Anti-VGLUT2 autoantibodies in neurological diseases

Autoantibodies are important biomarkers for the diagnosis of autoimmune diseases that help to determine treatment strategies and to understand disease pathology. Despite the increasing numbers of neuronal autoantibody discoveries, there are still patients presenting with neurological autoimmune diseases and so far uncharacterized autoantibodies. Between 12/2016 and 06/2024, we collected sera of 314 patients with a distinct uncharacterized IgG pattern in neuronal tissue indirect immunofluorescence assay (IIFA). By immunoprecipitation and mass spectrometry we identified vesicular glutamate transporter 2 (VGLUT2) as the autoantibody target and confirmed it in sera of 285/314 patients by recombinant IIFA with VGLUT2-expressing HEK293 cells, competitive inhibition assays and colocalization studies with a commercial antibody. The main diagnoses available of 87/285 patients (mean age 58, range 1-92) were encephalitis 25/87, dementia/cognitive impairment 17/87 and polyneuropathy 16/87. Detailed clinical data of 18 patients were collected retrospectively. The major symptoms of those index patients (mean age 56, range 2-78) involved cognitive changes (10/18) including memory impairment, aphasia and disorientation as well as sensorimotor disturbances (9/18) and gait abnormalities (9/18), accompanied by visual impairments (8/18). (Poly)neuropathy was observed in 10/18 cases. The majority of the anti-VGLUT2 index patients had coexisting diabetes mellitus type 2 or other chronic multisystem disorders. In 8/12 index patients, immunotherapy had beneficial effects, although only slight improvements could be obtained in most of the cases. All 17 analyzed index patient sera recognized a cytoplasmic epitope between amino acid 520-564 of VGLUT2, determined by immunoblot with recombinant antigen fragments. Anti-VGLUT2 autoantibody-associated neurological diseases may represent a new type of autoimmune disorders that might benefit from immunomodulatory treatment and predominantly manifests with encephalitis, cognitive deficits and neuropathy.