Novel Vaccine Strategy for Listeria monocytogenes

描述(由申请人提供)： 单核细胞增多性李斯特菌是一种细胞内细菌病原体，可导致孕妇、老年人、婴儿和免疫功能低下的人患上严重的食源性疾病。在所有已报告的食源性疾病中，单核细胞增多性乳杆菌感染的病死率最高。在标准的实验室条件下，单核细胞增多性乳杆菌可以很容易地在宿主细胞外培养，这使得单核细胞增多性乳杆菌成为一个重大的公共卫生风险和作为生物武器制剂的一个重大潜在威胁。动物模型表明，对单核细胞增多性李斯特菌的保护性免疫是由CD8+效应细胞介导的，CD8+效应细胞识别并清除受感染的宿主细胞。疫苗研究表明，刺激保护性CD8+效应细胞需要亚临床感染活细菌。然而，作为疫苗策略，用完全能够在细胞内复制的毒力细菌免疫人类会对任何人群施加重大的健康风险，特别是对那些天生有感染单核细胞增多性李斯特菌的人。我们最近开发了一种新的策略来生成复制缺陷细菌疫苗载体，该载体能够刺激保护性CD8+效应细胞反应。这项提议的重点是利用这种方法来生产能够产生保护性CD8+效应细胞反应的非复制型单核细胞增多性李斯特菌疫苗株。在特定的目标I中，我们将构建非复制型单核细胞增多性李氏杆菌疫苗载体，将保护性的天然细菌抗原传递到专业和非专业抗原提呈细胞(APC)的胞浆中，以进行内源性加工和MHC I类递呈。在特定的目标II中，我们将确定抗原递送到APC的动力学以及有效递送抗原所需的细菌生存能力。在特定的目标III中，我们将确定疫苗结构的摄取是否使单核细胞增多性乳杆菌特异性效应细胞识别的APC变得敏感。在特定的目标IV中，我们将确定复制缺陷疫苗构建体免疫后抗原特异性效应细胞是否被刺激，并评估对保护性抗李斯特菌免疫的刺激。我们的目标是，在完成拟议的研究后，将确定一种安全有效的复制缺陷疫苗配方，适合临床试验。也可以预见，这些研究将为使用类似方法开发针对其他细胞内病原体的复制缺陷疫苗载体提供基础。

DESCRIPTION (provided by applicant): Listeria monocytogenes is an intracellular bacterial pathogen that causes serious foodborne illness in pregnant women, the elderly, infants and immunocompromised individuals. L. monocytogenes infections have the highest case fatality rate of all reported foodborne illnesses. L. monocytogenes can be easily cultured outside of host cells under standard laboratory conditions, making L. monocytogenes a significant public health risk and a significant potential threat as a biological weapons agent. Animal models show that protective immunity to L. monocytogenes is mediated by CD8+ effector cells that recognize and eliminate infected host cells. Vaccine studies have demonstrated that stimulation of protective CD8+ effector cells requires subclinical infection with live bacteria. However, immunization of humans with virulent bacteria fully capable of intracellular replication imposes a significant health risk to any population as a vaccine strategy, especially for those individuals inherently at risk to L. monocytogenes infection. We have recently developed a novel strategy for the generation of replication-deficient bacterial vaccine vectors that are capable of stimulating protective CD8+ effector cell responses. The focus of this proposal is to utilize this approach to produce non-replicating L. monocytogenes vaccine strains capable of generating protective CD8+ effector cell responses. In Specific Aim I, we will construct non-replicating L. monocytogenes vaccine vectors to deliver protective native bacterial antigens to the cytosol of professional and nonprofessional antigen presenting cells (APC) for endogenous processing and MHC Class I presentation. In Specific Aim II, we will determine the kinetics of antigen delivery to APC and the requirement of bacterial viability for efficient antigen delivery. In Specific Aim III, we will determine whether uptake of the vaccine constructs sensitizes APC for recognition by L. monocytogenes-specific effector cells. In Specific Aim IV, we will determine whether antigen specific effector cells are stimulated following immunization with the replication-deficient vaccine constructs, and assess stimulation of protective antilisterial immunity. Our goal is that following completion of the proposed studies, a safe and effective replication-deficient vaccine formulation will be identified that is suitable for clinical trials. It is also envisioned that these studies will provide a foundation for the development of replication-deficient vaccine vectors against other intracellular pathogens using a similar approach.