Ikumi Katano

Current advances in humanized mouse models

Humanized mouse models that have received human cells or tissue transplants are extremely useful in basic and applied human disease research. Highly immunodeficient mice, which do not reject xenografts and support cell and tissue differentiation and growth, are indispensable for generating additional appropriate models. Since the early 2000s, a series of immunodeficient mice appropriate for generating humanized mice has been successively developed by introducing the IL-2Rγnull gene (e.g., NOD/SCID/γcnull and Rag2nullγcnull mice). These strains show not only a high rate of human cell engraftment, but also generate well-differentiated multilineage human hematopoietic cells after human hematopoietic stem cell (HSC) transplantation. These humanized mice facilitate the analysis of human hematology and immunology in vivo. However, human hematopoietic cells developed from HSCs are not always phenotypically and functionally identical to those in humans. More recently, a new series of immunodeficient mice compensates for these disadvantages. These mice were generated by genetically introducing human cytokine genes into NOD/SCID/γcnull and Rag2nullγcnull mice. In this review, we describe the current knowledge of human hematopoietic cells developed in these mice. Various human disease mouse models using these humanized mice are summarized.

Functional CD5+ B cells develop predominantly in the spleen of NOD/SCID/γcnull (NOG) mice transplanted either with human umbilical cord blood, bone marrow, or mobilized peripheral blood CD34+ cells

OBJECTIVE Human CD5+ B cells are the major B cell subset in fetal spleen and umbilical cord blood (CB), and their number gradually diminishes in both spleen and peripheral blood from infancy through childhood while conventional B cells increase. In this study, we investigated whether CD5+ cells differentiate from adult hematopoietic stem cells (HSCs) as well as fetal ones in immunodeficient mice. METHODS In our system, NOD/SCID/gammac(null) (NOG) mice were transplanted with CD34+ cells from CB (hCB model), adult bone marrow (hBM model), and mobilized peripheral blood (hMPB model). RESULTS In these model mice, a high proportion of CD19+IgM+CD5+ mature B cells appeared in the spleen, regardless of the CD34+ cell origin, 4 to 8 weeks after transplantation, while the majority were CD19+IgM-CD5- immature B cells in BM. The CD19+CD5- BM cells showed to express CD5 after the coculture with NOG spleen cells. In the sera of immunized hCB model mice with DNP-KLH, antigen-specific IgM but not IgG was enhanced. CONCLUSION Our results show that adult CD34+ cells develop into functional CD5+ B cells in NOG spleen as much as fetal CD34+ cells do.

Highly Sensitive Model for Xenogenic GVHD Using Severe Immunodeficient NOG Mice

Background. Several animal models for xenogenic (xeno) graft versus host disease (GVHD) have been developed in immunodeficient mice, such as C.B-17-scid and nonobese diabetes (NOD)/severe combined immunodeficiency (SCID), by human peripheral blood mononuclear cell (hPBMC) transplantation. However, these models pose problems because they require sublethal total body irradiation of the mice and a large number of hPBMCs to induce GVHD, and the timing of onset of GVHD is also unstable. The aim of this study is to establish improved murine models of xeno-GVHD using novel immunodeficient NOD/Shi-scid IL2rγnull (NOG) mice. Methods. In three strains of immunodeficient mice, NOG, BALB/cA-RAG2null IL2rγnull, and NOD/SCID mice, GVHD was induced by transplantation of hPBMCs with or without total body irradiation, and the GVHD symptoms in these strains were compared. Results. After intravenous transplantation of hPBMCs, NOG mice showed early onset of GVHD symptoms and a small number of hPBMCs (2.5×106) was sufficient to induce GVHD when compared with BALB/cA-RAG2null IL2rγnull and NOD/SCID mice. In addition, total body irradiation was not always necessary in the present model. Conclusions. These results indicate that our model using the NOG mouse is a useful tool to investigate GVHD and to develop effective drugs for GVHD.

Induction of human humoral immune responses in a novel HLA-DR-expressing transgenic NOD/Shi-scid/γcnull mouse

Mounting evidence has demonstrated that NOD-Shi/scid/γc(null) (NOG) mice are one of the most suitable mouse strains for humanized mouse technologies, in which various human cells or tissues can be engrafted without rejection and autonomously maintained. We have characterized and analyzed various features of the human immune system reconstituted in NOG mice by transplanting human hematopoietic stem cells (hu-HSC). One of the problems of the quasi-immune system in these hu-HSC NOG mice is that the quality of immune responses is not always sufficient, as demonstrated by the lack of IgG production in response to antigen challenge. In this study, we established a novel transgenic NOG sub-strain of mice bearing the HLA-DRA and HLA-DRB1:0405 genes, which specifically expresses HLA-DR4 molecules in MHC II-positive cells. This mouse strain enabled us to match the haplotype of HLA-DR between the recipient mice and human donor HSC. We demonstrated that T-cell homeostasis was differentially regulated in HLA-matched hu-HSC NOG mice compared with HLA-mismatched control mice, and antibody class switching was induced after immunization with exogenous antigens in HLA-matched mice. This novel mouse strain improves the reconstituted human immune systems that develop in humanized mice and will contribute to future studies of human humoral immune responses.

