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益生菌调节宿主免疫系统的机制，从而促进肠道感染的更快恢复。益生菌罗伊氏乳杆菌是人类和小鼠胃肠道的原生菌，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，并增加IgA， IgA是对许多肠道病原体免疫反应的关键因素，其机制尚不清楚。共生菌可以上调肠上皮细胞（lECs）中聚合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iecs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，我们的初步假设是，益生菌罗伊氏乳杆菌通过上调pIgR，增加肠道内IgA的转运，并诱导肠上皮细胞分泌细胞因子APRIL，增加IgA的产生，从而增强粘膜对轮状病毒感染的IgA反应。这一假设将通过两个具体目标进行检验。1)建立pIgR在益生菌罗伊氏乳杆菌介导的轮状病毒特异性IgA反应增强中的作用。将使用体外IgA转运试验、实时荧光定量PCR阵列以及野生型和pigr缺陷型益生菌处理小鼠。2)确定益生菌罗伊氏乳杆菌与感染的lECs相互作用是否诱导APRIL增强轮状病毒特异性IgA应答。将利用液头阵列平台，lECs和B细胞共培养，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中发挥作用的分子机制。

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.