Propagating Humanized BLT Mice for the Study of Human Immunology and Immunotherapy

Humanized mouse models: A valuable platform for preclinical evaluation of human cancer

Animal models are routinely employed to assess the treatments for human cancer. However, due to significant differences in genetic backgrounds, traditional animal models are unable to meet bioresearch needs. To overcome this restriction, researchers have generated and optimized immunodeficient mice, and then engrafted human genes, cells, tissues, or organs in mice so that the responses in the model mice could provide a more reliable reference for treatments. As a bridge connecting clinical application and basic research, humanized mice are increasingly used in the preclinical evaluation of cancer treatments, particularly after gene interleukin 2 receptor gamma mutant mice were generated. Human cancer models established in humanized mice support exploration of the mechanism of cancer occurrence and provide an efficient platform for drug screening. However, it is undeniable that the further application of humanized mice still faces multiple challenges. This review summarizes the construction approaches for humanized mice and their existing limitations. We also report the latest applications of humanized mice in preclinical evaluation for the treatment of cancer and point out directions for future optimization of these models.

Humanized mouse model for vaccine evaluation: an overview

Animal models are essential in medical research for testing drugs and vaccines. These models differ from humans in various respects, so their results are not directly translatable in humans. To address this issue, humanized mice engrafted with functional human cells or tissue can be helpful. We propose using humanized mice that support the engraftment of human hematopoietic stem cells (HSCs) without irradiation to evaluate vaccines that influence patient immunity. For infectious diseases, several types of antigens and adjuvants have been developed and evaluated for vaccination. Peptide vaccines are generally used for their capability to fight cancer and infectious diseases. Evaluation of adjuvants is necessary as they induce inflammation, which is effective for an enhanced immune response but causes adverse effects in some individuals. A trial can be done on humanized mice to check the immunogenicity of a particular adjuvant and peptide combination. Messenger RNA has also emerged as a potential vaccine against viruses. These vaccines need to be tested with human immune cells because they work by producing a particular peptide of the pathogen. Humanized mice with human HSCs that can produce both myeloid and lymphoid cells show a similar immune response that these vaccines will produce in a patient.

Targeting the IL1β Pathway for Cancer Immunotherapy Remodels the Tumor Microenvironment and Enhances Antitumor Immune Responses

High levels of IL1β can result in chronic inflammation, which in turn can promote tumor growth and metastasis. Inhibition of IL1β could therefore be a promising therapeutic option in the treatment of cancer. Here, the effects of IL1β blockade induced by the mAbs canakinumab and gevokizumab were evaluated alone or in combination with docetaxel, anti-programmed cell death protein 1 (anti-PD-1), anti-VEGFα, and anti-TGFβ treatment in syngeneic and humanized mouse models of cancers of different origin. Canakinumab and gevokizumab did not show notable efficacy as single-agent therapies; however, IL1β blockade enhanced the effectiveness of docetaxel and anti-PD-1. Accompanying these effects, blockade of IL1β alone or in combination induced significant remodeling of the tumor microenvironment (TME), with decreased numbers of immune suppressive cells and increased tumor infiltration by dendritic cells (DC) and effector T cells. Further investigation revealed that cancer-associated fibroblasts (CAF) were the cell type most affected by treatment with canakinumab or gevokizumab in terms of change in gene expression. IL1β inhibition drove phenotypic changes in CAF populations, particularly those with the ability to influence immune cell recruitment. These results suggest that the observed remodeling of the TME following IL1β blockade may stem from changes in CAF populations. Overall, the results presented here support the potential use of IL1β inhibition in cancer treatment. Further exploration in ongoing clinical studies will help identify the best combination partners for different cancer types, cancer stages, and lines of treatment.

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.

Generation and Characterization of a Humanized Lung Xenograft Mouse Model for Studying Henipavirus Pathogenesis

The development of humanized mouse models has recently opened new avenues in the field of infectious diseases. These models allow research on many human viruses that were once difficult to study, because finding suitable animal models of infection can be challenging, cost prohibitive, and often do not entirely recapitulate all parameters of the disease. Here, we describe the procedure of human immune system reconstitution (humanization) of NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG) mice by the bone marrow, liver, and thymus (BLT) reconstitution method as well as the process of human lung engraftment. We then describe how to infect these human lung grafts with the paramyxovirus Nipah virus (NiV) that can cause lethal respiratory disease in humans, and for which there is only limited understanding of pathogenesis to acute lung injury.

