Role of Interleukin-3 and Basophils in a Mouse Model of Cutaneous Leishmaniasis

皮肤利什曼病是由利什曼属原生动物寄生虫引起的媒介传播传染病，是世界上最重要的被忽视的传染病之一。目前，82个国家（主要是发展中国家）有1 000万人受到感染。感染者在身体暴露的部位出现一个或多个溃疡性皮肤损伤，导致严重残疾和永久性疤痕。大利什曼原虫是引起人类皮肤利什曼病的两种主要原虫之一，大利什曼原虫感染小鼠是一种成熟的实验模型，用于研究体内免疫的各个方面。大多数基因型感染L. major的小鼠会出现局部病变，几周后会自发愈合。然而，某些小鼠品系（如BALB/c小鼠）不能控制感染并发展为进行性病变和全身性疾病。小鼠对L. major感染的易感性或抗性的遗传易感性与导致疾病的白细胞介素(IL)-4驱动的Th2反应与促进愈合和寄生虫清除的IL- 12驱动的干扰素-3 （INF-3）主导的Th1反应的优势密切相关。从机制上讲，nf -3在巨噬细胞中触发诱导型一氧化氮合酶（iNOS）操作的利什manicidal系统，导致抗性表型，而IL-4使该机制失活，导致易感表型。最近对小鼠的研究已经确定了产生il -4的嗜碱性细胞在促进th2型免疫反应中的一个关键但以前未被认识到的作用。此外，大量研究报道IL-3可以促进嗜碱性粒细胞扩增，增强嗜碱性细胞因子的产生，IL-3的产生与BALB/c小鼠对L. major感染的易感性相关。然而，产生IL-3和il -4的嗜碱性粒细胞在皮肤利什曼病中的确切作用尚未得到解决。因此，我们建议利用令人兴奋的机会来分析IL-3和嗜碱性粒细胞在皮肤利什曼病小鼠模型中的作用。具体来说，我们将使用BALB/c il -3缺陷小鼠、嗜碱性粒细胞缺失的野生型小鼠和纯化的骨髓来源嗜碱性粒细胞群体来测试两个主要但相关的假设：1) IL-3的产生加重了疾病的严重程度，这反映在病变大小、寄生虫负担、T细胞细胞因子的产生和炎症效应细胞的浸润和功能上；2)嗜碱性细胞在感染后迁移到引流淋巴结和皮肤病变处，被L. major抗原先天激活。并释放促进Th2的细胞因子，如IL-4，导致BALB/c小鼠产生无效的Th2免疫反应，导致其对感染的易感性。

DESCRIPTION (provided by applicant): Cutaneous leishmaniasis, a vector-borne infectious disease caused by protozoan parasites of the genus Leishmania, is one of the most important neglected infectious diseases worldwide. Currently, 10 million people in 82 (mostly developing) countries are infected. Those infected develop one or more ulcerative skin lesions on the exposed parts of the body, causing serious disability and permanent scarring. Infection of mice with Leishmania major, one of the two main species that causes human cutaneous leishmaniasis, is a well- established experimental model used to study various aspects of immunity in vivo. Most mouse genotypes infected with L. major develop localized lesions that heal spontaneously after a few weeks. However, certain mouse strains - such as BALB/c mice - fail to control infection and develop progressive lesions and systemic disease. The genetic predisposition for susceptibility or resistance to L. major infection in mice strongly correlates with the dominance of an interleukin (IL)-4-driven Th2 response that causes disease versus an IL- 12-driven, interferon-3 (INF-3)-dominated Th1 response that promotes healing and parasite clearance. Mechanistically, INF-3 triggers inducible nitric oxide synthase (iNOS)-operated leishmanicidal systems in macrophages, resulting in the resistant phenotype, while IL-4 inactivates that mechanism resulting in a susceptible phenotype. Recent studies in mice have now defined a critical but previously unrecognized role for IL-4-producing basophils in promoting Th2-type immune responses. Furthermore, a number of studies have reported that IL-3 can promote basophil expansion and enhance basophil cytokine production, and that IL-3 production correlates with susceptibility of BALB/c mice to infection with L. major. However, the precise role of IL-3 and IL-4-producing basophils in cutaneous leishmaniasis has yet to be addressed. We therefore propose to take advantage of exciting opportunities to analyze the role of IL-3 and basophils in a mouse model of cutaneous leishmaniasis. Specifically, we will use BALB/c IL-3-deficient mice, wild-type mice depleted of basophils, and purified populations of bone marrow-derived basophils to test two major but related hypotheses: 1) that IL-3 production exacerbates the severity of disease as reflected by measures of lesion size, parasite burden, T cell cytokine production, and inflammatory effector cell infiltration and function, and 2) that basophils undergo migration to draining lymph nodes and cutaneous lesions in response to infection, become innately activated by L. major antigens, and release Th2-promoting cytokines such as IL-4 that result in BALB/c mice mounting an ineffective Th2 immune response responsible for their susceptibility to infection. PUBLIC HEALTH RELEVANCE: Human cutaneous leishmaniasis continues to rank among the most important infectious diseases on a worldwide basis. The overall goal of this project is to determine the role of white blood cells called basophils and the protein interleukin-3 in the immune response to the protozoan parasite Leishmania major. We believe these studies to be critical to identifying meaningful targets for vaccines, therapeutics, and diagnostics.