Analysis of GAD65 autoantibodies in Stiff-Person syndrome patients

Raghavan Pillai Raju, Jefferson Foote, J. Paul Banga, Tyler R. Hall, Carolyn J. Padoa, Marinos C. Dalakas, Eva Ortqvist, Christiane S. Hampe

Research output: Contribution to journalArticle

110 Citations (Scopus)

Abstract

Autoantibodies to the 65-kDa isoform of glutamate decarboxylase GAD65 (GAD65Ab) are strong candidates for a pathological role in Stiff-Person syndrome (SPS). We have analyzed the binding specificity of the GAD65Ab in serum and cerebrospinal fluid (CSF) of 12 patients with SPS by competitive displacement studies with GAD65-specific rFab-derived from a number of human and mouse mAbs specific for different determinants on the Ag. We demonstrate considerable differences in the epitope specificity when comparing paired serum and CSF samples, suggesting local stimulation of B cells in the CSF compartment of these patients. Moreover, these autoantibodies strongly inhibit the enzymatic activity of GAD65, thus blocking the formation of the neurotransmitter γ-aminobutyric acid. The capacity of the sera to inhibit the enzymatic activity of GAD65 correlated with their binding to a conformational C-terminal Ab epitope. Investigation of the inhibitory mechanism revealed that the inhibition could not be overcome by high concentrations of glutamate or the cofactor pyridoxal phosphate, suggesting a noncompetitive inhibitory mechanism. Finally, we identified a linear epitope on amino acids residues 4-22 of GAD65 that was recognized solely by autoantibodies from patients with SPS but not by serum from type 1 diabetes patients. A mAb (N-GAD65 mAb) recognizing this N-terminal epitope was successfully humanized to enhance its potential therapeutic value by reducing its overall immunogenicity.

Original languageEnglish (US)
Pages (from-to)7755-7762
Number of pages8
JournalJournal of Immunology
Volume175
Issue number11
DOIs
StatePublished - Dec 1 2005
Externally publishedYes

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Stiff-Person Syndrome
Autoantibodies
Epitopes
Cerebrospinal Fluid
Serum
Aminobutyrates
Pyridoxal Phosphate
Type 1 Diabetes Mellitus
Neurotransmitter Agents
Glutamic Acid
Protein Isoforms
B-Lymphocytes
Amino Acids

ASJC Scopus subject areas

  • Immunology

Cite this

Raju, R. P., Foote, J., Banga, J. P., Hall, T. R., Padoa, C. J., Dalakas, M. C., ... Hampe, C. S. (2005). Analysis of GAD65 autoantibodies in Stiff-Person syndrome patients. Journal of Immunology, 175(11), 7755-7762. https://doi.org/10.4049/jimmunol.175.11.7755

Analysis of GAD65 autoantibodies in Stiff-Person syndrome patients. / Raju, Raghavan Pillai; Foote, Jefferson; Banga, J. Paul; Hall, Tyler R.; Padoa, Carolyn J.; Dalakas, Marinos C.; Ortqvist, Eva; Hampe, Christiane S.

In: Journal of Immunology, Vol. 175, No. 11, 01.12.2005, p. 7755-7762.

Research output: Contribution to journalArticle

Raju, RP, Foote, J, Banga, JP, Hall, TR, Padoa, CJ, Dalakas, MC, Ortqvist, E & Hampe, CS 2005, 'Analysis of GAD65 autoantibodies in Stiff-Person syndrome patients', Journal of Immunology, vol. 175, no. 11, pp. 7755-7762. https://doi.org/10.4049/jimmunol.175.11.7755
Raju RP, Foote J, Banga JP, Hall TR, Padoa CJ, Dalakas MC et al. Analysis of GAD65 autoantibodies in Stiff-Person syndrome patients. Journal of Immunology. 2005 Dec 1;175(11):7755-7762. https://doi.org/10.4049/jimmunol.175.11.7755
Raju, Raghavan Pillai ; Foote, Jefferson ; Banga, J. Paul ; Hall, Tyler R. ; Padoa, Carolyn J. ; Dalakas, Marinos C. ; Ortqvist, Eva ; Hampe, Christiane S. / Analysis of GAD65 autoantibodies in Stiff-Person syndrome patients. In: Journal of Immunology. 2005 ; Vol. 175, No. 11. pp. 7755-7762.
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