The Role of Antibody-Mediated Protective Immunity Against Q fever

描述（由申请人提供）：伯氏克希菌是一种专性细胞内革兰氏阴性菌，引起世界性人畜共患疾病Q热。人类自然感染通常通过吸入传染性气溶胶发生，临床表现为非典型肺炎，并可发展为严重的致命慢性疾病。伯纳蒂胞杆菌是一种未充分研究的B类选择性病原体，在美国还没有获得许可的疫苗。研制一种安全有效的预防人类Q热的疫苗是一项重要的公共卫生和国家生物安全目标。该项目的长期目标是开发新的方法，以发现安全有效的疫苗，以防止气溶胶传播的细胞内细菌病原体。该应用程序的目的是确定抗体（Ab）介导的脂多糖（LPS）免疫在预防雾化伯纳氏梭菌肺部感染中的作用，这是实现这一目标的重要一步。为了实现这一目标，我们将验证免疫球蛋白结合伯氏胞杆菌I期LPS （PI-LPS）在保护接种过Q热疫苗的宿主中发挥重要作用的中心假设。这一假设是基于以下观察结果：1)从伯纳蒂胞杆菌i期疫苗（PIV）免疫小鼠中纯化的Ab被动转移，在未受感染的小鼠中具有对伯纳蒂胞杆菌感染的保护作用；2)PI-LPS具有对伯纳蒂胞杆菌攻击的保护作用。为了验证这一假设，本研究的重点是鉴定保护性抗体靶向的抗原，并了解抗体介导的针对雾化伯氏疏螺旋体的保护性免疫机制。该提案有两个具体目的：目的1：鉴定保护性抗体所靶向的抗原。我们将鉴定保护性抗体所识别的抗原，并确定伯纳氏C. PI-LPS是否是负责piv诱导保护的关键保护性抗原。目的2：确定抗体介导的抗肺伯氏原体攻击的保护机制。我们将确定i)保护性的Ab是否激活补体从而使胞外C. burnetii溶解，ii) b .介导的保护是否依赖于Fc受体介导的效应功能，iii) b . opsonized burnetii是否增强巨噬细胞吞噬，iv) IFN-？v)如果抗体介导的保护需要T细胞的帮助，并且识别对抗体介导的保护很重要的T细胞类型。作为这项研究的结果，我们希望确定PI-LPS是否是Q热保护的靶标，并了解体液和细胞免疫在疫苗诱导的针对伯纳蒂胞杆菌感染的保护性免疫中的作用。预计这将对人类（和动物）健康产生重大的积极影响，因为它将为Q热的疫苗设计和基于抗体的免疫治疗策略提供信息，并反过来导致开发新的策略来干扰其他危险的细胞内细菌病原体的气溶胶传播。公共卫生相关性：伯纳蒂克希菌是一种未充分研究的B类生物恐怖制剂，可引起人类急性Q热和慢性感染。为了填补保护性免疫机制的基本空白，开发安全有效的Q热疫苗，本研究将重点寻找识别保护性抗体的抗原靶点，了解抗体介导的抗伯纳蒂胞杆菌气溶胶感染的保护性免疫机制。

DESCRIPTION (provided by applicant): Coxiella burnetii is an obligate intracellular gram-negative bacterium that causes the worldwide zoonotic disease, Q fever. Natural human infections commonly occur via inhalation of infectious aerosols, manifest clinically as atypical pneumonia, and can develop into a severe, fatal chronic disease. C. burnetii is an understudied category B select agent, and there is no licensed vaccine in the US. Creation of a safe and effective vaccine for preventing human Q fever is an important public health and national biosecurity goal. The long-term goal of this program is to develop new approaches to discovery of safe, effective vaccines to aerosol-transmitted intracellular bacterial pathogens. The objective of this application, which is an important step toward this goal, is to determine the role of antibody (Ab)-mediated immunity to lipopolysaccharide (LPS) in protection against pulmonary infection with aerosolized C. burnetii. To achieve this objective, we will test the central hypothesis that immunoglobulins that bind to C. burnetii phase I LPS (PI-LPS) play an important role in protecting vaccinated hosts against Q fever. This hypothesis is based on observations that i) passive transfer of Ab purified from C. burnetii phase I vaccine (PIV)-immunized mice conferred protection against C. burnetii infection in naive recipient mice, and ii) PI-LPS conferred protection against C. burnetii challenge. To test this hypothesis, this proposal focuses on identifying antigens targeted by protective Ab and understanding the mechanisms of Ab-mediated protective immunity against aerosolized C. burnetii. The proposal has two specific aims: Aim 1: to identify antigens targeted by protective Ab. We will identify the protective Ab-recognized antigens and determine if C. burnetii PI-LPS is the key protective antigen responsible for PIV-induced protection. Aim 2: to determine the mechanisms of Ab-mediated protection against pulmonary C. burnetii challenge. We will determine i) if protective Ab activates complement and thus lysis of extracellular C. burnetii, ii) if Ab-mediated protection depends on Fc receptor-mediated effector functions, iii) if Ab-opsonized C. burnetii enhances macrophage phagocytosis, iv) IFN-? is required for Ab-mediated clearance of intracellular C. burnetii and v) if Ab-mediated protection requires help from T cells and to identify the T cell types that are important for Ab-mediated protection. As an outcome of this research, we expect to determine if PI-LPS is a target in protection against Q fever and to understand the contribution of humoral and cellular immunity in vaccine-induced protective immunity against C. burnetii infection. This is expected to have significant positive effects on human (and animal) health, because it will provide information for vaccine design and Ab-based immunotherapeutic strategies for Q fever, and in turn lead to development of new strategies to interfere with aerosol transmission of other dangerous intracellular bacterial pathogens. PUBLIC HEALTH RELEVANCE: Coxiella burnetii is an understudied category B bioterrorist agent that causes acute Q fever and chronic infections in humans. To fill the fundamental gap in knowledge regarding the mechanisms of protective immunity and to develop a safe and effective vaccine against Q fever, this proposal focuses on identifying the antigenic targets that recognize the protective antibody and understanding the mechanisms of antibody-mediated protective immunity against C. burnetii aerosol infection.