The development and improvement of immunodeficient mice and humanized immune system mouse models

Animal models play an indispensable role in the study of human diseases. However, animal models of different diseases do not fully mimic the complex internal environment of humans. Immunodeficient mice are deficient in certain genes and do not express these or show reduced expression in some of their cells, facilitating the establishment of humanized mice and simulation of the human environment in vivo. Here, we summarize the developments in immunodeficient mice, from the initial nude mice lacking T lymphocytes to NOD/SCID rg^null mice lacking T, B, and NK cell populations. We describe existing humanized immune system mouse models based on immunodeficient mice in which human cells or tissues have been transplanted to establish a human immune system, including humanized-peripheral blood mononuclear cells (Hu-PBMCs), humanized hematopoietic stem cells (Hu-HSCs), and humanized bone marrow, liver, thymus (Hu-BLT) mouse models. The different methods for their development involve varying levels of complexity and humanization. Humanized mice are widely used in the study of various diseases to provide a transitional stage for clinical research. However, several challenges persist, including improving the efficiency of reconstructing the human B cell immune response, extending lifespan, improving the survival rate of mice to extend the observation period, and improving the development of standardized commercialized models and as well as their use. Overall, there are many opportunities and challenges in the development of humanized immune system mouse models which can provide novel strategies for understanding the mechanisms and treatments of human disease.

Going with the Flow: Modeling the Tumor Microenvironment Using Microfluidic Technology

Simple Summary

The clinical success of cancer immunotherapy targeting immune checkpoints (e.g., PD-1, CTLA-4) has ushered in a new era of cancer therapeutics aimed at promoting antitumor immunity in hopes of offering durable clinical responses for patients with advanced, metastatic cancer. This success has also reinvigorated interest in developing tumor model systems that recapitulate key features of antitumor immune responses to complement existing in vivo tumor models. Patient-derived tumor models have emerged in recent years to facilitate study of tumor–immune dynamics. Microfluidic technology has enabled development of microphysiologic systems (MPSs) for the evaluation of the tumor microenvironment, which have shown early promise in studying tumor–immune dynamics. Further development of microfluidic-based “tumor-on-a-chip” MPSs to study tumor–immune interactions may overcome several key challenges currently facing tumor immunology.

Abstract

Recent advances in cancer immunotherapy have led a paradigm shift in the treatment of multiple malignancies with renewed focus on the host immune system and tumor–immune dynamics. However, intrinsic and acquired resistance to immunotherapy limits patient benefits and wider application. Investigations into the mechanisms of response and resistance to immunotherapy have demonstrated key tumor-intrinsic and tumor-extrinsic factors. Studying complex interactions with multiple cell types is necessary to understand the mechanisms of response and resistance to cancer therapies. The lack of model systems that faithfully recapitulate key features of the tumor microenvironment (TME) remains a challenge for cancer researchers. Here, we review recent advances in TME models focusing on the use of microfluidic technology to study and model the TME, including the application of microfluidic technologies to study tumor–immune dynamics and response to cancer therapeutics. We also discuss the limitations of current systems and suggest future directions to utilize this technology to its highest potential.

Methods for Studying Mouse and Human Invariant Natural Killer T Cells

Invariant natural killer T (iNKT) cells are a unique subset of T lymphocytes that recognize lipid antigens presented by nonpolymorphic major histocompatibility complex (MHC) I-like molecule CD1d. iNKT cells play essential roles in regulating immune responses against cancer, viral infection, autoimmune disease, and allergy. However, the study and application of iNKT cells have been hampered by their very small numbers (0.01-1% in mouse and human blood). Here, we describe protocols to (1) generate mouse iNKT cells from mouse mononuclear cells or from mouse hematopoietic stem cells engineered with iNKT T cell receptor (TCR) gene (denoted as mMNC-iNKT cells or mHSC-iNKT cells, respectively), (2) generate human iNKT cells from human peripheral blood mononuclear cells or from human HSC cells engineered with iNKT TCR gene (denoted as hPBMC-iNKT cells or hHSC-iNKT cells, respectively), and (3) characterize mouse and human iNKT cells in vitro and in vivo.

Patient-Derived Xenograft Models in Cervical Cancer: A Systematic Review

BACKGROUND

Patient-derived xenograft (PDX) models have been a focus of attention because they closely resemble the tumor features of patients and retain the molecular and histological features of diseases. They are promising tools for translational research. In the current systematic review, we identify publications on PDX models of cervical cancer (CC-PDX) with descriptions of main methodological characteristics and outcomes to identify the most suitable method for CC-PDX.

METHODS

We searched on PubMed to identify articles reporting CC-PDX. Briefly, the main inclusion criterion for papers was description of PDX created with fragments obtained from human cervical cancer specimens, and the exclusion criterion was the creation of xenograft with established cell lines.

