The Role of Antibody-Mediated Protective Immunity Against Q fever

描述(申请人提供)：伯氏柯克斯体是一种专性细胞内革兰氏阴性细菌，可引起世界范围内的人畜共患病Q热。人类自然感染通常通过吸入传染性气雾剂发生，临床表现为非典型肺炎，并可发展为一种严重的、致命的慢性疾病。伯氏杆菌是一种未被充分研究的B类选择剂，在美国还没有获得许可的疫苗。创造一种安全有效的疫苗来预防人类Q热是一项重要的公共卫生和国家生物安全目标。该计划的长期目标是开发新的方法，以发现安全、有效的疫苗来治疗气雾剂传播的细胞内细菌病原体。这项应用的目的是确定抗体(Ab)介导的脂多糖(LPS)免疫在预防伯氏弧菌雾化肺部感染中的作用，这是迈向这一目标的重要一步。为了实现这一目标，我们将检验一个中心假设，即与伯氏梭菌I相内毒素结合的免疫球蛋白(PI-内毒素)在保护接种的宿主免受Q热侵袭方面发挥重要作用。这一假说的基础是观察到：1)被动转移从伯氏弧菌I期疫苗(PIV)免疫的小鼠中提纯的抗体对幼稚受体小鼠具有抵抗伯氏弧菌感染的保护作用；2)PI-LPS对伯氏弧菌攻击具有保护作用。为了验证这一假设，这一建议侧重于识别保护性抗体靶向的抗原，并了解抗体介导的针对伯氏梭菌气雾化保护性免疫的机制。该提案有两个具体目标：目标1：识别保护性抗体靶向的抗原。我们将鉴定保护性抗体识别的抗原，并确定伯氏梭菌PI-LPS是否是负责PIV诱导保护的关键保护性抗原。目的：探讨抗体介导的抗伯氏弧菌攻击的机制。我们将确定：1)保护性抗体是否激活补体，从而裂解细胞外的伯氏弧菌；2)抗体介导的保护是否依赖Fc受体介导的效应功能；3)抗体调理的伯氏杆菌是否增强巨噬细胞吞噬功能；4)干扰素？如果抗体介导的保护需要T细胞的帮助，则需要抗体介导的清除细胞内的伯氏梭菌和v)，并确定对抗体介导的保护重要的T细胞类型。作为这项研究的结果，我们希望确定PI-内毒素是否是预防Q热的靶标，并了解体液免疫和细胞免疫在疫苗诱导的保护性免疫中对伯氏梭菌感染的贡献。预计这将对人类(和动物)的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。与公共卫生相关：伯氏柯克斯体是一种未被研究的B类生物恐怖分子，可在人类中引起急性Q热和慢性感染。为了填补保护性免疫机制方面的基本知识空白，开发一种安全有效的Q热疫苗，本研究的重点是确定识别保护性抗体的抗原靶点，并了解抗体介导的保护性免疫的机制。

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.