Novel Vaccine Strategy for Listeria monocytogenes

单核细胞增多性李斯特菌是一种细胞内细菌病原体，可导致严重的食源性疾病， 孕妇、老年人、婴儿和免疫功能低下的个体。L.单核细胞增生性感染 在所有报告的食源性疾病中病死率最高。L.单核细胞增多症很容易 在标准实验室条件下在宿主细胞外培养，使L.单核细胞增多症 公共卫生风险和作为生物武器制剂的重大潜在威胁。动物模型显示， 对L.单核细胞增多症由CD8？效应细胞介导， 感染的宿主细胞疫苗研究表明，刺激保护性CD8效应细胞 需要活细菌的亚临床感染。然而，用强毒细菌对人类进行免疫， 能够在细胞内复制作为疫苗策略对任何群体都有显著的健康风险， 特别是对于那些天生就有患L的风险的人。单核细胞增多症我们最近开发了 一种用于产生复制缺陷型细菌疫苗载体的新策略， 刺激保护性CD8效应细胞反应。本建议的重点是利用这一办法， 产生非复制型L.能产生保护性CD8效应细胞的单核细胞增多性疫苗株 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 对专职和非专职抗原呈递细胞胞质溶胶的保护性天然细菌抗原 (APC)用于内源性加工和MHC I类呈递。在具体目标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存活力的要求。在 具体目标III，我们将确定疫苗构建体的摄取是否使APC识别敏感 由L.单核细胞生成特异性效应细胞。在特异性目标IV中，我们将确定抗原特异性 在用复制缺陷型疫苗构建体免疫后刺激效应细胞， 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，将确定一种安全有效的复制缺陷型疫苗制剂， 临床试验还设想这些研究将为发展 复制缺陷型疫苗载体针对其他细胞内病原体使用类似的方法。

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.