HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) 079632.Supplemental data All Versions of this Article: clinchem.2006.079632v1 53/6/1137    most recent Submit an electronic Letter to the Editor about this paper Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Metzger, J. Articles by Luppa, P. B. Search for Related Content PubMed PubMed Citation Articles by Metzger, J. Articles by Luppa, P. B. Related Collections Clinical Immunology Proteomics and Protein Markers

Biosensor Analysis of ß2-Glycoprotein I–Reactive Autoantibodies: Evidence for Isotype-Specific Binding and Differentiation of Pathogenic from Infection-Induced Antibodies

¹ Institute of Clinical Chemistry and Pathobiochemistry, Klinikum Rechts der Isar der TU München, München, Germany.
² Institute of Clinical Chemistry and Laboratory Medicine, Johannes Gutenberg-Universität Mainz, Mainz, Germany.

^aAddress correspondence to this author at: Institute of Clinical Chemistry and Pathobiochemistry, Ismaninger Str. 22, D-81675 Munich, Germany. Fax 49-89-4140-4875; e-mail luppa{at}klinchem.med.tum.de.

Background: For the laboratory diagnosis of the antiphospholipid syndrome (APS) we developed a biosensor with the ability to distinguish between disease-relevant anti-ß2-glycoprotein I (ß2GPI) autoantibodies (anti-ß2GPI) and pathogen-specific ß2GPI cross-reactive antibodies that occur transiently during infections.

Methods: We used a surface plasmon resonance (SPR) biosensor device. For the detection of anti-ß2GPI in serum samples, affinity-purified human ß2GPI was covalently attached to a functionalized n-alkanethiol self-assembling monolayer on the biosensor chip. After verifying the specificity of the biosensor system with a panel of monoclonal antibodies to ß2GPI, we analyzed sera from healthy donors and patients suffering from APS, systemic lupus erythematosus (SLE), syphilis, or parvovirus B19 infections. The SPR results were compared with ß2GPI-specific ELISA.

Results: Using the SPR biosensor, we recorded antigen binding curves with response levels in the range of 50–500, resonance units (RU) for anti-ß2GPI ELISA-positive APS patient sera. The amplitudes of the antiphospholipid antibody (APL) responses in the biosensor correlated with the overall IgG and IgM anti-ß2GPI ELISA titers with a correlation coefficient of 0.87. Moreover, we observed immunoglobulin isotype-specific association and dissociation profiles for APL binding of different APS patient sera to the biosensor-immobilized ß2GPI. In contrast to APS patient samples, no significant anti-ß2GPI binding (response levels <35 RU) was observed in samples from healthy individuals or from patients suffering from SLE, syphilis, or parvovirus B19 infection.

Conclusions: The SPR biosensor system enables specific detection of APS-associated ß2GPI-reactive APL and differentiation from ß2GPI cross-reactive antibodies that occur frequently during acute infections. The established association/dissociation plot for anti-ß2GPI responses in APS patient sera gives additional information regarding the influence of anti-ß2GPI IgG and IgM isotype distribution.