Novel Vaccine Strategy for Listeria monocytogenes

描述（由申请人提供）： 单核细胞增生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者发生严重的食源性疾病。L.单核细胞增多症感染在所有报告的食源性疾病中病死率最高。L.单核细胞增多症可以在标准实验室条件下在宿主细胞外容易地培养，使得L.单核细胞增多症是一个重大的公共卫生风险，也是一个重大的生物武器战剂潜在威胁。动物模型表明，对L.单核细胞增多症由识别和消除受感染的宿主细胞的CD8+效应细胞介导。疫苗研究已经证明，保护性CD8+效应细胞的刺激需要活细菌的亚临床感染。然而，用完全能够在细胞内复制的毒力细菌免疫人类作为疫苗策略对任何人群都施加了显著的健康风险，特别是对于那些固有地处于L.单核细胞增多症我们最近开发了一种新的策略，用于产生能够刺激保护性CD8+效应细胞应答的复制缺陷型细菌疫苗载体。该方案的重点是利用这种方法生产非复制型L。单核细胞增多性疫苗株能够产生保护性CD8+效应细胞应答。在具体目标I中，我们将构建非复制L。单核细胞增多症疫苗载体将保护性天然细菌抗原递送至专职和非专职抗原呈递细胞（APC）的胞质溶胶以进行内源性加工和MHC I类呈递。在特异性目标II中，我们将确定抗原递送至APC的动力学和有效抗原递送的细菌活力的要求。在特异性目标III中，我们将确定疫苗结构的摄取是否使APC对L.单核细胞生成特异性效应细胞。在特异性目的IV中，我们将确定抗原特异性效应细胞在用复制缺陷型疫苗构建体免疫后是否被刺激，并评估保护性抗病毒免疫的刺激。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型疫苗制剂，适用于临床试验。还设想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型疫苗载体提供基础。

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.