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 Il2rg^null 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.

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.

Tacrolimus- and sirolimus-induced human β cell dysfunction is reversible and preventable

Posttransplantation diabetes mellitus (PTDM) is a common and significant complication related to immunosuppressive agents required to prevent organ or cell transplant rejection. To elucidate the effects of 2 commonly used agents, the calcineurin inhibitor tacrolimus (TAC) and the mTOR inhibitor sirolimus (SIR), on islet function and test whether these effects could be reversed or prevented, we investigated human islets transplanted into immunodeficient mice treated with TAC or SIR at clinically relevant levels. Both TAC and SIR impaired insulin secretion in fasted and/or stimulated conditions. Treatment with TAC or SIR increased amyloid deposition and islet macrophages, disrupted insulin granule formation, and induced broad transcriptional dysregulation related to peptide processing, ion/calcium flux, and the extracellular matrix; however, it did not affect regulation of β cell mass. Interestingly, these β cell abnormalities reversed after withdrawal of drug treatment. Furthermore, cotreatment with a GLP-1 receptor agonist completely prevented TAC-induced β cell dysfunction and partially prevented SIR-induced β cell dysfunction. These results highlight the importance of both calcineurin and mTOR signaling in normal human β cell function in vivo and suggest that modulation of these pathways may prevent or ameliorate PTDM.

Recovery of viable endocrine-specific cells and transcriptomes from human pancreatic islet-engrafted mice

Human pancreatic islets engrafted into immunodeficient mice serve as an important model for in vivo human diabetes studies. Following engraftment, islet function can be monitored in vivo by measuring circulating glucose and human insulin; however, it will be important to recover viable cells for more complex graft analyses. Moreover, RNA analyses of dissected grafts have not distinguished which hormone-specific cell types contribute to gene expression. We developed a method for recovering live cells suitable for fluorescence-activated cell sorting from human islets engrafted in mice. Although yields of recovered islet cells were relatively low, the ratios of bulk-sorted β, α, and δ cells and their respective hormone-specific RNA-Seq transcriptomes are comparable pretransplant and posttransplant, suggesting that the cellular characteristics of islet grafts posttransplant closely mirror the original donor islets. Single-cell RNA-Seq transcriptome analysis confirms the presence of appropriate β, α, and δ cell subsets. In addition, ex vivo perifusion of recovered human islet grafts demonstrated glucose-stimulated insulin secretion. Viable cells suitable for patch-clamp analysis were recovered from transplanted human embryonic stem cell-derived β cells. Together, our functional and hormone-specific transcriptome analyses document the broad applicability of this system for longitudinal examination of human islet cells undergoing developmental/metabolic/pharmacogenetic manipulation in vivo and may facilitate the discovery of treatments for diabetes.

Genome-wide Analysis of Salmonella enterica serovar Typhi in Humanized Mice Reveals Key Virulence Features

Salmonella enterica serovar Typhi causes typhoid fever only in humans. Murine infection with S. Typhimurium is used as a typhoid model, but its relevance to human typhoid is limited. Non-obese diabetic-scid IL2rγnull mice engrafted with human hematopoietic stem cells (hu-SRC-SCID) are susceptible to lethal S. Typhi infection. In this study, we use a high-density S. Typhi transposon library in hu-SRC-SCID mice to identify virulence loci using transposon-directed insertion site sequencing (TraDIS). Vi capsule, lipopolysaccharide (LPS), and aromatic amino acid biosynthesis were essential for virulence, along with the siderophore salmochelin. However, in contrast to the murine S. Typhimurium model, neither the PhoPQ two-component system nor the SPI-2 pathogenicity island was required for lethal S. Typhi infection, nor was the CdtB typhoid toxin. These observations highlight major differences in the pathogenesis of typhoid and non-typhoidal Salmonella infections and demonstrate the utility of humanized mice for understanding the pathogenesis of a human-specific pathogen.

AK002, a Humanized Sialic Acid-Binding Immunoglobulin-Like Lectin-8 Antibody that Induces Antibody-Dependent Cell-Mediated Cytotoxicity against Human Eosinophils and Inhibits Mast Cell-Mediated Anaphylaxis in Mice

INTRODUCTION

Pathologic accumulation and activation of mast cells and eosinophils are implicated in allergic and inflammatory diseases. Sialic acid-binding immunoglobulin-like lectin (Siglec)-8 is an inhibitory receptor selectively expressed on mast cells, eosinophils and, at a lower extent, basophils. When engaged with an antibody, Siglec-8 can induce apoptosis of activated eosinophils and inhibit mast cell activation. AK002 is a humanized, non-fucosylated IgG1 anti-Siglec-8 antibody undergoing clinical investigation for treatment of allergic, inflammatory, and proliferative diseases. Here we examine the human tissue selectivity of AK002 and evaluate the in vitro, ex vivo, and in vivo activity of AK002 on eosinophils and mast cells.