RESULTS

After the search process, 10 studies were found and included in the systematic review. Among 98 donor patients, 61 CC-PDX were established, and the overall success rate was 62.2%. The success rate in each article ranged from 0% to 75% and was higher when using severe immunodeficient mice such as severe combined immunodeficient (SCID), nonobese diabetic (NOD) SCID, and NOD SCID gamma (NSG) mice than nude mice. Subrenal capsule implantation led to a higher engraftment rate than orthotopic and subcutaneous implantation. Fragments with a size of 1-3 mm3 were suitable for CC-PDX. No relationship was found between the engraftment rate and characteristics of the tumor and donor patient, including histology, staging, and metastasis. The latency period varied from 10 days to 12 months. Most studies showed a strong similarity in pathological and immunohistochemical features between the original tumor and the PDX model.

CONCLUSION

Severe immunodeficient mice and subrenal capsule implantation led to a higher engraftment rate; however, orthotopic and subcutaneous implantation were alternatives. When using nude mice, subrenal implantation may be better. Fragments with a size of 1-3 mm3 were suitable for CC-PDX. Few reports have been published about CC-PDX; the results were not confirmed because of the small sample size.

Development of humanized mouse with patient-derived xenografts for cancer immunotherapy studies: A comprehensive review

Immunotherapy has revolutionized cancer treatment, however, not all tumor types and patients are completely responsive to this approach. Establishing predictive pre-clinical models would allow for more accurate and practical immunotherapeutic drug development. Mouse models are extensively used as in vivo system for biomedical research. However, due to the significant differences between rodents and human, it is impossible to translate most of the findings from mouse models to human. Pharmacological development and advancing personalized medicine using patient-derived xenografts relies on producing mouse models in which murine cells and genes are substituted with their human equivalent. Humanized mice (HM) provide a suitable platform to evaluate xenograft growth in the context of a human immune system. In this review, we discussed recent advances in the generation and application of HM models. We also reviewed new insights into the basic mechanisms, pre-clinical evaluation of onco-immunotherapies, current limitations in the application of these models as well as available improvement strategies. Finally, we pointed out some issues for future studies.

Targeting monoamine oxidase A for T cell-based cancer immunotherapy

Monoamine oxidase A (MAO-A) is an enzyme best known for its function in the brain, where it breaks down neurotransmitters and thereby influences mood and behavior. Small-molecule MAO inhibitors (MAOIs) have been developed and are clinically used for treating depression and other neurological disorders. However, the involvement of MAO-A in antitumor immunity has not been reported. Here, we observed induction of the Maoa gene in tumor-infiltrating immune cells. Maoa knockout mice exhibited enhanced antitumor T cell immunity and suppressed tumor growth. MAOI treatment significantly suppressed tumor growth in preclinical mouse syngeneic and human xenograft tumor models in a T cell-dependent manner. Combining MAOI and anti-PD-1 treatments generated synergistic tumor suppression effects. Clinical data correlation studies associated intratumoral MAOA expression with T cell dysfunction and decreased patient survival in a broad range of cancers. We further demonstrated that MAO-A restrains antitumor T cell immunity through controlling intratumoral T cell autocrine serotonin signaling. Together, these data identify MAO-A as an immune checkpoint and support repurposing MAOI antidepressants for cancer immunotherapy.

Genetic in vivo engineering of human T lymphocytes in mouse models

Receptor targeting of vector particles is a key technology to enable cell type-specific in vivo gene delivery. For example, T cells in humanized mouse models can be modified by lentiviral vectors (LVs) targeted to human T-cell markers to enable them to express chimeric antigen receptors (CARs). Here, we provide detailed protocols for the generation of CD4- and CD8-targeted LVs (which takes ~9 d in total). We also describe how to humanize immunodeficient mice with hematopoietic stem cells (which takes 12-16 weeks) and precondition (over 5 d) and administer the vector stocks. Conversion of the targeted cell type is monitored by PCR and flow cytometry of blood samples. A few weeks after administration, ~10% of the targeted T-cell subtype can be expected to have converted to CAR T cells. By closely following the protocol, sufficient vector stock for the genetic manipulation of 10-15 humanized mice is obtained. We also discuss how the protocol can be easily adapted to use LVs targeted to other types of receptors and/or for delivery of other genes of interest.

Humanized Mice for the Evaluation of Novel HIV-1 Therapies

With the discovery of antiretroviral therapy, HIV-1 infection has transitioned into a manageable but chronic illness, which requires lifelong treatment. Nevertheless, complete eradication of the virus has still eluded us. This is partly due to the virus’s ability to remain in a dormant state in tissue reservoirs, ‘hidden’ from the host’s immune system. Also, the high mutation rate of HIV-1 results in escape mutations in response to many therapeutics. Regardless, the development of novel cures for HIV-1 continues to move forward with a range of approaches from immunotherapy to gene editing. However, to evaluate in vivo pathogenesis and the efficacy and safety of therapeutic approaches, a suitable animal model is necessary. To this end, the humanized mouse was developed by McCune in 1988 and has continued to be improved on over the past 30 years. Here, we review the variety of humanized mouse models that have been utilized through the years and describe their specific contribution in translating HIV-1 cure strategies to the clinic.

