查菲埃立克体致病机制研究进展

查菲埃立克体(Ehrlichia chaffeensis)是一种侵染人单核细胞的专性细胞内寄生的革兰氏阴性菌。其所致疾病为人单核细胞埃立克体病(Human Monocytotropic Ehrlichiosis, HME),是一种经蜱传播的人兽共患病。查菲埃立克体通过受体介导的吞噬作用侵入宿主细胞,在细胞质空泡中生存和繁殖。其缺乏编码肽聚糖和脂多糖生物合成的基因,影响多种促炎细胞因子的产生,从而抑制宿主的天然或获得性免疫应答。其通过抑制吞噬体溶酶体融合、抑制宿主细胞凋亡、逃避宿主自噬清除、参与蛋白质翻译后修饰等多种方式逃避宿主杀伤而导致持续感染。本文对查菲埃立克体致病机制研究进展进行综述,为进一步了解其与宿主相互作用模式、持续感染机制提供新的研究思路。     

Minimal change nephrotic syndrome: a possible complication of ehrlichiosis

Ehrlichiae are rickettsial organisms recently shown to be human pathogens. Infections often cause fever, myalgia, and hematological abnormalities, and sometimes mild elevation in transaminases, creatinine, and urinary protein. We report a teenager with nephrotic syndrome from minimal change glomerulonephritis and serological evidence of ehrlichiosis. In the appropriate clinical setting, Ehrlichiae should be considered in the etiological assessment of patients with minimal change disease. Received: 27 April 1998 / Revised: 9 September 1998 / Accepted: 12 November 1998     

Prevalence of granulocytic Ehrlichia and Borrelia burgdorferi sensu lato in Ixodes ricinus ticks collected from Southwestern Finland and from Vormsi Island in Estonia

Altogether, 343 adult and 111 nymphal Ixodes ricinus ticks collected from parks in Turku and suburban and rural islands of the Turku archipelago, Finland, and 100 adult I. ricinus ticks collected from Vormsi Island, Estonia, were included in this study. Using the polymerase chain reaction the ticks were examined for 16S rDNA of the Ehrlichia phagocytophila genogroup and for Borrelia burgdorferi sensu lato recA and flagellin genes. None of the Finnish ticks was found to be infected with E. phagocytophila, whereas 3% of the Estonian ticks were positive for this organism. The rate of Finnish ticks infected with B. burgdorferi sensu lato varied from 0% to 11.6% (mean 5%; 9% for adult and 4% for nymphal ticks). The corresponding rate for Estonian ticks was 15%. Borrelia afzelii was the most common genospecies in both Finnish (2.6%) and Estonian (12%) ticks. B. burgdorferi sensu stricto was detected in 2.0% of the Finnish ticks, but in none of the Estonian ticks. These results suggest that the E. phagocytophila genogroup is very rare in Finnish ticks, although the ticks were collected from an area endemic for Lyme borreliosis. In Estonia, E. phagocytophila is found in ticks and may cause disease.     

Cloning and molecular analysis of genes encoding two immunodominant antigensofEhrlichia risticii

Ehrlichia risticii, the causative agent of Potomac horse fever, is an obligate intracellular rickettsial organism. To understand the role of 55 and 51 kilodalton immunodominant antigens ofE. risticiiin strain variation, their genes from the 25-D and 90-12 strains were cloned, sequenced, and expressed inE. coli.Sequence analysis revealed that the gene for the 55 kDa antigen was present in a heat shock operon along with the gene for a 10 kDa protein. Homology searches indicated that the 55 kDa antigen and the 10 kDa protein were homologues ofE. coliGroEL and GroES proteins, respectively. There was no nucleotide sequence difference between the genes of the 55 kDa antigen, nor between the entire operons, from both strains ofE. risticii.The sequence-based estimation of the sizes of the putative mature 51 kDa antigens of the 90-12 and 25-D strains were 52.7 kDa and 52.9 kDa, respectively. The 51 kDa antigens from the 90-12 and 25-D strains shared a 98% identity in their deduced amino acid sequences. The difference in some of the amino acids may be responsible for variation in their mobilities on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, where the 51 kDa antigen of the 25-D strain migrates towards a 2 kDa lower molecular weight region. In Western blots, a 155 kDa protein that appeared to be a trimer product of the 51 kDa antigen was identified. The 55 and 51 kDa antigens were overexpressed inE. coliusing a commercial expression system, pRSET A,B,C (Invitrogen Inc., San Diego, CA, U.S.A.). The purified recombinant proteins cross-reacted with antisera toE. canisandE. sennetsu.     

