Genetic Analysis of Borrelia burgdorferi lp54 Loci

描述（由申请人提供）：莱姆病，由螺旋体细菌伯氏疏螺旋体引起，是一种重新出现的媒介传播感染，在有数据可查的去年（2002年），美国报告的病例惊人地增加了40%。报告病例的增加，加上目前缺乏任何疫苗，使伯氏疏螺旋体成为一个重要的公共卫生问题，特别是在它造成严重发病率的流行州。伯氏疏螺旋体在哺乳动物中引起感染的能力需要在蜱虫传播后迅速适应哺乳动物宿主的条件。全基因组转录分析显示，线性质粒54 （Ip54）上的许多基因在哺乳动物或蜱虫施加的条件下表现出差异表达。本提案的目的是在对各种外部信号表现出差异表达的亚群中，鉴定莱姆病小鼠模型中感染性所需的Ip54基因。第一个具体目标是通过使用定制的转座子在五个特定的ip54编码基因中产生突变体，这将允许在体外选择后分离伯氏疏螺旋体中的突变体，并允许分析其在小鼠中的感染性表型。第二个具体目标是使用C3H/HeN小鼠确定突变体在莱姆病小鼠模型中的传染性水平。5个突变体的50%感染剂量（ID50）和组织传播特性将与它们的等基因亲本克隆进行比较。最终的具体目的是确定选定的Ip54基因在莱姆病小鼠模型保护性免疫中的作用，并确定基因产物介导的致病机制。这些研究将有助于表征对感染至关重要的疏螺旋体决定因素，这些决定因素可能具有作为急需的候选疫苗来预防莱姆病的效用。

DESCRIPTION (provided by applicant): Lyme disease, caused by the spirochetal bacterium Borrelia burgdorferi, is a re-emerging vector-borne infection with an alarming increase in 40% of the reported cases in the United States during the last year in which data is available (2002). This increase in reported cases, coupled with the lack of any current vaccine, makes B. burgdorferi an important public health issue particularly in endemic states where it contributes to significant morbidity. The ability of B. burgdorferi to cause infection in mammals requires rapid adaptation to the mammalian host conditions following transmission from ticks. Genome-wide transcriptional analysis has revealed that a number of genes on linear plasmid 54 (Ip54) exhibit differential expression to either mammalian or tick imposed conditions. The objective of this proposal is to identify genes on Ip54 required for infectivity in the murine model of Lyme disease among the subset that exhibit differential expression to various external signals. The first specific aim is to generate mutants in five specific Ip54-encoded genes by using a customized transposon that will allow for both isolation of mutants in B. burgdorferi following in vitro selection and permit analysis of their infectivity phenotype in mice. The second specific aim is to determine the levels of infectivity of the mutants in the murine model of Lyme disease using C3H/HeN mice. The 50% infectivity dose (ID50) and tissue dissemination characteristics of the five mutants will be determined in comparison with their isogenic parental clones. The final specific aim is to determine the role of selected Ip54 genes in protective immunity in the murine model of Lyme disease and ascertain the pathogenic mechanism(s) mediated by the gene products. These studies will help to characterize borrelial determinants on Ip54 that are critical for infection that may have utility as much needed vaccine candidates to protect against Lyme borreliosis.