METHODS

The affinity of AK002 for Siglec-8 and CD16 was determined by biolayer interferometry. Ex vivo activity of AK002 on human eosinophils from blood and dissociated human tissue was tested in apoptosis and antibody-dependent cell-mediated cytotoxicity (ADCC) assays. The in vivo activity of a murine precursor of AK002 (mAK002) was tested in a passive systemic anaphylaxis (PSA) humanized mouse model.

RESULTS

AK002 bound selectively to mast cells, eosinophils and, at a lower level, to basophils in human blood and tissue and not to other cell types examined. AK002 induced apoptosis of interleukin-5-activated blood eosinophils and demonstrated potent ADCC activity against blood eosinophils in the presence of natural killer cells. AK002 also significantly reduced eosinophils in dissociated human lung tissue. Furthermore, mAK002 prevented PSA in humanized mice through mast cell inhibition.

CONCLUSION

AK002 selectively evokes potent apoptotic and ADCC activity against eosinophils and prevents systemic anaphylaxis through mast cell inhibition.

Long-term implant fibrosis prevention in rodents and non-human primates using crystallized drug formulations

Implantable medical devices have revolutionized modern medicine. However, immune-mediated foreign body response (FBR) to the materials of these devices can limit their function or even induce failure. Here we describe long-term controlled-release formulations for local anti-inflammatory release through the development of compact, solvent-free crystals. The compact lattice structure of these crystals allows for very slow, surface dissolution and high drug density. These formulations suppress FBR in both rodents and non-human primates for at least 1.3 years and 6 months, respectively. Formulations inhibited fibrosis across multiple implant sites-subcutaneous, intraperitoneal and intramuscular. In particular, incorporation of GW2580, a colony stimulating factor 1 receptor inhibitor, into a range of devices, including human islet microencapsulation systems, electrode-based continuous glucose-sensing monitors and muscle-stimulating devices, inhibits fibrosis, thereby allowing for extended function. We believe that local, long-term controlled release with the crystal formulations described here enhances and extends function in a range of medical devices and provides a generalized solution to the local immune response to implanted biomaterials.

Abstract 1070: Evaluation of human NK cell responses to PDX tumors in humanized NOD-scid IL2rg null (NSG) mice expressing human IL15

Human innate immunity plays a critical role in tumor surveillance and in immunoregulation within the tumor microenvironment. Natural killer (NK) cells are innate lymphoid cells that have opposing roles in the tumor microenvironment, including NK cell subsets that mediate tumor cell cytotoxicity and subsets with regulatory function that contribute to the tumor immune suppressive environment. The balance between effector and regulatory NK cell subsets has been studied extensively in murine models of cancer, but there is a paucity of models to study human NK cell function in tumorigenesis. Humanized mice are a powerful alternative to syngeneic mouse tumor models for the study of human immuno-oncology and have proven effective tools to test immunotherapies targeting T cells. However human NK cell development and survival in humanized mice are severely limited. To enhance NK cell development, we have developed NSG mice that constitutively expresses human IL15 using a BAC containing the human IL15 gene: NSG-Tg(Hu-IL15) (NOD.Cg-Prkdcscid Il2rgtm1Wjl Tg(IL15)1Sz/SzJ; JAX stock number 030890). NSG-Tg(Hu-IL15) mice express a physiological level of human IL15 (7.1 ± 0.3 pg/ml) and support engraftment of human CD34+ hematopoietic stem cells (HSC). Following HSC-engraftment of NSG-Tg(Hu-IL15) mice, significantly higher levels of human CD56+ NK cells are detectable as compared to NSG mice in peripheral blood and within the spleen and bone marrow. Levels of circulating human CD3+ T cells, CD20+ B cells and CD33+ myeloid cells are similar between the HSC-engrafted NSG-Tg(Hu-IL15) and NSG mice. We have described that the human NK cells developing in HSC-engrafted NSG-Tg(Hu-IL15) mice are functional, mediating direct cytotoxicity and ADCC. We have now extended these observation by evaluating the ability of human NK cells to control growth of a PDX melanoma in humanized NSG-Tg(Hu-IL15) mice. Our observations indicate that the growth kinetics of the PDX melanoma are significantly delayed in HSC-engrafted NSG-Tg(Hu-IL15) mice as compared to HSC-engrafted NSG mice. Importantly PDX melanoma growth is not significantly different in NSG-Tg(Hu-IL15) and NSG that are not engrafted with human immune systems. To determine the immune cell subsets contributing to the delayed PDX growth in HSC-engrafted NSG-Tg(Hu-IL15) mice we performed experiments where either human CD8 T cells or human NK cells were depleted. Depletion of human CD8 T cells did not alter the PDX growth kinetics in HSC-engrafted NSG-Tg(Hu-IL15). In contrast, NK cell depletion abrogated the delayed growth of the PDX melanoma, suggesting that human NK cells are directly suppressing tumor growth in HSC-engrafted NSG-Tg(Hu-IL15) mice. Together these data demonstrate that HSC-engrafted NSG-Tg(Hu-IL15) mice support enhanced development of functional human NK cells and that these NK cells limit the growth of PDX tumors.

