Comparison Of CstII Gene In Guillain-barré Syndrome-associated Campylobacter Jejuni Strains

Objective:We compared the sialyltransferase gene--cstII gene from 8 Guillain-BarréSyndrome (GBS)-associated Campylobacter jejuni (C.jejuni) strains with that from 3 GBS-unrelated C.jejuni strains, getting the base and amino acid mutations, the changes of secondary structures and finding the region which may be responsible for the pathogenicity of C.jejuni inducing GBS. In this way, we may investigate the pathogenic mechanism of C.jejuni associated with GBS and provide strategy for gene modification.Methods:Select and culture 3 GBS-associated C.jejuni strains isolated from stools of GBS patients in north China, which has been confirmed as GBS-associated by animal model. After sequencing the genome of them, we get the nucleotide sequences of cstII gene through sequence alignment. The nucleotide sequences and deduced amini acid sequences of 3 GBS-associated cstII genes were compared with that from 3 GBS-unrelated C.jejuni strains through bioinformatics software, getting the base and amino acid mutations, the changes of secondary structures. We also align other 5 GBS-associated cstII genes to know whether the differences we got above makes sense. In this way we can find genetic differences between two kinds of C.jejuni strains and speculate the gene region relating to the pathogenicity of GBS.Results:The cstII gene of 3 GBS-associated C.jejuni strains were all composed of 876 base pairs. Compared with GBS-unrelated C.jejuni strains, there were 19 base mutations in lulei strains, resulting in 7 amino acid mutations, 9 base mutations and 3 amino acid mutations in qiaoyuntao strain, and 3 base mutations and 1 amino acid mutations in zhanxing strain. The 9 consistent mutation sites in cstII gene of lulei and qiaoyuntao stains were 342 A→T, 544-546 CCC→AAT, 805 G→A, leading to 3 consistent amino acid mutation:114 E→D,182 R→N,269 V→I. The amino acid mutation of 114 and 182 sites in lulei and qiaoyuntao stains existed in other 5 GBS-associated C.jejuni strains. The amino acid mutation of zhanxing strain was 169 E→G, which located near the 182 amino acid site. The changes of secondary structure in qiaoyuntao, lulei, and zhanxing strains were 165~182 segment, 45~67,172~187 segment and 165~180 segment, respectively. 75% of the GBS-associated cstII genes were Asn-51, while 25% of the GBS-associated and all of the GBS-unrelated cstII genes were Thr-51.Lulei strain showed 98.4% identity to qiaoyuntao strain and the genetic distance between them was 1.6%. The genetic distance between lulei and other strains was 0%~2.8%. Zhanxing strain showed 97% identity to lulei strain and the genetic distance between them was 3.0%. The genetic distance between zhanxing and other strains was 0.3%~3.0%. Qiaoyuntao strain showed 98.6% identity to zhanxing strain and the genetic distance between them was 1.4%.The genetic distance between qiaoyuntao and other strains was 1.0%~1.6%.Conclusions:The 165~180 segment of secondary structures in 3 local GBS-associated cstII amino acid sequences demonstrate the common trend, which also exists in other 5 GBS-associated C.jejuni strains. The results indicate that 165~180 segment of secondary structures in cstII gene may be the responsible region involved in inducing GBS. The senior structure changes in this region may affect the activity of sialyltransferase and the structures of ganglioside epitope, so that the C.jejuni can aquire the pathogenicity of GBS. The cstII genes of GBS-associated C.jejuni strains involved in this study mostly express bi-functional sialyltransferase versions whereas GBS-unrelated sialyltransferases are mono-functional, indicating that bi-functional sialyltransferase of C.jejuni may be related to the pathogenicity of GBS.