Increased resistance to low pH to improve Salmonella vaccine immunogenicity

描述（由申请方提供）：胃的低pH值为宿主提供了感染的保护屏障，必须克服这种低pH值才能使口服疫苗有效。沙门氏菌和其他肠道细菌已经开发出克服这种恶劣环境的策略。在沙门氏菌中，低pH值也作为进入细菌的信号，导致许多促进其与宿主相互作用的基因上调。重组减毒沙门氏菌疫苗是一种有效且廉价的方法，可以引起强烈的粘膜和体液免疫应答。然而，许多伤寒沙门氏菌疫苗比野生型菌株对酸更敏感，并且效力差。目前的策略依赖于中和或绕过胃酸的方法，这可能导致疫苗刺激强烈免疫反应的能力降低。我们将研究增强疫苗株耐酸性的方法，以消除中和或绕过胃的低pH环境的需要。我们将修改现有的沙门氏菌耐酸性系统，以上调其表达和活性，并从其他细菌中导入两个耐酸性系统。我们将在几种不同的减毒酸敏感沙门氏菌菌株中评估这些系统在体外赋予增加的耐酸性的能力。我们将开发一种“低pH”小鼠系统，在该系统中，我们将模拟人类胃的pH值，为我们提供一种体内系统来测试耐酸菌株。我们将评估耐酸性对口服S.与目前一些重组和非重组S.伤寒疫苗候选人。增加耐酸性代表了降低有效剂量和增强活S的免疫原性的手段。伤寒疫苗。 公共卫生相关性：表达异源抗原基因的有效活重组减毒沙门氏菌疫苗有望提供低成本、口服给药、针对多种疾病的终身保护。然而，虽然在动物模型中有效，但由于疫苗的免疫反应较差，人体试验的结果令人失望。该项目的目标是通过增加对人类胃的低pH环境的抵抗力来增强活的口服沙门氏菌疫苗的免疫原性。

DESCRIPTION (provided by applicant): The low pH of the stomach provides the host with a protective barrier to infection and must be overcome to allow oral vaccines to be effective. Salmonella and other enteric bacteria have developed strategies to surmount this harsh environment. In Salmonella, low pH also serves as a signal to the incoming bacterium resulting in the up regulation of a number of genes that facilitate its interaction with the host. Recombinant attenuated Salmonella vaccines are an effective and inexpensive way to elicit strong mucosal and humoral immune responses. However, many Salmonella Typhi vaccines are more sensitive to acid than the wild-type strain and have poor efficacy. Current strategies rely on ways to neutralize or by-pass stomach acid, which may result in reduction of the vaccine's ability to stimulate a strong immune response. We will investigate ways to enhance the acid resistance of vaccine strains to eliminate the need for neutralizing or bypassing the low pH environment of the stomach. We will modify an existing Salmonella acid resistance system to up regulate its expression and activity and import two acid resistance systems from other bacteria. We will evaluate these systems in several different attenuated, acid sensitive Salmonella strains for the ability to confer increased acid resistance in vitro. We will develop a 'low pH' mouse system in which we will model the pH of the human stomach providing us with an in vivo system to test the acid-resistant strains. We will evaluate the effects of acid-resistance on the immunogenicity of orally administered S. Typhimurium strains with genotypes similar to some current recombinant and non-recombinant S. Typhi vaccine candidates. Increasing acid resistance represents a means to reduce the efficacious dose and enhance the immunogenicity of live S. Typhi vaccines. PUBLIC HEALTH RELEVANCE: Effective live recombinant attenuated Salmonella vaccines expressing heterologous antigen genes hold the promise of providing low cost, orally administered, life-long protection against a variety of diseases. However, while effective in animal models, the results from human trials have been disappointing due to poor immune responses in vaccines. The goal of this project is to enhance the immunogenicity of live, oral Salmonella vaccines by increasing resistance to the low pH environment of the human stomach.