Targeting iron acquisition in Salmonella with siderophore-based immunization

描述（由申请人提供）：铁是宿主体内细菌复制的必需元素。细菌感染期间最重要的宿主策略之一是通过使用高亲和力铁结合蛋白（如转铁蛋白和乳铁蛋白）从微生物中螯合铁。为了克服这些宿主防御，细菌释放称为铁载体的小分子，这些小分子与铁协调，然后被细菌表达的专用吸收系统内化。宿主的对策是分泌脂质运载蛋白-2，它与一组选择性的铁载体结合，可有效减少细菌生长。 Lipocalin-2 可以控制大肠杆菌引起的菌血症，因为它可以螯合铁载体肠螯素，从而使大肠杆菌缺乏铁。然而，这一策略是 鼠伤寒沙门氏菌不能成功对抗血清型鼠伤寒沙门氏菌，因为这种病原体除了肠螯素之外，还产生一种不被 lipocalin-2 隔离的糖基化肠螯素（沙莫螯素）。由于大量证据表明宿主病原体的生长需要铁的获取，因此限制细菌定植的一种有前景的治疗策略是防止这些微生物获取铁。该应用的主要目的是开发新方法，通过使用基于铁载体的免疫来限制脊椎动物宿主中鼠伤寒沙门氏菌获取铁。我们的中心假设是，隔离铁载体肠杆菌素和沙莫螯合素将限制鼠伤寒沙门氏菌对铁的吸收，从而抑制在脊椎动物宿主中的定植。这一假设基于初步数据，这些数据表明铁的获取促进鼠伤寒沙门氏菌的生长和与其他微生物的竞争，并且用 CTB-Ent 缀合物接种小鼠会导致抗体产生。我们的长期目标是开发新的治疗方法来减少鼠伤寒沙门氏菌的生长和传播。我们计划通过追求以下具体目标来检验我们的假设并实现本申请的目标：（I）本计划的第一个目标是确定注射蛋白质-铁载体缀合物是否会导致结肠炎小鼠模型中鼠伤寒沙门氏菌的生长抑制，该模型模拟炎症性腹泻病。 (II) 本研究的第二个目的是确定注射蛋白质-铁载体缀合物是否会导致模拟全身感染的伤寒小鼠模型中鼠伤寒沙门氏菌的生长抑制。

DESCRIPTION (provided by applicant): Iron is an essential element for the replication of bacteria inside the host. One of the most important host strategies during bacterial infections is to sequester iron from microorganisms by employing high-affinity iron-binding proteins like transferrin and lactoferrin. To overcome these host defenses, bacteria release small molecules named siderophores, which coordinate iron and are then internalized by dedicated uptake systems expressed by bacteria. A countermeasure of the host is the secretion of the protein lipocalin-2, which binds to a selective group of siderophores and it is effective in reducing bacterial growth. Lipocalin-2 controls bacteremia caused by Escherichia coli, because it chelates the siderophore enterochelin, thereby starving E. coli of iron. This strategy, however, is not successful against Salmonella enterica serotype Typhimurium because this pathogen, in addition to enterochelin, produces a glucosylated enterochelin (salmochelin) which is not sequestered by lipocalin-2. Because of the substantial evidence for the necessity of iron acquisition for the growth of pathogens in the host, one promising therapeutic strategy to limit bacterial colonization is to prevent iron acquisition by these microbes. The primary objective of this application is to develop new methods to limit iron acquisition by S. Typhimurium in the vertebrate host by using siderophore-based immunization. Our central hypothesis is that sequestering the siderophores enterobactin and salmochelin will limit iron uptake by S. Typhimurium and thereby inhibit colonization in the vertebrate host. This hypothesis is based on preliminary data revealing that iron acquisition promotes S. Typhimurium growth and competition with other microbes, and that vaccination of mice with CTB-Ent conjugates results in antibody production. Our long-range goal is to develop new treatments to reduce the growth and dissemination of S. Typhimurium. We plan to test our hypothesis and fulfill the objectives of this application by pursuing the following Specific Aims: (I) The first objective of this initiativ is to determine whether injection of protein- siderophore conjugates results in growth inhibition of S. Typhimurium in the colitis mouse model, which models inflammatory diarrheal disease. (II) The second aim of this investigation is to determine whether injection of protein-siderophore conjugates results in growth inhibition of S. Typhimurium in the typhoid mouse model, which mimics systemic infection.