Mucosal live vector vaccine against recurrent Clostridium difficile infections

描述（由申请人提供）：细菌活载体疫苗是一种具有特殊灵活性的疫苗开发策略。在这种方法中，编码不相关细菌、病毒或寄生虫病原体的外源抗原的基因在减毒细菌疫苗株中表达，该菌株将这些外源抗原传递给免疫系统，从而引发相关的免疫反应。在研制减毒沙门氏菌伤寒血清型活疫苗方面取得了重大进展。在遗传稳定表达质粒、抗原输出系统以提高外源抗原特异性免疫以及在小鼠和非人灵长类动物中建立鼻内模型以表征对这些活载体的粘膜、体液和细胞免疫反应方面取得了进展。对未来临床试验至关重要的是，非抗生素质粒选择系统最近被设计用于提高这些疫苗的安全性。本研究计划的主要假设是，通过适当操纵伤寒沙门氏菌血清型活载体平台技术，我们可以构建一种黏膜给药的多价疫苗，以免疫复发性艰难梭菌感染（RCDI）。为了实现这一目标，我们将在单一菌株中设计非抗生素质粒和新型染色体表达系统，以协同表达三种艰难梭菌毒素的无毒细胞结合域；肠毒素A和肠毒素B和二元毒素该活载体菌株的免疫原性将通过小鼠鼻内免疫原性模型和基于异源启动/增强方法的疫苗接种策略来确定，该方法采用活载体和纯化蛋白递送艰难梭菌抗原，依次免疫宿主。有希望的候选药物能够引发针对所有三种艰难梭菌抗原的抗体反应，将在同样用多价菌株免疫的小鼠和用艰难梭菌流行菌株的孢子攻击的小鼠中进一步测试其保护作用。

DESCRIPTION (provided by applicant): Bacterial live vector vaccines represent a vaccine development strategy that offers exceptional flexibility. In this approach, genes that encode foreign antigens of unrelated bacterial, viral or parasitic pathogens are expressed in an attenuated bacterial vaccine strain that delivers these foreign antigens to the immune system, thereby eliciting relevant immune responses. Significant progress has been made in the development of attenuated Salmonella enterica serovar Typhi live vector vaccines. Advances have been made in genetically stabilized expression plasmids, antigen export systems to improve foreign antigen-specific immunity, and the establishment of intranasal models in both mice and non-human primates for characterizing mucosal, humoral, and cellular immune responses to these live vectors. Of critical importance to future clinical trials, non-antibiotic plasmid selection systems have recently been engineered to improve the safety of these vaccines. The broad hypothesis of this research plan is that by appropriate manipulation of the Salmonella enterica serovar Typhi live vector platform technologies, we can construct a mucosally administered multivalent vaccine to immunize against recurrent Clostridium difficile infections (RCDI). To accomplish this, we will engineer within a single strain both non-antibiotic plasmid-based and novel chromosomal expression systems to express in concert the non-toxic cell-binding domains of three C. difficile toxins; enterotoxins A and B and binary toxin. The immunogenicity of this live vector strain will be determined using a murine intranasal model of immunogenicity, and a vaccination strategy based on a heterologous prime/boost approach in which the host is immunized sequentially with C. difficile antigens delivered both using live vectors and as purified proteins. Promising candidates eliciting antibody responses against all three C. difficile antigens will be further tested for protection in mice similarly immunized with he multivalent strain and challenged orogastrically with spores from an epidemic strain of C. difficile.