Advances in Humanized Mouse Models to Improve Understanding of HIV-1 Pathogenesis and Immune Responses

Although antiretroviral therapy has transformed human immunodeficiency virus-type 1 (HIV-1) from a deadly infection into a chronic disease, it does not clear the viral reservoir, leaving HIV-1 as an uncurable infection. Currently, 1.2 million new HIV-1 infections occur globally each year, with little decrease over many years. Therefore, additional research is required to advance the current state of HIV management, find potential therapeutic strategies, and further understand the mechanisms of HIV pathogenesis and prevention strategies. Non-human primates (NHP) have been used extensively in HIV research and have provided critical advances within the field, but there are several issues that limit their use. Humanized mouse (Hu-mouse) models, or immunodeficient mice engrafted with human immune cells and/or tissues, provide a cost-effective and practical approach to create models for HIV research. Hu-mice closely parallel multiple aspects of human HIV infection and disease progression. Here, we highlight how innovations in Hu-mouse models have advanced HIV-1 research in the past decade. We discuss the effect of different background strains of mice, of modifications on the reconstitution of the immune cells, and the pros and cons of different human cells and/or tissue engraftment methods, on the ability to examine HIV-1 infection and immune response. Finally, we consider the newest advances in the Hu-mouse models and their potential to advance research in emerging areas of mucosal infections, understand the role of microbiota and the complex issues in HIV-TB co-infection. These innovations in Hu-mouse models hold the potential to significantly enhance mechanistic research to develop novel strategies for HIV prevention and therapeutics.

Building the Next Generation of Humanized Hemato-Lymphoid System Mice

Since the late 1980s, mice have been repopulated with human hematopoietic cells to study the fundamental biology of human hematopoiesis and immunity, as well as a broad range of human diseases in vivo. Multiple mouse recipient strains have been developed and protocols optimized to efficiently generate these “humanized” mice. Here, we review three guiding principles that have been applied to the development of the currently available models: (1) establishing tolerance of the mouse host for the human graft; (2) opening hematopoietic niches so that they can be occupied by human cells; and (3) providing necessary support for human hematopoiesis. We then discuss four remaining challenges: (1) human hematopoietic lineages that poorly develop in mice; (2) limited antigen-specific adaptive immunity; (3) absent tolerance of the human immune system for its mouse host; and (4) sub-functional interactions between human immune effectors and target mouse tissues. While major advances are still needed, the current models can already be used to answer specific, clinically-relevant questions and hopefully inform the development of new, life-saving therapies.

Advances in Human Immune System Mouse Models for Studying Human Hematopoiesis and Cancer Immunotherapy

Immunotherapy has established itself as a promising tool for cancer treatment. There are many challenges that remain including lack of targets and some patients across various cancers who have not shown robust clinical response. One of the major problems that have hindered the progress in the field is the dearth of appropriate mouse models that can reliably recapitulate the complexity of human immune-microenvironment as well as the malignancy itself. Immunodeficient mice reconstituted with human immune cells offer a unique opportunity to comprehensively evaluate immunotherapeutic strategies. These immunosuppressed and genetically modified mice, with some overexpressing human growth factors, have improved human hematopoietic engraftment as well as created more functional immune cell development in primary and secondary lymphoid tissues in these mice. In addition, several new approaches to modify or to add human niche elements to further humanize these immunodeficient mice have allowed a more precise characterization of human hematopoiesis. These important refinements have opened the possibility to evaluate not only human immune responses to different tumor cells but also to investigate how malignant cells interact with their niche and most importantly to test immunotherapies in a more preclinically relevant setting, which can ultimately lead to better success of these drugs in clinical trials.

Creation of BLT Humanized Mice for Sepsis Studies

Mice are a suitable animal model for sepsis studies because they recapitulate many aspects of the pathophysiology observed in septic human patients. It is ethically preferable to use mice for research over higher sentient species, when scientifically appropriate. Mice are also advantageous for research due to their small size, modest housing needs, the availability of genetically modified strains, and the broad range of reagents available for scientific assays on this species. Nevertheless, there are some intrinsic differences between mice and humans that should be recognized when considering the translational potential of sepsis therapies. It is often wise to complement traditional mouse studies with animal models that exhibit even greater similarity to humans, and in particular, models that better recapitulate the human immune response. Humanized mice are a promising tool to bridge this interspecies research gap. Herein, we provide a protocol to generate BLT humanized mice and describe their sepsis phenotype after cecal ligation and puncture (CLP).

