中国莱姆病螺旋体DnaK基因的人T细胞表位研究

Human T cell epitopes of DnaK of Chinese Borrelia burgdorferi

目的了解我国引起莱姆病的伯氏疏螺旋体重要抗原之一DnaK基因及其表位区的多样性,理解伯氏疏螺旋体与宿主之间的相互作用机制和伯氏疏螺旋体抗原分子引起的免疫应答反应。方法比对分析我国68株具有代表性的伯氏疏螺旋体菌株,包含了4个重要基因型。使用国际参考株B31(Borrelia burgdorferi sensu stricto,B.B.s.s)作为参考菌株。结果结果表明DnaK基因的T细胞抗原表位区有单核苷酸变异(SNP),但氨基酸序列与参考菌株没有差异。该基因序列90～1 838 bp的dN/dS值为0.03。同时,我国伯氏疏螺旋体主要致病基因型B.garinii的核酸变异较大。结论 DnaK基因的T抗原表位高度保守,可能是感染之后直接刺激免疫系统引起炎性反应的原因之一。此外在不改变蛋白功能的前提下,基因的多样性可能与其适应环境有关。

Objective Molecular biological characterization of Borrelia burgdorferi DnaK gene and its epitope may be helpful to better understand the immune response that the gene caused and the interaction between the host and DnaK gene.Methods DnaK gene of 68 representative strains including 4 subtypes of Borrelia burgdorferi found in China were sequenced using Illumina next-generation DNA sequencing method, and the sequences were compared with that sequence of the Borrelia burgdorferi sensu stricto(B.B.s.s) B31 strain. Results Comparative analyses showed that human T cell epitopes of DnaK gene had little sequence variation which led to no AA(amino acid) change and a lower overall ratio(0.03) of nonsynonymous to synonymous changes. The whole sequence variation of DnaK in Chinese main subtype B.garinii strains were more complicated. Conclusion These findings implied that hyperconserved T cell epitope in DnaK might trigger the immune system and lead to an inflammatory disease after infection. Furthermore, on the premise that protein function remains, gene variety might be related to the survival adaptation of the spirochete to the environment.