Pre-Exposure Prophylaxis Against Francisella tularensis

描述（由申请人提供）：土拉菌Francisella tularensis （Ft）引起土拉菌病，一种严重且可能致命的疾病。由于Ft具有非常高的传染性，导致高发病率和死亡率，相对容易培养和传播，并且以前曾被武器化，因此被列为a类潜在的生物恐怖主义制剂。由于暴露后预防并不是应对肺炎土菌病暴发的一种实用的公共卫生替代方法，因此需要一种安全有效的暴露前疫苗。这项应用的目标是研制一种比目前未经许可的、有毒的、不充分有效的疫苗（LVS）更安全、更有效的疫苗，以对抗雾化的Ft。我们的策略是利用一种减毒重组同源活载体——LVS疫苗的减毒形式（这种母疫苗已经在人体中进行了测试）——过度表达高度免疫保护性的Ft蛋白，如IglC，提出的第二代重组LVS （rLVS¿capB）疫苗将比LVS更安全，因为所提出的载体已被证明比LVS弱100万倍，但仍能诱导强烈的细胞介导和体液免疫反应。拟议的第二代rLVS¿capB疫苗将比LVS更有效，因为它将通过新的启动子过度表达大量具有高度免疫保护性的Ft蛋白。这种土拉菌病疫苗的策略模仿了在该实验室成功开发出的第一批比目前的卡介苗更安全、更有效的结核病疫苗；其中一种结核病疫苗已在人体试验中显示出安全性和增强的免疫原性。在本应用中，为了实现比LVS更安全、更有效的兔热病疫苗的目标，我们建议在第一代rLVS¿capB疫苗取得初步成功的基础上，构建上述新的第二代rLVS¿capB疫苗并对其进行系统的稳定性测试；细胞外和细胞内蛋白表达；安全;免疫原性;以及在小鼠模型中对致命Ft攻击的近期和长期疗效。同时，我们将确定最佳的粘膜和全身给药途径。在完成这个项目时，我们预计会有一种比LVS更安全、更有效的疫苗，适合在人体中进行试验。虽然我们的资助重点是兔热病疫苗，但我们的方法一般适用于针对细胞内病原体的疫苗。因此，在研制成功的兔热病疫苗过程中吸取的经验教训和制定的战略可能广泛适用。

DESCRIPTION (provided by applicant): Francisella tularensis (Ft) causes tularemia, a serious and potentially fatal disease. Because Ft has an extraordinarily high infectivity, causes high morbidity and mortality, is relatively easily cultured and dispersed, and has previously been weaponized, it is classified as a Category A potential agent of bioterrorism. As post- exposure prophylaxis is not a practical public health alternative for countering an outbreak of pneumonic tularemia, a safe and effective pre-exposure vaccine is needed. The goal of this application is a safer and more potent vaccine against aerosolized Ft than the current unlicensed, toxic, and insufficiently effective vaccine (LVS). Our strategy is to utilize a live attenuated recombinant homologous vector - an attenuated form of the LVS vaccine (this parent vaccine has already been tested in humans) - to overexpress highly immunoprotective Ft proteins such as IglC, previously demonstrated in this laboratory to enhance protective immunity against aerosolized Ft. The proposed 2nd generation recombinant LVS (rLVS¿capB) vaccine will be safer than LVS because the proposed vector already has been demonstrated to be >10,000 times more attenuated than LVS and yet induce strong cell-mediated and humoral immune responses. The proposed 2nd generation rLVS¿capB vaccine will be more potent than LVS because it will overexpress large amounts of highly immunoprotective Ft proteins via novel promoters. This strategy for a tularemia vaccine mimics that used successfully in this laboratory to develop the first vaccines against tuberculosis that are safer and more potent than the current BCG vaccine; one of these tuberculosis vaccines has already demonstrated safety and enhanced immunogenicity in human trials. In this application, to accomplish our goal of a vaccine against tularemia that is safer and more potent than LVS, we propose to build upon our preliminary success with 1st generation rLVS¿capB vaccines by constructing the aforementioned new 2nd generation rLVS¿capB vaccines and testing them systematically for stability; protein expression extracellularly and intracellularly; safety; immunogenicity; and near-term and long- term efficacy against lethal Ft challenge in a mouse model. At the same time we shall determine optimal mucosal and systemic routes for administration. By the completion of this project, we anticipate having a vaccine that is substantially safer and more potent than LVS and suitable for testing in humans. While the focus of our grant is on a tularemia vaccine, our approach is applicable to vaccines against intracellular pathogens in general. Thus, lessons learned and strategies developed during the development of a successful tularemia vaccine are likely to be broadly applicable.