Emergence of Nanotechnology to Fight HIV Sexual Transmission: The Trip of G2-S16 Polyanionic Carbosilane Dendrimer to Possible Pre-Clinical Trials

Development of new, safe, and effective microbicides to prevent human immunodeficiency virus HIV sexual transmission is needed. Unfortunately, most microbicides proved ineffective to prevent the risk of HIV-infection in clinical trials. We are working with G2-S16 polyanionic carbosilane dendrimer (PCD) as a new possible vaginal topical microbicide, based on its short reaction times, wide availability, high reproducibility, and quantitative yields of reaction. G2-S16 PCD exerts anti-HIV activity at an early stage of viral replication, by blocking gp120/CD4/CCR5 interaction, and providing a barrier against infection for long periods of time. G2-S16 PCD was stable at different pH values, as well as in the presence of seminal fluids. It maintained the anti-HIV activity against R5/X4 HIV over time, did not generate any type of drug resistance, and retained the anti-HIV effect when exposed to semen-enhanced viral infection. Importantly, G2-S16 PCD did not modify vaginal microbiota neither in vitro or in vivo. Histopathological examination did not show vaginal irritation, inflammation, lesions, or damage in the vaginal mucosa, after administration of G2-S16 PCD at different concentrations and times in female mice and rabbit animal models. Based on these promising data, G2-S16 PCD could become a good, safe, and readily available candidate to use as a topical vaginal microbicide against HIV.

Development and function of human dendritic cells in humanized mice models

Dendritic cells (DCs) are sentinel cells of the immune system arising from hematopoietic stem cells. DCs play a key role in the regulation of both adaptive and innate lymphocyte responses. As such, experimental models enabling a thorough analysis of human DCs development and function are needed. Humanized mice models (termed collectively as HIS mice, or human immune system mice models) provide unique opportunities to model human hematopoiesis and tackle the function of human immune cell types in vivo. Here, we review experimental approaches enabling to recapitulate the ontogeny of DC subsets in HIS mice and discuss studies addressing the biology of human DC subsets implementing HIS mice models.

The clonal repopulation of HSPC gene modified with anti-HIV-1 RNAi is not affected by preexisting HIV-1 infection

Despite advances in hematopoietic stem/progenitor cell (HSPC) transplant for HIV-1-infected patients, the impact of a preexisting HIV-1 infection on the engraftment and clonal repopulation of HSPCs remains poorly understood. We have developed a long terminal repeat indexing-mediated integration site sequencing (LTRi-Seq) method that provides a multiplexed clonal quantitation of both anti-HIV-1 RNAi (RNA interference) gene-modified and control vector-modified cell populations, together with HIV-1-infected cells-all within the same animal. In our HIV-1-preinfected humanized mice, both therapeutic and control HSPCs repopulated efficiently without abnormalities. Although the HIV-1-mediated selection of anti-HIV-1 RNAi-modified clones was evident in HIV-1-infected mice, the organ-to-organ and intra-organ clonal distributions in infected mice were indistinguishable from those in uninfected mice. HIV-1-infected cells showed clonal patterns distinct from those of HSPCs. Our data demonstrate that, despite the substantial impact of HIV-1 infection on CD4+ T cells, HSPC repopulation remains polyclonal, thus supporting the use of HSPC transplant for anti-HIV treatment.

Immunotherapies and Metastatic Cancers: Understanding Utility and Predictivity of Human Immune Cell Engrafted Mice in Preclinical Drug Development

Metastases cause high mortality in several cancers and immunotherapies are expected to be effective in the prevention and treatment of metastatic disease. However, only a minority of patients benefit from immunotherapies. This creates a need for novel therapies that are efficacious regardless of the cancer types and metastatic environments they are growing in. Preclinical immuno-oncology models for studying metastases have long been limited to syngeneic or carcinogenesis-inducible models that have murine cancer and immune cells. However, the translational power of these models has been questioned. Interactions between tumor and immune cells are often species-specific and regulated by different cytokines in mice and humans. For increased translational power, mice engrafted with functional parts of human immune system have been developed. These humanized mice are utilized to advance understanding the role of immune cells in the metastatic process, but increasingly also to study the efficacy and safety of novel immunotherapies. From these aspects, this review will discuss the role of immune cells in the metastatic process and the utility of humanized mouse models in immuno-oncology research for metastatic cancers, covering several models from the perspective of efficacy and safety of immunotherapies.

