Intestinal Mucosal Immunity

描述（由申请人提供）：许多急性病毒感染诱导早期T细胞非依赖性多克隆B细胞激活和抗原特异性IgA或IgG的产生，在经典T细胞依赖性B生发中心形成之前。然而，启动早期T细胞独立类开关重组（CSR）的必要信号尚不清楚。本应用程序的目的是确定驱动T细胞独立B细胞激活和IgA CSR的基本途径。我们提出利用小鼠轮状病毒感染模型，在病毒暴露后48小时内诱导Peyer's patch (PP) T细胞不依赖的多克隆B细胞活化，然后产生轮状病毒特异性IgA。轮状病毒诱导的B细胞体外活化需要树突状细胞。轮状病毒抗原存在于体内的PP树突状细胞中，这些细胞在B细胞激活时被激活，这表明树突状细胞是B细胞对轮状病毒反应的重要调节剂。我们发现B细胞激活依赖于轮状病毒颗粒的结构完整性，这表明轮状病毒可能通过模式识别诱导树突状细胞反应。初步实验表明，MyD88表达缺失导致B细胞活化减弱和肠道IgA水平显著降低。我们发现B细胞活化因子（BAFF）信号通路的突变也会导致B细胞活化的消融，这表明MyD88与BAFF之间存在潜在的联系。PP B细胞激活数天后，PP中TGF-2表达和IgA+ B细胞数量增加，提示TGF-2在PP对轮状病毒的多克隆应答中也起重要作用。因此，我们假设树突状细胞通过诱导MyD88、BAFF和TGF-2信号独立于抗原特异性BCR引起的多克隆B细胞应答来调节PP中快速T细胞独立的病原体特异性抗体的产生。我们将通过使用体外和体内方法来验证这一假设，以实现以下三个目标：目的1。确定轮状病毒是否诱导驱动B细胞反应的树突状细胞MyD88信号。目标2。确定MyD88信号是否导致BAFF和TGF-ss的产生。目标3。描述多克隆B细胞对轮状病毒的反应。在这一应用中提出的研究对于解决关于T细胞非依赖性抗体在肠道诱导的分子机制的悬而未决的问题具有重要意义。这项工作将为肠道免疫反应提供新的见解，并有助于改进粘膜疫苗策略。确定病原体如何诱导快速而特异性的抗体，对于确定早期抗体在限制病毒复制和传播以及提供保护方面的作用具有巨大的潜力。公共卫生相关性：本提案旨在了解肠道抗体对病毒病原体的反应是如何由宿主启动和调节的。具体来说，树突状细胞和B细胞之间需要诱导B细胞产生病毒特异性抗体的最早信号将被研究。获得的信息将通过定义新的信号通路提供对肠道免疫调节的更全面的理解，并将与治疗方法和粘膜疫苗的开发有关。

DESCRIPTION (provided by applicant): Many acute viral infections induce early T cell independent polyclonal B cell activation and production of antigen-specific IgA or IgG prior to the formation of classical T cell dependent B germinal centers. However, the necessary signals for initiation of early T cell independent class switch recombination (CSR) are not known. The objective of this application is to determine the essential pathways that drive T cell independent B cell activation and IgA CSR. We propose to utilize the murine model of rotavirus infection in which Peyer's patch (PP) T cell independent polyclonal B cell activation is induced within 48 hours after viral exposure followed by production of rotavirus- specific IgA. Rotavirus induced B cell activation in vitro requires dendritic cells. Rotavirus antigen is present in PP dendritic cells in vivo and these cells are activated at the time B cell activation occurs, suggesting that dendritic cells are important modulators of the B cell response to rotavirus. Our finding that B cell activation is dependent on the structural integrity of the rotavirus particles suggested the possibility that rotavirus induces dendritic cell responses as a result of pattern recognition. Preliminary experiments demonstrate that lack of MyD88 expression results in an ablation of B cell activation and substantial reduction in intestinal IgA levels. We find that a mutation in the B cell activating factor (BAFF) signaling pathway also results in the ablation of B cell activation, suggesting a potential link between MyD88 and BAFF. Several days following PP B cell activation there is an increase of TGF-2 expression and numbers of IgA+ B cells in the PP, suggesting TGF-2 also plays an important role in the PP polyclonal response to rotavirus. Therefore, we hypothesize that dendritic cells modulate the production of rapid T cell independent pathogen-specific antibody in the PP through induction of a polyclonal B cell response that results from MyD88, BAFF, and TGF-2 signaling independent of an antigen-specific BCR. We will test this hypothesis by using both in vitro and in vivo approaches to pursue the following three aims: Aim 1. Determine whether rotavirus induces dendritic cell MyD88 signaling that drives B cell responses. Aim 2. Determine whether MyD88 signaling results in BAFF and TGF-ss production. Aim 3. Characterize the polyclonal B cell responses to rotavirus. The studies proposed in this application are of importance in addressing unanswered questions regarding the molecular mechanisms of T cell independent antibody induction in the intestine. This work will provide new insights into intestinal immune responses as well as contribute to improved mucosal vaccine strategies. Defining how pathogens induce rapid but specific antibody has tremendous potential to define the role of early antibody in limiting viral replication and dissemination and providing protection. PUBLIC HEALTH RELEVANCE: This proposal aims to understand how the intestinal antibody response to a viral pathogen is initiated and regulated by the host. Specifically, the earliest signals between dendritic cells and B cells required to induce B cells to produce viral specific antibodies will be investigated. Information gained will provide a more comprehensive understanding of intestinal immune regulation by defining novel signaling pathways and will be pertinent to development of therapeutics and mucosal vaccines.