Cross-reactivity between annexin A2 and Beta-2-glycoprotein I in animal models of antiphospholipid syndrome
- 195 Downloads
Antiphospholipid syndrome (APS) affects coagulation and the brain by autoimmune mechanisms. The major antigen in APS is beta-2-glycoprotein I (β2-GPI) is known to complex with annexin A2 (ANXA2), and antibodies to ANXA2 have been described in APS. We measured these antibodies in mice with experimental APS (eAPS) induced by immunization with β2-GPI. Sera of these mice reacted significantly with recombinant ANXA2 by enzyme-linked immunosorbent assay (ELISA) and the eAPS mice had significantly high levels of immunoglobulin G (IgG) in the brain by immunoblot assays compared to adjuvant immunized controls. Immunoprecipitation performed by mixing eAPS brain tissue with protein-G beads resulted in identification of two autoantigens unique to the eAPS group, one of which was ANXA2. In order to study more directly and methodically the specific role of anti-ANXA2 antibodies in APS, we immunized mice with β2-GPI which contained no ANXA2 or with ANXA2 and measured antibodies to these proteins. Levels of antibodies to ANXA2 measured by ELISA were 0.72 ± 0.007 arbitrary units (a.u), 0.24 ± 0.03 and 0.02 ± 0.01 a.u for sera from ANXA2, β2-GPI and control mice, respectively (p < 0.0001 and p = 0.037 for the comparison of the ANXA2 and β2-GPI groups to the controls). Purified IgG from β2-GPI sera did not show cross-binding with ANXA2. Antibodies to β2-GPI and phospholipids were found in the β2-GPI immunized group only. The present study suggests an immune response to the β2-GPI–ANXA2 complex in eAPS and provides a novel ANXA2 immunization model which will serve to study the role of ANXA2 antibodies in of APS.
KeywordsAntiphospholipid syndrome Autoimmune Autoantibodies Annexin Anticardiolipin Beta-2-glycoprotein
We thank Ludmila Rachlin for technical assistance. This work was performed in partial fulfillment of the requirements for a Ph.D. degree by Ronen Weiss at the Sagol School of Neuroscience, Sackler Faculty of Medicine, Tel Aviv University, Israel.
- 8.Katzav A, Ben-Ziv T, Blank M, Pick CG, Shoenfeld Y, Chapman J. Antibody-specific behavioral effects: intracerebroventricular injection of antiphospholipid antibodies induces hyperactive behavior while anti-ribosomal-P antibodies induces depression and smell deficits in mice. J Neuroimmunol. 2014;272(1–2):10–5. doi: 10.1016/j.jneuroim.2014.04.003.CrossRefPubMedGoogle Scholar
- 18.Frauenknecht K, Katzav A, Grimm C, Chapman J, Sommer CJ. Neurological impairment in experimental antiphospholipid syndrome is associated with increased ligand binding to hippocampal and cortical serotonergic 5-HT1A receptors. Immunobiology. 2013;218(4):517–26. doi: 10.1016/j.imbio.2012.06.011.CrossRefPubMedGoogle Scholar
- 19.Frauenknecht K, Katzav A, Grimm C, Chapman J, Sommer CJ. Altered receptor binding densities in experimental antiphospholipid syndrome despite only moderately enhanced autoantibody levels and absence of behavioral features. Immunobiology. 2014;219(5):341–9. doi: 10.1016/j.imbio.2013.11.006.CrossRefPubMedGoogle Scholar
- 20.Frauenknecht K, Katzav A, Weiss Lavi R, Sabag A, Otten S, Chapman J, et al. Mice with experimental antiphospholipid syndrome display hippocampal dysfunction and a reduction of dendritic complexity in hippocampal CA1 neurones. Neuropathol Appl Neurobiol. 2015;41(5):657–71. doi: 10.1111/nan.12180.CrossRefPubMedGoogle Scholar
- 28.Ogawa H, Zhao D, Dlott JS, Cameron GS, Yamazaki M, Hata T, et al. Elevated anti-annexin V antibody levels in antiphospholipid syndrome and their involvement in antiphospholipid antibody specificities. Am J Clin Pathol. 2000;114(4):619–28. doi: 10.1309/298H-NLBU-E47G-8PYL.CrossRefPubMedGoogle Scholar
- 35.Nichols CD, Sanders-Bush E. Molecular genetic responses to lysergic acid diethylamide include transcriptional activation of MAP kinase phosphatase-1, C/EBP-beta and ILAD-1, a novel gene with homology to arrestins. J Neurochem. 2004;90(3):576–84. doi: 10.1111/j.1471-4159.2004.02515.x.CrossRefPubMedGoogle Scholar