IgG1 antibodies against phosphorylcholine are associated with protection in SLE and atherosclerosis: potential underlying mechanisms

Background

The risk of cardiovascular disease (CVD) and atherosclerosis is very high in SLE. This is a clinical problem, and could also shed light on immunity and atherosclerosis in general. IgM antibodies against phosphorylcholine (anti-PC) may be protective in atherosclerosis, cardiovascular disease (CVD) and systemic lupus erythematosus (SLE). We here study IgG1 and IgG2 anti-PC, with focus on atherosclerosis and SLE.

Methods

We determined anti-PC by ELISA in 116 SLE-patients and 110 age- and sex-matched controls. For functional studies, we used three in-house generated, fully human monoclonal IgG1 anti-PC (A01, D05, E01). Apoptosis was induced in Jurkat T-cells and pre-incubated with A01, D05, E01 or isotype control IgG1 and effects on efferocytosis by human macrophages studied. Anti-PC peptide/protein characterization was determined using a proteomics de novo sequencing approach.

Results

IgG1 but not IgG2 anti-PC levels were higher among SLE patients (p=0.02). IgG1 anti-PC was negatively associated with SLICC and SLEDAI (OR: 2,978 CI: 0.876–10.098, OR: 5.108 CI 1.3 20.067 respectively) and negatively associated with CVD, atherosclerotic plaques and echolucent (potentially vulnerable plaques) but the association for the two former was not significant after controlling for confounders. D05 had maximum effect on macrophage efferocytosis efficiency, followed by A01 and E01. The 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 PC on apoptotic cell surface and other neo-epitopes.

Conclusion

Anti-PC IgG1 is negatively associated with disease activity, and disease damage in SLE, but the negative association with CVD is also dependent on confounding risk factors. One potential underlying mechanism could be increased clearance of dead cells.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): Swedish Heart and Lung Foundation, Reumatikerfonden

THU0230 IGG1 ANTIBODIES AGAINST PHOSPHORYLCHOLINE ARE NEGATIVELY ASSOCIATED WITH DISEASE ACTIVITY, DISEASE DAMAGE, CARDIOVASCULAR DISEASE AND ATHEROSCLEROSIS IN SLE: POTENTIAL UNDERLYING MECHANISMS

Background:

Phosphorylcholine (PC) is an important component in cellular membranes and in lipoproteins that is exposed and recognized by the immune system, when cells undergo apoptosis or lipoproteins like LDL undergo oxidation. PC is also exposed in some microorganisms including nematodes and bacteria (non-self). We reported that IgM anti-PC is associated with protection in atherosclerosis, SLE, RA and other chronic inflammatory conditions.1We also reported potential underlying protective mechanisms: 1: increase in clearance of human dead cells,22: inhibition of uptake of oxLDL in macrophages, 3: inhibition of cell death.14: anti-inflammatory; 5: promotion of polarization of T regulatory cells in SLE-patients´ T cells from a low level and also in plaque T cells.3We generated in-house fully human IgG1 anti-PC clones for experimental studies to study anti-PC properties in humans. In contrast to mice, anti-PC are not germ-line encoded with a dominant clone.4

Objectives:

We here study IgG1 and IgG2 anti-PC, with focus on atherosclerosis and SLE and properties of fully human IgG1 clones, in relation to SLE.

Methods:

We determined anti-PC by ELISA in 116 SLE-patients and 110 age- and sex-matched controls. For functional studies, we used three in-house generated, fully human monoclonal IgG1 anti-PC (A01, D05, E01). Apoptosis was induced in Jurkat T-cells and pre-incubated with A01, D05, E01 or isotype control IgG1 and effects on efferocytosis by human macrophages studied. Anti-PC peptide/protein characterization was determined using a proteomics de novo sequencing approach.

Results:

IgG1 but not IgG2 anti-PC levels were higher among SLE patients (p=0.02). IgG1 anti-PC was negatively associated with SLICC and SLEDAI (OR: 2,978 CI: 0.876-10.098, OR: 5.108 CI 1.3 20.067 respectively) and negatively associated with CVD, atherosclerotic plaques and echolucent (potentially vulnerable plaques) but the association for the two former was not significant after controlling for confounders. D05 had maximum effect on macrophage efferocytosis efficiency, followed by A01 and E01. The 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 PC on apoptotic cell surface and other neo-epitopes.

Conclusion:

Anti-PC IgG1 is negatively associated with disease activity, and disease damage in SLE, but the negative association with CVD is also dependent on confounding risk factors. One potential underlying mechanism could be increased clearance of dead cells.

References:

[1]Frostegard J. Immunity, atherosclerosis and cardiovascular disease.BMC Med. 2013;11:117.

[2]Rahman M, Sing S, Golabkesh Z, Fiskesund R, Gustafsson T, Jogestrand T, Frostegard AG, Hafstrom I, Liu A and Frostegard J. IgM antibodies against malondialdehyde and phosphorylcholine are together strong protection markers for atherosclerosis in systemic lupus erythematosus: Regulation and underlying mechanisms.Clin Immunol. 2016;166-167:27-37.

