GP49, THE MAJOR GPI-ANCHORED ANTIGEN OF GIARDIA LAMBLIA

蓝氏贾第鞭毛虫是一种遗传学上原始的原生动物， 在热带和温带地区引起水传播的肠道疾病 区界限 G.引起人类腹泻的兰伯氏菌 目前未知。 尽管它们可能很重要， 已知滋养体表面的分子或它们之间的相互作用 肠上皮细胞。 表面抗原已经被 到目前为止，其特征是富含半胱氨酸的蛋白质， 甚至在单个分离物的亚克隆之间。 尽管它们的抗原 变化是有趣的，并可能有助于变化的 疾病过程中，重要的是要确定其他潜在的不变的， 表面蛋白 通过用[3 H]-脂肪酸进行生物合成标记， 发现G. Lamblia合成糖基磷脂酰肌醇（GPI） 锚定表面蛋白GP 49，其结构不同， 在生物学上与其他人描述的可变表面抗原不同。 此外，这种表面抗原存在于不同的分离株中， G.兰布利亚，因此可以是 被认为是化疗的潜在候选者， 免疫干预。因此，我建议研究GP 49， （1）确认我们的初步证据， 是一种不变抗原;（2）分析其不寻常的GPI锚结构， (3)阐明氨基糖和肌醇类似物对GPI的影响 锚合成，并分析中间糖脂， 积累特异性抑制剂（4），分离并测序其基因 以评估其结构和可能的功能，（5）研究 GP 49与培养人肠上皮细胞相互作用 因为我们发现可溶性或完整的GP 49升高了 细胞质Ca ~（2+）浓度表明可能在分泌 腹泻 我们的初步数据表明，这些研究可以摆脱 阐明贾第虫病的分子发病机制，并提出免疫学 对这一重大疾病的态度。

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.