Establishment of a Human Allergy Model Using Human IL-3/GM-CSF–Transgenic NOG Mice

The development of animal models that mimic human allergic responses is crucial to study the pathophysiology of disease and to generate new therapeutic methodologies. Humanized mice reconstituted with human immune systems are essential to study human immune reactions in vivo and are expected to be useful for studying human allergies. However, application of this technology to the study of human allergies has been limited, largely because of the poor development of human myeloid cells, especially granulocytes and mast cells, which are responsible for mediating allergic diseases, in conventional humanized mice. In this study, we developed a novel transgenic (Tg) strain, NOD/Shi-scid-IL2rγnull (NOG), bearing human IL-3 and GM-CSF genes (NOG IL-3/GM–Tg). In this strain, a large number of human myeloid cells of various lineages developed after transplantation of human CD34+ hematopoietic stem cells. Notably, mature basophils and mast cells expressing FcεRI were markedly increased. These humanized NOG IL-3/GM–Tg mice developed passive cutaneous anaphylaxis reactions when administered anti–4-hydroxy-3-nitrophenylacetyl IgE Abs and 4-hydroxy-3-nitrophenylacetyl. More importantly, a combination of serum from Japanese cedar pollinosis patients and cedar pollen extract also elicited strong passive cutaneous anaphylaxis responses in mice. Thus, to our knowledge, our NOG IL-3/GM–Tg mice are the first humanized mouse model to enable the study of human allergic responses in vivo and are excellent tools for preclinical studies of allergic diseases.

Predominant development of mature and functional human NK cells in a novel human IL-2-producing transgenic NOG mouse.

We generated a severe immunodeficient NOD/Shi-scid-IL-2Rγnull (NOG) mouse substrain expressing the transgenic human IL-2 gene (NOG–IL-2 Tg). Upon transfer of human cord blood–derived hematopoietic stem cells (HSCs), CD3−CD56highCD16+/− cells developed unexpectedly, predominantly in the NOG–IL-2 Tg (hu-HSC NOG–IL-2 Tg). These cells expressed various NK receptors, including NKp30, NKp44, NKp46, NKG2D, and CD94, as well as a diverse set of killer cell Ig-like receptor molecules at levels comparable to normal human NK cells from the peripheral blood, which is evidence of their maturity. They produced levels of granzyme A as high as in human peripheral blood–derived NK cells, and a considerable amount of perforin protein was detected in the plasma. Human NK cells in hu-HSC NOG–IL-2 Tg produced IFN-γ upon stimulation, and IL-2, IL-15, or IL-12 treatment augmented the in vitro cytotoxicity. Inoculation of K562 leukemia cells into hu-HSC NOG–IL-2 Tg caused complete rejection of the tumor cells, whereas inoculation into hu-HSC NOG fully reconstituted with human B, T, and some NK cells did not. Moreover, when a CCR4+ Hodgkin’s lymphoma cell line was inoculated s.c. into hu-HSC NOG–IL-2 Tg, the tumor growth was significantly suppressed by treatment with a therapeutic humanized anti-CCR4 Ab (mogamulizumab), suggesting that the human NK cells in the mice exerted active Ab-dependent cellular cytotoxicity in vivo. Taken together, these data suggest that the new NOG–IL-2 Tg strain is a unique model that can be used to investigate the biological and pathological functions of human NK cells in vivo.

Efficient Xenoengraftment in Severe Immunodeficient NOD/Shi-scid IL2rγnull Mice Is Attributed to a Lack of CD11c+B220+CD122+ Cells

Xenograft animal models using immunodeficient mice have been widely applied in medical research on various human diseases. NOD/Shi-scid-IL2rγnull (NOG) mice are known to show an extremely high engraftment rate of xenotransplants compared with conventional immunodeficient mice. This high engraftment rate of xenotransplants in NOG mice was substantially suppressed by the transfer of spleen cells from NOD-scid mice that were devoid of NK cells. These results indicate that cell types other than splenic NK cells present in NOD-scid mice but not in NOG mice may be involved in this suppression. To identify the cell types responsible for this effect, we transferred subpopulations of spleen cells from NOD-scid mice into NOG mice and assessed the levels of human cell engraftment after human PBMC (hPBMC) transplantation. These experiments revealed that CD11c+B220+ plasmacytoid dendritic cells (pDCs) from NOD-scid mice markedly inhibited engraftment of human cells. The CD11c+B220+CD122+ cells further fractionated from the pDCs based on the expression of CD122, which is an NK cell marker strongly inhibited during hPBMC engraftment in NOG mice. Moreover, the CD122+ cells in the pDC fraction were morphologically distinguishable from conventional CD122+ NK cells and showed a higher rejection efficiency. The current results suggest that CD11c+B220+CD122+ cells play an important role in xenograft rejection, and their absence in NOG mice may be critical in supporting the successful engraftment of xenotransplants.

