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

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 295aa 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 OppA2 (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 (191−225aa, 276−290aa and 381−400aa) were hyper conserved in three genotypes, which can be used as the candidate antigens for early diagnosis of Lyme disease in China.