Protection from enteric pathogens by beneficial microbes

描述（由申请人提供）：寄主及其共生菌群总体上保持和平共处；然而，少数细菌会破坏免疫稳态并引起疾病。例如，附着和清除（A/E）肠致病性和肠出血性大肠杆菌（EPEC和EHEC）导致腹泻疾病，每年影响20多亿人，造成150万儿童死亡。共生菌可以保护宿主免受肠道病原体引起的疾病；然而，人们对这种情况发生的机制知之甚少。我们最近发现，单次口服共生枯草芽孢杆菌或形式芽孢杆菌孢子可以保护小鼠免受a /E病原体，啮齿柠檬酸杆菌引起的疾病。相比之下，一种密切相关的共生地衣芽孢杆菌和两种枯草芽孢杆菌突变体hag和espH没有保护宿主。由于单剂量保护性芽孢杆菌比致病性啮齿c早24小时给予，保护不太可能是由于启动适应性免疫反应，而更可能是由于先天的抗炎免疫反应。另外，芽孢杆菌可以通过直接干扰啮齿鼠肠上皮的定位来预防疾病。在目标1中，我们将使用体内生物发光成像（IBIS）来确定保护性芽孢杆菌是否会改变致病性啮齿c的定植位置。其中一个非保护性枯草芽孢杆菌突变体缺乏鞭毛蛋白（TLR5的配体），另一个缺乏外多糖（TLR2的配体），在Aim 2中，我们将使用TLR激动剂和TLR敲除小鼠来确定保护是否通过TLR介导。同样，我们将使用nod样受体（NLR）激动剂和敲除小鼠来确定保护是否通过NLR介导。在Aim 3中，我们将测试枯草芽孢杆菌通过T调节细胞介导保护的可能性。

DESCRIPTION (provided by applicant): The host and its commensal microbiota generally maintain a peaceful coexistence; however, a few bacteria disrupt immune homeostasis and cause disease. For example, attaching and effacing (A/E) enteropathogenic and enterohemorrhagic E. coli (EPEC and EHEC) cause diarrheal diseases that affect more than 2 billion people and kill 1.5 million children annually. Commensal bacteria can protect the host from disease caused by enteric pathogens; however, the mechanisms by which this occurs are poorly understood. We recently found that a single oral dose of commensal Bacillus subtilis or Bacillus formis spores can protect mice from disease caused by the A/E pathogen, Citrobacter rodentium. In contrast, a closely related commensal Bacillus licheniformis, and two B. subtilis mutants, hag and espH, did not protect the host. Because the single dose of protective Bacillus spp. is given 24 hr prior to pathogenic C. rodentium, protection is not likely due to initiation of an adaptive immune response, but is more likely due to an innate anti-inflammatory immune response. Alternatively, Bacillus spp. could protect from disease by directly interfering with localization of C. rodentium to the intestinal epithelium. In Aim 1 we will use in vivo bioluminescence imaging (IBIS) to determine if protective Bacillus spp. alter the colonization site of pathogenic C. rodentium. One of the non-protective B. subtilis mutants is deficient in flagellin, a ligand for TLR5, and another is deficient in exopolysaccharide, presumed ligand for TLR2, and in Aim 2 we will use TLR agonists and TLR knockout mice to determine if protection is mediated through TLR. Similarly, we will use Nod-like receptor (NLR) agonists and knockout mice to determine if protection is mediated through NLR. In Aim 3, we will test the possibility that B. subtilis mediates protection through T regulatory cells. PUBLIC HEALTH RELEVANCE: We investigate a means of protecting against enteric pathogens that cause diarrheal disease by a single oral dose of spores from a commensal-like (beneficial) bacterium. The experiments are designed to determine the mechanism by which this protection occurs. We investigate the possibilities that the commensal bacterium interferes with colonization of the enteric pathogen, or stimulates an anti-inflammatory response in the host.