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Development of a Recombinant Cell-Based Indirect Immunofluorescence Assay (RC-IFA) for the Determination of Autoantibodies Against "Rings and Rods"-Associated inosine-5'-monophosphate Dehydrogenase 2 in Viral Hepatitis C

Development of a Recombinant Cell-Based Indirect Immunofluorescence Assay (RC-IFA) for the Determination of Autoantibodies Against "Rings and Rods"-Associated inosine-5'-monophosphate Dehydrogenase 2 in Viral Hepatitis C

Christian Probst, Christiane Radzimski, Inga Madeleine Blöcker, Bianca Teegen, Dimitrios P Bogdanos, Winfried Stöcker, Lars Komorowski

Clin Chim Acta. 2013 Mar 15;418:91-6.

PMID: 23333419

Abstract:

Background and aims:
Autoantibodies against so-called "rings and rods" structures, as determined by indirect immunofluorescence assay (IFA) using the human cell line HEp-2, have been described in chronic hepatitis C virus (HCV) infected patients treated with interferon/ribavirin. Recently, cytidine triphosphate synthase (CTPS) and inosine-5'-monophosphate dehydrogenase 2 (IMPDH2), the enzyme inhibited by ribavirin, were proposed as the target antigens. We wanted to confirm the identification and setup a robust system for autoantibody testing in routine laboratories.
Methods:
CTPS and IMPDH2 were individually expressed in HEK293 cells and the recombinant cells were used in IFA (RC-IFA) to analyze sera from 33 anti-"rings and rods" antibody positive individuals with unknown diagnosis, 50 patients with chronic HCV infection, 100 with autoimmune hepatitis, 50 with primary biliary cirrhosis and 50 healthy blood donors.
Results:
We found that all sera with anti-"rings and rods" reacted with recombinant IMPDH2 but none with CTPS. In western blot or ELISA, anti-IMPDH2 positive sera reacted only weakly, if at all, with Escherichia coli derived recombinant IMPDH2 indicating that the autoantibody reaction probably depends on the 3-dimensional conformation of the antigen. A rabbit hyperimmune serum raised against bacterially expressed IMPDH2 produced the ring/rods pattern in IFA using HEp-2.
Conclusions:
We conclude, that IMPDH2 is indeed the main target of anti-"rings and rods" while CTPS is an unlikely target. Moreover, the novel RC-IFA test system allows a standardized semi-quantitative determination of anti-IMPDH2 basing on a defined recombinant antigen.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
IAR42417527	Anti-phospho-EPB41 (pTyr660/418) antibody produced in rabbit			Price

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