Intestinal Mucosal Immunity

许多急性病毒感染诱导早期T细胞非依赖性多克隆B细胞激活和产生 在形成经典的T细胞依赖的B生发中心之前抗原特异性的IgA或Ig G。然而， 启动早期T细胞非依赖性类开关重组(CSR)所需的信号尚不清楚。 这项应用的目的是确定驱动T细胞非依赖B细胞的基本途径 激活和免疫球蛋白A CSR。 我们建议利用轮状病毒感染的小鼠模型，在该模型中，Peyer‘s Patch(PP)T细胞不依赖 多克隆B细胞在病毒暴露后48小时内被诱导激活，随后产生轮状病毒- 特异性免疫球蛋白A。轮状病毒体外诱导的B细胞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，这些细胞在B细胞激活时被激活，这表明 树突状细胞是B细胞对轮状病毒应答的重要调节器。我们的发现是B细胞的激活 依赖于轮状病毒颗粒的结构完整性暗示了轮状病毒诱导 树突状细胞的反应是模式识别的结果。初步实验表明，缺乏 MyD88的表达导致B细胞活化的消融和肠道IgA水平的大幅降低。 我们发现B细胞激活因子(BAFF)信号通路的突变也会导致B细胞的消融 细胞激活，提示MyD88和BAFF之间存在潜在的联系。PP B细胞后的几天 在PP中，转化生长因子-β的表达和IgA-B细胞数量增加，提示转化生长因子-β 在PP对轮状病毒的多克隆应答中也起着重要作用。因此，我们假设 树突状细胞调节快速T细胞非依赖性病原体特异性抗体的产生 通过诱导由MyD88、BAFF和转化生长因子β产生的多克隆B细胞反应来产生PP 信号不依赖于抗原特异性的BCR。我们将通过使用体外和体内实验来检验这一假设。 VIVO方法追求以下三个目标： 目的1.确定轮状病毒是否诱导树突状细胞MyD88信号驱动B细胞 回应。 目的2.确定MyD88信号是否导致BAFF和TGF-ss的产生。 目的3.检测多克隆B细胞对轮状病毒的反应。 本申请中提出的研究对于解决关于 肠道T细胞非依赖性抗体诱导的分子机制。这项工作将提供新的 对肠道免疫反应的洞察以及对改进的粘膜疫苗策略的贡献。 确定病原体如何诱导快速而特异的抗体具有巨大的潜力来确定早期 抗体在限制病毒复制和传播以及提供保护方面发挥了重要作用。

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-¿ expression and numbers of IgA+ B cells in the PP, suggesting TGF-¿ 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-¿ 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.