Mechanisms of Immunomodulation by Probiotic L. reuteri in Acute Gastroenteritis

描述(由申请人提供)：益生菌，或有益微生物，在预防和治疗多种胃肠道疾病方面显示出希望，但对益生菌如何改善急性胃肠炎知之甚少。长期目标是揭示肠道中的益生菌调节宿主免疫系统的机制，从而促进更快地从肠道感染中恢复。罗氏乳杆菌是人类和小鼠胃肠道特有的益生菌，通常被认为是一种安全的微生物，可以改善人类和小鼠的轮状病毒胃肠炎，并通过尚不清楚的机制增加IgA，IgA是许多肠道病原体免疫反应的关键成分。共生细菌可上调肠上皮细胞(LECs)多聚体Ig受体(PlgR)的表达，导致IgA向肠腔的转运增加。此外，多种肠道细菌刺激内皮细胞分泌APRIL(一种增殖诱导配体)，促进B细胞向IgA的类转换重组。因此，初步的假设是，益生菌通过上调pIgR和诱导肠上皮细胞分泌细胞因子APRLE来增强黏膜对轮状病毒感染的IgA应答，pIgR增加了肠腔内的IgA转运，而APRIL则促进了IgA的产生。这一假设将通过两个具体目标进行检验。1)确定pIgR在益生菌L.reuri介导的增强轮状病毒特异性IgA应答中的作用。将使用体外IgA转运试验、实时定量聚合酶链式反应阵列以及野生型和pIgR缺陷益生菌处理的小鼠。2)确定益生菌L.reuri与感染的LECs的相互作用是否诱导APRIL增强轮状病毒特异性的IgA应答。将利用液体微珠阵列平台，LECs和B细胞的共培养，以及野生型和APRIL缺陷小鼠。这些研究将确定在益生菌增强粘膜对病毒感染的免疫力方面发挥作用的分子机制。 公共卫生相关性：感染性腹泻是美国发病率的主要原因，特别是在儿童、国际旅行者和免疫缺陷患者中，也是全球儿童死亡的主要原因之一。揭示益生菌在急性胃肠炎中的免疫调节机制对改善人类健康具有巨大的潜力，因为加强对有益微生物的了解将有助于益生菌工程和合理选择自然菌株，以促进感染后更快的恢复。在严重疾病和长期并发症出现之前预防或治疗急性胃肠炎将极大地减少住院、医疗成本和残疾调整寿命年。

DESCRIPTION (provided by applicant): Probiotics, or beneficial microbes, show promise in the prevention and treatment of multiple gastrointestinal diseases, but little is known about how probiotics ameliorate acute gastroenteritis. The long-term objective is to uncover mechanisms by which probiotic bacteria in the intestine modulate the host immune system and thus facilitate more rapid recovery from enteric infections. Probiotic Lactobacillus reuteri is indigenous to the human and mouse gastrointestinal tracts, is generally recognized as a safe microorganism, ameliorates rotaviral gastroenteritis in humans and mice, and increases IgA, a key element in the immune response to many enteric pathogens, by mechanisms that are still unknown. Commensal bacteria can upregulate expression of the polymeric Ig receptor (plgR) in intestinal epithelial cells (lECs), leading to increased transport of IgA to the intestinal lumen. Furthermore, a variety of intestinal bacteria stimulate I ECs to secrete APRIL (a proliferation-inducing ligand), which facilitates class-switch recombination in B cells to IgA. Therefore, the primary hypothesis is that probiotic Lactobacillus reuteri enhances the mucosal IgA response to rotavirus infection by upregulating pIgR, which increases luminal IgA transport, and by inducing intestinal epithelial cells to secrete the cytokine APRIL, which enhances IgA production. This hypothesis will be tested with two specific aims. 1) Establish the role of pIgR in the enhanced rotavirus-specific IgA response mediated by probiotic L. reuteri. An in vitro IgA transport assay, quantitative real-time PCR arrays, and both wild type and pIgR-deficient probiotic-treated mice will be used. 2) Determine whether interaction of probiotic L. reuteri with infected lECs induces APRIL to enhance the rotavirus-specific IgA response. A liquid bead array platform, co-cultures of lECs and B cells, and both wild type and APRIL-deficient mice will be utilized. These studies will identify molecular mechanisms that play a role in probiotic enhancement of mucosal immunity to viral infections. PUBLIC HEALTH RELEVANCE: Infectious diarrhea is a leading cause of morbidity in the United States, especially among children, international travelers, and immunocompromised patients, and is one of the leading causes of global childhood mortality. Uncovering the mechanisms of immunomodulation by probiotic bacteria in acute gastroenteritis has enormous potential to improve human health, in that an enhanced understanding of beneficial microbes will facilitate probiotic engineering and rational selection of natural strains to promote more rapid recovery following infection. Preventing or treating acute gastroenteritis before severe disease and long-term complications develop would dramatically reduce hospitalizations, medical costs, and disability-adjusted life years.