Cloning and expression of beta(2)-glycoprotein 1 recognized by antiphospholipid antibodies and its clinical investigation

Objective To investigate cloning and expression of beta(2)-glycoprotein 1 ( beta(2)GP1) recognized by antiphospholipid antibodies and to study the clin ical significance of anti-beta(2)GP1 antibodies in patients with autoimmune disease. Methods By using reverse transcription-PCR method, two kinds of expression plasmid which expressed beta(2)GP1 and the fifth domain or beta(2)-glycopro tein 1 (beta(2)GP1-D5) proteins respectively were constructed in this study . Their antigenic activities were identified by immunoblots using rabbit an ti-beta(2)GP1 antibodies. Anti-r beta(2)GP1 and anti-r beta(2)GP1-D5 antibo dies in the 112 patents were detected by ELISA using r beta(2)GP1 and r bet a(2)GP1-D5 as coating antigens. Results A significant correlation in statistics (r = 0.667, P < 0.01) betwe en the levels of anti-r beta(2)GP1 and anticardiolipin antibodies (aCL) was found. The presence of anti-r beta 2GP1 antibodies was associated with an increased frequency of history of thrombosis and/or recurrent abortion. Ant i-r beta(2)GP1 assay provided better specificity than conventional aCL assa y. The binding of anti-r beta(2)GP1 from the sera of patients with antiphos pholipid syndrome (APS) to r beta(2)GP1 was inhibited by r beta(2)GP1-D5. M eanwhile, of 27 patients who had positive anti-r beta(2)GP1 antibodies in s era, 27 (96.4%) had positive anti-r beta(2)GP1-D5 antibodies. Conclusion It is indicated that antigenic epitope of beta(2)GP1 might be lo cated in its fifth domain. Detection of anti-r beta(2)GP1 antibodies may be of potential value for evaluating the risk of thrombosis and/or other APS associated symptom.