Citation Format: Ken-Edwin Aryee, Lisa Burzenski, Dale L. Greiner, Giles F. Whalen, Li-Chin Yao, Leonard D. Shultz, James G. Keck, Michael A. Brehm. Evaluation of human NK cell responses to PDX tumors in humanized NOD-scid IL2rgnull (NSG) mice expressing human IL15 [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 1070.

α Cell Function and Gene Expression Are Compromised in Type 1 Diabetes

Many patients with type 1 diabetes (T1D) have residual β cells producing small amounts of C-peptide long after disease onset but develop an inadequate glucagon response to hypoglycemia following T1D diagnosis. The features of these residual β cells and α cells in the islet endocrine compartment are largely unknown, due to the difficulty of comprehensive investigation. By studying the T1D pancreas and isolated islets, we show that remnant β cells appeared to maintain several aspects of regulated insulin secretion. However, the function of T1D α cells was markedly reduced, and these cells had alterations in transcription factors constituting α and β cell identity. In the native pancreas and after placing the T1D islets into a non-autoimmune, normoglycemic in vivo environment, there was no evidence of α-to-β cell conversion. These results suggest an explanation for the disordered T1D counterregulatory glucagon response to hypoglycemia.

Humanized mouse models of immunological diseases and precision medicine

With the increase in knowledge resulting from the sequencing of the human genome, the genetic basis for the underlying differences in individuals, their diseases, and how they respond to therapies is starting to be understood. This has formed the foundation for the era of precision medicine in many human diseases that is beginning to be implemented in the clinic, particularly in cancer. However, preclinical testing of therapeutic approaches based on individual biology will need to be validated in animal models prior to translation into patients. Although animal models, particularly murine models, have provided significant information on the basic biology underlying immune responses in various diseases and the response to therapy, murine and human immune systems differ markedly. These fundamental differences may be the underlying reason why many of the positive therapeutic responses observed in mice have not translated directly into the clinic. There is a critical need for preclinical animal models in which human immune responses can be investigated. For this, many investigators are using humanized mice, i.e., immunodeficient mice engrafted with functional human cells, tissues, and immune systems. We will briefly review the history of humanized mice, the remaining limitations, approaches to overcome them and how humanized mouse models are being used as a preclinical bridge in precision medicine for evaluation of human therapies prior to their implementation in the clinic.

Development of a humanized mouse model for functional testing of biomaterial fibrosis

Implanted biomedical devices reside within tens of millions of patients in the United States alone, and are involved in millions of new surgeries every year. They comprise a major component of modern medicine and are essential for many clinical applications ranging from hip/knee replacement, tissue repair/reconstruction, controlled release, sensing, and cell transplantation. Limiting therapeutic performance and lifespan, immune-mediated foreign body rejection results in sequestration behind dense layers of fibrotic scar tissue. Deeper understanding of wildtype rodent and non-human primate foreign body responses was leveraged to generate a variant of humanized mice that is capable of recapitulating fibrosis following implantation. Cellular and cytokine responses were also determined with multiple biomaterials—hydrogel alginate and polymers polystyrene and polydimethylsiloxane (PDMS), as well as across multiple implant sites. Innate immune macrophages were verified as essential in the development of fibrosis in this model, and that they were capable of crosstalk with mouse fibroblasts for collagen matrix deposition. Cytokine and cytokine-receptor array analysis confirmed core signaling in the fibrotic cascade. Lastly, high-resolution microscopy coupled with multiplexed antibody-capture analyses revealed spatial resolution of rejection responses. This model allows us to investigate dynamic human immune cell interactions with implantables, and offers a surrogate pre-clinical diagnostic for screening biomaterial immunogenicity.

Ectonucleoside Triphosphate Diphosphohydrolase-3 Antibody Targets Adult Human Pancreatic β Cells for In Vitro and In Vivo Analysis

Identification of cell-surface markers specific to human pancreatic β cells would allow in vivo analysis and imaging. Here we introduce a biomarker, ectonucleoside triphosphate diphosphohydrolase-3 (NTPDase3), that is expressed on the cell surface of essentially all adult human β cells, including those from individuals with type 1 or type 2 diabetes. NTPDase3 is expressed dynamically during postnatal human pancreas development, appearing first in acinar cells at birth, but several months later its expression declines in acinar cells while concurrently emerging in islet β cells. Given its specificity and membrane localization, we utilized an NTPDase3 antibody for purification of live human β cells as confirmed by transcriptional profiling, and, in addition, for in vivo imaging of transplanted human β cells. Thus, NTPDase3 is a cell-surface biomarker of adult human β cells, and the antibody directed to this protein should be a useful new reagent for β cell sorting, in vivo imaging, and targeting.