OX40L-JAG1-Induced Expansion of Lineage-Stable Regulatory T Cells Involves Noncanonical NF-κB Signaling

Foxp3⁺T regulatory cells (Tregs) control autoimmune response by suppressing proliferation and effector functions of self-reactive Foxp3^-CD4⁺/CD8⁺ T cells and thereby maintain the critical balance between self-tolerance and autoimmunity. Earlier, we had shown that OX40L-JAG1 cosignaling mediated through their cognate receptors OX40 and Notch3 preferentially expressed on murine Tregs can selectively induce their proliferation in the absence of TCR stimulation. However, the differential molecular mechanisms regulating TCR-independent versus TCR-dependent Treg proliferation and lineage stability of the expanded Tregs remained unknown. In this study, we show that OX40L-JAG1 treatment induced TCR-independent proliferation of Tregs in the thymus and periphery. The use of Src kinase inhibitor permitted us to demonstrate selective inhibition of TCR-dependent T cell proliferation with little to no effect on OX40L-JAG1-induced TCR-independent Treg expansion in vitro, which was critically dependent on noncanonical NF-κB signaling. OX40L-JAG1-expanded Tregs showed sustained lineage stability as indicated by stable demethylation marks in Treg signature genes such as Foxp3, Il2ra, Ctla4, Ikzf2, and Ikzf4. Furthermore, OX40L-JAG1 treatment significantly increased CTLA4⁺ and TIGIT⁺ Tregs and alleviated experimental autoimmune thyroiditis in mice. Relevance of our findings to humans became apparent when human OX40L and JAG1 induced TCR-independent selective expansion of human Tregs in thymocyte cultures and increased human Tregs in the liver tissue of humanized NSG mice. Our findings suggest that OX40L-JAG1-induced TCR-independent Treg proliferation is a conserved mechanism that can be used to expand lineage-stable Tregs to treat autoimmune diseases.

Mouse models in hematopoietic stem cell gene therapy and genome editing

Gene therapy has become an important treatment option for a variety of hematological diseases. The biggest advances have been made with CAR T cells and many of those studies are now FDA approved as a routine treatment for some hematologic malignancies. Hematopoietic stem cell (HSC) gene therapy is not far behind with treatment approvals granted for beta-hemoglobinopathies and adenosine deaminase severe combined immune deficiency (ADA-SCID), and additional approbations currently being sought. With the current pace of research, the significant investment of biotech companies, and the continuously growing toolbox of viral as well as non-viral gene delivery methods, the development of new ex vivo and in vivo gene therapy approaches is at an all-time high. Research in the field of gene therapy has been ongoing for more than 4 decades with big success stories as well as devastating drawbacks along the way. In particular, the damaging effect of uncontrolled viral vector integration observed in the initial gene therapy applications in the 90s led to a more comprehensive upfront safety assessment of treatment strategies. Since the late 90s, an important read-out to comprehensively assess the quality and safety of cell products has come forward with the mouse xenograft model. Here, we review the use of mouse models across the different stages of basic, pre-clinical and translational research towards the clinical application of HSC-mediated gene therapy and editing approaches.

Essential Role of Human T Cell Leukemia Virus Type 1 orf-I in Lethal Proliferation of CD4+ Cells in Humanized Mice

Human T cell leukemia virus type 1 (HTLV-1) is the ethological agent of adult T cell leukemia/lymphoma (ATLL) and a number of lymphocyte-mediated inflammatory conditions, including HTLV-1-associated myelopathy/tropical spastic paraparesis. HTLV-1 orf-I encodes two proteins, p8 and p12, whose functions in humans are to counteract innate and adaptive responses and to support viral transmission. However, the in vivo requirements for orf-I expression vary in different animal models. In macaques, the ablation of orf-I expression by mutation of its ATG initiation codon abolishes the infectivity of the molecular clone HTLV-1_p12KO In rabbits, HTLV-1_p12KO is infective and persists efficiently. We used humanized mouse models to assess the infectivity of both wild-type HTLV-1 (HTLV-1_WT) and HTLV-1_p12KO We found that NOD/SCID/γ_C ^-/- c-kit⁺ mice engrafted with human tissues 1 day after birth (designated NSG-1d mice) were highly susceptible to infection by HTLV-1_WT, with a syndrome characterized by the rapid polyclonal proliferation and infiltration of CD4⁺ CD25⁺ T cells into vital organs, weight loss, and death. HTLV-1 clonality studies revealed the presence of multiple clones of low abundance, confirming the polyclonal expansion of HTLV-1-infected cells in vivo HTLV-1_p12KO infection in a bone marrow-liver-thymus (BLT) mouse model prone to graft-versus-host disease occurred only following reversion of the orf-I initiation codon mutation within weeks after exposure and was associated with high levels of HTLV-1 DNA in blood and the expansion of CD4⁺ CD25⁺ T cells. Thus, the incomplete reconstitution of the human immune system in BLT mice may provide a window of opportunity for HTLV-1 replication and the selection of viral variants with greater fitness.IMPORTANCE Humanized mice constitute a useful model for studying the HTLV-1-associated polyclonal proliferation of CD4⁺ T cells and viral integration sites in the human genome. The rapid death of infected animals, however, appears to preclude the clonal selection typically observed in human ATLL, which normally develops in 2 to 5% of individuals infected with HTLV-1. Nevertheless, the expansion of multiple clones of low abundance in these humanized mice mirrors the early phase of HTLV-1 infection in humans, providing a useful model to investigate approaches to inhibit virus-induced CD4⁺ T cell proliferation.

