Live Attenuated Recombinant Bacterial Delivery of Polysaccharide Vaccine Antigens

描述(由申请人提供)：细菌多糖是疫苗开发的极佳靶标，因为它们暴露在表面，通常是病原体上表达的最具保护性的抗原。然而，纯化的多糖通常是免疫原性差的，特别是如果它们的免疫原性不能通过与蛋白质的结合而增强的话。这种多糖-蛋白质结合疫苗往往生产复杂、成本高昂，而且很难交付。为了证明一种利用多糖作为候选疫苗的新方法的潜力，我们在减毒鼠伤寒沙门氏菌上表达了铜绿假单胞菌脂多糖(IPS)的O抗原部分。我们在小鼠模型系统中比较了不同的免疫途径来预防急性铜绿假单胞菌肺炎，发现鼻腔注射疫苗比口服或腹腔注射提供了更好的保护。然而，我们不知道是否是抗体反应的位置、水平和/或类型负责这种保护。我们还发现，鼻腔注射该疫苗可以保护小鼠免受角膜创伤或烧伤后铜绿假单胞菌的感染，但尚不知道在这些不同部位诱导免疫的最佳途径，也不知道囊性纤维化等宿主因素对减毒重组鼠伤寒沙门氏菌诱导免疫的调节作用。同样不清楚的是，这种疫苗是否可以缓解与多糖-蛋白质结合疫苗相关的问题，包括亚型特异性和亚型抑制，以及排除对酸敏感的O抗原。这笔拨款的具体目的是(1)确定重组鼠伤寒沙门氏菌O抗原疫苗介导的对铜绿假单胞菌急性肺炎的保护性免疫的基础，(2)确定预防角膜损伤或烧伤后铜绿假单胞菌感染的最佳免疫途径，(3)确定疫苗是否能保护CF小鼠免受铜绿假单胞菌肺部感染，以及(4)测试其他基于O抗原的疫苗的多糖表达、免疫原性和保护作用。总体而言，该项目的长期目标是了解针对这些不同感染的保护基础，这反过来将使我们能够为针对这种重要的机会性病原体的疫苗开发制定合理的战略。我们预计，这一知识也将适用于其他病原体。

DESCRIPTION (provided by applicant): Bacterial polysaccharides are excellent targets for vaccine development as they are surface exposed and often the most protective antigens expressed on a pathogen. However, purified polysaccharides are generally poor immunogens, particularly if their immunogenicity is not enhanced by conjugation to a protein. Such polysaccharide-protein conjugate vaccines are often complicated and expensive to produce and difficult to deliver. In order to demonstrate the potential of a novel approach to utilize polysaccharides as vaccine candidates, we have expressed the O antigen portion of Pseudomonas aeruginosa lipopolysaccharide (IPS) on an attenuated strain of Salmonella typhimurium. We compared different routes of immunization to protect against acute P. aeruginosa pneumonia in a mouse model system and found that intranasal administration of the vaccine provides better protection than either oral or intraperitoneal delivery. However, we do not know whether it is the location, level, and/or type of antibody response that is responsible for this protection. We have also shown that intranasal delivery of this vaccine can protect mice against P. aeruginosa infections after corneal trauma or after burns, but do not know the optimal route of immunization to induce immunity at these different sites, nor do we know the effect of host factors such as cystic fibrosis on modulating the immunity induced by the attenuated recombinant S. typhimurium. Also unclear is whether such vaccines can alleviate problems associated with polysaccharide-protein conjugate vaccines including subtype specificity and subtype inhibition, and the exclusion of acid-liable O antigens. The specific aims of this grant are to (1) determine the basis for protective immunity to P. aeruginosa acute pneumonia mediated by the attenuated recombinant S. typhimurium O antigen-based vaccine, (2) determine the optimal route of immunization to protect against P. aeruginosa infections after corneal injury or burns, (3) determine whether the vaccine can protect CF mice from P. aeruginosa lung infections, and (4) test additional O antigen-based vaccines for polysaccharide expression, immunogenicity, and protection. Overall, the long-term goal of this project is to understand the basis of protection against these varied infections, which in turn will allow us to develop rational strategies for vaccine development against this important opportunistic pathogen. We anticipate that this knowledge will also be applicable to other pathogens.