中国莱姆病螺旋体菌株OppA2基因中人B细胞表位多态性分析

The polymorphisms of human B cell epitopes in OppA2 of Borrelia burgdorferi sensu lato in China

目的研究中国莱姆病螺旋体菌株中OppA2基因及其人B细胞抗原表位区的序列多态性,了解不同地域OppA2的变化特征,为中国莱姆病的早期诊断提供线索和依据。方法选取59株莱姆病螺旋体分离株,PCR扩增其OppA2基因并测序后,结合3种基因型参考菌株序列,与免疫表位数据库(IEDB)中查询到的B细胞表位序列进行比对分析。结果中国莱姆病螺旋体中OppA2基因序列在Borrelia burgdorferi sensu strict(B.b.s.s), Borrelia garinii(B.g)和Borrelia afzelii(B.a)3个基因型间存在明显的多态性。但OppA2基因序列在B.b.s.s和B.a型内保守;在B.g型内存在异义突变。B细胞表位改变主要发生在B.g基因型的亚簇2、亚簇3以及JC2-2分离株。B.g基因型的亚簇2、亚簇3以及JC2-2菌株的296aa变异和亚簇3的295aa变异使3个B细胞抗原表位受影响;JC2-2菌株的372aa变异使1个B细胞抗原表位受影响;这些表位区的变异使部分B细胞表位序列(4/7,57.1%)呈现多态性。结论中国莱姆病螺旋体OppA2基因及其人B细胞抗原表位区在3个基因型间和B.g型内存在多态性;其中有3个B细胞抗原表位区(191～225aa、276～290aa和381～400aa)在B.b.s.s,B.g和B.a三种基因型内高度保守,可作为中国莱姆病早期诊断的候选抗原。

Objective To study the polymorphism of OppA2 gene and its human B cell epitopes of Borrelia burgdorferi strains isolated in China,understand the change trend of OppA2 gene in different areas and provide evidence for the early diagnosis of Lyme disease.Methods The OppA2 sequences of 59 Borrelia burgdorferi strains were obtained by PCR and sequencing.They were compared with the human B cell epitope sequences originated from immune epitope database(IEDB)based on the reference strains of each genotype.Results OppA2 sequences of Chinese strains showed polymorphism among three genotypes,i.e.Borrelia burgdorferi sensu strict(B.b.s.s),Borrelia garinii(B.g) and Borrelia afzelii(B.a),but OppA2 sequences were hyper-conserved in genotype B.b.s.s and B.a strains.However,non-synonymous mutations existed in B.g strains.The changed B cell epitopes were mainly found in subcluster 2,subcluster 3 and non-clustered JC2-2 strains of B.garinii.The non-synonymous mutation of 296 amino acid(aa) in subcluster 2,subcluster 3 and JC2-2 strains,and 295 aa in subcluster 3 of B.g strains affected three B cell epitopes.Non-synonymous mutation of 372 aa in JC2-2 strain affected one B cell epitopes.These mutations resulted in the polymorphism of part of B cell epitopes of Opp A2(4/7,57.1%).Conclusion The polymorphism were widely existed in OppA2 and its B cell epitopes in B.g and among three genotypes of Borrelia burgdorferi strains selected in China.However,three B cell epitopes(191-225 aa,276-290 aa and 381-400 aa) were hyper conserved in three genotypes,which can be used as the candidate antigens for early diagnosis of Lyme disease in China.