Details

Autor(en) / Beteiligte

• Wyatt, R. C.
• Brigatti, C.
• Liberati, D.
• Grace, S. L.
• Gillard, B. T.
• Long, A. E.
• Marzinotto, I.
• Shoemark, D. K.
• Chandler, K. A.
• Achenbach, P.
• Gillespie, K. M.
• Piemonti, L.
• Lampasona, V.
• Williams, A. J. K.

Titel

The first 142 amino acids of glutamate decarboxylase do not contribute to epitopes recognized by autoantibodies associated with Type 1 diabetes

Ist Teil von

• Diabetic medicine, 2018-07, Vol.35 (7), p.954-963

Ort / Verlag

England: Wiley Subscription Services, Inc

Erscheinungsjahr

2018

Quelle

MEDLINE

Beschreibungen/Notizen

• Aims Glutamate decarboxylase (GAD) antibodies are the most widely used predictive marker for Type 1 diabetes, but many individuals currently found to be GAD antibody‐positive are unlikely to develop diabetes. We have shown previously that radioimmunoassays using N‐terminally truncated 35S‐GAD65(96–585) offer better disease specificity with similar sensitivity to full‐length 35S‐GAD65(1–585). To determine whether assay performance could be improved further, we evaluated a more radically truncated 35S‐GAD65(143–585) radiolabel. Methods Samples from people with recent‐onset Type 1 diabetes (n = 157) and their first‐degree relatives (n = 745) from the Bart's–Oxford family study of childhood diabetes were measured for GAD antibodies using 35S‐labelled GAD65(143–585). These were screened previously using a local radioimmunoassay with 35S‐GAD65(1–585). A subset was also tested by enzyme‐linked immunosorbent assay (ELISA), which performs well in international workshops, but requires 10 times more serum. Results were compared with GAD antibody measurements using 35S‐GAD65(1–585) and 35S‐GAD65(96–585). Results Sensitivity of GAD antibody measurement was maintained using 35S‐GAD65(143–585) compared with 35S‐GAD65(1–585) and 35S‐GAD65(96–585). Specificity for Type 1 diabetes was improved compared with 35S‐GAD65(1–585), but was similar to 35S‐GAD65(96–585). Relatives found to be GAD antibody‐positive using these truncated labels were at increased risk of diabetes progression within 15 years, compared with those positive for GAD(1–585) antibody only, and at similar risk to those found GAD antibody‐positive by ELISA. Conclusions The first 142 amino acids of GAD65 do not contribute to epitopes recognized by Type 1 diabetes‐associated GAD antibodies. Low‐volume radioimmunoassays using N‐terminally truncated 35S‐GAD65 are more specific than those using full‐length GAD65 and offer practical alternatives to the GAD antibody ELISA for identifying children at increased risk of Type 1 diabetes. What's new? The N‐terminus of glutamate decarboxylase (GAD65) contributes little to epitopes recognized by Type 1 diabetes associated GAD antibodies. Radioimmunoassays using N‐terminally truncated 35S‐GAD65(96–585) improve the specificity of GAD antibody measurement. We show that using a more radically truncated 35S‐GAD65(143–585) radiolabel to measure GAD antibodies does not impact assay sensitivity and improves diabetes specificity compared with full‐length 35S‐GAD65(1–585). Relatives of people with Type 1 diabetes who were GAD antibody‐positive using truncated radiolabels had increased risk of progression to diabetes within 15 years compared with those positive for GAD(1–585) antibody alone, and were at similar risk to those found positive using a high‐performing commercial GAD antibody enzyme‐linked immunosorbent assay.