Antitumor Effect of Programmed Death-1 (PD-1) Blockade in Humanized the NOG-MHC Double Knockout Mouse.

Purpose: Humanized mouse models using NOD/Shi-scid-IL2rγnull (NOG) and NOD/LtSz-scid IL2rγnull (NSG) mouse are associated with several limitations, such as long incubation time for stem cell engraftment and the development of xenograft versus host disease in mice injected with peripheral blood mononuclear cells (PBMCs). To solve problems, we used humanized major histocompatibility class I- and class II-deficient NOG mice (referred to as NOG-dKO) to evaluate the antitumor effect of anti-programmed death-1 (PD-1) antibody. Experimental Design: Humanized NOG-dKO mice, in which human PBMCs and human lymphoma cell line SCC-3, or glioblastoma cell line U87 were transplanted, were used as an immunotherapy model to investigate the effect of anti-PD-1 antibody. A biosimilar anti-PD-1 mAb generated in our laboratory was administered to humanized NOG-dKO mice transplanted with tumors. Results: Within 4 weeks after transplantation, human CD45+ cells in antibody-treated mice constituted approximately 70% of spleen cells. The injection of anti-PD-1 antibody reduced by more 50% the size of SCC-3 and U87 tumors. In addition, induction of CTLs against SCC-3 cells and upregulation of natural killer cell activity was observed in the antibody-treated group. Tumor-infiltrating lymphocyte profiling showed that more exhausted marker (PD1+TIM3+LAG3+) positive T cells maintained in anti-PD-1 antibody–treated tumor. A greater number of CD8+ and granzyme-producing T cells infiltrated the tumor in mice treated with the anti-PD-1 antibody. Conclusions: These results suggest that NOG-dKO mice might serve as a good humanized immunotherapy model to evaluate the efficacy of anti-PD-1 antibody prior to the clinical treatment. Clin Cancer Res; 23(1); 149–58. ©2016 AACR.

A novel xenogeneic graft‐versus‐host disease model for investigating the pathological role of human CD4+ or CD8+ T cells using immunodeficient NOG mice

Graft‐versus‐host disease (GVHD) is a major complication of allogenic bone marrow transplantation and involves the infiltration of donor CD4+ and/or CD8+ T cells into various organs of the recipient. The pathological role of human CD4+ and CD8+ T cells in GVHD remains controversial. In this study, we established two novel xenogeneic (xeno)‐GVHD models. Human CD4+ or CD8+ T cells were purified from peripheral blood and were transplanted into immunodeficient NOD/Shi‐scid IL2rgnull (NOG) mice. Human CD8+ T cells did not induce major GVHD symptoms in conventional NOG mice. However, CD8+ T cells immediately proliferated and induced severe GVHD when transferred into NOG mice together with at least 0.5 × 106 CD4+ T cells or into NOG human interleukin (IL)‐2 transgenic mice. Human CD4+ T cell–transplanted NOG mice developed skin inflammations including alopecia, epidermal hyperplasia, and neutrophilia. Pathogenic T helper (Th)17 cells accumulated in the skin of CD4+ T cell–transplanted NOG mice. Further, an anti‐human IL‐17 antibody (secukinumab) significantly suppressed these skin pathologies. These results indicate that pathogenic human Th17 cells induce cutaneous GVHD via IL‐17–dependent pathways. This study provides fundamental insights into the pathogenesis of xeno‐GVHD, and these humanized mouse models may be useful as preclinical tools for the prevention of GVHD.

Rapid histone deacetylation and transient HDAC association in the IL-2 promoter region of TSST-1-stimulated T cells.

It remains unclear how superantigen induces unresponsiveness in stimulated T cells. We analyzed the chromatin status of the interleukin-2 (IL-2) promoter region in T cells stimulated with toxic shock syndrome toxin-1 (TSST-1) superantigen using T cell receptor-transgenic T cells responding to ovalbumin (OVA) and TSST-1. Compared to OVA stimulation, naïve T cells cultured with TSST-1 showed lower IL-2 expression after transient enhancement. Coincidentally, the acetylated histone H3 (AcH3) level at the IL-2 promoter region was first enhanced, and then decreased, in TSST-1-stimulated T cells. At the reduction stage of AcH3, histone deacetylase-1 (HDAC1) was markedly associated with the IL-2 promoter region in a TSST-1-specific manner without HDAC1 over-expression. The enhancement of HDAC1 association and IL-2 suppression was prevented by pre-treatment with HDAC inhibitor, but not once the anergy status was established. These results suggest that recruitment of HDAC1 in the IL-2 promoter region at the early stimulation stage with TSST-1 plays a pivotal role in sAg-induced anergy.