Humoral responses to Lyme Borreliosis: A mouse model

描述(由申请人提供)：这项提案是对美国国立卫生研究院关于非生物防御性新发传染病研究机会的计划公告的回应，涉及莱姆疏螺旋体病。这种疾病是由伯氏杆菌引起的，是美国和欧洲最常见的节肢动物传播疾病，报告的感染人数每年都在增加。在未经治疗的患者中，螺旋体会导致持续性感染和慢性疾病，并伴有一连串的关节炎和心脏炎。我们的长期目标是阐明BB在完全免疫活性宿主持续感染期间逃避有效免疫的机制。以前的研究已经确认抗体是疾病解决(但不是清除螺旋体)和被动保护的主要免疫媒介。虽然早期感染中的抗体在疾病解决和被动保护能力方面具有很强的功能，但随着疾病的进展，保护能力减弱。这项建议的目的是评估调节BB特异性体液反应的潜在机制，以确定是否可以利用增强的体液反应用于治疗或预防。根据初步发现，我们的目标是检验假设，即BB特异的B细胞通过短寿命的浆细胞提供抗体反应，而高亲和力的B细胞和长寿命的浆细胞是由于缺乏功能性的CD4辅助T细胞激活而产生的。螺旋体感染的小鼠模型将被用来进行三个特定的目标。具体目标#1将确定早期诱导的特定IgM和/或IgG反应在多大程度上主动抑制保护性免疫，使用不能分泌某些Ig同型的基因改变的小鼠。具体目标#2将测试BB是否将淋巴B细胞的反应从生发中心的反应中分离出来。这可能导致缺乏亲和力成熟和寿命，并可能导致功能的损失，随着时间的推移，观察到莱姆疏螺旋体。检测将包括多色流式细胞术，以确定诱导反应的性质和质量。此外，将确定有反应的B细胞亚群，并评估CD4T细胞对它们的调节。此外，长寿浆细胞缺乏亲和力成熟和发育在多大程度上是BB特异性抗体反应的功能缺陷，将通过研究脱蛋白结合蛋白抗体作为原型反应来确定。具体目标#3将确定缺乏对疏螺旋体的长期功能性B细胞反应诱导是由于主动抑制和/或功能性CD4辅助T细胞反应诱导的失败，还是B细胞对T细胞帮助反应能力的内在缺陷是莱姆型疏螺旋体病缺乏生发中心反应的基础。这些研究将共同阐明导致强健但最终缺陷的B细胞反应失败的机制，以促进疏螺旋体感染的清除。 与公共卫生相关：莱姆病是一种由扁虱叮咬引起的慢性致残疾病。扁虱将一种名为伯氏疏螺旋体的细菌传播给患者，这种细菌可以持续存在于包括关节和心脏在内的各种器官中，在那里它可以导致致残疾病，如慢性关节炎和心肌疾病。人体会产生一种免疫反应，最初可以抵御疾病，但无法清除感染。因此，如果感染得不到治疗，持续性疾病就很常见。这项建议旨在确定为什么足以帮助减少疾病的免疫反应最终无法清除感染。这些信息对于开发这种日益流行的疾病的疫苗和治疗方法是必要的。

DESCRIPTION (provided by applicant): This proposal, which is responsive to the NIH Program Announcement on Non-Biodefense Emerging Infectious Diseases Research Opportunities, is concerned with Lyme borreliosis. This disease is caused by B. burgdorferi (Bb) and is the most commonly reported arthropod-borne illness in the US and Europe with the number of reported infections raising each year. The spirochetes cause persistent infections and chronic disease with bouts of arthritis and carditis in untreated patients. Our long-term objective is to delineate the mechanisms with which Bb evades effective immunity during persistent infection of fully immunocompetent hosts. Previous studies have identified antibodies as a main immune mediator of disease resolution (but not clearance of the spirochete) and passive protection. While antibodies in early infection are strongly functional with respect to disease-resolution and passive protective capacity, the protective capacity wanes as disease progresses. The objective of this proposal is to assess the mechanisms underlying the regulation of the Bb- specific humoral response, to ascertain whether strengthening of humoral responses could be exploited for therapeutic or prophylactic use. Based upon preliminary findings, we aim to test the hypothesis that Bb- specific B cells provide antibody responses by short-lived plasma cells at the expense of higher affinity B cells and long-lived plasma cells due to a lack of functional CD4 helper T cell activation. A murine model of Borrelia infection will be used to conduct three Specific Aims. Specific Aim #1 will determine the extent to which the early-induced specific IgM and/or IgG responses actively inhibit protective immunity using genetically altered mice unable to secrete certain Ig isotypes. Specific Aim #2 will test whether Bb drives lymph node B cell responses away from germinal center responses. This could result in the lack of affinity maturation and longevity and could cause a loss of functionality over time, as observed in Lyme Borrelioses. Assays will include multicolor flow cytometry to determine the nature and quality of the induced response. Furthermore, the responding B cell subsets will be identified and their regulation by CD4 T cells will be assessed. Also, the extent to which a lack of affinity maturation and development of long-lived plasma cells underlies the functional defect in the Bb-specific antibody responses will be determined by studying antibodies to decarin-binding protein as a prototype response. Specific Aim #3 will determine whether the lack of long- term functional B cell response induction to Borrelia is due to active inhibition and/or a failure of functional CD4 helper T cell response induction or whether an intrinsic defect in the ability of B cells to respond to T cell help underlies the lack of germinal center responses seen in Lyme Borreliosis. Together these studies will elucidate mechanisms that lead to the failure of the vigorous but ultimately deficient B cell response to facilitate clearance from Borrelia infection. PUBLIC HEALTH RELEVANCE: Lyme Disease is a chronic disabling disease resulting from a tick-bite. The tick transfers a bacterium, Borrelia burgdorferi, to the patient, which can persist in various organs, including the joints and heart, where it can cause disabling disease such as chronic arthritis and heart muscle disease. The body develops an immune response that can initially fend off disease but cannot clear the infection. Thus, if infections are not treated continuing disease is common. This proposal aims to determine why the immune response that is sufficient to help to reduce disease ultimately fails to clear the infection. Such information is necessary to develop vaccines and treatments for this increasingly prevalent disease.