Identification and functional analysis of non-antigenic factors of intracellular bacteria essential for the induction of cell-mediated protective immunity

本研究探讨了细胞内细菌抗原以外的因子在诱导T细胞介导的保护性免疫中的作用及其机制。研究结果总结如下：1。内源性γ-干扰素-γ (IFN-γ)的产生对于诱导th1依赖性细胞内细菌免疫至关重要。在这个过程中，IL-12在巨噬细胞产生的各种细胞因子中起重要作用。其中一种非抗原因子，来自单核增生李斯特菌的LLO，具有很强的诱导细胞因子的能力。在体内使用脂质体包裹的LLO，可以诱导内源性细胞因子达到与活菌（实际感染）免疫诱导水平相当的水平。应用脂质体包封的低聚脂作为佐剂，低聚脂加灭菌或低聚脂阴性菌株免疫小鼠后可诱导产生较强的保护性免疫，单独使用时均不能诱导产生保护作用。TH-1依赖性保护归因于主要由IFN-γ诱导的巨噬细胞活化。在活化的巨噬细胞中，细菌杀伤增强的表达是由于活性氧中间体或活性氮中间体，这取决于活化的时间和巨噬细胞水平的细菌感染。申氏孢子丝（一种可能的细胞内寄生真菌）的感染似乎与上述机制相似。在LLO诱导IFN-γ的过程中，IL-12和IL-18在LLO刺激巨噬细胞的初始阶段都是非常重要的。初步推测，膜上的15000 kDa蛋白参与了初始触发。在LLO分子的4个结构域中，第4个结构域对膜损伤的表达是必不可少的。相反，结构域1到3似乎对细胞因子诱导能力的表达至关重要。

This study investigated the mechanism and the role of factors other than antigens from intracellular bacteria in the induction of T cell-mediated protective immunity. Results summarized as follows have been obtained.1. The endogenous production of γ-interferon-γ (IFN-γ) was essential for the induction of TH1-dependent immunity against intracellular bacteria. In this process, IL-12 was important among various cytokines produced by macrophages.2. One of the non-antigenic factor, LLO from Listeria monocytogenes, was highly capable of inducing cytokines. By using the liposome-encapsulated LLO in vivo, it was possible to induce the endogenous cytokines to the level comparable to that induced by immunization with viable bacteria (actual infection).3. Application of liposome-encapsulated LLO as a sort of adjuvant, a strong protective immunity could be induced after immunization of mice with LLO plus killed bacteria or LLO-negative strain, both of which are incapable of inducing protection if used alone.4. TH-1 dependent protection was ascribed to the activation of macrophages mainly induced by IFN-γ. The expression of enhanced bacterial killing in activated macrophages was due either to reactive oxygen intermediates or to reactive nitrogen intermediates, depending on the timing of activation and bacterial infection in macrophage level.5. A mechanism similar to the above appeared to be involved in the infection by Sporothrix schenkii, a possible intracellular parasitic fungus.6. In the induction of IFN-γ by LLO, both IL-12 and IL-18 were highly essential at the initial stage of macrophage stimulation by LLO. It was suggested that 15,000 kDa protein of the membrane was involved in the initial triggering.7. Among 4 domains of LLO molecule, 4th domain was indispensable for the expression of membrane damage. In contrast, domains 1 through 3 seemed to be essential for the expression of cytokine-inducing ability.