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Characteristics of in-vitro phenotypes of glutamic acid decarboxylase 65 autoantibodies in high-titre individuals
2013 (English)In: Clinical and Experimental Immunology, ISSN 0009-9104, E-ISSN 1365-2249, Vol. 171, no 3, 247-254Article in journal (Refereed) Published
Abstract [en]

Previous studies have indicated phenotypical differences in glutamic acid decarboxylase 65 autoantibodies (GADA) found in type 1 diabetes (T1D) patients, individuals at risk of developing T1D and stiff-person syndrome (SPS) patients. In a Phase II trial using aluminium-formulated GAD65 (GAD-alum) as an immunomodulator in T1D, several patients responded with high GADA titres after treatment, raising concerns as to whether GAD-alum could induce GADA with SPS-associated phenotypes. This study aimed to analyse GADA levels, immunoglobulin (Ig)G1–4 subclass frequencies, b78- and b96·11-defined epitope distribution and GAD65 enzyme activity in sera from four cohorts with very high GADA titres: T1D patients (n = 7), GAD-alum-treated T1D patients (n = 9), T1D high-risk individuals (n = 6) and SPS patients (n = 12). SPS patients showed significantly higher GADA levels and inhibited the in-vitro GAD65 enzyme activity more strongly compared to the other groups. A higher binding frequency to the b78-defined epitope was found in the SPS group compared to T1D and GAD-alum individuals, whereas no differences were detected for the b96·11-defined epitope. GADA IgG1–4 subclass levels did not differ between the groups, but SPS patients had higher IgG2 and lower IgG4 distribution more frequently. In conclusion, the in-vitro GADA phenotypes from SPS patients differed from the T1D- and high-risk groups, and GAD-alum treatment did not induce SPS-associated phenotypes. However, occasional overlap between the groups exists, and caution is indicated when drawing conclusions to health or disease status.

Keyword [en]
GAD65 immunotheraphy; GADA; stiff-person syndrome; type 1 diabetes
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-84840 (URN)10.1111/cei.12026 (DOI)000314655100003 (ISI)oai:DiVA.org:liu-84840 (OAI)diva2:562436 (DiVA)
Note

The title of the article in manuscript form was "Characteristics of GAD65 autoantibodies (GADA) in high titer individuals".

Available from2012-10-24 Created:2012-10-24 Last updated:2013-03-14Bibliographically approved
In thesis
1. Characteristics of GADA in Type 1 Diabetes following Immunomodulation with GAD65
Open this publication in new window or tab >>Characteristics of GADA in Type 1 Diabetes following Immunomodulation with GAD65
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Type 1 diabetes (T1D) is a serious autoimmune disease which increases worldwide and affects children at a young age, but there still is no cure available. Clinical intervention trials in recent onset T1D patients are therefore very important, since even a modest preservation of β-cell function has proven to reduce end-organ complications. Glutamic acid decarboxylase 65 (GAD65) is one of the major antigens in T1D, to which autoantibodies (GADA) are formed. Immunomodulation with aluminum-formulated GAD65 (GAD-alum) has been considered both in the prevention and intervention of T1D. In a phase II trial using GADalum we showed clinical benefits in C-peptide preservation, but unfortunately a following larger European phase III trial failed to reach primary end-point. The general aim of this thesis was to study the characteristics and phenotypes of GADA following immunomodulation with GAD-alum in T1D patients during a phase II and III trial.

In the phase II trial, a transient increase of the GADA IgG3 and IgG4 subclasses, and a decrease in IgG1 was detected as part of the treatment-induced GADA levels after 2 GADalum doses, a result interpreted to be T helper (Th) 2-associated. This Th2-associated immune response was also observed, in parallel to increased GADA levels, during the following phase III trial including a larger group of patients. However, enhanced Th2-like IgG subclass distribution, reflected as increased IgG4 frequency, was in contrast only observed in the group treated with 4 doses of GAD-alum. In addition, the GADA fold-change was associated with in vitro GAD65-stimulated cytokine secretion, but only in patients receiving 2 GAD-alum doses. Furthermore, a 4-year follow-up of the phase II trial showed that the effect of GAD-alum treatment was long-lasting as GADA titers remained elevated. Even though the phase III trial did not reach primary end-point, and was closed after 15 months, preservation of β-cell function was observed in the small sub-group of Swedish patients receiving 2 GAD-alum doses that completed the 30 months trial-period. During the trials, concerns were raised whether the elevated GADA titers might induce Stiff person syndrome (SPS), a disease affecting the nervous system, but in vitro analysis of GADA phenotypes showed that the GAD65-enzyme activity and GADA epitope distribution differed from that detected in SPS patients.

Continued research to clarify how immunomodulation with autoantigens affects immune responses and also to identify which patients are suitable for treatment, is crucial for optimizing future T1D intervention- and prevention trials.

Publisher, range
Linköping: Linköping University Electronic Press, 2012. 83 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1337
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-84842 (URN)978-91-7519-774-6 (ISBN)
Public defence
2012-11-15, Berzeliussalen, Hälsouniversitetet, Campus US, Linköpings universitet, Linköping, 13:00 (English)
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Available from2012-10-24 Created:2012-10-24 Last updated:2012-10-30Bibliographically approved

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Chéramy, MikaelHampe, Christiane S.Ludvigsson, JohnnyCasas, Rosaura
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PediatricsFaculty of Health SciencesDepartment of Medicine, University of Washington, Seattle, WA, USADepartment of Paediatrics in Linköping
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