Axonal Guillain-Barré syndrome: carbohydrate mimicry and pathophysiology.

Acute motor axonal neuropathy (AMAN), an axonal subtype of Guillain-Barré syndrome (GBS), is characterized by pure motor involvement, frequent antecedent infection by Campylobacter jejuni, association with anti-GM1 or anti-GD1a immunoglobulin G (IgG) antibodies, and the electrophysiological features of axonal degeneration and reversible conduction block. Molecular mimicry exists between GM1 and GD1a gangliosides and lipooligosaccharides (LOSs) of C. jejuni isolates from AMAN. Sensitization of rabbits with GM1 or C. jejuni LOS induces anti-GM1 IgG antibodies and subsequent flaccid paralysis. Pathological changes seen in rabbit model peripheral nerves are identical to those in human AMAN. Immunohistochemistry of AMAN rabbits shows disruption of nodal sodium channel clusters and detachment of paranodal myelin terminal loops, similar to paranodal demyelination, which would significantly reduce the safety factor for impulse transmission and might be responsible for the rapidly reversible conduction block frequently present in human AMAN. C. jejuni sialyltransferase (Cst-II), which functions in the biosynthesis of ganglioside-like LOSs, determines the transferase activity. Strains with cst-II (Thr51) express GM1 and GD1a epitopes, whereas GBS patients infected with cst-II (Thr51) strains have anti-GM1 or anti-GD1a IgG antibodies. The cst-II gene is responsible for the development of GBS. Immunological, pathological, electrophysiological, and bacteriological studies have provided strong evidence of carbohydrate mimicry being a cause of AMAN and clarified the mechanisms of nerve conduction failure in AMAN.