Intestinal cytokine and T cell homeostasis in SIV infection

描述（申请人提供）：前线粘膜免疫防御在预防和限制HIV感染，控制肠道病原体传播和微生物易位方面至关重要。HIV导致粘膜防御的破坏，导致肠道和肠道微生物的定植和微生物易位。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，并支持病毒持久性，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发病机制中的研究尚不充分。由于早期粘膜反应是精心安排的，高度调控的，并且涉及一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SIV感染的恒河猴体内建立一种新的肠环模型，以捕捉宿主-微生物在粘膜部位相互作用的早期事件，并表征粘膜防御的关键成分的反应和保护的相关因素。我们之前的研究发现，在SIV感染的恒河猴中，Th17 CD4+ T细胞对鼠伤寒沙门菌感染的肠道黏膜和细菌的全身传播反应减弱，而在SIV阴性的恒河猴中则没有。我们假设SIV感染导致肠道黏膜DC功能障碍，导致Th17 CD4+ T细胞反应钝化，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。

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.