A Humanized Mouse Model to Study HIV/Mtb Co-infection

描述（由申请人提供）：人类免疫缺陷病毒（HIV）感染正在推动机会性结核病（TB）作为全球突发卫生事件的重新出现，并与多重或广泛耐药结核病（MDR-, XDR-TB）的发展密切相关。由于HIV对人类宿主的亲和性，目前还没有研究HIV/Mtb合并感染的动物模型。BLT人源化小鼠模型正迅速应用于研究几种缺乏合适动物模型的病原体，包括HIV、疟疾和HIV/HCV合并感染。本提案的目的是在人源化小鼠中建立HIV/Mtb合并感染的小动物模型，用于对Mtb疫苗开发至关重要的免疫学研究。在HIV/Mtb合并感染人源化小鼠模型中，中心假设是HIV感染会增加Mtb的发病机制，并降低疫苗诱导的对Mtb的细胞介导免疫。提出这项研究的基本原理是，人类HIV/Mtb合并感染的小动物模型将大大促进对HIV抑制Mtb CMI的这些机制和其他机制的了解，并加速针对HIV+人群的结核病疫苗的设计和筛选。验证这一中心假设的具体目的是：1)建立相关的小鼠模型来研究Mtb和HIV/Mtb感染的发病机制；2)确定HIV如何改变牛分枝杆菌bcg疫苗人源化小鼠对Mtb的保护性CMI。这些目标将通过使用植入人胎肝和胸腺组织的NOD-SCID/3cnull小鼠，并静脉注射来自同一组织来源的CD34+胎肝细胞来实现。通过体内荧光定量（tdTomato Mtb H37Rv）、病理和组织细菌负荷以及存活来监测HIV感染引起的结核分枝杆菌疾病严重程度的差异。未接种和卡介苗（热灭活）疫苗的动物因HIV引起的CMI变化将通过以下分析来确定：细胞因子谱；结核分枝杆菌感染部位的白细胞分布、组织及T细胞效应分子表达；CD4+和CD8+ T细胞对mtb感染巨噬细胞的体外抗细菌活性。拟议的工作将建立艾滋病毒/结核分枝杆菌合并感染的小动物模型，该模型具有确定的程度、时间过程和结核分枝杆菌所致疾病的结果。此外，将确定和评估疫苗接种后抗结核T细胞功能受损的具体机制，以保护人们免受结核分枝杆菌的攻击。这种共感染模型将成为发现共感染和疾病干预的基础生物学的有力研究工具。该模型的发展具有重要意义，因为这些结果将为确定HIV损害CMI对Mtb的保护性反应的机制提供新的机会。这一模式系统的积极影响将是大大提高设计和筛选用于艾滋病毒免疫系统受损人群的创新型结核病预防和治疗方法的能力。

DESCRIPTION (provided by applicant): Human immunodeficiency virus (HIV) infection is driving the re-emergence of opportunistic tuberculosis (TB) as a global health emergency, and is strongly associated with the development of multi- or extensively- drug resistant TB (MDR-, XDR-TB). Currently there are no animal models to study HIV/Mtb co-infection due to the human host tropism of HIV. The BLT humanized mouse model is being rapidly applied to study several pathogens where suitable animal models are deficient, including HIV, malaria, and HIV/HCV co-infection. The objective of this proposal is to develop a small animal model of HIV/Mtb co-infection in the humanized mouse for immunological studies critical to Mtb vaccine development. The central hypothesis is that HIV infection will increase the pathogenesis of Mtb and compromise vaccine-induced cell-mediated immunity to Mtb in a humanized mouse model of HIV/Mtb co-infection. The rationale for the proposed research is that a small animal model of human HIV/Mtb co-infection would greatly enhance progress towards understanding these and other mechanisms whereby HIV suppresses CMI to Mtb and accelerate design and screening of TB vaccines for HIV+ populations. The specific aims to test this central hypothesis are 1) To develop a relevant mouse model to study the pathogenesis of Mtb and HIV/Mtb infection and 2) To determine how HIV alters protective CMI to Mtb in M. bovis BCG-vaccinated, humanized mice. These aims will be accomplished by using the NOD-SCID/3cnull mouse engrafted with human fetal liver and thymic tissue, and injected intravenously with CD34+ fetal liver cells from the same tissue source. Differences in Mtb disease severity due to HIV infection will be monitored by in vivo fluorescent quantification (tdTomato Mtb H37Rv), pathology and bacterial load in tissues, and survival. Alterations in CMI in naive and BCG (heat-inactivated)-vaccinated animals due to HIV will be determined by analysis of: cytokine profiles; leukocyte distribution and organization, and T cell effector molecule expression, at sites of Mtb infection; and ex vivo antimycobacterial activity of CD4+ and CD8+ T cells against Mtb-infected macrophages. The proposed work will establish a small animal model of HIV/Mtb co-infection with a defined magnitude, time course, and outcome of disease due to Mtb. Further, specific mechanisms of post-vaccination antimycobacterial T cell function that are impaired by HIV will be identified and assessed relative to protection from Mtb challenge. This co-infection model will be a powerful research tool for discoveries in the basic biology of co-infection and disease intervention. Development of this model is significant, as these results will provide new opportunities to identify the mechanisms whereby HIV compromises the protective CMI response to Mtb. The positive impact of this model system will be greatly enhanced capabilities to design and screen innovative prophylactics and therapeutics for TB to use in populations with HIV-compromised immune systems. PUBLIC HEALTH RELEVANCE: The proposed research is relevant to public health because it will significantly advance our fundamental understanding of how HIV dysregulation of the immune system promotes the susceptibility to Mycobacterium tuberculosis. The results of these studies will enable informed guidance for the development of vaccines and therapeutics to protect HIV+ patients from tuberculosis.