Mucosal live vector vaccine against recurrent Clostridium difficile infections

描述(由申请人提供)：细菌活载体疫苗代表了一种提供非凡灵活性的疫苗开发战略。在这种方法中，编码无关细菌、病毒或寄生虫的外来抗原的基因在减毒细菌疫苗株中表达，该疫苗株将这些外来抗原输送到免疫系统，从而引发相关的免疫反应。伤寒减毒沙门氏菌活载体疫苗的研制已取得重大进展。在基因稳定表达载体、提高外来抗原特异性免疫的抗原输出系统以及在小鼠和非人类灵长类动物中建立鼻腔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。对于未来的临床试验至关重要的是，最近设计了非抗生素质粒选择系统来提高这些疫苗的安全性。这项研究计划的广泛假设是，通过对伤寒沙门氏菌活载体平台技术的适当操作，我们可以构建一种粘膜接种的多价疫苗来免疫反复发作的艰难梭菌感染(Clostridium Difficile Inhibition，RCDI)。为了实现这一目标，我们将在单个菌株中设计基于非抗生素质粒的和新的染色体表达系统，以协同表达艰难梭菌三种毒素：肠毒素A和B以及二元毒素的无毒细胞结合域。该活载体株的免疫原性将通过小鼠鼻内免疫原性模型和基于异源Prime/Boost方法的疫苗策略来确定，在该方法中，艰难梭菌抗原以活载体和纯化蛋白递送的方式依次免疫宿主。有希望的候选者将对所有三种艰难梭菌抗原产生抗体反应，并将进一步在用多价菌株免疫的小鼠身上进行保护测试，并用艰难梭菌流行菌株的孢子对其进行口腔学攻击。

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.