GP49, THE MAJOR GPI-ANCHORED ANTIGEN OF GIARDIA LAMBLIA

蓝氏贾第鞭毛虫是一种系统发育原始的原生动物，也是一种主要的 热带和温带地区水源性肠道疾病的病因 区域。蓝氏菌引起人类腹泻的机制是 目前尚不清楚。尽管它们可能很重要，但相对较少 已知滋养体表面的分子或它们的相互作用 肠道上皮细胞。已经形成的表面抗原 到目前为止，其特征是富含半胱氨酸的蛋白质，这些蛋白质在不同的菌株之间存在差异。 甚至在单个分离物的亚克隆之间。尽管它们的抗原性 变化是很有趣的，可能会导致 疾病过程中，重要的是确定其他潜在的不变因素 表面蛋白。通过用[~3H]-脂肪酸进行生物合成标记，我已经 蓝氏贾第鞭毛虫合成糖基磷脂酰肌醇(GPI) 锚定表面蛋白，GP49，它在结构上和 从生物学上讲来自其他人所描述的可变表面抗原。 此外，这种表面抗原存在于不同的分离株和 兰氏革兰氏菌单个分离株的可变亚克隆，因此可以 被认为是化疗的潜在候选者以及 免疫干预。因此，我建议用 具体目标如下：(L)确认我们的初步证据是 是一个不变的抗原；(2)分析其异常的GPI锚定结构， (3)阐明氨基糖和肌醇类似物对GPI的影响 锚定合成，并分析中间糖脂 用特异性抑制物(4)积累分离其基因并测序 以评估其结构和可能的功能，以及(5)研究 GP49与培养的人肠上皮细胞的相互作用 单层，因为我们发现可溶性或完整的GP49升高 胞浆内钙离子浓度在细胞分泌中的可能作用 拉肚子。我们的初步数据表明，这些研究可能会 贾第鞭毛虫病的分子发病机制及免疫学建议 治疗这种重要疾病的方法。

Giardia lamblia is a phylogenetically primitive protozoan and a major cause of waterborne enteric disease throughout tropical and temperate zones. The mechanism by which G. lamblia causes diarrhea in humans is currently unknown. Despite their likely importance, relatively little is known of the molecules on the trophozoite surface or of their interactions with intestinal epithelial cells. The surface antigens which have been characterized to date are cysteine-rich proteins which vary among isolates and even between subclones of a single isolate. Although their antigenic variation is interesting and could contribute to the variability of the disease process, it is important to identify other, potentially invariant surface proteins. By biosynthetic labeling with [3H]-fatty acids, I have found that G. lamblia synthesizes a glycosylphosphatidylinositol (GPI) anchored surface protein, GP49, which differs structurally and biologically from the variable surface antigens described by others. Moreover, this surface antigen is present in different isolates and in variable subclones of a single isolate of G. lamblia and can therefore be considered as a potential candidate for chemotherapeutic as well as immunologic intervention. Accordingly, I propose to study GP49 with the following Specific Aims: (l) to confirm our preliminary evidence that it is an invariant antigen; (2) to analyze its unusual GPI anchor structure, (3) to elucidate the effect of amino sugar and inositol analogs on GPI anchor synthesis, and to analyze the intermediate glycolipids that accumulate with specific inhibitors (4) to isolate and sequence its gene in order to evaluate its structure and possible function, and (5) to study the interactions of GP49 with cultured human intestinal epithelial cell monolayers since we have found that soluble or intact GP49 elevates cytoplasmic Ca2+ concentration suggesting a possible role in secretory diarrhea. Our preliminary data suggest that these studies could shed light on the molecular pathogenesis of giardiasis and suggest immunologic approaches to this important disease.