-10, IL-2, IL-4 and TNF) was detected in both PBMC-injected NSG and NSG-SGM3 mice, the overall cytokine levels were significantly higher in NSG-SGM3 mouse. Moreover, a lower PBMC concentration was compared in NSG and SGM3 mice for measuring CRS. Overall our results indicate that NSG-SGM3 mice humanized with PBMC are a precise and sensitive model to measure human CRS with cancer immune-therapies.
Citation Format: Chunting Ye, Michael Brehm, Mingshan Cheng, Leonard Shultz, Dale Greiner, James Keck. Increased sensitivity for detecting cytokine release syndrome with cancer immunotherapy using a PBMC humanized NSG-SGM3 mouse model [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 3902.