Lack of acute xenogeneic graft- versus-host disease, but retention of T-cell function following engraftment of human peripheral blood mononuclear cells in NSG mice deficient in MHC class I and II expression

Immunodeficient mice engrafted with human peripheral blood mononuclear cells (PBMCs) support preclinical studies of human pathogens, allograft rejection, and human T-cell function. However, a major limitation of PBMC engraftment is development of acute xenogeneic graft- versus-host disease (GVHD) due to human T-cell recognition of murine major histocompatibility complex (MHC). To address this, we created 2 NOD- scid IL-2 receptor subunit γ ( IL2rg) null (NSG) strains that lack murine MHC class I and II [NSG-β-2-microglobulin ( B2M) null ( IA IE)null and NSG -( Kb Db) null ( IAnull)]. We observed rapid human IgG clearance in NSG- B2Mnull ( IA IE) null mice whereas clearance in NSG -( Kb Db) null ( IAnull) mice and NSG mice was comparable. Injection of human PBMCs into both strains enabled long-term engraftment of human CD4+ and CD8+ T cells without acute GVHD. Engrafted human T-cell function was documented by rejection of human islet allografts. Administration of human IL-2 to NSG -( Kb Db) null ( IAnull) mice via adeno-associated virus vector increased human CD45+ cell engraftment, including an increase in human regulatory T cells. However, high IL-2 levels also induced the development of GVHD. These data document that NSG mice deficient in murine MHC support studies of human immunity in the absence of acute GVHD and enable evaluation of human antibody therapeutics targeting human T cells.-Brehm, M. A., Kenney, L. L., Wiles, M. V., Low, B. E., Tisch, R. M., Burzenski, L., Mueller, C., Greiner, D. L., Shultz, L. D. Lack of acute xenogeneic graft- versus-host disease, but retention of T-cell function following engraftment of human peripheral blood mononuclear cells in NSG mice deficient in MHC class I and II expression.

Human Anti-HIV-1 gp120 Monoclonal Antibodies with Neutralizing Activity Cloned from Humanized Mice Infected with HIV-1

Broadly neutralizing, anti-HIV-1 gp120 mAbs have been isolated from infected individuals, and there is considerable interest in developing these reagents for Ab-based immunoprophylaxis and treatment. As a means to identify potentially new anti-HIV Abs, we exploited humanized NOD-scid IL2rγ^null mice systemically infected with HIV-1 to generate a wide variety of Ag-specific human mAbs. The Abs were encoded by a diverse range of variable gene families and Ig classes, including IgA, and several showed significant levels of somatic mutation. Moreover, the isolated Abs not only bound target Ags with similar affinity as broadly neutralizing Abs, they also demonstrated neutralizing ability against multiple HIV-1 clades. The use of humanized mice will allow us to use our knowledge of HIV-1 gp120 structure and function, and the immune response targeting this protein, to generate native human prophylactic Abs to reduce the infection and spread of HIV-1.

Ectopic high endothelial venules in pancreatic ductal adenocarcinoma: A unique site for targeted delivery

BACKGROUND

Nanomedicine offers an excellent opportunity to tackle treatment-refractory malignancies by enhancing the delivery of therapeutics to the tumor site. High endothelial venules (HEVs) are found primarily in lymph nodes or formed de novo in peripheral tissues during inflammatory responses. They express peripheral node addressin (PNAd), which is recognized by the monoclonal antibody MECA79.

METHODS

Here, we demonstrated that HEVs form de novo in human pancreatic ductal adenocarcinoma (PDAC). We engineered MECA79 coated nanoparticles (MECA79-NPs) that recognize these ectopic HEVs in PDAC.

FINDINGS

The trafficking of MECA79-NPs following intravenous delivery to human PDAC implanted in a humanized mouse model was more robust than non-conjugated NPs. Treatment with MECA79-Taxol-NPs augmented the delivery of Paclitaxel (Taxol) to the tumor site and significantly reduced the tumor size. This effect was associated with a higher apoptosis rate of PDAC cells and reduced vascularization within the tumor.

INTERPRETATION

Targeting the HEVs of PDAC using MECA79-NPs could lay the ground for the localized delivery of a wide variety of drugs including chemotherapeutic agents. FUND: National Institutes of Health (NIH) grants: T32-EB016652 (B·B.), NIH Cancer Core Grant CA034196 (L.D.S.), National Institute of Allergy and Infectious Diseases grants R01-AI126596 and R01-HL141815 (R.A.).

