Tick Midgut Thrombin Inhibitor as a Vaccine Target

描述(由申请人提供)：我们在这项提案中寻求开发一种扁虱疫苗来阻止扁虱的摄食和病原体向脊椎动物宿主的传播。扁虱可以携带细菌、病毒和原生动物病原体，受感染的扁虱在进食过程中将病原体传播给哺乳动物宿主，在世界各地引发人和牛的疾病。硬蜱是专性食血节肢动物，以脊椎动物宿主为食，持续4-10天以获取血粉，这是完成其生命周期所必需的事件。对扁虱饲养至关重要的分子可以作为疫苗靶标，阻止扁虱饲养和病原体传播。因为人们都知道，为了成功地获得血粉，蜱虫必须破坏宿主凝血级联反应，特别是在载体-宿主界面，因此人们一直在叫嚣着要确定扁虱唾液的抗凝机制。因此，在过去十年左右的时间里，我们的团队和其他人都描述了在不同物种的唾液或唾液腺中使用抗凝血剂。唾液腺蛋白质组中结构和功能相关的抗凝血剂分子是抵抗宿主免疫压力的关键适应物质，然而，唾液腺蛋白质组中与结构和功能相关的抗凝剂分子的阐述，已经成为这些唾液抗凝剂成功开发为壁虱疫苗的瓶颈。我们现在提供了一种绕过瓶颈的方法，并将注意力集中在扁虱抗凝策略的一个较少被研究的方面，即扁虱肠道在阻止宿主凝血中的作用。黑腿硬蜱是多种人类病原体的主要媒介，包括北美莱姆病的病原体伯氏疏螺旋体，并将在这项提议中作为模式扁虱。我们提供的初步证据表明，肩胛鱼的肠道表达一种有效的凝血酶抑制物，凝血酶是宿主促凝血级联反应的关键成分。我们推测，扁虱肠道中的凝血酶抑制物在防止吸入的血液凝结、保持血粉液体以促进补充过程中起着关键作用。因此，扁虱肠道凝血酶抑制物提供了一种新的疫苗靶点，以阻止扁虱的进食和随后的病原体传播。我们还推断，与唾液抗凝剂不同，肠道抗凝剂代表的是一种隐藏的抗原，它可能没有进化成避开宿主免疫反应；因此更容易中和。为了测试和验证这项建议的假设，在第一阶段研究中，我们将表征扁虱肠道凝血酶抑制物，以下称为Gotti(G Gut of T ut tick T ick凝血酶I凝血酶抑制物)，并在莱姆病小鼠模型中研究Gotti在扁虱喂养和疏螺旋体传播方面的疫苗潜力。未来的研究将确定Gotti作为疫苗的能力，以阻止其他扁虱传播的病原体的传播。 与公共卫生的相关性：为了阻止疾病传播而研制出阻断扁虱饲养的疫苗的成功仍然难以捉摸。这项提案将把重点放在肩部硬蜱身上，这是多种病原体的媒介，包括北美莱姆病的病原体伯氏疏螺旋体。我们将检查Gotti的疫苗潜力，Gotti是一种肩胛肌中肠抗凝剂，可能是实现扁虱喂养的关键。Gotti是一种隐藏的抗原(通常不被宿主看到)，它可能没有进化成逃避宿主免疫反应的抗原，可能更容易被用作疫苗靶标来阻止扁虱的摄食和随后的病原体传播。

DESCRIPTION (provided by applicant): We seek in this proposal to develop a tick vaccine to block tick feeding and pathogen transmission to the vertebrate host. Ticks can harbor bacterial, viral and protozoan pathogens and infected ticks transmit pathogens to the mammalian host during feeding, causing human and cattle disease worldwide. Ixodid ticks are obligate hematophagous arthropods that feed on vertebrate hosts for 4-10 days to obtain their bloodmeal, an event essential to complete their life cycle. Molecules critical for tick feeding can serve as vaccine targets to block tick feeding and pathogen transmission. Since it is well understood that ticks must impair host coagulation cascades, especially at the vector-host interface, in order to obtain the bloodmeal successfully, there has been a clamor to define anticoagulation mechanisms of tick saliva. As a result, in the last decade or so anticoagulants have been described, both by our group and others, in the saliva or salivary glands of diverse tick species. The elaboration of structurally and functionally related anticoagulant molecules in the salivary gland proteome, a critical adaptation to resist host immune pressures, has however posed a bottleneck in the successful development of these salivary anticoagulants as tick vaccines. We now offer an approach to circumvent the bottleneck and draw attention to a less examined facet of tick anticoagulation strategies, i.e, the role of the tick gut in thwarting host coagulation. Ixodes scapularis, the blacklegged tick, is the predominant vector of multiple human pathogens including Borrelia burgdorferi the agent of Lyme disease in North America and will serve as a model tick in this proposal. We provide preliminary evidence that the gut of I. scapularis expresses a potent inhibitor of Thrombin, a key component of the host pro-coagulation cascade. We postulate that the thrombin inhibitor in the tick gut plays a critical role in preventing the ingested blood from clotting, keeping the blood meal fluid to facilitate the process of repletion. The tick gut thrombin inhibitor therefore provides a novel vaccine target to thwart tick feeding and block consequent pathogen transmission. We also reason that unlike the salivary anticoagulants, the gut anticoagulant representing a concealed antigen, may not have evolved to circumvent host immune responses; hence easier to neutralize. To test and validate the postulate of this proposal, we will, in Phase I studies, characterize the tick gut thrombin inhibitor, henceforth referred to as Gotti (G Gut of T ut Tick T ick Thrombin I hrombin Inhibitor) and address the vaccine potential of Gotti in the context of tick feeding and Borrelia transmission in a murine model of Lyme disease. Future studies will determine the ability of Gotti to serve as a vaccine to block transmission of other tick-transmitted pathogens. PUBLIC HEALTH RELEVANCE: Success towards developing vaccines to block tick feeding with the goal of thwarting disease transmission has remained elusive. This proposal will focus on Ixodes scapularis the vector of multiple pathogens, including Borrelia burgdorferi the agent of Lyme disease in the North America. We will examine the vaccine potential of Gotti, an I. scapularis midgut anticoagulant that may be critical to enable tick feeding. Gotti being a concealed antigen (not normally seen by the host) may not have evolved to escape the host immune responses and may be easier to exploit as a vaccine target to block tick feeding and the consequent pathogen transmission.