Intestinal cytokine and T cell homeostasis in SIV infection

描述（由申请人提供）：前线粘膜免疫防御在预防和限制HIV感染以及控制肠道病原体传播和微生物易位方面至关重要。HIV引起粘膜防御的破坏，导致肠道和管腔微生物的定植和微生物移位。这有助于HIV感染中的慢性免疫激活和免疫功能障碍，并支持病毒持续存在，尽管机制尚未完全确定。树突状细胞（DC）是粘膜前线防御的重要组成部分，但在HIV发病机制中研究不足。由于早期粘膜反应是精心策划的，高度调节的，并且涉及前线粘膜细胞之间的快速串扰，因此需要代表体内肠道微环境的实验模型来研究对HIV和微生物的早期粘膜反应。我们建议利用一种新的体内肠环模型在SIV感染恒河猴捕捉早期事件的宿主-微生物相互作用的粘膜网站和特征的粘膜防御的关键组成部分的反应和相关的保护。我们以前的研究发现，钝的Th 17 CD 4 + T细胞反应鼠伤寒沙门氏菌感染的肠道粘膜和全身传播的细菌在SIV感染的恒河猴，但不是在SIV阴性动物。我们假设SIV感染导致肠道粘膜中DC功能障碍，导致Th 17 CD 4 + T细胞应答减弱，并导致无法预防肠道病原体和微生物易位，导致慢性免疫激活。 该竞争性继续申请的总体目标是在SIV感染的恒河猴模型中研究HIV诱导的肠道粘膜对细菌病原体的前线防御机制功能障碍。该提案利用了我们在SIV模型中的肠道致病性研究的经验;通过多色流式细胞术进行免疫表型分析;用于粘膜反应和细菌易位的体内研究的连接肠袢模型;分离的粘膜细胞的高通量基因表达谱，以及可视化多种细胞类型的成像技术。我们建议确定在原发性和慢性SIV感染期间SIV感染对肠粘膜中DC的表型和功能特征的影响（具体目标1）。我们的研究将利用一种创新的结扎回肠环模型，在同一动物的小肠内建立多达12个独立的、分离的体内实验环境，以研究树突状细胞和CD 4 + Th 17细胞对SIV感染动物和健康未感染对照中肠道病原体或管腔益生菌的攻击的分子机制（具体目标2）。拟议的研究将为一线肠道粘膜反应的分子相关性提供重要的见解，这些分子相关性可以确定治疗性增强DC功能和改善对病毒和继发性病原体的粘膜免疫的新靶点。 公共卫生相关性：病毒储库的持续存在和慢性免疫激活对实现HIV感染患者的完全免疫恢复构成了重大挑战，即使在长期治疗期间也是如此。前线粘膜免疫防御在预防和限制HIV感染以及控制肠道病原体的传播和微生物易位中至关重要。HIV引起粘膜防御的破坏，导致肠道和管腔微生物的定植和微生物移位。这有助于HIV感染中的慢性免疫激活和免疫功能障碍，并支持病毒持续存在，尽管机制尚未完全确定。拟议的研究将在SIV感染的恒河猴模型中研究HIV诱导的肠道粘膜对细菌病原体的前线反应功能障碍，并确定导致宿主无法控制这些感染的机制。深入了解对维持肠道粘膜健康至关重要的粘膜免疫防御，对于确定粘膜保护免受病毒和合并感染的治疗靶点至关重要。

DESCRIPTION (provided by applicant): The frontline mucosal immune defenses are crucial in preventing and limiting HIV infection and controlling spread of enteric pathogens and microbial translocation. HIV causes breach in the mucosal defense leading to colonization and microbial translocation of enteric and luminal microbes. This contributes to chronic immune activation and immune dysfunction in HIV infection and supports viral persistence, although mechanisms have not been fully defined. Dendritic cells (DC) are an important component of the mucosal frontline defense but are under-investigated in HIV pathogenesis. Since the early mucosal response is well orchestrated, highly regulated and involves a rapid cross talk among the frontline mucosal cells, an experimental model representing an in vivo gut microenvironment is required to investigate early mucosal responses to HIV and microbes. We propose to utilize a novel in vivo intestinal loop model in SIV infected rhesus macaques to capture early events of host-microbe interactions at the mucosal site and characterize the responses of the key components of mucosal defense and the correlates of protection. Our previous studies identified blunted Th17 CD4+ T cell responses to Salmonella typhimurium infection in gut mucosa and systemic dissemination of the bacteria in SIV infected rhesus macaques but not in SIV-negative animals. We hypothesize that SIV infection causes DC dysfunction in the gut mucosa that leads to blunting of the Th17 CD4+ T cell response and contributes to the inability to prevent enteric pathogens and microbial translocation leading to chronic immune activation. The overall objective of this competing continuation application is to investigate HIV induced dysfunction in the frontline gut mucosal defense mechanisms to bacterial pathogens in the SIV infected rhesus macaque model. The proposal capitalizes on our experience of enteropathogenic studies in the SIV model; immunophenotypic analysis by multi-color flow cytometry; ligated intestinal loop model for in vivo studies of mucosal responses and bacterial translocation; high throughput gene expression profiling of isolated mucosal cells, and imaging technologies to visualize multiple cell types. We propose to determine the effects of SIV infection on the phenotypic and functional characteristics of DC in the gut mucosa during primary and chronic SIV infection (Specific Aim 1). Our investigation will utilize an innovative ligated ileal loop model that creates up to 12 independent, isolated in vivo experimental settings within the small intestine of the same animal to investigate the molecular mechanisms of dendritic cells and CD4+ Th17 cell responses to challenge from either enteric pathogens or luminal probiotic bacteria in SIV infected animals and healthy uninfected controls (Specific Aim 2). Proposed studies will provide important insights into molecular correlates of frontline gut mucosal responses that may identify novel targets for therapeutically enhancing DC functions and improving mucosal immunity against both virus and secondary pathogens. PUBLIC HEALTH RELEVANCE: The persistence of viral reservoirs and chronic immune activation pose major challenges for achieving complete immune recovery in HIV infected patients, even during long-term therapy. The frontline mucosal immune defenses are crucial in preventing and limiting HIV infection and controlling spread of enteric pathogens and microbial translocation. HIV causes breach in the mucosal defense leading to colonization and microbial translocation of enteric and luminal microbes. This contributes to chronic immune activation and immune dysfunction in HIV infection and supports viral persistence, although mechanisms have not been fully defined. The proposed studies will investigate HIV induced dysfunction in the frontline gut mucosal responses to bacterial pathogens in the SIV infected rhesus macaque model and determine the mechanisms contributing to the inability of the host to control these infections. Gaining insights into the mucosal immune defenses critical in maintaining gut mucosal health will be crucial in identifying therapeutic targets for mucosal protection against the virus and co-infections.