Human insulin as both antigen and protector in type 1 diabetes

Type 1 diabetes (T1D) is characterized by T-cell responses to islet antigens. Investigations in humans and the nonobese diabetic (NOD) mouse model of T1D have revealed that T-cell reactivity to insulin plays a central role in the autoimmune response. As there is no convenient NOD-based model to study human insulin (hIns) or its T-cell epitopes in the context of spontaneous T1D, we developed a NOD mouse strain transgenically expressing hIns in islets under the control of the human regulatory region. Female NOD.hIns mice developed T1D at approximately the same rate and overall incidence as NOD mice. Islet-infiltrating T cells from NOD.hIns mice recognized hIns peptides; both CD8 and CD4 T-cell epitopes were identified. We also demonstrate that islet-infiltrating T cells from HLA-transgenic NOD.hIns mice can be used to identify potentially patient-relevant hIns T-cell epitopes. Besides serving as an antigen, hIns was expressed in the thymus of NOD.hIns mice and could serve as a protector against T1D under certain circumstances, as previously suggested by genetic studies in humans. NOD.hIns mice and related strains facilitate human-relevant epitope discovery efforts and the investigation of fundamental questions that cannot be readily addressed in humans.

Nuclear factor kappa B-dependent persistence of Salmonella Typhi and Paratyphi in human macrophages

Salmonella serovars Typhi and Paratyphi cause a prolonged illness known as enteric fever, whereas other serovars cause acute gastroenteritis. Mechanisms responsible for the divergent clinical manifestations of nontyphoidal and enteric fever Salmonella infections have remained elusive. Here, we show that S. Typhi and S. Paratyphi A can persist within human macrophages, whereas S. Typhimurium rapidly induces apoptotic macrophage cell death that is dependent on Salmonella pathogenicity island 2 (SPI2). S. Typhi and S. Paratyphi A lack 12 specific SPI2 effectors with pro-apoptotic functions, including nine that target nuclear factor κB (NF-κB). Pharmacologic inhibition of NF-κB or heterologous expression of the SPI2 effectors GogA or GtgA restores apoptosis of S. Typhi-infected macrophages. In addition, the absence of the SPI2 effector SarA results in deficient signal transducer and activator of transcription 1 (STAT1) activation and interleukin 12 production, leading to impaired TH1 responses in macrophages and humanized mice. The absence of specific nontyphoidal SPI2 effectors may allow S. Typhi and S. Paratyphi A to cause chronic infections.

IMPORTANCE

Salmonella enterica is a common cause of gastrointestinal infections worldwide. The serovars Salmonella Typhi and Salmonella Paratyphi A cause a distinctive systemic illness called enteric fever, whose pathogenesis is incompletely understood. Here, we show that enteric fever Salmonella serovars lack 12 specific virulence factors possessed by nontyphoidal Salmonella serovars, which allow the enteric fever serovars to persist within human macrophages. We propose that this fundamental difference in the interaction of Salmonella with human macrophages is responsible for the chronicity of typhoid and paratyphoid fever, suggesting that targeting the nuclear factor κB (NF-κB) complex responsible for macrophage survival could facilitate the clearance of persistent bacterial infections.

Genetic risk converges on regulatory networks mediating early type 2 diabetes

Type 2 diabetes mellitus (T2D), a major cause of worldwide morbidity and mortality, is characterized by dysfunction of insulin-producing pancreatic islet β cells1,2. T2D genome-wide association studies (GWAS) have identified hundreds of signals in non-coding and β cell regulatory genomic regions, but deciphering their biological mechanisms remains challenging3-5. Here, to identify early disease-driving events, we performed traditional and multiplexed pancreatic tissue imaging, sorted-islet cell transcriptomics and islet functional analysis of early-stage T2D and control donors. By integrating diverse modalities, we show that early-stage T2D is characterized by β cell-intrinsic defects that can be proportioned into gene regulatory modules with enrichment in signals of genetic risk. After identifying the β cell hub gene and transcription factor RFX6 within one such module, we demonstrated multiple layers of genetic risk that converge on an RFX6-mediated network to reduce insulin secretion by β cells. RFX6 perturbation in primary human islet cells alters β cell chromatin architecture at regions enriched for T2D GWAS signals, and population-scale genetic analyses causally link genetically predicted reduced RFX6 expression with increased T2D risk. Understanding the molecular mechanisms of complex, systemic diseases necessitates integration of signals from multiple molecules, cells, organs and individuals, and thus we anticipate that this approach will be a useful template to identify and validate key regulatory networks and master hub genes for other diseases or traits using GWAS data.

