Zhi N, Ohashi N, Rikihisa Y
Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio 43210-1093, USA.
J Biol Chem. 1999 Jun 18;274(25):17828-36. doi: 10.1074/jbc.274.25.17828.
Human granulocytic ehrlichiosis (HGE) is caused by infection with an obligatory intracellular bacterium, the HGE agent. We previously cloned a gene encoding HGE agent 44-kDa major outer membrane protein and designated it p44. In this study, we (i) identified five different mRNAs that are transcribed from p44-homologous genes in the HGE agent cultivated in HL-60 cells; (ii) cloned genes corresponding to the mRNAs from the genomic DNA of the HGE agent; (iii) showed that the genes being expressed were not clustered in the HGE agent genome; (iv) estimated that a minimum copy number of the p44-homologous genes in the genome is 18; (v) detected two different P44-homologous proteins expressed by the HGE agent; and (vi) demonstrated existence of antibodies specific to the two proteins in sera from patients with HGE. These findings showed that p44 multigenes have several active expression sites and the expression is regulated at transcriptional level, suggesting a potentially unique mechanism for generating the diversity in major antigenic outer membrane proteins of the HGE agent. Characterization of p44-homologous genes expressed by the HGE agent in a tissue culture would assist in understanding a role of the p44 multigene family in pathogenesis and immune response in HGE.
人粒细胞埃立克体病（HGE）由一种 obligatory 细胞内细菌——HGE 病原体感染引起。我们之前克隆了一个编码 HGE 病原体 44kDa 主要外膜蛋白的基因，并将其命名为 p44。在本研究中，我们：（i）在 HL-60 细胞中培养的 HGE 病原体中，鉴定出了从 p44 同源基因转录而来的五种不同 mRNA；（ii）从 HGE 病原体的基因组 DNA 中克隆了与这些 mRNA 对应的基因；（iii）表明所表达的基因在 HGE 病原体基因组中并非成簇分布；（iv）估计基因组中 p44 同源基因的最小拷贝数为 18；（v）检测到 HGE 病原体表达的两种不同 P44 同源蛋白；（vi）证明 HGE 患者血清中存在针对这两种蛋白的特异性抗体。这些发现表明 p44 多基因有多个活性表达位点，且表达在转录水平受到调控，提示在 HGE 病原体主要抗原性外膜蛋白产生多样性方面可能存在独特机制。对在组织培养中由 HGE 病原体表达的 p44 同源基因进行表征，将有助于理解 p44 多基因家族在 HGE 发病机制和免疫反应中的作用。
