[Comparative study on the role of parent Campylobacter jejuni and galE mutant in inducing experimental peripheral...

A comparative study on the role of Campylobacter jejuni (CJ) HB9313 and galE mutant in inducing experimental sciatic nerve damage was conducted in guinea pigs in order to explore whether CJ lipo-oligosaccharide (LOS) is critical component associated with peripheral nerve lesions and find experimental evidence for the presumption of molecular mimicry on the pathogenesis of Guillain-Barre syndromes (GBS) with CJ antecedent infection.

A total of 32 guinea pigs were randomly divided into four groups: parental strain group (n = 10), galE mutant group (n = 10), control group (n = 6) and PBS group (n = 6), and immunized with the whole cell antigens of CJ HB9313 with Freund's adjuvant (FA), the whole cell antigens of galE mutant (without ganglioside-like structure) with FA, PBS with FA, and PBS alone, respectively. Enzyme-linked immunosorbent assay (ELISA) was employed to detect anti-LOS and anti-ganglioside GM1 antibodies in sera of these animals, and comparative morphologic studies of pathologic changes were carried out on the sciatic nerves, including examination of teasing fibers, examination of semithin sections made from epon-embedded tissue blocks under light microscope and transmission electron microscope.

ELISA results indicated that after immunization, the levels of anti-LOS IgG antibody were significantly elevated in animals from parental strain group and galE mutant group as compared with those before immunization (P < 0.01). No statistically significant difference was found between the two groups. However, the mean optical densities (ODs) of IgG antibody against GM1 at 14 and 28 day after immunization, in parental strain group, were 0.661 +/- 0.290 and 0.984 +/- 0.025, respectively, significantly higher than those of galE mutant group, which were 0.193 +/- 0.078 and 0.180 +/- 0.063 (P < 0.01). The results of morphologic examination on sciatic nerves showed that for teased-fiber study, incidence of pathologic abnormalities of teased fibers from animals of galE mutant group was 4.9% (98/2000), significantly lower than that from parental strain group, which was 16% (320/2000), characterized by predominantly axonal degeneration. The difference between them was highly significant statistically (P < 0.01). Examination of semithin sections of sciatic nerves also revealed that obvious pathological changes occurred in the animals from parental strain group, while only minimal abnormalities could be seen from galE mutant group, there was a significant differences between them (P < 0.01). In parental strains group, the predominant pathologicanl change was axonal degeneration with considerable variation in severity. These morphologic changes were confirmed by electron microscopy.

Compared with parental strain, galE mutant without ganglioside-like structure no longer could induce anti-GM1 antibodies, nor induce obvious immune damage of peripheral nerves in experimental guinea pigs. The results of this study provide a strong support to the hypothesis of molecular mimicry as a pathogenesis in patients with GBS following CJ antecedent infection.