Identification of a humanized mouse model for functional testing of immune-mediated biomaterial foreign body response

Biomedical devices comprise a major component of modern medicine, however immune-mediated fibrosis and rejection can limit their function over time. Here, we describe a humanized mouse model that recapitulates fibrosis following biomaterial implantation. Cellular and cytokine responses to multiple biomaterials were evaluated across different implant sites. Human innate immune macrophages were verified as essential to biomaterial rejection in this model and were capable of cross-talk with mouse fibroblasts for collagen matrix deposition. Cytokine and cytokine receptor array analysis confirmed core signaling in the fibrotic cascade. Foreign body giant cell formation, often unobserved in mice, was also prominent. Last, high-resolution microscopy coupled with multiplexed antibody capture digital profiling analysis supplied spatial resolution of rejection responses. This model enables the study of human immune cell-mediated fibrosis and interactions with implanted biomaterials and devices.

Simultaneous evaluation of treatment efficacy and toxicity for bispecific T-cell engager therapeutics in a humanized mouse model

Immuno-oncology (IO)-based therapies such as checkpoint inhibitors, bi-specific antibodies, and CAR-T-cell therapies have shown significant success in the treatment of several cancer indications. However, these therapies can result in the development of severe adverse events, including cytokine release syndrome (CRS). Currently, there is a paucity of in vivo models that can evaluate dose-response relationships for both tumor control and CRS-related safety issues. We tested an in vivo PBMC humanized mouse model to assess both treatment efficacy against specific tumors and the concurrent cytokine release profiles for individual human donors after treatment with a CD19xCD3 bispecific T-cell engager (BiTE). Using this model, we evaluated tumor burden, T-cell activation, and cytokine release in response to bispecific T-cell-engaging antibody in humanized mice generated with different PBMC donors. The results show that PBMC engrafted NOD-scid Il2rgnull mice lacking expression of mouse MHC class I and II (NSG-MHC-DKO mice) and implanted with a tumor xenograft predict both efficacy for tumor control by CD19xCD3 BiTE and stimulated cytokine release. Moreover, our findings indicate that this PBMC-engrafted model captures variability among donors for tumor control and cytokine release following treatment. Tumor control and cytokine release were reproducible for the same PBMC donor in separate experiments. The PBMC humanized mouse model described here is a sensitive and reproducible platform that identifies specific patient/cancer/therapy combinations for treatment efficacy and development of complications.

NOD-scid IL2rγnull mice lacking TLR4 support human immune system development and the study of human-specific innate immunity

Agents that induce inflammation have been used since the 18th century for the treatment of cancer. The inflammation induced by agents such as Toll-like receptor agonists is thought to stimulate tumor-specific immunity in patients and augment control of tumor burden. While NOD-scid IL2rγnull mice lack murine adaptive immunity (T cells and B cells), these mice maintain a residual murine innate immune system that responds to Toll-like receptor agonists. Here we describe a novel NOD-scid IL2rγnull mouse lacking murine TLR4 that fails to respond to lipopolysaccharide. NSG-Tlr4null mice support human immune system engraftment and enable the study of human-specific responses to TLR4 agonists in the absence of the confounding effects of a murine response. Our data demonstrate that specific stimulation of TLR4 activates human innate immune systems and delays the growth kinetics of a human patient-derived xenograft melanoma tumor.

I-Ag7 β56/57 polymorphisms regulate non-cognate negative selection to CD4+ T cell orchestrators of type 1 diabetes

Genetic susceptibility to type 1 diabetes is associated with homozygous expression of major histocompatibility complex class II alleles that carry specific beta chain polymorphisms. Why heterozygous expression of these major histocompatibility complex class II alleles does not confer a similar predisposition is unresolved. Using a nonobese diabetic mouse model, here we show that heterozygous expression of the type 1 diabetes-protective allele I-Ag7 β56P/57D induces negative selection to the I-Ag7-restricted T cell repertoire, including beta-islet-specific CD4+ T cells. Surprisingly, negative selection occurs despite I-Ag7 β56P/57D having a reduced ability to present beta-islet antigens to CD4+ T cells. Peripheral manifestations of non-cognate negative selection include a near complete loss of beta-islet-specific CXCR6+ CD4+ T cells, an inability to cross-prime islet-specific glucose-6-phosphatase catalytic subunit-related protein and insulin-specific CD8+ T cells and disease arrest at the insulitis stage. These data reveal that negative selection on non-cognate self-antigens in the thymus can promote T cell tolerance and protection from autoimmunity.

