Increased resistance to low pH to improve Salmonella vaccine immunogenicity

描述（由申请人提供）：胃的低pH值为宿主提供了一个防止感染的保护屏障，必须克服这个屏障才能使口服疫苗有效。沙门氏菌和其他肠道细菌已经发展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，导致一些基因的上调，促进其与宿主的相互作用。重组减毒沙门氏菌疫苗是一种有效且廉价的方法，可引起强烈的粘膜和体液免疫反应。然而，许多伤寒沙门氏菌疫苗比野生型菌株对酸更敏感，效果较差。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。我们将研究如何增强疫苗株的耐酸性，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系统，以提高其表达和活性，并从其他细菌中引入两个耐酸系统。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增强耐酸能力的能力。我们将开发一种“低pH值”小鼠系统，我们将在其中模拟人类胃的pH值，为我们提供一个体内系统来测试耐酸菌株。我们将评估耐酸对口服鼠伤寒沙门氏菌菌株免疫原性的影响，这些菌株的基因型与目前一些重组和非重组鼠伤寒沙门氏菌候选疫苗相似。增强抗酸能力是降低伤寒沙门氏菌活疫苗有效剂量和增强免疫原性的一种手段。

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.