The Role of NKG2D/DAP10 in Toxoplasma gondii Infection

描述(申请人提供)：食物和水传播的原虫感染是全世界严重人类疾病的常见原因。顶端复合体由许多致病原虫组成，包括疟原虫、弓形虫、隐孢子虫和巴贝斯虫。弓形虫是一种B类优先致病原，具有良好的小动物模型，并可进行遗传操作。易感品系的小鼠经口腔感染弓形虫会导致炎症和回肠炎。在评估弓形虫天然免疫的研究中，我们已经确定信号转接蛋白DAP10在保护小鼠免受致死性感染、弓形虫复制和回肠炎方面具有重要作用。DAP10是激活免疫受体NKG2D的信号适配器，它识别应激、感染和转化细胞上的配体。DAP10基因缺陷小鼠在NK细胞上表达NKG2D，但在CD8+T细胞或γ/Delta-T细胞上不表达。这些小鼠更容易受到弓形虫的口服攻击。DAP10-/-小鼠有更严重的肠道炎症和坏死，脾中的寄生虫负担更高，并在野生型小鼠常规存活的弓形虫剂量下死亡。这项研究旨在确定DAP10-/-小鼠的易感性增加是由于表达CD8+T细胞、巨噬细胞和树突状细胞的DAP10缺乏免疫反应，导致肠道内弓形虫复制增加，还是由于NKG2D/DAP10介导的肠道CD8+T细胞调节功能丧失而导致肠道坏死。我们还将直接测试DAP10-/-小鼠的易感性增加是由于缺乏NKG2D信号的假设。这些研究将进一步阐明弓形虫对口服攻击的先天免疫应答，并为顶体复合体免疫学和口腔黏膜免疫提供重要的见解。与公共卫生相关：弓形虫是一种常见和重要的人类病原体，也是包括疟疾在内的其他原生动物病原体的模型。我们已经确定了激活的免疫受体NKG2D对于对病原体的自然、先天免疫反应非常重要。这项赠款研究的目的是确定它在弓形虫口腔感染中的作用。

DESCRIPTION (provided by applicant): Food and waterborne protozoal infections are a common cause of severe human disease worldwide. The Apicomplexa consist of numerous protozoa which cause disease, including Plasmodium, Toxoplasma, Cryptosporidia, and Babesia. Toxoplasma gondii is a Category B Priority pathogen which has an excellent small animal model, and is amenable to genetic manipulation. Oral infection with T. gondii in susceptible mouse strains results in inflammation and ileitis. In studies evaluating innate immunity to T. gondii, we have identified the signaling adaptor protein, DAP10, as important in protecting mice from lethal infection, toxoplasma replication, and ileitis. DAP10 is the signaling adaptor for the activating immunoreceptor NKG2D, which recognizes ligands on stressed, infected and transformed cells. Mice deficient in DAP10 express NKG2D on NK cells, but not on CD8+ T cells or gamma/delta-T cells. These mice are more susceptible to oral challenge with T. gondii. DAP10-/- mice have more severe intestinal inflammation and necrosis, higher parasite burdens in the spleen, and succumb to infection at doses of T. gondii which wild type mice routinely survive. Studies outlined in this proposal aim to determine whether the increased susceptibility of DAP10-/- mice is due to increased replication of T. gondii in the intestine due to lack of immune response by DAP10 expressing CD8+ T cells, macrophages and dendritic cells, or due to intestinal necrosis secondary to the loss of NKG2D/DAP10 mediated regulatory function of CD8+ T cells in the intestine. We will also directly test the hypothesis that the increased susceptibility in DAP10-/- mice is due to lack of NKG2D signaling. These studies will further delineate the innate immune response to oral challenge with T. gondii, and provide important insights to apicomplexan immunology as well as mucosal immunity to oral pathogens. Relevance to public health: Toxoplasma gondii is a common and important human pathogen, and is a model for other protozoal pathogens, including malaria. We have identified the activating immune receptor, NKG2D, as important for the natural, innate immune response to pathogens. Studies in this grant aim to define its role in oral infection with T. gondii.