Humanized mouse models for immuno-oncology research

Immunotherapy has emerged as a promising treatment paradigm for many malignancies and is transforming the drug development landscape. Although immunotherapeutic agents have demonstrated clinical efficacy, they are associated with variable clinical responses, and substantial gaps remain in our understanding of their mechanisms of action and specific biomarkers of response. Currently, the number of preclinical models that faithfully recapitulate interactions between the human immune system and tumours and enable evaluation of human-specific immunotherapies in vivo is limited. Humanized mice, a term that refers to immunodeficient mice co-engrafted with human tumours and immune components, provide several advantages for immuno-oncology research. In this Review, we discuss the benefits and challenges of the currently available humanized mice, including specific interactions between engrafted human tumours and immune components, the development and survival of human innate immune populations in these mice, and approaches to study mice engrafted with matched patient tumours and immune cells. We highlight the latest advances in the generation of humanized mouse models, with the aim of providing a guide for their application to immuno-oncology studies with potential for clinical translation.

An Early Islet Transcriptional Signature Is Associated With Local Inflammation in Autoimmune Diabetes

Identifying the early islet cellular processes of autoimmune type 1 diabetes (T1D) in humans is challenging given the absence of symptoms during this period and the inaccessibility of the pancreas for sampling. In this article, we study temporal events in pancreatic islets in LEW.1WR1 rats, in which autoimmune diabetes can be induced with virus infection, by performing transcriptional analysis of islets harvested during the prediabetic period. Single-cell RNA-sequencing and differential expression analyses of islets from prediabetic rats reveal subsets of β- and α-cells under stress as evidenced by heightened expression, over time, of a transcriptional signature characterized by interferon-stimulated genes, chemokines including Cxcl10, major histocompatibility class I, and genes for the ubiquitin-proteasome system. Mononuclear phagocytes show increased expression of inflammatory markers. RNA-in situ hybridization of rat pancreatic tissue defines the spatial distribution of Cxcl10+ β- and α-cells and their association with CD8+ T cell infiltration, a hallmark of insulitis and islet destruction. Our studies define early islet transcriptional events during immune cell recruitment to islets and reveal spatial associations between stressed β- and α-cells and immune cells. Insights into such early processes can assist in the development of therapeutic and prevention strategies for T1D.

Clathrin light chain-conjugated drug delivery for cancer

Targeted drug delivery systems hold the remarkable potential to improve the therapeutic index of anticancer medications markedly. Here, we report a targeted delivery platform for cancer treatment using clathrin light chain (CLC)-conjugated drugs. We conjugated CLC to paclitaxel (PTX) through a glutaric anhydride at high efficiency. Labeled CLCs localized to 4T1 tumors implanted in mice, and conjugation of PTX to CLC enhanced its delivery to these tumors. Treatment of three different mouse models of cancer-melanoma, breast cancer, and lung cancer-with CLC-PTX resulted in significant growth inhibition of both the primary tumor and metastatic lesions, as compared to treatment with free PTX. CLC-PTX treatment caused a marked increase in apoptosis of tumor cells and reduction of tumor angiogenesis. Our data suggested HSP70 as a binding partner for CLC. Our study demonstrates that CLC-based drug-conjugates constitute a novel drug delivery platform that can augment the effects of chemotherapeutics in treating a variety of cancers. Moreover, conjugation of therapeutics with CLC may be used as means by which drugs are delivered specifically to primary tumors and metastatic lesions, thereby prolonging the survival of cancer patients.

Abstract 2049: A novel, rapid, sensitive, and reproducible in vivo platform to assess efficacy and toxicity of bispecific antibodies

A bispecific T-cell engager (BiTE) enhances the antitumor capabilities of T-cells by directing them to recognize a tumor-specific antigen. Several BiTEs are currently in clinical trials, and there is one FDA-approved BiTE for cancer therapy at the moment. However, one of the biggest challenges BiTE is currently facing is cytokine release syndrome (CRS). While most patients have mild flu-like symptoms, some patients experience a severe inflammatory syndrome, which could ultimately cause multi-system organ failure and death. Thus, the key is to accurately predict the risk-benefit ratio of each individual before starting the treatment. Unfortunately, there is no reliable in vitro or in vivo model to predict the toxicity and efficacy of BiTE at the moment. Additionally, one of the most challenging factors for pre-clinical evaluation of BiTEs for toxicity and efficacy is the inherent differences among patients’ immune systems. Here, we developed an in vivo PBMC-humanized mouse model that can evaluate both toxicity and efficacy of BiTE and other immune-oncology therapeutics in each individual mouse. The platform was validated using an anti-CD28 superagonist (TGN1412), which none of the pre-clinical in vitro assays and in vivo studies, including non-human primates, executed before clinical trials were able to predict the observed clinical toxicities. This model uses luciferase-tagged human B-cell lymphoma Raji tumor cells to allow the measurement of tumor burden and response to treatment, along with toxicity simultaneously. In addition, we showed that this platform can determine individual PBMC donor differences, and potential adverse drug combinations and drug dose-response with efficacy and safety on individual PBMC donors. The model we developed can potentially be used as a predictive and reproducible platform to identify patient, cancer, and therapy combinations at risk for developing CRS. This model will also help to optimize the therapeutic drug dose range to improve the safety profile of BiTE and other immune-oncology drugs. We believe this platform will greatly benefit not only the scientific community but potentially cancer patients as well.

