Expanded polyglutamine repeats have been proposed to cause neuronal degeneration in Huntington's disease (HD) and related disorders, through abnormal interactions with other proteins containing short polyglutamine tracts such as the transcriptional coactivator CREB binding protein, CBP. We found that CBP was depleted from its normal nuclear location and was present in polyglutamine aggregates in HD cell culture models, HD transgenic mice, and human HD postmortem brain. Expanded polyglutamine repeats specifically interfere with CBP-activated gene transcription, and overexpression of CBP rescued polyglutamine-induced neuronal toxicity. Thus, polyglutamine-mediated interference with CBP-regulated gene transcription may constitute a genetic gain of function, underlying the pathogenesis of polyglutamine disorders.

Bickerstaff reported eight patients who, in addition to acute ophthalmoplegia and ataxia, showed drowsiness, extensor plantar responses or hemisensory loss. This condition has been named Bickerstaff's brainstem encephalitis (BBE). One patient had gross flaccid weakness in the four limbs. Presumably because of the rarity of this disorder, there has been no reported study on a large number of patients with BBE. To clarify its clinical features, we reviewed detailed clinical profiles and laboratory findings for 62 cases of BBE diagnosed by the strict criteria of progressive, relatively symmetrical external ophthalmoplegia and ataxia by 4 weeks, and disturbance of consciousness or hyperreflexia. Ninety-two per cent of the patients involved had had an antecedent illness. Besides ophthalmoplegia and ataxia, disturbance of consciousness was frequent (74%), and facial diplegia (45%), Babinski's sign (40%) and pupillary abnormality and bulbar palsy (34%) were present. Almost all the patients had a monophasic remitting course and generally a good outcome. Serum anti-GQ1b IgG antibody was positive in 66%, and MRI showed brain abnormality in 30% of the patients. Another striking feature was the association with flaccid symmetrical tetraparesis, seen in 60% of the patients. An autopsy study of a BBE patient clearly showed the presence of definite inflammatory changes in the brainstem: there was perivascular lymphocytic infiltration with oedema and glial nodules. Electrodiagnostic study results suggested peripheral motor axonal degeneration. Limb weakness in the BBE cases studied was considered the result of overlap with the axonal subtype of Guillain-Barré syndrome. These findings confirm that BBE constitutes a clinical entity and provide additional clinical and laboratory features of BBE. A considerable number of BBE patients have associated axonal Guillain-Barré syndrome, indicative that the two disorders are closely related and form a continuous spectrum.

Molecular mimicry between microbial and self-components is postulated as the mechanism that accounts for the antigen and tissue specificity of immune responses in postinfectious autoimmune diseases. Little direct evidence exists, and research in this area has focused principally on T cell-mediated, antipeptide responses, rather than on humoral responses to carbohydrate structures. Guillain-Barré syndrome, the most frequent cause of acute neuromuscular paralysis, occurs 1-2 wk after various infections, in particular, Campylobacter jejuni enteritis. Carbohydrate mimicry [Gal␤1-3GalNAc␤1-4(NeuAc␣2-3)Gal␤1-] between the bacterial lipooligosaccharide and human GM1 ganglioside is seen as having relevance to the pathogenesis of Guillain-Barré syndrome, and conclusive evidence is reported here. On sensitization with C. jejuni lipooligosaccharide, rabbits developed anti-GM1 IgG antibody and flaccid limb weakness. Paralyzed rabbits had pathological changes in their peripheral nerves identical with those present in GuillainBarré syndrome. Immunization of mice with the lipooligosaccharide generated a mAb that reacted with GM1 and bound to human peripheral nerves. The mAb and anti-GM1 IgG from patients with Guillain-Barré syndrome did not induce paralysis but blocked muscle action potentials in a muscle-spinal cord coculture, indicating that anti-GM1 antibody can cause muscle weakness. These findings show that carbohydrate mimicry is an important cause of autoimmune neuropathy.