PROTECTIVE IMMUNE MECHANISMS IN HUMAN SHIGELLA VACCINES

口服志贺菌减毒活菌的临床试验 在CVD保护只有少数接种者从志贺氏菌病， 野生型的挑战。 在后续研究中，这些志愿者 再次挑战。 大多数接触过野生型志贺氏菌的人 没有受到疾病症状的影响。 这项研究证实 实地证据表明，保护可以通过 志贺氏菌感染 检测志贺氏菌抗体的存在 在这些志愿者中， 挑战之后。众所周知，细胞介导免疫 是抵御许多细胞内病原体的关键，包括 细菌 最近的研究表明，细胞介导的免疫可能 在防治志贺氏菌病方面发挥重要作用。这个目标 研究是评估系统性细胞介导的免疫是否与 预防志贺氏菌病。如果找到这样的参数， 大大增强了我们对潜在机制的理解 志贺氏菌病的保护和志贺氏菌疫苗的开发。 具体地，使用获得的外周血单核细胞（PBMC）， 来自用野生型和减毒株免疫的志愿者， S. flexneri 2a，我们建议：（1）测试假设，接种 使用减毒菌株或野生型福氏2a志贺菌的志愿者 循环中特异性细胞毒性T淋巴细胞出现 反应（CTL）。如果确实观察到CTL活性，我们将检测 假设这种免疫应答由CD 8+细胞介导， 它受到I类MHC分子的限制。 (2)检验这一假设 除了CTL应答， 减毒菌株或野生型福氏志贺菌2a使 增殖和产生特异性T淋巴细胞的循环 干扰素-γ（和1型细胞因子）对志贺氏菌应答 抗原 如果观察到增殖和/或细胞因子反应，我们 将检验这些免疫应答由CD 4+介导的假设 细胞，并受到II类MHC分子的限制。 (3)测试 假设CTL应答和/或干扰素-γ产生 与保护力相关，以攻击与毒性志贺氏菌菌株 通过将这些免疫效应器机制与保护相关联， 用野生型福氏志贺菌2a攻击的志愿者。 (4)确定 是否可以通过以下方法在志贺菌抗原中鉴定保护性表位： 研究PBMC来源的T细胞克隆的精细抗原特异性 从受保护或未受保护的志愿者中获得， 用野生型福氏志贺菌2a攻击。

Clinical trials of live attenuated Shigella strains administered orally at the CVD protected only a minority of vaccinees from shigellosis upon challenge with wild-type. In a follow up study, these volunteers were re-challenged. Most of these who had been exposed to wild-type Shigella were protected from the symptoms of the disease. This study confirms field evidence in suggesting that protection can be conferred by exposure to Shigella. The presence of antibodies to Shigella measured in these volunteers did not correlate with resistance to illness following challenge. It is well established that cell-mediated immunity is the key to protection against many intracellular pathogens, including bacteria. Recent studies have suggested that cell mediated immunity may play a significant role in combating shigellosis. The goal of this research is to assess whether systemic cell mediated immunity correlates with protection from shigellosis. If such a parameter is found it will considerably enhance our understanding of the mechanisms underlying protection in shigellosis and the development of Shigella vaccines. Specifically, using peripheral blood mononuclear cells (PBMC) obtained from volunteers immunized with both wild-type and attenuated strains of S. flexneri 2a, we propose to: (1) Test the hypothesis that inoculation of volunteers with attenuated strains or wild-type S.flexneri 2a elicits the appearance in circulation of specific cytotoxic T lymphocyte responses (CTL). If CTL activity is indeed observed, we will test the hypothesis that this immune response is mediated by CD8+ cells and that it is restricted by class I MHC molecules. (2) Test the hypothesis that, in addition to CTL responses, inoculation of volunteers with attenuated strains or wild-type S.flexneri 2a elicits the appearance in circulation of specific T lymphocytes that proliferate and produce interferon-gamma (and type-1" cytokines) in response to Shigella antigens. If proliferative and/or cytokine responses are observed, we will test the hypothesis that these immune response are mediated by CD4+ cells and are restricted by class II MHC molecules. (3) Test the hypothesis that CTL responses and/or interferon-gamma production correlates with protection to challenge with virulent Shigella strains by correlating these immune effector mechanisms with protection in volunteers challenged with wild-type S.flexneri 2a. (4) Determine whether protective epitopes can be identified in Shigella antigens by studying the fine antigen specificity of T cell clones derived from PBMC obtained from volunteers that were protected or non-protected after challenge with wild-type S.flexneri 2a.