Citation Format: Jiwon Yang, Jing Jiao, Kyle Draheim, Danying Cai, Michael A. Brehm, Leonard D. Shultz, Dale L. Greiner, Mingshan Cheng, James G. Keck. A novel, rapid, sensitive, and reproducible in vivo platform to assess efficacy and toxicity of bispecific antibodies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2049.

Abstract 2875: Development of a new tumor-bearing humanized mouse model to evaluate the efficacy and toxicity of bispecific T cell engagers

Background: T cell-based immunotherapies, especially the bispecific T cell engager (BiTE), which recruit T cells to tumor cells, have been developed rapidly for treatment of malignancies. However, the wide application of BiTE therapies is limited by accompanying severe adverse effects such as cytokine release syndrome (CRS). Since human cancer cells are not incorporated in the CRS evaluation, currently used in vivo animal models and in vitro human immune cell activation assays do not reliably evaluate the induction of CRS by immune drugs that is seen in BiTE treated cancer patients. In addition, the differences between human and mouse immune systems hamper the development of new immune-oncology therapeutic drugs. Thus, establishing a predictive in vivo animal model that can screen both efficacy of cancer therapy and risk of developing CRS is critical for improving the safety of immune drug development for treatment of cancer patients.

Method: Humanized mice were developed in NSG-MHC class I/II double knock out (DKO) mouse recipients following reconstitution with human peripheral blood mononuclear cells. The MDA-MB-231/Luciferase-2A-GFP stable breast cancer cell line (MDA), which expressed epidermal growth factor receptor (EGFR), were implanted in mice 5 days after PBMC engraftment. Following EGFRxCD3 BiTE treatment whole-body tumor burden was quantified by an in vivo imaging system. To evaluate the CRS levels in response to BiTE therapy, cytokine levels were analyzed by BD cytometric bead array. Clinical observations, CRS scores, body weight changes and human immune cell activation were also monitored for CRS assessment.

Results: PBMC humanized models were successfully established with breast cancer cell engraftment. After treatment with EGFRxCD3 BiTE, the mice exhibited elevated serum levels of human IFNgamma, TNF-a, IL-6, IL-10, IL-2 and IL-4 compared to a vehicle control group. This cytokine production was dose-dependent and was associated with an increase of toxic mouse clinical evaluation score. In contrast, there was no significant inflammatory cytokine production in PBMC humanized mice without MDA cell implantation, suggesting T cell activation by BiTE followed binding to the cancer cells. BiTE treatment for 2-4 days significantly suppressed tumor growth in lung as measured by luciferin imaging. With serial doses of BiTE treatment, we observed a dose-dependent inhibition of tumor growth.

Conclusion: We developed a novel in vivo PBMC humanized mouse model bearing human tumor cells that can be used to determine the optimal dose of BiTE for inhibition of tumor growth with low toxicity risk. This model provides a growth environment similar to that of patients and has important application values in simultaneously evaluating the efficacy and safety of any T cell-based immunotherapies including BiTE to define optimal approaches for clinical cancer treatment.

Citation Format: Guoxiang Yang, Li-Chin Yao, Michael A. Brehm, Dale L. Greiner, Leonard D. Shultz, Danying Cai, MIngshan Cheng, James G. Keck. Development of a new tumor-bearing humanized mouse model to evaluate the efficacy and toxicity of bispecific T cell engagers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2875.

Abstract 1640: Enhanced development of functional human innate immune cells in a novel FLT3nullNSG mouse strain expressing human FLT3L

Humanized mice are being applied widely to study human immune system homeostasis, function, and as a testing platform for cancer immunotherapies. A major limitation for many humanized mouse models is the lack of functional and mature human innate immune cells, which are critical for effective human immune system-tumor interactions. Previous studies have demonstrated that delivery of human FLT3L into immunodeficient mice that lack mouse FLT3, promotes the development of human innate immune cell subsets following engraftment with human hematopoietic stem cells (HSC). Here we describe a NOD-scid IL2rgnull (NSG) mouse that lacks the expression of mouse FLT3 and expresses human FLT3L transgenically (NSG-mFLT3nullTg (HuFLT3L) or NSG-FLT3L. In these studies, NSG-FLT3L and NSG mice were engrafted with human umbilical cord blood (UCB) CD34+ HSC and compared for human immune system development and function. HSC-engrafted NSG-FLT3L and NSG mice show similar levels of total human CD45+ cells in blood over the course of 18 weeks post-engraftment. However, HSC-engrafted NSG-FLT3L mice show significantly higher levels of human CD141+ and CD1c+ DC subsets, CD123+ pDC, CD14+ monocytes, CD56+ NK cells and CD3+ T cells in the blood as compared to NSG mice. CD34-FLT3L mice also show increased levels of human immune cell infiltration into the gut mucosa. CD56+ NK cells and CD3+ T cells from HSC-engrafted NSG-FLT3L mice express granzyme A and granzyme B, indicating cytotoxic activity. Following treatment of HSC-engrafted NSG-FLT3L mice with LPS, heightened levels of human cytokines were detected in serum samples, confirming innate immune system function. The growth kinetics of tumor cells from a triple negative breast cancer cell line MDA-MB-231 and a lung PDX model LG1306 in HSC-engrafted NSG-FLT3L mice are work in progress and will be compared with HSG-engrafted NSG mice. Overall these results demonstrate that the NSG-FLT3L model supports enhanced development of functional, human innate immune cells and is a novel tool to study human immuno-oncology.