[3]Sun J, Lundstrom SL, Zhang B, Zubarev RA, Steuer J, Gillgren P, Rahman M, Ajeganova S, Liu A and Frostegard J. IgM antibodies against phosphorylcholine promote polarization of T regulatory cells from patients with atherosclerotic plaques, systemic lupus erythematosus and healthy donors.Atherosclerosis. 2018;268:36-48.

[4]Fiskesund R, Steen J, Amara K, Murray F, Szwajda A, Liu A, Douagi I, Malmstrom V and Frostegard J. Naturally occurring human phosphorylcholine antibodies are predominantly products of affinity-matured B cells in the adult.J Immunol. 2014;192:4551-9.

Disclosure of Interests: :

Divya Thiagarajan: None declared, Roland Fiskesund: None declared, Johanna Steen: None declared, Mizanur Rahman: None declared, Susanna Lundström: None declared, Johan Frostegård Grant/research support from: Unconditional competitive grant from Amgen, related only to PCSK9, not the topic of this abstract

Immunoglobulin G1 Antibodies Against Phosphorylcholine Are Associated With Protection in Systemic Lupus Erythematosus and Atherosclerosis: Potential Underlying Mechanisms

OBJECTIVE

Immunoglobulin M antibodies against phosphorylcholine (anti-PCs) may be protective in atherosclerosis, cardiovascular disease (CVD), and systemic lupus erythematosus (SLE). We study immunoglobulin G1 (IgG1) and immunoglobulin G2 (IgG2) anti-PCs, with a focus on atherosclerosis and SLE.

METHODS

We determined anti-PCs by using the enzyme-linked immunosorbent assay in 116 patients with SLE and 110 age- and sex-matched controls. For functional studies, we used three in-house-generated, fully human monoclonal IgG1 anti-PCs (A01, D05, and E01). Apoptosis was induced in Jurkat T cells and preincubated with A01, D05, E01, or IgG1 isotype control, and effects on efferocytosis by human macrophages were studied. Anti-PC peptide/protein characterization was determined using a proteomics de novo sequencing approach.

RESULTS

IgG1, but not IgG2, anti-PC levels were higher among patients with SLE (P = 0.02). IgG1 anti-PCs were negatively associated with Systemic Lupus International Collaborating Clinics (SLICC) damage index and Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) scores (odds ratio [OR]: 2.978 [confidence interval (CI): 0.876-10.098] and OR: 5.108 [CI 1.3-20.067], respectively) and negatively associated with CVD, atherosclerotic plaques, and echolucent plaques (potentially vulnerable plaques), but the association for the two former was not significant after controlling for confounders. D05 had a maximum effect on macrophage efferocytosis efficiency, followed by A01 and E01. The monoclonal antibodies showed differential binding specificity to PC and PC-associated neoepitopes. A peptide analysis showed a difference in the complementarity-determining region 3 of the three IgG1 anti-PC clones that are crucial for recognition of PC on apoptotic cell surfaces and other neoepitopes.

CONCLUSION

IgG1 anti-PCs are negatively associated with disease activity and disease damage in SLE, but the negative association with CVD is also dependent on confounding risk factors. One potential underlying mechanism could be increased clearance of dead cells.

Inhibition spectrum studies of microthecin and other anhydrofructose derivatives using selected strains of Gram-positive and -negative bacteria, yeasts and moulds, and investigation of the cytotoxicity of microthecin to malignant blood cell lines

AIMS

To prepare 1,5-anhydro-d-fructose (AF) derivatives, test their microbial inhibition spectrum, and to further examine the most effective AF derivative against Pseudomonas aeruginosa and malignant blood cell lines.

METHODS AND RESULTS

Microthecin and nine other AF derivatives were synthesized from AF. The 10 compounds were tested in vitro against Gram-positive (GP) and Gram-negative (GN) bacteria, yeasts and moulds using a well diffusion method and in a Bioscreen growth analyser. Of the test compounds, microthecin exhibited the most significant antibacterial activity at 100-2000 ppm against both GP and GN bacteria, including Ps. aeruginosa. Further tests with three malignant blood cell lines (Mutu, Ramos, Raji) and one normal cell line indicated that microthecin was a cell toxin, with a cell mortality >85% at 50 ppm. The other nine AF derivatives demonstrated low or no antimicrobial activity.

CONCLUSIONS

Microthecin was active 100-2000 ppm against GP and GN bacteria including Ps. aeruginosa, but was inactive against yeasts and moulds. Microthecin was also a cytotoxin to some mammalian cell lines.

SIGNIFICANCE AND IMPACT OF THE STUDY

Microthecin might have potential for development as a novel drug against Ps. aeruginosa and to target cancer cells. It might also be developed as a food processing aid to control bacterial growth.