Immune checkpoint inhibitors (ICIs) have revolutionized the treatment of cancer in the clinic. Further discovery of novel drugs or therapeutic protocols that enhance efficacy requires reliable animal models that recapitulate human immune responses to ICI treatment in vivo. In this study, we utilized an immunodeficient NOG mouse substrain deficient for mouse FcγR genes, NOG-FcγR−/− mice, to evaluate the anti-cancer effects of nivolumab, an anti-programmed cell death-1 (PD-1) antibody. After reconstitution of human immune systems by human hematopoietic stem cell transplantation (huNOG-FcγR−/− mice), four different programmed death-ligand 1 (PD-L1)-positive human cancer cell lines were tested. Among them, the growth of three cell lines was strongly suppressed by nivolumab in huNOG-FcγR−/− mice, but not in conventional huNOG mice. Accordingly, immunohistochemistry demonstrated the enhanced infiltration of human T cells into tumor parenchyma in only nivolumab-treated huNOG-FcγR−/− mice. Consistently, the number of human T cells was increased in the spleen in huNOG-FcγR−/− mice by nivolumab but not in huNOG mice. Furthermore, human PD-L1 expression was strongly induced in the spleen of huNOG-FcγR−/− mice. Collectively, our results suggest that the anti-cancer effects of anti-PD-1 antibodies can be detected more clearly in NOG-FcγR−/− mice than in NOG mice.

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Food allergy is a common disease caused by the intake of allergen-containing foods, such as milk, eggs, peanuts, and wheat. Systemic anaphylaxis is a severe hypersensitive allergic reaction resulting from degranulation of mast cells or basophils after crosslinking of surface high affinity IgE receptors (Fcε-RI) with allergen-specific IgE and allergens. In this study, we developed a novel human mast cell/basophil-engrafted mouse model that recapitulates systemic anaphylaxis triggered by β-lactoglobulin (BLG), the major allergen found in milk. Human CD34 + hematopoietic stem cells were transferred into NOG (non-Tg) or NOG hIL-3/hGM-CSF transgenic (Tg) mice. After 14–16 weeks, bovine BLG-specific human IgE was intravenously injected into the humanized mice, followed by intravenous or oral bovine BLG exposure 1 day later. Body temperature in Tg, but not in non-Tg, mice gradually decreased within 10 minutes, and 80% of Tg mice died within 1 hour by intravenous BLG exposure. Serum histamine levels and anaphylaxis scores in Tg mice were markedly increased compared to non-Tg mice. Furthermore, these allergic symptoms were significantly inhibited by epinephrine treatment into the Tg mice. Therefore, the current NOG hIL-3/hGM-CSF Tg mouse model may be useful for development of novel anaphylaxis drugs for the treatment of food allergies and for safety assessment of low-allergenicity extensively hydrolyzed cow’s milk whey protein-based infant formulas.

Despite recent advances in immunodeficient mouse models bearing human red blood cells (hRBCs), the elimination of circulating hRBCs by residual innate immune systems remains a significant challenge. In this study, we evaluated the role of mouse complement C3 in the elimination of circulating hRBCs by developing a novel NOG substrain harboring a truncated version of the murine C3 gene (NOG-C3ΔMG2-3). Genetic C3 deletion prolonged the survival of transfused hRBCs in the circulation. Chemical depletion and functional impairment of mouse macrophages, using clodronate liposomes (Clo-lip) or gadolinium chloride (GdCl3), respectively, further extended the survival of hRBCs in NOG-C3ΔMG2-3 mice. Low GdCl3 toxicity allowed the establishment of hRBC-bearing mice, in which hRBCs survived for more than 4 weeks with transfusion once a week. In addition, erythropoiesis of human hematopoietic stem cells (hHSCs) was possible in NOG-C3ΔMG2-3/human GM-CSF-IL-3 transgenic mice with Clo-lip treatment. These findings indicate that mouse models harboring hRBCs can be achieved using NOG-C3ΔMG2-3 mice, which could facilitate studies of human diseases associated with RBCs.

Humanized mice with human hematopoietic and immune systems have been frequently used for examining in vivo anti-cancer effects of various drugs, including immune checkpoint inhibitors (ICIs) like anti-PD-1 or anti-CTLA-4 antibodies, yet the reliability of the mouse models to be improved. We have recently developed NOD-scid, IL-2Rγ KO (NOG) mice deficient for the mouse FcεRI and FcγIIb genes, thus lacking the expression of functional mouse FcγRs, (NOG-FcγR-/-) and the activity of endogenous antibody-dependent cellular cytotoxicity (ADCC). Reconstitution experiments with human hematopoietic stem cells (HSC) showed that NOG-FcγR-/- mice had higher engraftment capacity for human leucocytes than NOG mice, namely the numbers of HSC-derived human CD19+ B cells and CD33+ myeloid cells, but not CD3+ T cells, were higher in the various tissues in NOG-FcγR-/- mice than those in NOG mice. In tumor-bearing experiments using those reconstituted mice, it was of interest that humanized NOG-FcγR-/- mice (huNOG-FcγR-/-) could invoke strong tumor growth suppression or rejection in response to anti-PD-1 antibody (Nivolumab) treatment in several cancer cell lines, which was absent in conventional huNOG mice. Accordingly, Nivolumab treatment in huNOG-FcγR-/- mice induced a significant increase of human T cells in number in the spleen and infiltration of human T cells with Granzyme B and Perforin-expression into tumor. Furthermore, the composition of activated T cells was different between huNOG-FcγR-/- and huNOG mice. HuNOG-FcγR-/- mice had elevated numbers of activated T cells, both T central memory cells (TCM) and T effector memory cells (TEM), whereas huNOG mice showed an opposite trend, reduced TCM and TEM and increase of naïve T cells. Our results suggest that the novel NOG-FcγR-/- mice become a good model for elucidating the cellular and molecular mechanisms of human tumor rejection by human T cells, and that they will provide a superior in vivo platform for evaluation of anti-cancer drugs, especially, in combination with ICIs like Nivolumab. Citation Format: Ikumi Katano, Asami Hanazawa, Iyo Otsuka, Takuya Yamaguchi, Misa Mochiduki, Kenji Kawai, Ryoji Ito, Motohito Goto, Takahiro Kagawa, Takeshi Takahashi. A novel humanized mouse model based on NOG-FcgR-/-mice recapitulates anti-tumor immune reactions by human immune systems in response to anti-PD-1 antibody (Nivolumab) [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 6026.