Reddy G R, Sulsona C R, Barbet A F, Mahan S M, Burridge M J, Alleman A R
Department of Pathobiology, College of Veterinary Medicine, University of Florida, Gainesville 32610, USA.
Biochem Biophys Res Commun. 1998 Jun 29;247(3):636-43. doi: 10.1006/bbrc.1998.8844.
Antisera against different Ehrlichiae recognize an immunodominant, cross-reacting approximately 28 kDa surface antigen defined as the MAP1 in Cowdria ruminantium. These antigens are considered valuable in developing serodiagnostic tests and recombinant vaccines for Ehrlichiae infections. To evaluate the relationship in three closely related Ehrlichiae, Ehrlichia chaffeensis, Ehrlichia canis, and C. ruminantium, the structure of the 28 kDa antigen genes was analyzed. We describe the cloning and characterization of DNA encoding genes homologous to MAP1 from E. chaffeensis and E. canis. The cloned segment of E. chaffeensis contains one expressed and four transcriptionally silent tandemly arranged, nonidentical genes; the E. canis locus consists of two nonidentical genes. Comparative analysis of these genes revealed the presence of four conserved regions separated by three highly variable regions. B-cell epitope analysis identified three major cross-reacting epitopes that map to the variable regions. Location of the epitopes at the variable regions and the presence of multigene family with only one expressed copy suggest a mechanism of immune evasion in these Ehrlichiae.
针对不同埃立克体的抗血清可识别一种免疫显性、交叉反应的约28 kDa表面抗原，该抗原在反刍动物考德里氏体中被定义为MAP1。这些抗原在开发用于埃立克体感染的血清诊断检测和重组疫苗方面被认为具有重要价值。为了评估三种密切相关的埃立克体——恰菲埃立克体、犬埃立克体和反刍动物考德里氏体之间的关系，对28 kDa抗原基因的结构进行了分析。我们描述了来自恰菲埃立克体和犬埃立克体的与MAP1同源的DNA编码基因的克隆和特征。恰菲埃立克体的克隆片段包含一个表达基因和四个转录沉默的串联排列、不相同的基因；犬埃立克体基因座由两个不相同的基因组成。对这些基因的比较分析揭示了由三个高变区隔开的四个保守区的存在。B细胞表位分析确定了三个主要的交叉反应表位，这些表位位于高变区。表位位于高变区以及多基因家族中只有一个表达拷贝的存在表明这些埃立克体存在免疫逃避机制。