Alginate encapsulation as long-term immune protection of allogeneic pancreatic islet cells transplanted into the omental bursa of macaques

The transplantation of pancreatic islet cells could restore glycaemic control in patients with type-I diabetes. Microspheres for islet encapsulation have enabled long-term glycaemic control in diabetic rodent models; yet human patients transplanted with equivalent microsphere formulations have experienced only transient islet-graft function, owing to a vigorous foreign-body reaction (FBR), to pericapsular fibrotic overgrowth (PFO) and, in upright bipedal species, to the sedimentation of the microspheres within the peritoneal cavity. Here, we report the results of the testing, in non-human primate (NHP) models, of seven alginate formulations that were efficacious in rodents, including three that led to transient islet-graft function in clinical trials. Although one month post-implantation all formulations elicited significant FBR and PFO, three chemically modified, immune-modulating alginate formulations elicited reduced FBR. In conjunction with a minimally invasive transplantation technique into the bursa omentalis of NHPs, the most promising chemically modified alginate derivative (Z1-Y15) protected viable and glucose-responsive allogeneic islets for 4 months without the need for immunosuppression. Chemically modified alginate formulations may enable the long-term transplantation of islets for the correction of insulin deficiency.

Abstract 5674: Transgenic expression of human IL15 in NOD-scid IL2rg null (NSG) mice enhances the development and survival of functional human NK cells

The human innate immune system plays critical roles in tumor surveillance and in immunoregulation within the tumor microenvironment. Natural killer (NK) cells are innate lymphoid cells that mediate tumor cell killing by antibody-dependent cell mediated cytotoxicity (ADCC), through direct recognition, and by the expression of chimeric antigen receptors that directly target tumors. However, NK cell subsets with regulatory functionality also contribute to the tumor immune suppressive environment that enables tumor growth. The balance between effector and regulatory NK cell subsets has been studied extensively in murine models of cancer, but there is a paucity of models to study human NK cell function in tumorigenesis, which is restricted primarily to in vitro experiments. Humanized mice are a powerful alternative to syngeneic mouse tumor models for the study of human immuno-oncology and have proven effective tools to test immunotherapies targeting T cells. However human NK cell development and survival in humanized mice are severely limited. Previous studies have demonstrated that injection or transient expression of human IL15 enables efficient development of functional human NK cells within immunodeficient mice that were engrafted with CD34+ HSC. Based on these results we established NSG mice that constitutively expresses human IL15. The NSG-Tg(Hu-IL15) mice were generated using a BAC containing the human IL15 gene, and express a physiological level of human IL15 (7.1 ± 0.3 pg/ml). To evaluate human NK cell development, 8 to 12-week-old NSG and NSG-Tg(Hu-IL15) mice received 200 cGy irradiation and were then injected intravenously with 1x105 CD34+ HSC derived from umbilical cord blood. No difference in overall survival of HSC-engrafted NSG-Tg(Hu-IL15) mice compared to NSG mice were observed during the experiment, indicating that expression of IL15 did not increase mortality. Levels of circulating human CD45+ cells, T cells and B cells were similar between the HSC-engrafted NSG-Tg(Hu-IL15) and NSG mice. Significantly higher levels of human CD56+ NK cells were found in NSG-Tg(Hu-IL15) mice as compared to NSG mice at all time points tested in the peripheral blood and within the spleen and bone marrow. A higher proportion of human CD56+ NK cells recovered from the blood and spleen of NSG-Tg(Hu-IL15) mice expressed granzyme A, granzyme B and perforin as compared to NK cells from NSG mice, suggesting that the NK cells were functional. Moreover, human NK cells enriched from the NSG-Tg(Hu-IL15) mice lysed K562 cells in an in vitro cytotoxicity assay. These data demonstrate that HSC-engrafted NSG mice expressing human IL15 support enhanced development of functional human NK cells and suggest that HSC-engrafted NSG-Tg(Hu-IL15) mice are a powerful model to study the role of NK cells in tumor-immune system interactions and to test immunotherapies targeting NK cells.

Citation Format: Ken-Edwin Aryee, Lisa Burzenski, Dale L. Greiner, Raymond M. Welsh, Leonard D. Shultz, James G. Keck, Michael A. Brehm. Transgenic expression of human IL15 in NOD-scid IL2rgnull (NSG) mice enhances the development and survival of functional human NK cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5674.

Alloimmune Responses of Humanized Mice to Human Pluripotent Stem Cell Therapeutics

There is growing interest in using embryonic stem cell (ESC) and induced pluripotent stem cell (iPSC) derivatives for tissue regeneration. However, an increased understanding of human immune responses to stem cell-derived allografts is necessary for maintaining long-term graft persistence. To model this alloimmunity, humanized mice engrafted with human hematopoietic and immune cells could prove to be useful. In this study, an in-depth analysis of graft-infiltrating human lymphocytes and splenocytes revealed that humanized mice incompletely model human immune responses toward allogeneic stem cells and their derivatives. Furthermore, using an “allogenized” mouse model, we show the feasibility of reconstituting immunodeficient mice with a functional mouse immune system and describe a key role of innate immune cells in the rejection of mouse stem cell allografts.