Citation Format: Li-Chin Yao, Shantashri Vaidya, Pali Kaur, James G. Keck, Leonard D. Shultz, Dale L. Greiner, MIchael A. Brehm. Enhanced development of functional human innate immune cells in a novel FLT3nullNSG mouse strain expressing human FLT3L [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1640.

Modeling human T1D-associated autoimmune processes

BACKGROUND

Type 1 diabetes (T1D) is an autoimmune disease characterized by impaired immune tolerance to β-cell antigens and progressive destruction of insulin-producing β-cells. Animal models have provided valuable insights for understanding the etiology and pathogenesis of this disease, but they fall short of reflecting the extensive heterogeneity of the disease in humans, which is contributed by various combinations of risk gene alleles and unique environmental factors. Collectively, these factors have been used to define subgroups of patients, termed endotypes, with distinct predominating disease characteristics.

SCOPE OF REVIEW

Here, we review the gaps filled by these models in understanding the intricate involvement and regulation of the immune system in human T1D pathogenesis. We describe the various models developed so far and the scientific questions that have been addressed using them. Finally, we discuss the limitations of these models, primarily ascribed to hosting a human immune system (HIS) in a xenogeneic recipient, and what remains to be done to improve their physiological relevance.

MAJOR CONCLUSIONS

To understand the role of genetic and environmental factors or evaluate immune-modifying therapies in humans, it is critical to develop and apply models in which human cells can be manipulated and their functions studied under conditions that recapitulate as closely as possible the physiological conditions of the human body. While microphysiological systems and living tissue slices provide some of these conditions, HIS mice enable more extensive analyses using in vivo systems.

Analysis of Salmonella Typhi Pathogenesis in a Humanized Mouse Model

Efforts to understand molecular mechanisms of pathogenesis of the human-restricted pathogen Salmonella enterica serovar Typhi, the causative agent of typhoid fever, have been hampered by the lack of a tractable small animal model. This obstacle has been surmounted by a humanized mouse model in which genetically modified mice are engrafted with purified CD34+ stem cells from human umbilical cord blood, designated CD34+ Hu-NSG (formerly hu-SRC-SCID) mice. We have shown that these mice develop a lethal systemic infection with S. Typhi that is dependent on the presence of engrafted human hematopoietic cells. Immunological and pathological features of human typhoid are recapitulated in this model, which has been successfully employed for the identification of bacterial genetic determinants of S. Typhi virulence. Here we describe the methods used to infect CD34+ Hu-NSG mice with S. Typhi in humanized mice and to construct and analyze a transposon-directed insertion site sequencing S. Typhi library, and provide general considerations for the use of humanized mice for the study of a human-restricted pathogen.

Modeling Type 1 Diabetes In Vitro Using Human Pluripotent Stem Cells

Understanding the root causes of autoimmune diseases is hampered by the inability to access relevant human tissues and identify the time of disease onset. To examine the interaction of immune cells and their cellular targets in type 1 diabetes, we differentiated human induced pluripotent stem cells into pancreatic endocrine cells, including β cells. Here, we describe an in vitro platform that models features of human type 1 diabetes using stress-induced patient-derived endocrine cells and autologous immune cells. We demonstrate a cell-type-specific response by autologous immune cells against induced pluripotent stem cell-derived β cells, along with a reduced effect on α cells. This approach represents a path to developing disease models that use patient-derived cells to predict the outcome of an autoimmune response.

