Tick Midgut Thrombin Inhibitor as a Vaccine Target

描述（由申请人提供）：我们在此申请中寻求开发一种蜱疫苗，以阻止蜱的摄食和病原体传播给脊椎动物宿主。蜱虫可以携带细菌、病毒和原生动物病原体，受感染的蜱虫在进食过程中将病原体传播给哺乳动物宿主，在世界范围内引起人类和牛的疾病。硬蜱是专性食血节肢动物，以脊椎动物宿主为食4-10天，这是完成其生命周期所必需的事件。蜱虫取食的关键分子可以作为阻断蜱虫取食和病原体传播的疫苗靶点。众所周知，蜱虫必须破坏宿主的凝血级联，特别是在媒介-宿主界面，才能成功获得血，因此人们一直在努力确定蜱虫唾液的抗凝血机制。因此，在过去十年左右的时间里，我们的研究小组和其他人都在不同蜱类的唾液或唾液腺中发现了抗凝血剂。唾液腺蛋白质组中与结构和功能相关的抗凝血分子是抵抗宿主免疫压力的关键适应性，然而，这对这些唾液抗凝血剂作为蜱虫疫苗的成功开发构成了瓶颈。我们现在提供了一种绕过瓶颈的方法，并提请注意蜱抗凝策略的一个较少检查的方面，即蜱肠道在阻碍宿主凝血中的作用。肩胛骨蜱，黑腿蜱，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，将在本提案中作为模型蜱。我们提供的初步证据表明，肩胛棘猴的肠道表达凝血酶的有效抑制剂，宿主促凝级联的关键组成部分。我们假设蜱肠道中的凝血酶抑制剂在防止摄入的血液凝固，保持血液液体以促进补充过程中起着关键作用。因此，蜱肠道凝血酶抑制剂提供了一种新的疫苗靶点，以阻止蜱的摄食和阻止随之而来的病原体传播。我们还推断，与唾液抗凝剂不同，肠道抗凝剂代表一种隐藏的抗原，可能没有进化到可以规避宿主的免疫反应；因此更容易中和。为了测试和验证这一建议的假设，我们将在I期研究中表征蜱肠道凝血酶抑制剂，因此称为Gotti （G gut of T - tick T - tick凝血酶I抑制剂），并在莱姆病小鼠模型中探讨Gotti在蜱食和伯氏螺旋体传播背景下的疫苗潜力。未来的研究将确定Gotti作为疫苗阻止其他蜱传播病原体传播的能力。

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.