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Innate immunity is crucial in rejection of minor HA mismatched grafts

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Stem cell alloimmune responses modeled with an “allogenized mouse”

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Humanized mice are unable to fully model immune responses to stem cell allografts

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Splenocytes and graft-infiltrating lymphocytes display an exhausted phenotype

Transgenic expression of human IL15 in NOD-scid IL2rg null (NSG) mice enhances the development and survival of functional human NK cells

Human NK cells have critical roles in tumor surveillance and in immunoregulation within the tumor microenvironment. The balance between effector and regulatory NK cell subsets has been studied extensively in murine models of cancer, but there is a paucity of models to study human NK cell function. Humanized mice are a powerful alternative to study of human immuno-oncology and have proven effective tools to test immunotherapies targeting T cells. However human NK cell development and survival in humanized mice are severely limited. Based on previous studies showing the importance of human IL15 for NK cell development, we established NSG mice that constitutively expresses human IL15 (7.1 ± 0.3 pg/ml). To evaluate human NK cell development, 8 to 12-week-old NSG and NSG-Tg(Hu-IL15) mice were irradiated and injected intravenously with CD34+ HSC derived from umbilical cord blood. Levels of circulating human CD45+ cells, T cells and B cells were similar between the HSC-engrafted NSG-Tg(Hu-IL15) and NSG mice. Significantly higher levels of human CD56+ NK cells were found in NSG-Tg(Hu-IL15) mice as compared to NSG mice at all time points and in all tissues tested. A higher proportion of human CD56+ NK cells recovered from the blood and spleen of NSG-Tg(Hu-IL15) mice expressed granzyme A, granzyme B and perforin as compared to NK cells from NSG mice, suggesting that the NK cells were functional. Moreover, human NK cells enriched from the NSG-Tg(Hu-IL15) mice lysed K562 cells in an in vitro cytotoxicity assay. These data demonstrate that HSC-engrafted NSG mice expressing human IL15 support enhanced development of functional human NK cells and suggest that HSC-engrafted NSG-Tg(Hu-IL15) mice are a powerful model to study human NK cells.

NOD-scid IL2rg null (NSG) mice deficient in murine MHC Class I and Class II expression support engraftment of functional human T cells in the absence of acute xenogeneic GVHD following injection of PBMC

Humanized mice are emerging as an exciting platform to study human immuno-oncology and provide preclinical tools to test cutting edge immunotherapies. An effective and simplistic approach to engraft immunodeficient mice with functional human T cells is the injection of human peripheral blood mononuclear cells (PBMC). This PBMC engraftment model (termed Hu-PBL-SCID) has supported studies of human immune system-tumor interactions following injection of human PBMC into immunodeficient mice implanted with patient-derived (PDX) tumors. However, a major limitation of this model is the development of acute xenogeneic GVHD due to human T cell recognition of murine MHC class I and class II. To address this limitation, we created two strains of NSG mice that lack murine MHC antigens, one by crossing NSG-B2Mnullwith NSG-(IA IEnull) mice, the second by knocking out the MHC class II IAb gene in NSG-(KbDb)null mice using TALEN technology. We observed that human IgG clearance was rapid in NSG-B2Mnull(IA IEnull) mice that lack functional FcRn activity whereas clearance in NSG-(KbDb)null(IAnull) mice was comparable to that observed in NSG mice. Injection of human PBMC into both strains led to long term engraftment of human T cells without development of acute GVHD. The engrafted human T cells were functional as documented by their ability to reject human islet allografts. Moreover, NSG-(KbDb)null(IAnull) mice injected with a PDX tumor and PBMC from an allogeneic donor supported significant tumor growth in the absence of acute GVHD. These data document that NSG mice deficient in murine MHC class I and class II support studies of human immune system-tumor interactions in the absence of acute GVHD and provide a model to evaluate human antibody therapeutics.