Prostaglandin E2 stimulates cAMP signaling and resensitizes human leukemia cells to glucocorticoid-induced cell death

Glucocorticoid (GC) resistance remains a clinical challenge in pediatric acute lymphoblastic leukemia where response to GC is a reliable prognostic indicator. To identify GC resistance pathways, we conducted a genome-wide, survival-based, short hairpin RNA screen in murine T-cell acute lymphoblastic leukemia (T-ALL) cells. Genes identified in the screen interfere with cyclic adenosine monophosphate (cAMP) signaling and are underexpressed in GC-resistant or relapsed ALL patients. Silencing of the cAMP-activating Gnas gene interfered with GC-induced gene expression, resulting in dexamethasone resistance in vitro and in vivo. We demonstrate that cAMP signaling synergizes with dexamethasone to enhance cell death in GC-resistant human T-ALL cells. We find the E prostanoid receptor 4 expressed in T-ALL samples and demonstrate that prostaglandin E2 (PGE2) increases intracellular cAMP, potentiates GC-induced gene expression, and sensitizes human T-ALL samples to dexamethasone in vitro and in vivo. These findings identify PGE2 as a target for GC resensitization in relapsed pediatric T-ALL.

Abstract 5632: PBMC-humanized mouse model for the assessment of cytokine release syndrome caused by checkpoint and bispecific immunotherapy

Immunotherapeutic antibodies and cell therapies have proven to be highly effective cancer therapy for solid tumors, leukemia and lymphomas. The immunotherapy acts in part by stimulating and redirecting the immune system to attack cancer cells, and cytokines can be released during the process. As a consequence cytokine release syndrome (CRS) is a common adverse effect caused by immunotherapy which could be very severe in patients.

The animal models and in vitro human PBMC assays presently in use unfortunately can't reliably predict the CRS in patients. To address the gap between pre-clinical testing and clinical trials we have developed a rapid, sensitive and reproducible humanized mouse model for quantitating CRS. Immunodeficient NSG™ mice were irradiated and injected with human PBMCs intravenously. In general PBMC-engrafted mice had 10-20% human immune cells (hCD45+) in blood with ~70% of the hCD45+ cells being CD3+ T cells and ~20% being CD56+ NK cells. PBMC-engrafted mice were used for treatment within 6 days. We demonstrated that a number of human cytokines including IFN-γ, IL-2, IL-4, IL-6, IL-10 and TNF-α were elevated in blood in the humanized mice treated with monoclonal antibodies and bispecifics including anti-CD3, anti-CD28, anti-PD-1 and BiTE molecules. The cytokine release was dependent on the dose and time of treatment, and PBMCs from every human donor tested were capable of responding to produce cytokines. Notably the amount of cytokines produced varied from donor to donor in >40 different PBMCs tested so far and cytokine levels of >10-fold difference were frequently observed, indicating that the animal model could reveal individual differences in human donors. As a result human donors could be divided into three types as high, medium or low responders. PBMC-engrafted mice implanted with tumors could also be used. Tumor-bearing PBMC-humanized model would be required to evaluate molecules such as BiTE since CRS activity was most evident when both targets for BiTE molecules were present during the assay.

PBMC-engrafted NSG™ mice were used for CRS assessment prior to the development of acute graft-vs-host disease (GVHD) in all of the experiments. We were able to reproduce the data using a NSG™ strain [NSG-(Kb Db)null (IAnull)] doubly deficient in murine MHC class I and II molecules, or double knockout (KO) mice. The double KO mice are known to engraft human PBMCs in a manner very similar to NSG™ and have a significantly delayed onset of GVHD [Brehm et al., FASEB J. 33, 3137 (2019)]. Results from the double KO mice further validated cytokine release was not GvHD related and the NSG™ mice is a robust model for CRS assessment of immunotherapy in vivo. We have described a PBMC-humanized model using NSG™ mice that offers rapid assessment of potential risks of therapeutic agents in causing CRS in vivo. The model could differentiate individual human differences based on the cytokine release.

Citation Format: Danying Cai, Jing Jiao, Chunting Ye, Hongyuan Yang, Mingshan Cheng, Michael A. Brehm, Dale L. Greiner, Leonard D. Shultz, James G. Keck. PBMC-humanized mouse model for the assessment of cytokine release syndrome caused by checkpoint and bispecific immunotherapy [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5632.

A rapid, sensitive, and reproducible in vivo PBMC humanized murine model for determining therapeutic-related cytokine release syndrome

Immunotherapy is a powerful treatment strategy being applied to cancer, autoimmune diseases, allergies, and transplantation. Although therapeutic monoclonal antibodies (mAbs) have demonstrated significant clinical efficacy, there is also the potential for severe adverse events, including cytokine release syndrome (CRS). CRS is characterized by the rapid production of inflammatory cytokines following delivery of therapy, with symptoms ranging from mild fever to life‐threating pathology and multi‐organ failure. Overall there is a paucity of models to reliably and accurately predict the induction of CRS by immune therapeutics. Here, we describe the development of a humanized mouse model based on the NOD‐scid IL2rg^null (NSG) mouse to study CRS in vivo. PBMC‐engrafted NSG, NSG‐MHC‐DKO, and NSG‐SGM3 mice were used to study cytokine release in response to treatment with mAb immunotherapies. Our data show that therapeutic‐stimulated cytokine release in these PBMC‐based NSG models captures the variation in cytokine release between individual donors, is drug dependent, occurs in the absence of acute xeno‐GVHD, highlighting the specificity of the assay, and shows a robust response following treatment with a TGN1412 analog, a CD28 superagonist. Overall our results demonstrate that PBMC‐engrafted NSG models are rapid, sensitive, and reproducible platforms to screen novel therapeutics for CRS.

