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Williams, A.J.* ; Somerville, M.* ; Rokni, S.* ; Bonifacio, E.* ; Yu, L.* ; Eisenbarth, G.S.* ; Akolkar, B.* ; Steffes, M.W.* ; Bingley, P.J.*

Azide and Tween-20 reduce binding to autoantibody epitopes of islet antigen-2; implications for assay performance and reproducibility.

J. Immunol. Methods 351, 75-79 (2009)
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Autoantibodies to islet antigen 2 (IA-2A) are important markers for predicting diabetes in children and young adults. Harmonization of IA-2A assay measurement is essential if results from different laboratories are to be compared. We investigated whether sodium azide, a bacteriostatic agent added to some assays, could affect IA-2A binding and thereby contribute to differences in IA-2A measurement between laboratories. Addition of 0.1% azide to assay buffer was found to reduce median IA-2A binding of 18 selected sera from IA-2A positive patients with type 1 diabetes and their relatives by 41% (range, 78 to -33%, p<0.001). The effect on binding was epitope specific; median IA-2A binding by 14 sera with antibodies to the protein tyrosine phosphatase region of IA-2 was reduced by 48% (range, 11 to 78%, p<0.001), while binding by 4 sera with antibodies specific to only the juxtamembrane region of IA-2 showed no change (median increase 16% (range 6 to 33%, p=0.125). When the Tween-20 concentration was reduced from 1% to 0.15% the median reduction in IA-2A binding with azide by the 18 sera was only 10% (range, -12 to 41%, p<0.001). Tween-20 also exerted an independent effect, since median IA-2A binding increased by 23% (range 3% to 86%, p<0.001) when Tween-20 concentration was reduced from 1% to 0.15% in the absence of azide. We conclude that common assay reagents such as azide and Tween-20 can strongly influence IA-2A binding in an epitope-related manner, and their use may explain some of the differences between laboratories in IA-2A measurement.
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Publication type Article: Journal article
Document type Scientific Article
ISSN (print) / ISBN 0022-1759
e-ISSN 1872-7905
Quellenangaben Volume: 351, Issue: 1-2, Pages: 75-79 Article Number: , Supplement: ,
Publisher Elsevier
Reviewing status Peer reviewed
Institute(s) Institute for Pancreatic Beta Cell Research (IPI)