TRANS-SIALIDASE OF INSECT-DERIVED FORMS OF T CRUZI

克氏锥虫是一种引起人类恰加斯病的原生动物。 它在媒介昆虫的中肠中分裂， 感染性的亚循环形式。 在哺乳动物宿主体内， 细胞内，当细胞溶解时，锥鞭毛体的形式， 释放到血液中 从宿主中出现的锥鞭毛体 细胞含有很少或不含唾液酸，但在其表面上携带 转唾液酸酶（TS）。 TS快速从宿主转移唾液酸 糖缀合物到血液衍生的锥鞭毛体的表面，形成 阶段特异性表位（Ssp3）。 代谢环类也获得唾液酸 从哺乳动物宿主，但他们的唾液酸化分子和TS是 结构上不同。 T. cruzi不合成唾液酸， 唾液酸获得的高效率表明，这是一种 完成其生命周期的重要过程。 一些证据表明 唾液酸对细胞侵袭很重要 这可能涉及到 逃避寄生虫的免疫反应， 到特定的组织 在这项提案中，我们的目标是了解TS和唾液酸的作用， 受体。 在母公司赠款中，主要关注TS和唾液酸 哺乳动物形式的寄生虫的酸受体。 这里我们将 集中研究昆虫衍生的T. cruzi，这是形式 在自然感染中第一次与人类宿主接触。 我们将：1. 从亚环形式中分离和表征TS。 我们将 确定TS在这些形式中是否受到发育调节，如果 它与锥鞭毛体的唾液酸酶或TS有任何相似之处 鉴定、纯化和克隆昆虫TS基因的cDNA， T的衍生形式。克鲁兹 2.鉴别唾液酸受体 在T. cruzi和确定是否唾液酸 含酸分子参与了对细菌的入侵和抵抗， 宿主免疫攻击

Trypanosoma cruzi is a protozoan that causes Chagas' disease in humans. It divides in th midgut of insect vectors until it transforms into infective metacyclic forms. In the mammalian host the parasite divides intracellularly and, when the cells lyse, trypomastigote forms are released into the blood stream. Trypomastigotes emerging from the host cells contain little or no sialic acid, but carry on their surface a trans-sialidase enzyme (TS). TS rapidly transfers sialic acid from host glycoconjugates to the surface of blood-derived trypomastigotes, forming a stage-specific epitope (Ssp3). Metacyclics also acquire sialic acid from the mammalian host, but their sialylated molecules and TS are structurally different. T. cruzi does not synthesize sialic acid, and the high efficiency of sialic acid acquisition suggests that this is an important process in completing its life cycle. Some evidence suggests that sialic acid is important for cell invasion. It could be involved in escape from athe host's immune response, and in directing the parasite to defined tissues. In this proposal we aim to understand the role of TS and the sialic acid acceptors. In the parent grant the main focus was on the TS and sialic acid acceptors of mammalian forms of the parasite. Here we will concentrate on the insect-derived forms of T. cruzi, which are the forms that first enter into contact with the human host in natural infections. We will: 1. Isolate and characterize TS from metacyclic forms. We will determine whether in those forms TS is developmentally regulated, and if it has any resemblance to sialidase or TS from trypomastigotes We plan to identify, purify and clone CDNA that codes for TS in the insect- derived forms of T. cruzi. 2. Identify the acceptor(s) for sialic acid in the insect-derived forms of T. cruzi and determine whether the sialic acid-containing molecules are involved in invasion and resistance to the host immune attacks.