Human Studies of Attenuated Salmonella Vectors

说明（申请人提供）：接种疫苗是一种有效而经济的预防疾病的方法。希望口服疫苗能得到最广泛的应用，并在粘膜表面诱导免疫。口服减毒活菌载体在动物模型中非常有效。本项目的目的是通过在人类志愿者中研究表达临床相关HIV-1抗原的鼠伤寒沙门菌原型疫苗生物体，获得鼠伤寒沙门菌载体的重要安全性和免疫原性数据。该提案描述了一个综合实验室和临床项目。该申请建议完成正在进行的表达HIV-1 Gag （CKS257）的鼠伤寒沙门菌载体的I期剂量递增研究，并描述了旨在增强人类对HIV-1 Gag免疫反应的后续研究。这些实验包括多次给药、经皮增强和研究“粘膜初始/全身增强”策略，如果可能的话。phoP/phoQ/ aroa缺失的细菌载体和表达系统是基于临床前实验室和动物研究选择的，这些研究表明该菌株是安全的，并且对载体抗原产生细胞免疫反应。phoP/phoQ和aroA基因对沙门氏菌在哺乳动物体内的持久性和毒力有重要影响；这些基因的缺失导致了主要的衰减。合理设计的HIV-1 Gag抗原在平衡致死质粒中表达，并通过III型分泌系统（TTSS）从沙门氏菌载体中分泌出来。在小鼠中，通过TTSS分泌的抗原比载体相关抗原产生更好的免疫反应和更大的疫苗效力。临床安全性和疫苗脱落被仔细评估，体液、粘膜和细胞免疫反应的载体和HIV-Gag被测量。此外，将在实验室产生新的结构，以临床测试一种在动物模型中增强沙门氏菌载体抗原的免疫原性的有希望的方法：从phop激活的启动子中驱动抗原，但从未在人类中进行过测试。这将需要使用不同于特性良好的PhoP/PhoQ零菌株的载体衰减策略，因此需要大量的临床前工作。该实验室在活细菌载体的转化研究方面有丰富的经验。该项目的主要目标是提供人类实际的安全性和免疫原性数据，这将有助于有效地指导活细菌载体的开发。

DESCRIPTION (provided by applicant): Vaccination is an effective and economical method of preventing disease. It is hoped that orally administered vaccines will have the widest application and induce immunity at mucosal surfaces. Live, orally administered attenuated bacterial vectors have been very effective in animal models. The purpose of this project is to gain important safety and immunogenicity data on Salmonella typhimurium vectors expressing a clinically relevant HIV-1 antigen by studying this prototype vaccine organism in human volunteers. The proposal describes an integrated laboratory and clinical project. The application proposes completion of an ongoing Phase I dose escalation study of a Salmonella typhimurium vector expressing HIV-1 Gag (CKS257), and describes follow-up studies designed to enhance immune responses to HIV-1 Gag in humans. These experiments include multi-dosing, transcutaneous boosting, and study of a "mucosal prime/systemic boost" strategy, if possible. The phoP/phoQ/aroA-deleted bacterial vector and expression system were chosen based upon pre-clinical laboratory and animal studies which suggest that this strain will be safe and engender cellular immune responses to the vectored antigen. The phoP/phoQ and aroA genes are important for Salmonella persistence/virulence within mammals; deletion of these genes results in major attenuation. A rationally-engineeered HIV-1 Gag antigen is expressed from a balanced-lethal plasmid and secreted from the Salmonella vector via the Type III Secretion System(TTSS). In mice, antigens secreted via the TTSS results in superior immune responses and greater vaccine efficacy than vector associated antigens. Clinical safety and vaccine shedding is carefully evaluated and humoral, mucosal and cellular immune responses to the vector and HIV-Gag are measured. In addition, new constructs will be generated in the laboratory to clinically test a promising approach which enhances the immunogenicity of Salmonella-vectored antigens in animal models, but has never been tested in humans: driving antigens from PhoP-activated promoters. This will necessitate using a vector attenuation strategy different from the well-characterized PhoP/PhoQ null strains, and therefore require significant preclinical work. The laboratory has significant experience in translational investigation of live bacterial vectors. The major goal of the project is to provide practical safety and immunogenicity data in humans which will help efficiently direct development of live bacterial vectors.