Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, Louisiana, United States of America.
PLoS One. 2011 Jan 25;6(1):e16396. doi: 10.1371/journal.pone.0016396.
Rickettsial diversity is intriguing in that some species are transmissible to vertebrates, while others appear exclusive to invertebrate hosts. Of particular interest is Rickettsia felis, identifiable in both stored product insect pests and hematophagous disease vectors. To understand rickettsial survival tactics in, and probable movement between, both insect systems will explicate the determinants of rickettsial pathogenicity. Towards this objective, a population of Liposcelis bostrychophila, common booklice, was successfully used for rickettsial isolation in ISE6 (tick-derived cells). Rickettsiae were also observed in L. bostrychophila by electron microscopy and in paraffin sections of booklice by immunofluorescence assay using anti-R. felis polyclonal antibody. The isolate, designated R. felis strain LSU-Lb, resembles typical rickettsiae when examined by microscopy. Sequence analysis of portions of the Rickettsia specific 17-kDa antigen gene, citrate synthase (gltA) gene, rickettsial outer membrane protein A (ompA) gene, and the presence of the R. felis plasmid in the cell culture isolate confirmed the isolate as R. felis. Variable nucleotide sequences from the isolate were obtained for R. felis-specific pRF-associated putative tldD/pmbA. Expression of rickettsial outer membrane protein B (OmpB) was verified in R. felis (LSU-Lb) using a monoclonal antibody. Additionally, a quantitative real-time PCR assay was used to identify a significantly greater median rickettsial load in the booklice, compared to cat flea hosts. With the potential to manipulate arthropod host biology and infect vertebrate hosts, the dual nature of R. felis provides an excellent model for the study of rickettsial pathogenesis and transmission. In addition, this study is the first isolation of a rickettsial pathogen from a non-hematophagous arthropod.
立克次体多样性令人着迷，因为有些物种可以传播给脊椎动物，而有些物种似乎只存在于无脊椎动物宿主中。特别有趣的是猫栉首蚤传播的无形体（Rickettsia felis），它可在仓储性害虫和吸血病媒昆虫中被识别。了解立克次体在昆虫系统中的生存策略及其可能的传播途径，将阐明立克次体致病性的决定因素。为了实现这一目标，我们成功地利用了一种常见的书虱（Liposcelis bostrychophila）种群进行了 ISE6（蜱衍生细胞）中的立克次体分离。通过电子显微镜观察和使用抗无形体多克隆抗体的石蜡切片免疫荧光检测，也在书虱中观察到了立克次体。该分离株被命名为无形体 LSU-Lb 株，通过显微镜检查，其形态与典型的立克次体相似。对 17kDa 抗原基因、柠檬酸合酶（gltA）基因、立克次体外膜蛋白 A（ompA）基因的部分序列和细胞培养分离株中的无形体质粒的分析证实了该分离株为无形体。从分离株中获得了可变核苷酸序列，用于鉴定无形体特异性 pRF 相关推定的 tldD/pmbA。使用单克隆抗体验证了 LSU-Lb 中的无形体外膜蛋白 B（OmpB）的表达。此外，使用定量实时 PCR 检测方法，鉴定出书虱中的无形体负荷中位数明显高于猫蚤宿主。由于无形体具有操纵节肢动物宿主生物学和感染脊椎动物宿主的潜力，因此它为研究立克次体发病机制和传播提供了一个极好的模型。此外，本研究是首次从非吸血性节肢动物中分离出立克次体病原体。
