Emerging flea-borne rickettsial diseases: vector competence and transmission biology

 描述（由申请人提供）：猫立克次体最初于1991年在美国被确定为人类病原体，目前与北美和南美、欧洲、非洲、亚洲和大洋洲的人类感染有关。我们这项研究的最终目标是阐明跳蚤传播立克次体的生物学和分子机制，以便更好地了解跳蚤传播立克次体疾病的流行病学，并确定新的干预点。建议的研究结果将决定是否R。FELS利用多种机制在跳蚤之间进行快速水平传播，而不依赖于立克次体脊椎动物宿主。这是媒介传播立克次体疾病的一个新范例。此外，一种新的立克次体反应发生在节肢动物宿主中的可能性，并以某种方式与立克次体传播有关，长期以来一直是媒介传播立克次体疾病的租户;然而，这从未在实际的传播系统中进行过测试。本申请的实验重点是通过比较分析两种不同节肢动物载体中的三种不同立克次体菌株来描绘水平传播机制， 猫蚤和鼠蚤。立克次体衍生的分子是立克次体传播的基础。跳蚤宿主中的猫是未知的。研究还将采用立克次体诱变来确定跳蚤传播系统中的传播决定因素。病媒/疾病管理的两个限制因素和推进该领域的障碍是：1）对R.猫和，2）立克次体衍生的传播决定因素。通过完成本申请中概述的具体目标，这些研究将通过评估跳蚤传播立克次体（具体目标1）和鉴定传播事件所必需的立克次体衍生分子成分（具体目标2）来克服障碍。因此，这是一种多方面的方法来破译传播所必需的载体和病原体相关因素，并将提供一个平台来检查其他跳蚤传播的细菌病原体。目标1。描述猫立克次体被节肢动物感染和传播的机制。某些媒介传播的病原体的稳定垂直传播消除了对脊椎动物宿主的需要;然而，除非这种传播事件是100%有效的，否则需要额外的水平扩增来维持病原体在环境中的存在。我们将测试假设，如果垂直传播的R。猫经蚤传播率不是100%，则R.猫必须出现在跳蚤之间。本研究的目的是确定新的R. felis收购跳蚤和评估内和种间传播的R。猫目标2.定义立克次体传播媒介的分子成分。载体携带的细菌病原体在传播到脊椎动物宿主之前在载体中经历必要的分子转化。我们将检验假设：如果R.猫表达独特的立克次体蛋白质谱，其协调节肢动物的感染和随后的传播，则关键分子的破坏将阻碍感染和/或传播。为了验证这一假设，我们将集中在（a）在R。（B）蚤感染和传播中的同基因立克次体突变体的分析。

 DESCRIPTION (provided by applicant): Rickettsia felis was originally identified in the United States as a human pathogen in 1991 and is now associated with human infection in North and South America, Europe, Africa, Asia, and Oceania. Our ultimate goal for this research is to elucidate the biological and molecular mechanisms that are critical to rickettsial transmission by fleas in order to better understand the epidemiology of flea-borne rickettsial diseases and identify novel points of intervention. The results of the proposed studies will determine if R. fels utilizes multiple mechanisms for rapid horizontal transmission between fleas independent of a rickettsemic vertebrate host. This is a new paradigm for vector-borne rickettsial diseases. Also, the probability that a novel rickettsial response occurs in the arthropod host, and is somehow associated with rickettsial transmission, has long been a tenant of vector-borne rickettsial diseases; however, this has never been tested in an actual transmission system. The experimental focus of this application is to delineate horizontal transmission mechanisms through comparative analyses three distinct rickettsial strains in two different arthropod vectors, cat fleas and rat fleas. The rickettsial-derived molecules underlying the transmission of R. felis in flea hosts are not known. Studies will also employ rickettsial mutagenesis to identify transmission determinants in a flea transmission system. Two limiting factors for vector/disease management and the barriers to advancing the field are the scant knowledge of 1) basic transmission biology of R. felis and, 2) the rickettsial-derived determinants of transmission. Through completion of the specific aims outlined in this application, these studies will overcome the hurdles by assessing rickettsial transmission by fleas (Specific Aim 1) and through identification of Rickettsia-derived molecular constituents essential to transmission events (Specific Aim 2). Thus, this is a multifaceted approach to decipher the vector and pathogen-associated factors essential to transmission and will provide a platform to examine other flea-borne bacterial pathogens. Aim 1. Delineate the mechanism by which Rickettsia felis is acquired and transmitted by arthropods. Stable vertical transmission of certain vector-borne pathogens eliminates the need for a vertebrate host; however, unless this transmission event is 100% efficient, additional horizontal amplification is required for maintenance of the pathogen in the environment. We will test the hypothesis that if vertical transmission of R. felis by fleas is not 100%, then horizontal transmission of R. felis must occur between fleas. The objective of this aim is to identify novel routes of R. felis acquisition by fleas and assess the intra- and inter-specific transmission of R. felis. Aim 2. Define the Rickettsia-derived molecular constituents of transmission by flea vectors. Vector-borne bacterial pathogens undergo essential molecular transformation in the vector prior to transmission to the vertebrate host. We will test the hypothesis that if R. felis expresses a distinct rickettsial protein profile that orchestrates infetion of arthropods and subsequent transmission, then disruption of key molecules will impede infection and/or transmission. To test this hypothesis, we will focus on (a) targeted mutagenesis in R. felis and (b) analysis of isogenic rickettsial mutants in flea-infection and transmission.