Abstract
Background To report a novel autoantibody against Purkinje cell in a patient with autoimmune cerebellar ataxia (ACA) associated to Sjogren’s syndrome (SS).Methods The Patients on one centre with cerebellar ataxia of unknown cause, who were tested positive with tissue-based indirect immunofluorescence assay (TBA) on rat cerebellum sections and negative for comprehensive anti-neural autoantibodies panel, were investigated for novel autoantibody identification. Among them, one patient with comorbid ACA and SS was qualified for further exploration. His-immunoprecipitation (HIP) combined with mass spectrometric (MS) analysis was used to identify the target antigen, which was confirmed by recombinant cell based assay (CBA) and antibody neutralization experiments. Results TBA of the patient’s serum and cerebrospinal fluid (CSF) for autoantibody testing revealed binding of IgG antibody, mainly IgG1, to Purkinje cell and granular layer of rat cerebellum. Rab6A was identified as the autoantigen by MS and Western blot, subsequently verified by CBA with HEK293 cells expressing human Rab6A/Rab6B. Furthermore, recombinant human Rab6A/Rab6B protein to neutralize the autoantibodies’ tissue reaction was performed by a parallel confirmed approach.Conclusion Autoantibody against Rab6A/Rab6B may be a novel biomarker in diagnosis of ACA, especially in patients with comorbid ACA and SS. The role of the antibody in mechanism of ACA warrants further study.
Early-onset Purkinje cell dysfunction underlies cerebellar ataxia in peroxisomal multifunctional protein-2 deficiency