Innate immune response to microbial PAMPs in the schistosome-transmitting snail,

描述（由申请人提供）：血吸虫与其蜗牛中间宿主之间的兼容性部分取决于幼虫寄生虫与宿主先天内部防御系统（IDS）相互作用的结果。与其他先天免疫系统一样，病媒蜗牛光螺的入侵识别被认为依赖于模式识别受体（PRRs）对病原体相关分子模式（PAMPs）的识别。然而，在血吸虫-蜗牛相互作用中重要的PAMPs和PRRs都没有得到很好的理解。提出的研究的具体目的是确定一种或多种特定的PAMPs，这些PAMPs是白刺草IDS响应的，然后在转录组学水平上表征这种响应。近年来，研究人员在抗血吸虫（但不敏感）的光斑拟南蝽的造血变形虫产生器官（APO）中观察到对注射的大肠杆菌粗脂多糖（LPS）产生有丝分裂反应，其有丝分裂活性模式与先前描述的对注射的血吸虫提取物的有丝分裂活性模式非常相似。这一观察结果为首次鉴定在血吸虫传播的蜗牛中触发免疫反应的特定PAMP提供了机会。如果这种有丝分裂活动实际上是针对LPS的，那么它代表了一种独特的无脊椎动物对最具特征的微生物PAMP的反应，并且鉴定出负责的PAMP可能为蜗牛IDS识别不相容的血吸虫幼虫提供了见解，可能在最近获得血吸虫寄生虫之前，蜗牛IDS在很大程度上是为了应对微生物病原体而进化的。拟议的研究将测试在粗LPS（即LPS，肽聚糖，未甲基化的富含cpg的DNA）中发现的最有可能的候选PAMPs的有丝分裂活性，如果活性与LPS本身相关，则将确定LPS的活性成分（即脂质A或O多糖）。这些研究将利用注射蜗牛apo细胞分裂的组织学分析。最后，通过使用微阵列分析，将APO中对注射活性细菌PAMP的基因表达模式与先前报道的对其他形式非自身的反应进行比较。

DESCRIPTION (provided by applicant): Compatibility between schistosomes and their snail intermediate hosts is determined in part by the outcome of the interaction of the larval parasite with the host's innate internal defense system (IDS). As in other innate immune systems, the IDS of the vector snail Biomphalaria glabrata is thought to rely on recognition of pathogen-associated molecular patterns (PAMPs) by pattern recognition receptors (PRRs). However, both the PAMPs and PRRs important in schistosome-snail interactions are not well understood. The specific aims of the proposed research are to identify one or more specific PAMPs to which the IDS of B. glabrata responds, and then to characterize this response at the transcriptomic level. Recently, a mitotic response to injected crude lipopolysaccharide (LPS) from Escherichia coli has been observed in the hematopoietic amebocyte-producing organ (APO) of schistosome-resistant (but not schistosome- susceptible) B. glabrata, and the pattern of mitotic activity is quite similar to that previously described against injected schistosome extracts. This observation provides an opportunity to identify for the first time a specific PAMP that triggers an immune response in a schistosome-transmitting snail. Should this mitotic activity in fact be directed against LPS, it represents a unique invertebrate response against one of the best characterized microbial PAMPs, and identification of the responsible PAMP(s) may provide insights on recognition of incompatible schistosome larvae by the snail IDS, which presumably evolved largely in response to microbial pathogens long before the recent acquisition of schistosome parasites. The proposed research will test the mitogenic activity of the most likely candidate PAMPs found in crude LPS (i.e., LPS, peptidoglycan, unmethylated CpG-rich DNA), and if activity is associated with LPS itself, then the active component of LPS (i.e., lipid A or the O polysaccharide) will be identified. These studies will utilize histological analysis of cell division in APOs of injected snails. Finally, with the use of microarray analysis, the pattern of gene expression in the APO in response to injection with the active bacterial PAMP will be compared to that previously reported in response to other forms of nonself. PUBLIC HEALTH RELEVANCE: The capacity for a snail to serve as an intermediate host for medically important digenetic trematodes hinges in part on the interaction of the parasite with the host's innate immune system. The proposed research seeks to identify for the first time a specific bacterial molecule that triggers an innate immune response (hematopoiesis) in the schistosome-transmitting snail, Biomphalaria glabrata, and then to characterize the pattern of gene expression in response to this molecule. Results of this study may provide new information on immune recognition of bacterial molecular patterns, as well as insights on the underlying mechanisms of snail-schistosome compatibility.