Analysis of Ehrlichia ruminantium-specific T1/T2 responses during vaccination with a protective killed vaccine and challenge of goats

Ehrlichia ruminantium is an obligate intracellular bacterium that causes heartwater in ruminants and for which T-cell-mediated immunity is believed to play an important role in protection. To better characterize protective cellular immunity, E. ruminantium-specific IFN-gamma and IL-4 recall responses in major T-cell subsets were analysed by flow cytometry during immunization of goats with a killed vaccine and following a virulent challenge. The killed vaccine elicited both CD8+ and CD4+ subsets to produce cytoplasmic IFN-gamma in the absence of IL-4, thus indicating a biased T1 response. The relative capacity of CD8+ T-cells to produce IFN-gamma was significantly higher than CD4+ T-cells but the final contribution of both subsets was comparable. Circulating ER-specific CD4 and CD8 effectors substantially decreased in numbers after the booster injection and could not be detected in most animals during challenge, which warrants further investigation in immune compartments other than blood. Since IFN-gamma inhibits the growth of the pathogen in target cells, the information provided in this study on E. ruminantium-specific T1 responses will be valuable to develop cellular tools for the identification of potential protective antigens.     

Tickborne pathogen detection, Western Siberia, Russia

Ixodes persulcatus (n = 125) and Dermacentor reticulatus (n = 84) ticks from Western Siberia, Russia, were tested for infection with Borrelia, Anaplasma/Ehrlichia, Bartonella, and Babesia spp. by using nested polymerase chain reaction assays with subsequent sequencing. I. persulcatus ticks were infected with Borrelia burgdorferi sensu lato (37.6% +/- 4.3% [standard deviation]), Anaplasma phagocytophilum (2.4% +/- 1.4%), Ehrlichia muris (8.8% +/- 2.5%), and Bartonella spp. (37.6% +/- 4.3%). D. reticulatus ticks contained DNA of B. burgdorferi sensu lato (3.6% +/- 2.0%), Bartonella spp. (21.4% +/- 4.5%), and Babesia canis canis (3.6% +/- 2.0%). Borrelia garinii, Borrelia afzelii, and their mixed infections were observed among I. persulcatus, whereas B. garinii NT29 DNA was seen in samples from D. reticulatus. Among the I. persulcatus ticks studied, no Babesia spp. were observed, whereas B. canis canis was the single subspecies found in D. reticulatus.     

Naturally occurring Ehrlichia chaffeensis infection in two prosimian primate species: ring-tailed lemurs (Lemur catta) and ruffed lemurs (Varecia variegata)

A naturally occurring infection of Ehrlichia chaffeensis in lemurs is described. DNA of Ehrlichia chaffeensis was identified by polymerase chain reaction in peripheral blood from six of eight clinically ill lemurs. Organisms were cultured from the blood of one lemur exhibiting clinical and hematologic abnormalities similar to those of humans infected with E. chaffeensis.     

应用半巢式PCR检测我国北方一些蜱种中的查菲埃立克体

目的 :了解我国北方一些蜱种中是否携带查菲埃立克体 (Ehrlichiachaffeensis,简写为EC)。方法 :应用半巢式PCR检测蜱的带菌率 ,利用 16SrRNA基因测序方法鉴定所测序列。结果 :从内蒙古莫尔道嘎林业局采集的全沟硬蜱和森林革蜱中扩增出查菲埃立克体的 16SrRNA基因 ,阳性率分别是 39.0 6 %和 10 .0 0 % ;并从新疆精河采集的全沟硬蜱和草原革蜱中也测到相同的序列 ,最小阳性率分别为 5.79%和 1.6 7%。对莫尔道嘎采集的蜱标本进行 12 2 0bp的EC16SrRNA基因分析 ,结果与美国 1株查菲埃立克体 (GenBankU2 350 3)的相应序列只差 1个碱基。结论 :所使用的两套半巢式PCR扩增引物 ,可以简便快速地检测和分析蜱标本中可能存在的EC     

查菲埃立克体120 000表面抗原蛋白基因的克隆与表达

目的 构建查菲埃立克特异性表面抗原P120基因的原核表达质粒,并使该基因在E.coli中高效表达。方法 依据查菲埃立克体P120基因序列设计一对特异性引物,用PCR从查菲埃立体克体的基因中扩增含有编码P120原决定簇的基因片段,而后将PCR产物用T载体克隆。用酶将PCR产物从T载体切下,将它定向插入原核表达质粒PET11C构建PET11C／p120基因。PET12C／p120重组质粒转化的E．coli在TPTG的诱导下产生一分子量为41000的天然蛋白,它的产量占细菌蛋白总量的28％,用免疫印迹分析证明它能特异地与查菲埃立体克感染病人血清反应。结论 查菲埃立克体特异性的P120抗原在原核表达系统被高效表达,该抗原的研制成功为制备人单核细胞埃立克体病诊断抗原和疫苗奠定了基础。