Protection from enteric pathogens by beneficial microbes

描述(申请人提供)：宿主与其共生的微生物区系通常保持和平共处；然而，少数细菌破坏免疫动态平衡而致病。例如，附着和清除(A/E)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多亿人并导致150万儿童死亡。共生细菌可以保护宿主免受肠道病原体引起的疾病；然而，这种情况发生的机制尚不清楚。我们最近发现，单剂口服共生枯草芽孢杆菌或形成芽孢杆菌可以保护小鼠免受A/E病原体-轮状柠檬酸杆菌引起的疾病。相反，与之密切相关的地衣芽孢杆菌和两个枯草芽孢杆菌突变体hag和espH不能保护宿主。因为单剂保护性芽孢杆菌。在致病性轮状芽胞杆菌之前24小时给予保护，这不太可能是由于启动了适应性免疫反应，而更有可能是由于固有的抗炎免疫反应。另一种是芽孢杆菌。可以通过直接干扰轮状芽胞杆菌在肠道上皮细胞的定位来预防疾病。在目标1中，我们将使用体内生物发光成像(IBIS)来确定是否具有保护性芽孢杆菌。改变致病轮状念珠菌的定植部位。其中一个非保护性枯草杆菌突变体缺乏鞭毛蛋白，鞭毛蛋白是TLR5的配体，另一个缺乏胞外多糖，推测是TLR2的配体，在目标2中，我们将使用TLR激动剂和TLR基因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)激动剂和基因敲除小鼠来确定保护是否通过NLR介导。在目标3中，我们将测试枯草杆菌通过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.