THE SIALIC ACID RESIDUE OF CAMPYLOBACTER JEJUNI IS THE CRITICAL COMPONENT FOR ALLOWING LIPOOLIGOSACCHARIDES TO MIMIC GANGLIOSIDES IN PERIPHERAL NEUROPATHY

Objectives: To investigate the role of sialic acid residue (N-acetyl neuraminic acid, NANA) in C. jejuni lipooligosaccharides (LOS) to mimic human gangliosides.

Methods: The DNA fragment containing kanamycin resistance cassette and neuB1 (encodes NANA synthetase, which is required for the synthesis of NANA) intragenic fragments flanking the Kmr cassette was cloned into the pGEM-T vector and transformed to a C. jejuni Penner O:19 wild strain isolated from a GBS patient. Cholera toxin B (CTB) subunit binding assay was performed to detect GM1-like structure and NANA was detected by acidic ninhydrin reagent reaction and periodate-resorcinol reaction on both mutant and wide strain LOS. Serum anti-GM1 IgG antibodies were detected by ELISA and sciatic nerves were histologically observed through teased fibers, semithin sections and electron microscope on guinea pigs immunized with both LOSs and normal saline (control group).

Results: (1) RT-PCR confirmed the absence of neuB1 in mutant strain. (2) CTB binding asay can bind wild LOS but failed to the mutant. (3) NANA can't be detected in mutant LOS but presence in the wild. (4) Compared with guinea pigs immunized with mutant LOS, sera anti-GM1 IgG antibodies were significantly increased (P<0.05) and pathological changes at sciatic nerves were more notable (P<0.05) in those immunized with wild LOS, but there were no statistical difference of the both parameters between the mutant and control group.

Conclusion: (1) NeuB1 mutant C. jejuni O:19 strain was constructed successfully. (2) NANA is the critical molecular epitope that determine the mimicry between the human gangliosides and LOS of Guillain-Barre syndrome associated C. jejuni.