Rational development of a vaccine against tick-borne rickettsioses

摘要 立克次体是一组与节肢动物相关的细胞内专性革兰氏阴性细菌，它们与 相关但可能会在人类中引起危及生命的感染。壁虱传播立克次体病(TBR)是 由于发病率的增加和缺乏，对美国的公共健康构成日益严重的威胁 市面上有预防用疫苗。因此，一种安全有效的TBRs疫苗将是 这是一个重要的资源，将确保国家预防这类疾病的能力。我们的长- 长期目标是开发安全有效的TBRs免疫预防的新方法。我们最近 已发表的和初步研究表明，减毒帕氏杆菌突变株3A2具有完全保护作用。 在小鼠模型中对抗两种高毒力立克次体的致死性攻击，并产生高滴度 对几种致病立克次体有反应的抗体和显著升高的1型T细胞 记忆免疫力。这些发现支持概念验证，即减毒活疫苗候选者 预防TBRs的可行有效途径和研究疫苗诱导的TBRs记忆免疫。 因此，R01应用的目标是产生一种安全有效的减毒活疫苗 (LAV)抗结核分枝杆菌，定义LAV对同源和异种立克次体的保护效力 菌株，并从机械上确定疫苗诱导的抗蚤保护的免疫相关性 Tbr的传播。为了实现这些目标，我们提出了三个具体目标来测试中央 假设LAV将诱导高质量的CD8+T记忆细胞和立克次体特异性中和 抗体作为一种安全有效的多价抗体，可完全预防自然获得的TBR 候选疫苗。目标1将对帕氏杆菌突变体进行遗传优化，以降低毒力，增强安全性，同时 保持免疫原性。目标2将确定遗传优化的帕克氏杆菌突变体在 在针刺法和壁虱传播法动物模型中预防TBR。目标3将确定 疫苗诱导的TBRs保护作用的免疫学相关性。在完成建议的 研究，我们希望定义第一个用于TBR的多价候选疫苗，并揭示新的元素 宿主免疫负责预防TBR的自然传播。这将产生重大的积极影响 对人类健康的影响，因为它将提供最终开发安全、 有效的、易处理的TBRS疫苗。

Abstract Rickettsiae are a group of arthropod-associated, obligately intracellular Gram-negative bacteria that are closely related but potentially cause life-threatening infection in humans. Tick-borne rickettsioses (TBRs) are increasingly posing serious threat to the public health in the US due to increased incidence and lack of commercially available vaccine for prevention. Therefore, a safe and effective vaccine against TBRs will be an important resource that will ensure the Nation’s capability to prevent this group of diseases. Our long- term goal is to develop novel approaches for safe and effective immunoprophylaxis of TBRs. Our recently published and pilot studies demonstrated that live-attenuated R. parkeri mutant 3A2 conferred full protection against lethal challenge of two highly virulent rickettsiae in mouse models, accompanied by generating high titers of IgG antibodies reactive against several pathogenic rickettsial species and significantly elevated type 1 T cell memory immunity. These findings support the proof-of-concept that live-attenuated vaccine candidate serves a feasible and effective approach to prevent TBRs and study vaccine-induced memory immunity against TBRs. Thus, the objectives of this R01 application are to generate a safe and efficacious live-attenuated vaccine (LAV) against TBRs, define the protective efficacy of LAV against homologous and heterologous rickettsial strains, and mechanistically determine the immune correlates of vaccine-elicited protection against tick transmission of TBRs. To achieve these objectives, we propose three specific aims to test the central hypothesis that the LAV will elicit high quality CD8+ T memory cells and rickettsiae-specific neutralizing antibodies to confer complete protection against natural acquisition of TBRs as a safe and efficacious polyvalent vaccine candidate. Aim 1 will optimize R. parkeri mutants genetically to reduce virulence, enhance safety while maintaining immunogenicity. Aim 2 will define the efficacy of genetically optimized R. parkeri mutants in protecting against TBRs in both needle-challenge and tick transmission animal models. Aim 3 will identify the immunological correlates of vaccine-induced protection against TBRs. Upon the completion of the proposed research, we expect to define the first multivalent vaccine candidate for TBR and reveal the novel elements of host immunity responsible for prevention from natural transmission of TBRs. This will have significant positive effects on human health because it will provide the basic information required to ultimately develop a safe, effective, and tractable vaccine against TBRs.