Cross-Protective Vaccines vs. Emerging Infectious Agents

描述（由申请人提供）：开发可预防多种菌株的疫苗对于防御生物战剂和新出现的传染病至关重要，因为几种不同菌株的感染可能会超越单一疫苗引起的免疫力，并且在接种疫苗的个体中可能产生致病性菌株，使我们目前的疫苗无效。这项建议的长期目标是开发安全的疫苗，并赋予针对各种感染原的有效交叉保护免疫状态。最近，我们和其他人已经证实，缺乏功能性DNA腺嘌呤甲基化酶（Dam）的鼠伤寒沙门氏菌的毒力显著减弱，并引发了一种强有力的保护性免疫状态，以抵抗亲本Dam +菌株的攻击。（AIM 1）我们计划评估鼠伤寒沙门氏菌减毒株如何影响幼稚宿主的先天防御，以及它们如何影响专业抗原呈递细胞向幼稚CD4+和CD8+ T细胞呈递抗原。我们还将分析口服接种鼠伤寒沙门氏菌的aroA、坝、aroA坝、坝过量（DamOP）或aroA DamOP突变体是否会在幼稚宿主体内诱导长期的细胞介导和体液免疫反应，包括全身和粘膜表面。治疗指数，即治疗效果与毒性的比值，决定了沙门氏菌疫苗的成功与否。目前，最有希望的候选菌株包括其产物涉及关键生物合成途径的基因突变（aroA aroD），调节基因（cya crp和phoP phoQ），编码应激蛋白的基因（htrA）和这些突变的组合。在这里，我们建议评估大坝突变株与这些减毒突变的一个或多个组合的安全性和有效性。（AIM 3）我们的数据表明，在小鼠和鸟类伤寒模型中，单次口服免疫dam-或DamOP鼠伤寒沙门氏菌可引起对一种以上沙门氏菌菌株的显著但不完全的交叉保护性免疫。我们建议确定是否对dam-或DamOP突变体进行多次免疫，单独或联合，可以对多种沙门氏菌临床分离株产生强烈的交叉保护免疫反应。（AIM 4）大坝突变沙门氏菌菌株引起的免疫增强提高了一种可能性，即当大坝突变疫苗表达来自微生物感染源的乘客抗原时，将引发针对同源病原体的保护性免疫反应。我们将重点关注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，也是将效应蛋白分泌到靶细胞和引发前抑制反应所需的毒力因子。我们建议在沙门氏菌突变疫苗中表达假结核耶尔森菌LcrV，并在小鼠耶尔森菌血症模型中检测接种动物是否对假结核耶尔森菌感染有保护作用。

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.