Anti-polysaccharide antibody responses in humanized mice

描述（由申请人提供）：啮齿动物模型在阐明基本免疫机制方面的作用是毋庸置疑的。不幸的是，这些机制的特定方面可能是物种特异性的。此外，许多人类感染性病原体不能在啮齿动物宿主中建立生产性感染。这些因素使从这些实验动物获得的知识转化为预防、诊断和治疗人类疾病的更好方法变得复杂。 免疫缺陷小鼠新品系的开发，可以持久异种移植与人类造血细胞提供了一个潜在的解决方案，上述问题。我们利用NOD/SCID/共同细胞因子受体g链敲除（NSG）小鼠品系和人脐带血（UCB）CD 34+造血干细胞（HSC）来创建造血人源化小鼠（HIS小鼠）。我们已经发现，这些小鼠的血液、脾脏和一定程度的淋巴结中可重复和稳定地植入人B淋巴细胞。然而，这些小鼠中B细胞区室的主要亚群表现为表型不成熟。 用螺旋体细菌赫氏疏螺旋体感染这些HIS小鼠导致感染过程和经由IgM应答的消退，所述IgM应答在性质上类似，但不如IgM应答那么稳健。 在受感染的人类和小鼠模型中观察到的那些。而对B. hermsii在小鼠中的免疫应答是T细胞非依赖性（TI）应答，该应答通过Toll样受体（TLR）的细菌刺激而增强。除非TLR配体作为佐剂，否则HIS小鼠也不能对纯化的多糖抗原产生抗体应答。最后，HIS小鼠对T细胞依赖性抗原产生抗体应答，但这些应答很弱，IgM是产生的主要同种型。 这些观察结果使我们假设，如上所述产生的HIS小鼠由于其淋巴细胞区室发育不完全，对各种病原体和抗原失败或反应不佳。我们推测这部分是由于宿主产生的鼠细胞因子对移植造血细胞缺乏有效的人细胞因子受体交叉刺激。在本申请中，我们提出通过产生表达人IL-7和人BLyS（BAFF）的NSG小鼠以用作UCB HSC的受体来测试该假设。我们预测，这两种修饰将产生具有更成熟和多样化的B细胞区室的HIS小鼠，其能够对各种抗原和病原体产生强大的免疫应答。因此，我们预测，由此产生的HIS小鼠将作为更好的模型，用于诊断和治疗人类疾病的策略的发展。

DESCRIPTION (provided by applicant): The power of rodent models for the elucidation of basic immunological mechanisms is unquestioned. Unfortunately, particular aspects these mechanisms may be species specific. In addition, many human infectious pathogens are incapable of establishing productive infections in rodent hosts. These factors complicate the translation of knowledge gained from such experimental animals to better approaches for the prevention, diagnosis and treatment of human diseases. The development of new strains of immunodeficient mice that can be durably xenografted with human hematopoietic cells provides a potential solution to the problems mentioned above. We have utilized the NOD/SCID/common cytokine receptor g chain knockout (NSG) strain of mice and human umbilical cord blood (UCB) CD34+ hematopoietic stem cells (HSCs) to create hematopoietically humanized mice (HISmice). We have found that these mice are reproducibly and stably engrafted with human B lymphocytes in the blood, spleen and to some extent in the lymph nodes. However, major subpopulations of the B cell compartment in these mice appear phenotypically immature. Infection of these HISmice with the spirochete bacteria Borrelia hermsii results in a course of infection and resolution via an IgM response that is qualitatively similar, but is not as robust as those observed in infected humans and mouse models. While the protective immune response to B. hermsii in mice is a T cell independent (TI) response, this response is augmented by bacterial stimulation of Toll-like receptors (TLRs). HISmice also failed to make an antibody response to purified polysaccharide antigens unless TLR ligands were given as an adjuvant. Finally, HISmice mount antibody responses to T cell dependent antigens, but these responses are weak and IgM is the predominant isotype produced. These observations lead us to hypothesize that HISmice generated as describe above, fail or respond sub optimally to a variety of pathogens and antigens due to incomplete development of their lymphocyte compartments. We hypothesize that this is due, in part, to lack of efficient cross stimulation of human cytokine receptors on engrafting hematopoietic cells by host-produced murine cytokines. In this application, we propose to test this hypothesis by generating human IL-7 and human BLyS (BAFF) expressing NSG mice for use as recipients for UCB HSCs. We predict that both of these modifications will yield HISmice with more mature and diverse B cell compartments capable of mounting robust immune responses to a variety of antigens and pathogens. As such, we predict that the resulting HISmice will serve as far better models for the development of strategies for the diagnosis and treatment of human disease.