THU0216 IGG1 ANTIBODIES AGAINST PHOSPHORYLCHOLINE ARE ASSOCIATED WITH PROTECTION IN SLE AND ATHEROSCLEROSIS: POTENTIAL UNDERLYING MECHANISMS
Authors: Divya Thiagarajan, Nina Oparina, Johanna Steen, Mizanur Rahman, Max Vikström, Roman Zubarev, Susanna Lundström, Johan Frostegård
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background:</h3> IgM antibodies against phosphorylcholine (anti-PC) may be protective in atherosclerosis, cardiovascular disease (CVD) and systemic lupus erythematosus (SLE). Less is known about other anti-PC isotypes and subclasses. In this study, we study the role of IgG1 and IgG2 anti-PC, with focus on atherosclerosis and SLE. <h3>Objectives:</h3> To study the role of IgG1 and IgG2 anti-PC, with focus on atherosclerosis and SLE, both in a clinical setting and by experimental studies, where we use our in-house produced monoclonal IgG1 anti-PC. <h3>Methods:</h3> We determined IgG1 and IgG2 anti-PC in our SLE cohort study (SLEVIC), among 116 SLE-patients from Karolinska University Hospital Huddinge and 110 population controls matched for age and gender. The level of antibodies was measured by ELISA. For functional studies, we used three of our in-house generated, fully human monoclonal IgG1 anti-PC (A01, D05, E01). Primary human macrophages were derived from peripheral blood. Apoptosis was induced in Jurkat T-cells and pre-incubated with A01, D05, E01 or isotype control IgG1 and effect on phagocytosis by marcophages studied. Anti-PC peptide/protein characterization was determined in anti-PC clones compared to isotype control using a proteomics de novo sequencing approach. <h3>Results:</h3> IgG1 but not IgG2 anti-PC levels were higher among SLE patients than controls (p=0.02). IgG1 anti-PC was negatively associated with prevalence of atherosclerotic plaques, below 10<sup>th</sup>percentile, (OR: 2.48, CI: 0.69-9.00). IgG1 Anti-PC was negatively associated with CVD, SLICC and SLEDAI (OR: 4.74 CI: 1.29-17.39, OR: 2,978 CI: 0.876-10.098, OR: 5.108 CI 1.3 20.067 respectively). Monoclonal D05 had maximum effect on macrophage efferocytosis efficiency, followed by A01 and E01. This is because anti-PC IgG1s bind to phosphorylcholine exposed on apoptotic cells and facilitate the uptake by macrophage. The in-house produced monoclonal antibodies showed differential binding specificity to PC and PC associated neo-epitopes. Peptide analysis showed difference in the CDR3 region of the three anti-PC IgG1 clones which are crucial for recognition of the phosphorylcholine on the apoptotic cell surface and other neo-epitopes. Conclusion: anti-PC IgG1 is negatively associated with disease activity and atherosclerosis in SLE. One potential underlying mechanism could be increased phagocytosis and clearance of dead cells. Our findings raise the possibility of prevention and/or treatment of SLE (and atherosclerosis) to raise anti-PC levels, by passive or active immunization. <h3>References:</h3> [1] Frostegard J. Immunity, atherosclerosis and cardiovascular disease. BMC Med. 2013;11:117. [2] Anania C, Gustafsson T, Hua X, Su J, Vikstrom M, de Faire U, Heimburger M, Jogestrand T and Frostegard J. Increased prevalence of vulnerable atherosclerotic plaques and low levels of natural IgM antibodies against phosphorylcholine in patients with systemic lupus erythematosus. Arthritis Res Ther. 2010;12:R214. <h3>Disclosure of Interests:</h3> Divya Thiagarajan: None declared, Nina Oparina: None declared, Johanna Steen: None declared, Mizanur Rahman: None declared, Max Vikström: None declared, Roman Zubarev: None declared, Susanna Lundström: None declared, Johan Frostegård Shareholder of: Minor shareholder and inventor in startup-company Athera Biotechnologies, but they do not produce drugs yet and rheumatology is not in their focus.