Dapagliflozin Does Not Directly Affect Human α or β Cells

Selective inhibitors of sodium glucose cotransporter-2 (SGLT2) are widely used for the treatment of type 2 diabetes and act primarily to lower blood glucose by preventing glucose reabsorption in the kidney. However, it is controversial whether these agents also act on the pancreatic islet, specifically the α cell, to increase glucagon secretion. To determine the effects of SGLT2 on human islets, we analyzed SGLT2 expression and hormone secretion by human islets treated with the SGLT2 inhibitor dapagliflozin (DAPA) in vitro and in vivo. Compared to the human kidney, SLC5A2 transcript expression was 1600-fold lower in human islets and SGLT2 protein was not detected. In vitro, DAPA treatment had no effect on glucagon or insulin secretion by human islets at either high or low glucose concentrations. In mice bearing transplanted human islets, 1 and 4 weeks of DAPA treatment did not alter fasting blood glucose, human insulin, and total glucagon levels. Upon glucose stimulation, DAPA treatment led to lower blood glucose levels and proportionally lower human insulin levels, irrespective of treatment duration. In contrast, after glucose stimulation, total glucagon was increased after 1 week of DAPA treatment but normalized after 4 weeks of treatment. Furthermore, the human islet grafts showed no effects of DAPA treatment on hormone content, endocrine cell proliferation or apoptosis, or amyloid deposition. These data indicate that DAPA does not directly affect the human pancreatic islet, but rather suggest an indirect effect where lower blood glucose leads to reduced insulin secretion and a transient increase in glucagon secretion.

Characterization and use of human insulin transgenic mouse models for type 1 diabetes

Type 1 diabetes (T1D) is characterized by T cell-mediated islet-specific autoimmunity leading to β cell destruction and loss of insulin production. Insulin is the primary antigen produced by β cells and due to incomplete conservation between the mouse and human insulin genes, some of the important disease-relevant T cell epitopes can be missed in the widely studied non-obese diabetic (NOD) mouse model. Thus, considering the limitations of NOD mice, we generated a novel NOD mouse model transgenically expressing human insulin (NOD.hIns mice) under the control of the human promoter. Female NOD.hIns mice spontaneously developed autoimmune diabetes as early as 15 weeks (incidence 62% by 30 weeks of age, n=21) vs NOD mice (41%, n=24), accompanied by numerous hallmarks of human T1D (including thymic human insulin expression and variable degrees of pancreatic islet infiltration by immune cells). Next, we cultured islet-infiltrating CD8 T cells from NOD.hIns mice and tested them for recognition of peptides unique to human preproinsulin. These efforts uncovered at least three T cell epitopes, validating that human insulin is a target of the autoimmune response in NOD.hIns mice. This concept was confirmed using T cells derived from NOD.hIns mice deficient in both murine insulin genes (NOD.Ins1ko.Ins2ko.hIns mice). NOD.hIns mice expressing human class I MHC molecules associated with T1D (HLA-A*24:02 and B*39:06) are currently being studied. Such well-characterized, and highly human-relevant, T1D models can be used to develop robust immune monitoring tools and to test and refine antigen-specific therapeutic strategies for T1D.

Louis P, Burzenski L, Greiner DL, Brehm MA, Shultz LD. Enhanced development of functional human innate immune cells in a novel mouse FLT3null NSG mouse strain expressing human FLT3L

Humanized mice are being applied widely to study human immune system homeostasis, function, and as a testing platform for therapeutics. A significant limitation for many humanized mouse models is the lack of mature human innate immune cells with full functionality. Previous studies have demonstrated that delivery of human FLT3L into immunodeficient mice that lack mouse FLT3, promotes the development of human innate immune subsets following engraftment with human HSC. Here we describe a NOD-scid IL2rgnull (NSG) mouse that lacks the expression of mouse FLT3 and expresses human FLT3L transgenically (NSG-mFLT3null Tg(HuFLT3L) or NSG-FLT3L. In these studies, NSG-FLT3L and NSG mice were engrafted with human UCB CD34+ HSC and compared for human immune system development and function. HSC-engrafted NSG-FLT3L and NSG mice show similar levels of total human CD45+ cells in blood over the course of 18 weeks post-engraftment. However, HSC-engrafted NSG-FLT3L mice show significantly increased levels of human immune cells reconstituting the gut mucosa. HSC-engrafted NSG-FLT3L mice show significantly higher levels of human CD141+ and CD1c+ DC subsets, CD123+ pDC, CD14+ monocytes, CD56+ NK cells and CD3+ T cells in the blood as compared to NSG mice. CD56+ NK cells and CD3+ T cells from HSC-engrafted NSG-FLT3L mice express granzyme A and granzyme B, indicating cytotoxic activity. Following treatment of HSC-engrafted NSG-FLT3L mice with LPS, significant levels of human cytokines were detected in serum samples, confirming innate immune system function. Overall these results demonstrate that the NSG-FLT3L model supports enhanced development of functional, human innate immune cells and is a novel tool to study human immunobiology.