Humanized mice in studying efficacy and mechanisms of PD-1-targeted cancer immunotherapy

Establishment of an in vivo small animal model of human tumor and human immune system interaction would enable preclinical investigations into the mechanisms underlying cancer immunotherapy. To this end, nonobese diabetic (NOD).Cg-Prkdc^scidIL2rg^tm1Wjl/Sz (null; NSG) mice were transplanted with human (h)CD34⁺ hematopoietic progenitor and stem cells, which leads to the development of human hematopoietic and immune systems [humanized NSG (HuNSG)]. HuNSG mice received human leukocyte antigen partially matched tumor implants from patient-derived xenografts [PDX; non–small cell lung cancer (NSCLC), sarcoma, bladder cancer, and triple-negative breast cancer (TNBC)] or from a TNBC cell line-derived xenograft (CDX). Tumor growth curves were similar in HuNSG compared with nonhuman immune-engrafted NSG mice. Treatment with pembrolizumab, which targets programmed cell death protein 1, produced significant growth inhibition in both CDX and PDX tumors in HuNSG but not in NSG mice. Finally, inhibition of tumor growth was dependent on hCD8⁺ T cells, as demonstrated by antibody-mediated depletion. Thus, tumor-bearing HuNSG mice may represent an important, new model for preclinical immunotherapy research.—Wang, M., Yao, L.-C., Cheng, M., Cai, D., Martinek, J., Pan, C.-X., Shi, W., Ma, A.-H., De Vere White, R. W., Airhart, S., Liu, E. T., Banchereau, J., Brehm, M. A., Greiner, D. L., Shultz, L. D., Palucka, K., Keck, J. G. Humanized mice in studying efficacy and mechanisms of PD-1-targeted cancer immunotherapy.

Generation of Immunodeficient Mice Bearing Human Immune Systems by the Engraftment of Hematopoietic Stem Cells

Immunodeficient mice are being used as recipients of human hematopoietic stem cells (HSC) for in vivo analyses of human immune system development and function. The development of several stocks of immunodeficient Prkdc (scid) (scid), or recombination activating 1 or 2 gene (Rag1 or Rag2) knockout mice bearing a targeted mutation in the gene encoding the IL2 receptor gamma chain (IL2rγ), has greatly facilitated the engraftment of human HSC and enhanced the development of functional human immune systems. These "humanized" mice are being used to study human hematopoiesis, human-specific immune therapies, human-specific pathogens, and human immune system homeostasis and function. The establishment of these model systems is technically challenging, and levels of human immune system development reported in the literature are variable between laboratories. The use of standard protocols for optimal engraftment of HSC and for monitoring the development of the human immune systems would enable more direct comparisons between humanized mice generated in different laboratories. Here we describe a standard protocol for the engraftment of human HSC into 21-day-old NOD-scid IL2rγ (NSG) mice using an intravenous injection approach. The multiparameter flow cytometry used to monitor human immune system development and the kinetics of development are described.

Survival Advantage of Both Human Hepatocyte Xenografts and Genome-Edited Hepatocytes for Treatment of α-1 Antitrypsin Deficiency

Hepatocytes represent an important target for gene therapy and editing of single-gene disorders. In α-1 antitrypsin (AAT) deficiency, one missense mutation results in impaired secretion of AAT. In most patients, lung damage occurs due to a lack of AAT-mediated protection of lung elastin from neutrophil elastase. In some patients, accumulation of misfolded PiZ mutant AAT protein triggers hepatocyte injury, leading to inflammation and cirrhosis. We hypothesized that correcting the Z mutant defect in hepatocytes would confer a selective advantage for repopulation of hepatocytes within an intact liver. A human PiZ allele was crossed onto an immune-deficient (NSG) strain to create a recipient strain (NSG-PiZ) for human hepatocyte xenotransplantation. Results indicate that NSG-PiZ recipients support heightened engraftment of normal human primary hepatocytes as compared with NSG recipients. This model can therefore be used to test hepatocyte cell therapies for AATD, but more broadly it serves as a simple, highly reproducible liver xenograft model. Finally, a promoterless adeno-associated virus (AAV) vector, expressing a wild-type AAT and a synthetic miRNA to silence the endogenous allele, was integrated into the albumin locus. This gene-editing approach leads to a selective advantage of edited hepatocytes, by silencing the mutant protein and augmenting normal AAT production, and improvement of the liver pathology.

Age-dependent human β cell proliferation induced by glucagon-like peptide 1 and calcineurin signaling

Inadequate pancreatic β cell function underlies type 1 and type 2 diabetes mellitus. Strategies to expand functional cells have focused on discovering and controlling mechanisms that limit the proliferation of human β cells. Here, we developed an engraftment strategy to examine age-associated human islet cell replication competence and reveal mechanisms underlying age-dependent decline of β cell proliferation in human islets. We found that exendin-4 (Ex-4), an agonist of the glucagon-like peptide 1 receptor (GLP-1R), stimulates human β cell proliferation in juvenile but not adult islets. This age-dependent responsiveness does not reflect loss of GLP-1R signaling in adult islets, since Ex-4 treatment stimulated insulin secretion by both juvenile and adult human β cells. We show that the mitogenic effect of Ex-4 requires calcineurin/nuclear factor of activated T cells (NFAT) signaling. In juvenile islets, Ex-4 induced expression of calcineurin/NFAT signaling components as well as target genes for proliferation-promoting factors, including NFATC1, FOXM1, and CCNA1. By contrast, expression of these factors in adult islet β cells was not affected by Ex-4 exposure. These studies reveal age-dependent signaling mechanisms regulating human β cell proliferation, and identify elements that could be adapted for therapeutic expansion of human β cells.