Development of Hematopoietic Stem Cell-Engineered Invariant Natural Killer T Cell Therapy for Cancer

Invariant natural killer T (iNKT) cells are potent immune cells for targeting cancer; however, their clinical application has been hindered by their low numbers in cancer patients. Here, we developed a proof-of-concept for hematopoietic stem cell-engineered iNKT (HSC-iNKT) cell therapy with the potential to provide therapeutic levels of iNKT cells for a patient's lifetime. Using a human HSC engrafted mouse model and a human iNKT TCR gene engineering approach, we demonstrated the efficient and long-term generation of HSC-iNKT cells in vivo. These HSC-iNKT cells closely resembled endogenous human iNKT cells, could deploy multiple mechanisms to attack tumor cells, and effectively suppressed tumor growth in vivo in multiple human tumor xenograft mouse models. Preclinical safety studies showed no toxicity or tumorigenicity of the HSC-iNKT cell therapy. Collectively, these results demonstrated the feasibility, safety, and cancer therapy potential of the proposed HSC-iNKT cell therapy and laid a foundation for future clinical development.

T Lymphocyte Development and Activation in Humanized Mouse Model

Humanized mice, containing engrafted human cells and tissues, are emerging as an important in vivo platform for studying human diseases. Since the development of Nod scid gamma (NSG) mice bearing mutations in the IL-2 receptor gamma chain, many investigators have used NSG mice engrafted with human hematopoietic stem cells (HSCs) to generate functional human immune systems in vivo, results in high efficacy of human cell engraftment. The development of NSG mice has allowed significant advances to be made in studies on several human diseases, including cancer and graft-versus-host-disease (GVHD), and in regenerative medicine. Based on the human HSC transplantation, organ transplantation including thymus and liver in the renal capsule has been performed. Also, immune reconstruction of cells, of the lymphoid as well as myeloid lineages, has been partly accomplished. However, crosstalk between pluripotent stem cell derived therapeutic cells with human leukocyte antigen (HLA) mis/matched types and immune CD3 T cells have not been fully addressed. To overcome this hurdle, human major histocompatibility complex (MHC) molecules, not mouse MHC molecules, are required to generate functional T cells in a humanized mouse model. Here, we briefly summarize characteristics of the humanized mouse model, focusing on development of CD3 T cells with MHC molecules. We also highlight the necessity of the humanized mouse model for the treatment of various human diseases.

Development of Severe Combined Immunodeficient (SCID) Pig Models for Translational Cancer Modeling: Future Insights on How Humanized SCID Pigs Can Improve Preclinical Cancer Research

Within the last decade there have been several severe combined immunodeficient (SCID) pig models discovered or genetically engineered. The animals have mutations in ARTEMIS, IL2RG, or RAG1/2 genes, or combinations thereof, providing SCID pigs with NK cells, but deficient in T and B cells, or deficient in NK, T, and B cells for research studies. Biocontainment facilities and positive pressure isolators are developed to limit pathogen exposure and prolong the life of SCID pigs. Raising SCID pigs in such facilities allows for completion of long-term studies such as xenotransplantation of human cells. Ectopically injected human cancer cell lines develop into tumors in SCID pigs, thus providing a human-sized in vivo model for evaluating imaging methods to improve cancer detection and therapeutic research and development. Immunocompromised pigs have the potential to be immunologically humanized by xenotransplantation with human hematopoietic stem cells, peripheral blood leukocytes, or fetal tissue. These cells can be introduced through various routes including injection into fetal liver or the intraperitoneal (IP) space, or into piglets by intravenous, IP, and intraosseous administration. The development and maintenance of transplanted human immune cells would be initially (at least) dependent on immune signaling from swine cells. Compared to mice, swine share higher homology in immune related genes with humans. We hypothesize that the SCID pig may be able to support improved engraftment and differentiation of a wide range of human immune cells as compared to equivalent mouse models. Humanization of SCID pigs would thus provide a valuable model system for researchers to study interactions between human tumor and human immune cells. Additionally, as the SCID pig model is further developed, it may be possible to develop patient-derived xenograft models for individualized therapy and drug testing. We thus theorize that the individualized therapeutic approach would be significantly improved with a humanized SCID pig due to similarities in size, metabolism, and physiology. In all, porcine SCID models have significant potential as an excellent preclinical animal model for therapeutic testing.

