Polymorphism of P66 in Borrelia Burgdorferi Strains in China

To study the polymorphism in P66 and its human B-cell epitopes of Borrelia burgdorferi strains in China.

Polymerase chain reaction (PCR) and sequencing were used to obtain the P66 sequences of 59 Chinese B. burgdorferi. Then the sequences were analyzed by MEGA 5.10 software and compared with the human B-cell epitope sequences from the Immune Epitope Database (IEDB) based on the reference strain of each genotype.

Results showed that genetic and amino acid diversity presented in the 66 kD protein of all 59 Chinese strains, especially in Borrelia garinii ( B.g) and Borrelia afzelii ( B.a) strains. B.g strains were divided into three subclusters and two scattered strains JC1-7 and JC2-2 according to the amino acid sequences of P66. The P66 sequences of 15 Xinjiang strains represented by XI91-12 in the B.g subcluster 1, changed from CAA to TAA codon at 508aa position, resulting in early termination. Bases A and C were inserted at sequence position 1 523 bp of strains FP1, LB20, LB21, and SZ21 in the B.a genotype, which resulted to early termination at position 511 aa. G base was inserted at 438 bp of LIP94-11 strain, which led to early termination at position 172 aa.

In P66 of 59 Chinese strains, polymorphisms were widely distributed. More importantly, the P66 amino acid sequences of B.g strains had a certain regional character. One of the characteristics of Xinjiang B.g isolates might be the variation at the 508aa location in 15 Xinjiang B.g strains, which may be related to the strains' pathogenicity in this area.