Intestinal cytokine and T cell homeostasis in SIV infection

描述(由申请人提供)：前线粘膜免疫防御对于预防和限制艾滋病毒感染以及控制肠道病原体的传播和微生物易位至关重要。艾滋病毒导致粘膜防御的破坏，导致肠道和腔内微生物的定植和微生物移位。这有助于艾滋病毒感染中的慢性免疫激活和免疫功能障碍，并支持病毒的持久性，尽管机制尚未完全确定。树突状细胞(DC)是黏膜前线防御的重要组成部分，但在HIV发病机制中的研究还不够深入。由于早期的粘膜反应是精心安排的，高度调控的，涉及前线粘膜细胞之间的快速串扰，因此需要一个代表体内肠道微环境的实验模型来研究早期粘膜对HIV和微生物的反应。我们建议在感染SIV的恒河猴体内利用一种新的肠环模型来捕捉粘膜部位宿主-微生物相互作用的早期事件，并表征粘膜防御的关键成分和保护相关因素的反应。我们以前的研究发现，肠道粘膜中的鼠伤寒沙门氏菌对Th17CD4T细胞的反应迟钝，这种细菌在SIV感染的恒河猴中全身性传播，但在SIV阴性动物中不存在。我们假设SIV感染导致肠粘膜DC功能障碍，导致Th17 CD4T细胞反应迟钝，并导致无法阻止肠道病原体和微生物移位导致慢性免疫激活。 这一竞争性继续应用的总体目标是在SIV感染的恒河猴模型中研究HIV诱导的一线肠道粘膜防御机制对细菌病原体的功能障碍。该建议利用了我们在SIV模型中的肠道病理学研究的经验；多色流式细胞仪的免疫表型分析；用于在体研究粘膜反应和细菌易位的结扎肠环模型；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SIV感染对原发和慢性SIV感染期间肠粘膜DC的表型和功能特征的影响(特定目标1)。我们的研究将利用一种创新的结扎回肠回肠循环模型，在同一动物的小肠内创建多达12个独立的、隔离的在体实验环境，以研究SIV感染动物和健康未感染对照(特定目标2)中树突状细胞和CD4 Th17细胞对肠道病原体或腔内益生菌攻击的分子机制。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，可能确定在治疗上增强DC功能和提高针对病毒和继发性病原体的粘膜免疫力的新靶点。 公共卫生相关性：病毒库的持久性和慢性免疫激活对实现艾滋病毒感染患者的完全免疫恢复构成重大挑战，即使在长期治疗期间也是如此。前线粘膜免疫防御对于预防和限制艾滋病毒感染以及控制肠道病原体的传播和微生物易位至关重要。艾滋病毒导致粘膜防御的破坏，导致肠道和腔内微生物的定植和微生物移位。这有助于艾滋病毒感染中的慢性免疫激活和免疫功能障碍，并支持病毒的持久性，尽管机制尚未完全确定。这项拟议的研究将在SIV感染的恒河猴模型中调查HIV诱导的一线肠道粘膜对细菌病原体的反应障碍，并确定导致宿主无法控制这些感染的机制。深入了解粘膜免疫防御对维持肠道粘膜健康至关重要，这对于确定针对病毒和混合感染的粘膜保护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.