Doyle C Kuyler, Nethery Kimberly A, Popov Vsevolod L, McBride Jere W
Department of Pathology, University of Texas Medical Branch, Galveston, TX 77555, USA.
Infect Immun. 2006 Jan;74(1):711-20. doi: 10.1128/IAI.74.1.711-720.2006.
Ehrlichia canis major immunoreactive proteins of 36 and 19 kDa elicit the earliest detectable antibody responses during the acute phase of canine monocytic ehrlichiosis. Genes encoding the major immunoreactive 36-kDa protein of E. canis and the corresponding ortholog of E. chaffeensis (47 kDa) were identified and the proteins characterized. The molecular masses of the strongly immunoreactive recombinant proteins were larger than predicted (26.7 and 32.9 kDa, respectively) but were consistent with those of the corresponding native proteins (36 and 47 kDa). Similar to other reported ehrlichial immunoreactive glycoproteins, carbohydrate was detected on the recombinant expressed proteins, indicating that they were glycoproteins. Both glycoproteins (gp36 and gp47) have carboxy-terminal serine/threonine-rich tandem repeat regions containing repeats that vary in number (4 to 16 repeats) and amino acid sequence among different isolates of each species. E. canis gp36 was recognized by early acute-phase antibodies (day 14), and species-specific antibody epitopes were mapped to C-terminal nonhomologous repeat units of gp36 and gp47. Periodate treatment of recombinant gp36 reduced the antibody reactivity, and nonglycosylated synthetic peptide repeat units from E. canis gp36 and E. chaffeensis gp47 were substantially less immunoreactive than corresponding recombinant peptides, demonstrating that glycans are important epitope determinants that are structurally conserved on the recombinant proteins expressed in Escherichia coli. E. canis gp36 and E. chaffeensis gp47 were differentially expressed only on the surface of dense-cored ehrlichiae and detected in the Ehrlichia-free supernatants, indicating that these proteins are released extracellularly during infection.
犬埃立克体主要免疫反应性蛋白36 kDa和19 kDa在犬单核细胞埃立克体病急性期引发最早可检测到的抗体反应。编码犬埃立克体主要免疫反应性36 kDa蛋白及恰菲埃立克体相应直系同源蛋白（47 kDa）的基因被鉴定出来，并对这些蛋白进行了表征。强免疫反应性重组蛋白的分子量比预测值大（分别为26.7 kDa和32.9 kDa），但与相应天然蛋白（36 kDa和47 kDa）一致。与其他报道的埃立克体免疫反应性糖蛋白相似，在重组表达蛋白上检测到碳水化合物，表明它们是糖蛋白。两种糖蛋白（gp36和gp47）都有富含羧基末端丝氨酸/苏氨酸的串联重复区域，不同菌株中重复次数（4至16次重复）和氨基酸序列各不相同。犬埃立克体gp36能被急性期早期抗体（第14天）识别，物种特异性抗体表位被定位到gp36和gp47的C末端非同源重复单元。高碘酸盐处理重组gp36降低了抗体反应性，犬埃立克体gp36和恰菲埃立克体gp47的非糖基化合成肽重复单元的免疫反应性明显低于相应重组肽，表明聚糖是重要的表位决定簇，在大肠杆菌中表达的重组蛋白上结构保守。犬埃立克体gp36和恰菲埃立克体gp47仅在致密核心埃立克体表面差异表达，并在无埃立克体的上清液中检测到，表明这些蛋白在感染期间释放到细胞外。