Contribution of Human Lung Parenchyma and Leukocyte Influx to Oxidative Stress and Immune System-Mediated Pathology following Nipah Virus Infection

Nipah virus (NiV) is a zoonotic emerging paramyxovirus that can cause fatal respiratory illness or encephalitis in humans. Despite many efforts, the molecular mechanisms of NiV-induced acute lung injury (ALI) remain unclear. We previously showed that NiV replicates to high titers in human lung grafts in NOD-SCID/γ mice, resulting in a robust inflammatory response. Interestingly, these mice can undergo human immune system reconstitution by the bone marrow, liver, and thymus (BLT) reconstitution method, in addition to lung tissue engraftment, giving altogether a realistic model to study human respiratory viral infections. Here, we characterized NiV Bangladesh strain (NiV-B) infection of human lung grafts from human immune system-reconstituted mice in order to identify the overall effect of immune cells on NiV pathogenesis of the lung. We show that NiV-B replicated to high titers in human lung grafts and caused similar cytopathic effects irrespective of the presence of human leukocytes in mice. However, the human immune system interfered with virus spread across lung grafts, responded to infection by leukocyte migration to small airways and alveoli of the lung grafts, and accelerated oxidative stress in lung grafts. In addition, the presence of human leukocytes increased the expression of cytokines and chemokines that regulate inflammatory influx to sites of infection and tissue damage. These results advance our understanding of how the immune system limits NiV dissemination and contributes to ALI and inform efforts to identify therapeutic targets.IMPORTANCE Nipah virus (NiV) is an emerging paramyxovirus that can cause a lethal respiratory and neurological disease in humans. Only limited data are available on NiV pathogenesis in the human lung, and the relative contribution of the innate immune response and NiV to acute lung injury (ALI) is still unknown. Using human lung grafts in a human immune system-reconstituted mouse model, we showed that the NiV Bangladesh strain induced cytopathic lesions in lung grafts similar to those described in patients irrespective of the donor origin or the presence of leukocytes. However, the human immune system interfered with virus spread, responded to infection by leukocyte infiltration in the small airways and alveolar area, induced oxidative stress, and triggered the production of cytokines and chemokines that regulate inflammatory influx by leukocytes in response to infection. Understanding how leukocytes interact with NiV and cause ALI in human lung xenografts is crucial for identifying therapeutic targets.

Choosing wisely - Preclinical test models in the era of precision medicine

Through the introduction of a steadily growing variety of preclinical test models drug development and biomarker research has advanced. Next to classical used 2D cell line cultures, tissue-slice cultures, 3D organoid cell cultures, genetically engineered mouse models, cell line derived mouse models and patient derived xenografts may be selected for a specific question. All models harbor advantages and disadvantages. This review focuses on the available preclinical test models, novel developments such as humanized mice and discusses for which question a particular model should be employed.

Adjuvant effects of a sequence-engineered mRNA vaccine: translational profiling demonstrates similar human and murine innate response

Background

Prophylactic and therapeutic vaccines often depend upon a strong activation of the innate immune system to drive a potent adaptive immune response, often mediated by a strong adjuvant. For a number of adjuvants immunological readouts may not be consistent across species.

Methods

In this study, we evaluated the innate immunostimulatory potential of mRNA vaccines in both humans and mice, using a novel mRNA-based vaccine encoding influenza A hemagglutinin of the pandemic strain H1N1pdm09 as a model. This evaluation was performed using an in vitro model of human innate immunity and in vivo in mice after intradermal injection.

Results

Results suggest that immunostimulation from the mRNA vaccine in humans is similar to that in mice and acts through cellular RNA sensors, with genes for RLRs [ddx58 (RIG-1) and ifih1 (MDA-5)], TLRs (tlr3, tlr7, and tlr8-human only), and CLRs (clec4gp1, clec2d, cledl1) all significantly up-regulated by the mRNA vaccine. The up-regulation of TLR8 and TLR7 points to the involvement of both mDCs and pDCs in the response to the mRNA vaccine in humans. In both humans and mice activation of these pathways drove maturation and activation of immune cells as well as production of cytokines and chemokines known to attract and activate key players of the innate and adaptive immune system.

Conclusion

This translational approach not only allowed for identification of the basic mechanisms of self-adjuvantation from the mRNA vaccine but also for comparison of the response across species, a response that appears relatively conserved or at least convergent between the in vitro human and in vivo mouse models.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-1111-6) contains supplementary material, which is available to authorized users.