Luo Tian, Zhang Xiaofeng, McBride Jere W
Department of Pathology, University of Texas Medical Branch, Galveston, TX 77555-0609, USA.
Clin Vaccine Immunol. 2009 Jul;16(7):982-90. doi: 10.1128/CVI.00048-09. Epub 2009 May 6.
Ehrlichia chaffeensis and E. canis have a small subset of tandem repeat (TR)-containing protein orthologs, including p120/p140, which elicit strong antibody responses. The TR regions of these protein orthologs are immunoreactive, but the molecular characteristics of the p120/p140 epitopes have not been determined. In this study, the immunodeterminants of the E. chaffeensis p120 and E. canis p140 were identified and molecularly defined. Major antibody epitope-containing regions of both p120 and p140 were localized to the TR regions, which reacted strongly by Western immunoblotting with antibodies in sera from E. chaffeensis-infected dogs or patients and E. canis-infected dogs, respectively. Single continuous species-specific major epitopes within the E. chaffeensis p120 and E. canis p140 TRs were mapped to homologous surface-exposed glutamate/aspartate-rich regions (19 to 22 amino acids). In addition, minor cross-reactive epitopes were localized to homologous N- and C-terminal regions of p120 and p140. Furthermore, although the native and recombinant p120 and p140 proteins exhibited higher-than-predicted molecular masses, posttranslational modifications were not present on abnormally migrating p120 and p140 TR recombinant proteins as determined by matrix-assisted laser desorption ionization-time of flight mass spectrometry.
恰菲埃立克体和犬埃立克体有一小部分含有串联重复序列（TR）的蛋白质直系同源物，包括p120/p140，它们能引发强烈的抗体反应。这些蛋白质直系同源物的TR区域具有免疫反应性，但p120/p140表位的分子特征尚未确定。在本研究中，鉴定并从分子层面界定了恰菲埃立克体p120和犬埃立克体p140的免疫决定簇。p120和p140的主要含抗体表位区域均定位于TR区域，通过蛋白质免疫印迹法检测，它们分别与恰菲埃立克体感染犬或患者以及犬埃立克体感染犬血清中的抗体发生强烈反应。恰菲埃立克体p120和犬埃立克体p140的TR区域内单一连续的物种特异性主要表位被定位到同源的富含谷氨酸/天冬氨酸的表面暴露区域（19至22个氨基酸）。此外，次要的交叉反应表位定位于p120和p140的同源N端和C端区域。此外，尽管天然和重组的p120和p140蛋白表现出高于预测的分子量，但通过基质辅助激光解吸电离飞行时间质谱法测定，异常迁移的p120和p140 TR重组蛋白上不存在翻译后修饰。
