Cross-Protective Vaccines vs. Emerging Infectious Agents

描述(由申请人提供)：针对多种毒株的疫苗的开发对防御生物制剂和新出现的传染病至关重要，因为感染几种不同的毒株可能会超过单一疫苗引发的免疫力，而致病毒株可能会在接种疫苗的个体中发展，从而使我们当前的疫苗无效。这项提议的长期目标是开发安全的疫苗，并赋予对各种传染病病原体的有效交叉保护免疫力。最近，我们和其他人发现，缺乏功能性DNA腺嘌呤甲基酶(DAM)的鼠伤寒沙门氏菌的毒力显著减弱，并诱导出对亲本DAM+株攻击的有效保护性免疫状态。(目的1)我们计划评估减毒鼠伤寒沙门氏菌如何影响幼稚宿主的天然防御，以及它们如何影响专业抗原提呈细胞将抗原递呈给幼稚的CD4+和CD8+T细胞。我们还将分析口服鼠伤寒沙门氏菌的Aroa、DAM、Aroa Dam、Dam过量(DamOP)或Aroa DamOP突变株是否会在幼稚宿主中诱导系统和粘膜表面的持久细胞介导和体液免疫反应的存在。(目的2)治疗指数，即治疗效果与毒性的比率，决定了沙门氏菌疫苗的成功。目前，最有希望的候选基因包括突变菌株，其产物涉及关键生物合成途径的基因(Aroa Arod)、调节基因(cyA-CRP和Phop PhoQ)、以及编码应激蛋白(HtrA)的基因及其组合。在这里，我们建议结合这些减毒突变中的一个或多个来评估DAM突变株的安全性和有效性。(目的3)我们的数据表明，在伤寒的小鼠和禽类模型中，单次口服丹姆沙门氏菌或Damop鼠伤寒沙门氏菌可引起对一种以上沙门氏菌株的显著但不完全的交叉保护免疫。我们建议确定dam-或DamOP突变体的多次免疫，单独或联合使用，是否能够针对多个沙门氏菌临床分离株产生强大的交叉保护性免疫反应。目的(4)沙门氏菌DAM突变株诱导的免疫力增强，增加了微生物感染源的乘客抗原在DAM突变疫苗表达后，对同源病原体产生保护性免疫应答的可能性。我们将重点介绍来自假结核耶尔森菌的LcrV乘客抗原，因为它是一种已知的免疫原，也是一种毒力因子，需要将效应蛋白分泌到靶细胞中，并激发前抑制反应。我们建议在沙门氏菌DAM突变疫苗中表达假结核杆菌LcrV，并在耶尔森菌菌血症小鼠模型上测试接种疫苗的动物对假结核杆菌感染的保护作用。

DESCRIPTION (provided by applicant): The development of vaccines that protect against more than one strain is paramount to the defense against biowarfare agents and emerging infectious diseases as infection with several different strains may override the immunity elicited by a single vaccine, and pathogenic strains can develop in vaccinated individuals that make our current vaccines ineffective. The long-range objective of this proposal is to develop vaccines that are safe, and confer a potent state of cross-protective immunity against a variety of infectious agents. It has recently been established by us and others that S. typhimurium lacking a functional DNA adenine methylase (Dam) are significantly attenuated for virulence and elicit a potent state of protective immunity against challenge with the parental dam+ strain. (AIM 1) We plan to evaluate how attenuated strains of S. typhimurium influence innate defenses of naive hosts, and how they influence professional antigen-presenting cells to present antigens to naive CD4+ and CD8+ T cells. We will also analyze whether oral vaccination with aroA, dam, aroA dam, Dam overproducing (DamOP), or aroA DamOP mutants of S. typhimurium will induce in naive hosts the presence of long lasting cell-mediated and humoral immune responses, both systemically and at the mucosal surfaces. (AIM 2) The therapeutic index, or the ratio of the efficacy of the therapy over the toxicity, determines the success of Salmonella based vaccines. Currently, the most promising candidates include strains harboring mutations in genes whose products are involved in key biosynthetic pathways (aroA aroD), regulatory genes (cya crp and phoP phoQ), and genes encoding stress proteins (htrA) and combinations of these mutations. Here we propose to evaluate the safety and efficacy of dam mutant strains in combination with one or more of these attenuating mutations. (AIM 3) Our data show that a single oral immunization of dam- or DamOP S. typhimurium elicits significant but incomplete cross-protective immunity to more than one Salmonella strain in murine and avian models of typhoid fever. We propose to determine if multiple immunizations of dam- or DamOP mutants, alone and in combination, can confer strong cross-protective immune responses against multiple Salmonella clinical isolates. (AIM 4) The heightened immunity elicited by Salmonella dam mutant strains raises the possibility that passenger antigens from microbial infectious agents, when expressed by dam mutant vaccines, will elicit a protective immune response against the cognate pathogens. We will focus on the LcrV passenger antigen from Yersinia pseudotuberculosis since it is a known immunogen, and a virulence factor required for secretion of effector proteins into target cells and elicitation of pro-inhibitory responses. We propose to express Y. pseudotuberculosis LcrV in Salmonella dam mutant vaccines, and test whether vaccinated animals are protected against Y. pseudotuberculosis infection in a mouse model for Yersinia bacteremia.