Targeting iron acquisition in Salmonella with siderophore-based immunization

说明(申请人提供)：铁是细菌在宿主体内复制所必需的元素。细菌感染过程中最重要的宿主策略之一是利用高亲和力的铁结合蛋白，如转铁蛋白和乳铁蛋白，从微生物中隔离铁。为了克服这些宿主防御，细菌释放名为铁载体的小分子，这些小分子协调铁，然后被细菌表达的专用吸收系统内化。宿主的一个对策是分泌Lipocalin-2蛋白，它与一组选择性的铁载体结合，有效地减少细菌的生长。Lipocalin-2可以控制由大肠杆菌引起的菌血症，因为它能螯合铁载体肠球蛋白，从而使大肠杆菌缺铁。然而，这一战略是 对鼠伤寒沙门氏菌血清型没有成功，因为这种病原体除了肠球蛋白外，还产生一种不被Lipocalin-2隔离的葡萄糖基化的肠球蛋白(Salmochelin)。由于大量证据表明获得铁对于病原体在宿主中的生长是必要的，因此限制细菌定植的一个有前途的治疗策略是防止这些微生物获得铁。这项应用的主要目标是开发新的方法，通过基于铁载体的免疫来限制鼠伤寒沙门氏菌在脊椎动物宿主中对铁的获取。我们的中心假设是，隔离铁载体、肠杆菌素和沙莫胆碱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。这一假说是基于初步数据显示，铁的获取促进了鼠伤寒沙门氏菌的生长和与其他微生物的竞争，用CTB-Ent结合物接种小鼠会产生抗体。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这项应用的目标：(I)这项倡议的第一个目标是确定注射蛋白质-铁载体结合物是否导致在建立炎症性腹泻疾病模型的结肠炎小鼠模型中抑制鼠伤寒沙门氏菌的生长。(Ii)这项研究的第二个目的是确定注射蛋白质-铁载体结合物是否导致在模拟全身感染的伤寒小鼠模型中抑制鼠伤寒沙门氏菌的生长。

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.