Improved Detection of in vivo Human NK Cell-Mediated Antibody-Dependent Cellular Cytotoxicity Using a Novel NOG-FcγR-Deficient Human IL-15 Transgenic Mouse.

Ikumi Katano,Ryoji Ito,Kenji Kawai,Takeshi Takahashi

doi:10.3389/fimmu.2020.532684

Abstract

We generated an NOD/Shi-scid-IL2Rγnull (NOG) mouse deficient for the Fcer1g and Fcgr2b genes (NOG-FcγR−/− mice), in which monocytes/macrophages do not express activating (FcγRI, III, and IV) or inhibitory (FcγRIIB) Fcγ receptors. Antibody-dependent cellular cytotoxicity (ADCC) by innate immune cells was strongly reduced in this strain. Thus, while the growth of xenogeneic human tumors engrafted in conventional NOG mice was suppressed by innate cells upon specific antibody treatment, such growth inhibition was abrogated in NOG-FcγR−/− mice. Using this novel strain, we further produced NOG-FcγR−/−-mice expressing human IL-15 (NOG-FcγR−/−-hIL-15 Tg). The mice inherited unique features from each strain, i.e., the long-term sustenance of human natural killer (NK) cells, and the elimination of mouse innate cell-mediated ADCC. As a result, segregation of human NK cell-mediated ADCC from mouse cell-mediated ADCC was possible in the NOG-FcγR−/−-hIL-15 Tg mice. Our results suggest that NOG-FcγR−/−-hIL-15 Tg mice are useful for validating the in vivo function of antibody drug candidates.

Highlights

Antibody-dependent cellular cytotoxicity (ADCC) by natural killer (NK) cells has been considered a critical mechanism in antibody therapy for various malignant diseases, including hematopoietic malignancies and some solid tumors [1]
Our group previously reported that two NOG variant strains, that express either human IL-2 or human IL-15; NOG-hIL-2 transgenic (Tg) or NOG-hIL15 Tg, respectively, are suitable for human NK cell development [17] and/or long-term persistence of human NK cells [18]
NOG mice and NOD-FcγR−/− mice were crossed to introduce the defective mutations in both alleles of the scid, IL-2rg, Fcer1g, and Fcgr2b loci

Summary

INTRODUCTION

Antibody-dependent cellular cytotoxicity (ADCC) by natural killer (NK) cells has been considered a critical mechanism in antibody therapy for various malignant diseases, including hematopoietic malignancies and some solid tumors [1]. Humanized mice, which stably and autonomously maintain human tissues, have attracted significant attention [7,8,9] Immunodeficient mice, such as NOD/Shi-scidIL2Rγnull (NOG) [10], NOD/LtSz-scid IL-2Rγnull (NSG) [11], or BALB-RAG2−/−-IL-2Rγ−/− double knockout (BRG) mice [12] or the derivative strain, BRG-human signal-regulatory protein α (SIRPA) (BRGS) [13], are among the best platforms for the reconstitution of human hematopoietic and immune systems, by transplantation of human hematopoietic stem cells (HSCs) or human peripheral blood mononuclear cells (PBMCs). Our group previously reported that two NOG variant strains, that express either human IL-2 (hIL-2) or human IL-15 (hIL-15); NOG-hIL-2 transgenic (Tg) or NOG-hIL15 Tg, respectively, are suitable for human NK cell development [17] and/or long-term persistence of human NK cells [18] These human NK cells suppress human tumor growth in vivo by cognate or therapeutic antibody-dependent mechanisms [17, 18]. We generated an NOG-FcγR−/−-hIL-15 Tg mouse, and demonstrated that specific detection of human NK cellmediated ADCC was possible, suppressing interference from mouse innate cells

MATERIALS AND METHODS

RESULTS AND DISCUSSION

ETHICS STATEMENT