Abstract B72: Humanized NSG-Tg(Hu-IL15) mice support preclinical immune-oncology efficacy for testing of NK cell-based immunotherapy

The JAX® Onco-Hu® platform utilizes humanized mice engrafted with tumors to enable in vivo investigation of the interactions between the human immune system and human cancer. We have shown that humanized NOD-scid IL2Rγ null (NSG) mice bearing patient-derived xenografts (PDX) allow efficacy studies of checkpoint inhibitors. A major avenue of our investigation is to generate humanized mouse models containing a more complete human hematopoietic system and robust innate immune cell population. Nature killer (NK) cells are important players of innate defense against cancerous cells by a number of mechanisms, including antibody-dependent cell-mediated cytotoxicity (ADCC). To overcome limited NK cell development in humanized NSG mice, we have developed NSG-Tg(Hu-IL15) (JAX stock number 030890) mice constitutively expressing human IL15. Following HSC-engraftment of NSG-Tg(Hu-IL15) mice, significantly higher levels of human CD16+CD56+ NK cells are detectable as compared to NSG mice in peripheral blood during the whole course of the study (18 weeks). Levels of circulating human CD45+ cells, CD3+ T cells, CD19+ B cells, and CD33+ myeloid cells are similar between the HSC-engrafted NSG-Tg(Hu-IL15) and NSG mice. Previously we have described that the human NK cells developing in HSC-engrafted NSG-Tg(Hu-IL15) mice are functional and can lyse the NK-sensitive target cells K562 by in vitro cytotoxicity assay. We also showed that NK cells limit the growth of a PDX melanoma xenograft. Here we show that humanized NSG-Tg(Hu-IL15) mice mediate efficient ADCC against Daudi B lymphoma cells in vivo. Administration of anti-human CD20 antibody (rituximab) resulted in significant tumor growth inhibition, in both tumor volume and tumor weight. We observed consistent ADCC efficacy in humanized NSG-Tg (Hu-IL15) mice engrafted with three different HSC donors. Together these data demonstrate that HSC-engrafted NSG-Tg(Hu-IL15) mice support enhanced development of functional human NK cells and that this mouse model enables NK cell-targeted cancer immunotherapy for preclinical testing.

Citation Format: Li-Chin Yao, Mingshan Cheng, Leonard D. Shultz, Dale L. Greiner, Michael A. Brehm, James G. Keck. Humanized NSG-Tg(Hu-IL15) mice support preclinical immune-oncology efficacy for testing of NK cell-based immunotherapy [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr B72.

Proteomic and Transcriptional Profiles of Human Stem Cell-Derived β Cells Following Enteroviral Challenge

Enteroviral infections are implicated in islet autoimmunity and type 1 diabetes (T1D) pathogenesis. Significant β-cell stress and damage occur with viral infection, leading to cells that are dysfunctional and vulnerable to destruction. Human stem cell-derived β (SC-β) cells are insulin-producing cell clusters that closely resemble native β cells. To better understand the events precipitated by enteroviral infection of β cells, we investigated transcriptional and proteomic changes in SC-β cells challenged with coxsackie B virus (CVB). We confirmed infection by demonstrating that viral protein colocalized with insulin-positive SC-β cells by immunostaining. Transcriptome analysis showed a decrease in insulin gene expression following infection, and combined transcriptional and proteomic analysis revealed activation of innate immune pathways, including type I interferon (IFN), IFN-stimulated genes, nuclear factor-kappa B (NF-κB) and downstream inflammatory cytokines, and major histocompatibility complex (MHC) class I. Finally, insulin release by CVB4-infected SC-β cells was impaired. These transcriptional, proteomic, and functional findings are in agreement with responses in primary human islets infected with CVB ex vivo. Human SC-β cells may serve as a surrogate for primary human islets in virus-induced diabetes models. Because human SC-β cells are more genetically tractable and accessible than primary islets, they may provide a preferred platform for investigating T1D pathogenesis and developing new treatments.