PATHOGENIC/IMMUNOGENIC/STUDIES/CRYPTOSPORIDIUM GENOTYPES

描述（由申请人提供）：C。细小孢子虫是感染大多数哺乳动物物种的胃肠道的肠道原生动物，并且是人类隐孢子虫病的主要原因。C. Parvum包括两种已知的基因型，1型和2型。1型（人畜共患病）仅在人类中发现，而2型（人畜共患病）在包括人类在内的所有哺乳动物中发现。C.隐孢子虫（感染鸟类和哺乳动物）最近也与人类隐孢子虫病有关。C. 1型细小病毒是大多数人类感染的原因，在许多方面与2型不同。来自本实验室和乌干达儿童的动物研究的证据表明，1型和2型显示出几种可重复的不同表型特征，包括子孢子蛋白。2型感染啮齿类动物，而不是1型。混合感染 这两种类型的动物没有表现出基因重组的证据，因此，它们很可能保持独立的生殖周期。相反，2型分离株之间的重组已被实验证明。此外，1型和2型表面蛋白gp 40/IS的DNA和氨基酸序列存在显著差异。这些观察结果表明，这两种类型表现出显着的基因型和表型差异，因此，可能属于不同的隐孢子虫物种。而C. parvum types 1和2和C.虽然它们的宿主范围不同，但它们有一个共同点，即所有三种病毒似乎都能感染人类。几种I型分离株最近已成功地适应在无菌仔猪中连续繁殖，从而首次能够开始对1型分离株的研究，并将其与已知的2型分离株进行比较。在这个应用中，研究人员的目标是利用小猪模型来定义C。小卷蛾1型和2型。C.棘腹鱼（唯一已知的跨越脊椎动物类屏障的物种）也已成功适应在仔猪中持续繁殖，并将纳入本比较研究，主要是因为其具有重大的流行病学和公共卫生意义。 候选人研究的长期目标是表征分子，功能和 与毒力和保护相关的免疫寄生虫抗原。拟议的研究是朝着这一方向迈出的第一步，其结果将为今后的研究提供基础。以下是本研究将检验的几个假设：1）如在人类志愿者研究中观察到的，1型、2型和C型分离株之间的毒力存在差异。从临床表现、传染性、粘膜损伤的范围和分布等方面对胃肠道线虫进行了研究（目的1）;和2）虽然系统和粘膜免疫应答的性质在隐孢子虫的三种类型/物种中可能几乎相同，但将鉴定免疫显性抗原差异（目的2和4），这将导致更大的交叉保护内同源分离物比异源，和C。Aimagridis与这两种类型有很大的不同（目标3）。本研究的主要目的是：1）比较C. parvum types 1和2和C.在特定菌群仔猪模型中，研究了猪隐孢子虫的疾病表现和发病机制; 2）描述了针对C. parvum types 1和2和C.知生植物中的黑胫病 仔猪模型; 3）确定C. 1型和2型小孢子虫， C.在无菌仔猪模型中鉴定嗜水气单胞菌;以及4）鉴定 每个C都是独一无二的。parvum type和C. A. agridis，以及C. parvum types和C.这将有助于鉴定关键的特异性和交叉保护性寄生虫抗原。

DESCRIPTION (provided by applicant): C. parvum is an enteric protozoan that infects the gastrointestinal tract of most mammalian species and is the major cause of cryptosporidiosis in humans. C. Parvum comprises two known genotypes, type 1 and type 2. Type 1 (anthroponotic) is found exclusively in humans, while type 2 (zoonotic) is found in all mammals including humans. C. meleagridis (which infects birds and mammals) has also been associated with human cryptosporidiosis recently. C. Parvum type 1 is responsible for the majority of human infections and differs from type 2 in many aspects. Evidence from animal studies in this laboratory and in Ugandan children indicates that types 1 and 2 display several reproducibly distinct phenotypic traits including sporozoite proteins. Type 2 infects rodents but not type 1. Co-infections of animals with both types show no evidence of genetic recombination, and, therefore, it is likely that they maintain independent reproductive cycles. In contrast, recombination among type 2 isolates has been demonstrated experimentally. In addition, significant differences in DNA and amino acid sequences of types 1 and 2 surface protein gp40/IS exist. These observations suggest that the two types exhibit prominent genotypic and phenotypic differences and consequently, may belong to separate species of Cryptosporidium. While C. parvum types 1 and 2 and C. meleagridis display differences in host range, they share a common denominator in that all three appear to infect humans. Several type I isolates have recently been successfully adapted to continuously propagate in gnotobiotic piglets, enabling for the first time to begin studies on type 1 isolates and compare them with what is already know about type 2 isolates. In this application, the investigators aim to exploit the piglet model to define differences, if any, between C. parvum types 1 and 2. C. meleagridis (the only known species to cross the vertebrate class barrier) has also been successfully adapted to propagate continuously in piglets and will be included in this comparative study, largely because of its major epidemiologic and public health significance. The long-term goal of the candidate's research is to characterize molecular, functional, and immunologic parasite antigens associated with virulence and protection. The proposed study is the first step in that direction and the outcomes will provide basis for the future studies. The following are several hypotheses that will be tested in this study: 1) as observed in human volunteer studies, there will be differences in virulence among isolates of type 1, 2, and C. meleagridis, in terms of clinical manifestation, infectivity, and the extent and distribution of the mucosal damage (Aim 1); and 2) while the nature of systemic and mucosal immune responses are likely to be almost identical among the three types/species of Cryptosporidium, immunodominant antigenic differences will be identified (Aims 2 and 4) which will result in greater cross-protection within homologous isolates than heterologous, and that C. meleagridis will be considerably different than either type (Aim 3). The following specific aims are designed to address these hypotheses: 1) compare the nature of host parasite interaction of C. parvum types 1 and 2, and C. meleagridis in the gnotobiotic piglet model with respect to disease manifestation and pathogenesis; 2) characterize systemic as well as local cellular and humoral immune responses against C. parvum types 1 and 2 and C. meleagridis in the gnotobiotic piglet model; 3) determine the extent of cross-protection between C. parvum types 1 and 2 and C. meleagridis in the gnotobiotic piglet model; and 4) identify immunodominant molecules that are unique to each C. parvum type and C. meleagridis, and also that are common among C. parvum types and C. meleagridis, which will help in identification of key specific- and cross-protective parasite antigens.