Induction of Immunological Tolerance to Islet Allografts

T-cell dependent activation of resting B cells involves the interaction of gp39 on T cells with its receptor, CD40, on B cells. We administered either a combination of T-cell-depleted splenic lymphocytes and anti-gp39 monoclonal antibody or antibody alone to establish islet allografts in mice without continuous immunosuppression. Fully allogeneic H-2q FVB islets were permanently accepted by chemically diabetic H-2b C57BL/6 mice provided that the recipients were pretreated with both T-cell-depleted donor spleen cells and anti-gp39 antibody. Antibody alone was less effective in prolonging allograft survival, but we did observe that anti-gp39 mAb alone can exert an independent, primary effect on islet allograft survival that was dose dependent. Targeting gp39, in combination with lymphocyte transfusion, might prove suitable for tolerance induction and allotransplantation without immunosuppression.

Blockade of Cd40-Cd154 Interferes with Human T cell Engraftment in Scid Mice

Antibodies to the ligand for CD40 (CD154) have been shown to exert profound effects on the development of cell-mediated immune responses in mice. The present study shows that an antibody to human CD154 (hCD40L) inhibits in vivo Tetanus toxoid (TT) specific secondary antibody responses in hu-PBL-scid mice, as well as the expansion of xenoreactive human T cells in the scid mice. A possible cause for the reduced expansion of xenoreactive, human T cells, was the decreased expression of murine B7.1 and B7.2 caused by the administration of anti-hCD40L. Therefore, it may be that defective maturation of murine antigen-presenting cells impeded the priming and expansion of human xenoreactive T cells.

Possible type 1 diabetes risk prediction: Using ultrasound imaging to assess pancreas inflammation in the inducible autoimmune diabetes BBDR model

Background/Aims

Studies of human cadaveric pancreas specimens indicate that pancreas inflammation plays an important role in type 1 diabetes pathogenesis. Due to the inaccessibility of pancreas in living patients, imaging technology to visualize pancreas inflammation is much in need. In this study, we investigated the feasibility of utilizing ultrasound imaging to assess pancreas inflammation longitudinally in living rats during the progression leading to type 1 diabetes onset.

Methods

The virus-inducible BBDR type 1 diabetes rat model was used to systematically investigate pancreas changes that occur prior to and during development of autoimmunity. The nearly 100% diabetes incidence upon virus induction and the highly consistent time course of this rat model make longitudinal imaging examination possible. A combination of histology, immunoblotting, flow cytometry, and ultrasound imaging technology was used to identify stage-specific pancreas changes.

Results

Our histology data indicated that exocrine pancreas tissue of the diabetes-induced rats underwent dramatic changes, including blood vessel dilation and increased CD8+ cell infiltration, at a very early stage of disease initiation. Ultrasound imaging data revealed significant acute and persistent pancreas inflammation in the diabetes-induced rats. The pancreas micro-vasculature was significantly dilated one day after diabetes induction, and large blood vessel (superior mesenteric artery in this study) dilation and inflammation occurred several days later, but still prior to any observable autoimmune cell infiltration of the pancreatic islets.

Conclusions

Our data demonstrate that ultrasound imaging technology can detect pancreas inflammation in living rats during the development of type 1 diabetes. Due to ultrasound’s established use as a non-invasive diagnostic tool, it may prove useful in a clinical setting for type 1 diabetes risk prediction prior to autoimmunity and to assess the effectiveness of potential therapeutics.

Colony stimulating factor-1 receptor is a central component of the foreign body response to biomaterial implants in rodents and non-human primates

Host recognition and immune-mediated foreign body response to biomaterials can compromise the performance of implanted medical devices. To identify key cell and cytokine targets, here we perform in-depth systems analysis of innate and adaptive immune system responses to implanted biomaterials in rodents and non-human primates. While macrophages are indispensable to the fibrotic cascade, surprisingly neutrophils and complement are not. Macrophages, via CXCL13, lead to downstream B cell recruitment, which further potentiated fibrosis, as confirmed by B cell knockout and CXCL13 neutralization. Interestingly, colony stimulating factor-1 receptor (CSF1R) is significantly increased following implantation of multiple biomaterial classes: ceramic, polymer and hydrogel. Its inhibition, like macrophage depletion, leads to complete loss of fibrosis, but spares other macrophage functions such as wound healing, reactive oxygen species production and phagocytosis. Our results indicate that targeting CSF1R may allow for a more selective method of fibrosis inhibition, and improve biomaterial biocompatibility without the need for broad immunosuppression.