Genetic Analysis of Borrelia burgdorferi lp54 Loci

描述(申请人提供)：莱姆病，由伯氏疏螺旋体细菌引起，是一种重新出现的媒介传播感染，在可获得数据的最后一年(2002年)，美国报告的病例中有40%惊人地增加。报告病例的增加，加上目前缺乏任何疫苗，使伯氏杆菌成为一个重要的公共卫生问题，特别是在流行该病的州，在这些州，它导致了严重的发病率。伯氏伯氏杆菌在哺乳动物中引起感染的能力需要在从扁虱传播后迅速适应哺乳动物的宿主条件。全基因组转录分析表明，线性质粒54(IP54)上的一些基因在哺乳动物或壁虱施加的条件下表现出差异表达。这项建议的目的是在对各种外部信号表现出差异表达的子集中识别在莱姆病小鼠模型中感染性所需的IP54上的基因。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，该转座子将允许在体外选择后分离伯氏杆菌的突变，并允许在小鼠中分析它们的感染性表型。第二个具体目标是用C3H/HEN小鼠确定突变的莱姆病小鼠模型中的传染性水平。5个突变体的半数感染剂量(ID50)和组织传播特性将与它们的同基因亲本克隆进行比较。最终的特异性目的是确定选定的IP54基因在莱姆病小鼠模型中的保护性免疫作用，并确定该基因产物介导的致病机制(S)。这些研究将有助于确定IP54上的疏螺旋体决定因素的特征，这些决定因素对感染可能具有实用价值，因为它们可能是预防莱姆疏螺旋体病急需的候选疫苗。

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.