Pre-Exposure Prophylaxis Against Francisella tularensis

描述(申请人提供)：图拉氏方济氏菌(Ft)引起图拉热症，这是一种严重的、可能致命的疾病。由于福尔马林具有极高的传染性，导致高发病率和死亡率，相对容易培养和分散，以前曾被武器化，因此被列为A类潜在生物恐怖主义毒剂。由于暴露后预防并不是对抗肺炎图拉热症暴发的切实可行的公共卫生替代方案，因此需要一种安全有效的暴露前疫苗。这项应用的目标是获得一种比目前无证、有毒和不够有效的疫苗(LVS)更安全、更有效的喷雾化Ft疫苗。我们的策略是利用活的减毒重组同源载体--LVS疫苗的减毒形式(这种母疫苗已经在人类身上进行了测试)--过表达高度免疫保护的Ft蛋白，如IglC，以前在实验室中证明了这种蛋白可以增强对雾化Ft的保护性免疫。拟议的第二代重组LVS(RLV？CAPB)疫苗将比LVS更安全，因为已经证明所建议的载体的减毒效果是LVS的10,000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RLV？CAPB疫苗将比LV更有效，因为它将通过新的启动子过度表达大量高度免疫保护的Ft蛋白。这种图拉热病疫苗的策略模仿了在本实验室成功使用的第一批结核病疫苗，这些疫苗比目前的卡介苗更安全、更有效；其中一种结核病疫苗已经在人体试验中证明了安全性和增强的免疫原性。在这项应用中，为了实现我们的目标，即研制出比LVS更安全、更有效的图拉热症疫苗，我们建议在我们第一代RLV？CAPB疫苗的初步成功的基础上，构建上述新的第二代RLV？CAPB疫苗，并在小鼠模型中系统地测试它们的稳定性、细胞外和细胞内的蛋白表达、安全性、免疫原性以及对抗致命Ft攻击的短期和长期疗效。同时，我们将确定最佳的粘膜和全身给药途径。到该项目完成时，我们预计将拥有一种比LVS更安全和更有效的疫苗，并适合在人体上进行试验。虽然我们的资助重点是图拉热病疫苗，但我们的方法适用于一般针对细胞内病原体的疫苗。因此，在开发一种成功的图拉热病疫苗的过程中吸取的经验教训和制定的战略很可能广泛适用。

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.