Background Systemic lupus erythematosus (SLE) is an autoimmune disease which may be caused by development of the autoantibodies. On the other hand, SLE is a high-risk group ofatherosclerosis, so it is possible that some of autoantibodies in SLE are the result of atherosclerosis-related diseases such as cerebral infarction (CI), cardiovascular disease (CVD) and diabetes mellitus (DM).
Objectives In the present study, we have comprehensively screened autoantigens in the sera of patients with SLE by the protein array method. We then selected and identified autoantigens specific for cerebral infarction (CI), CVD and/or diabetes mellitus (DM).
Methods 1) Protein array screening Initial screening was performed using ProtoArrays. A total of 11 sera, 6 from patients and 5 from healthy donors, were used to detect antigens recognized specifically by IgG antibodies in the sera of patients. 2) Peptide synthesis Three epitope sites in the candidate antigen proteins were predicted using the program ProPred. N-terminal biotinylated 15mer peptides were synthesized and used in the second and third screening. AlphaLISA (Amplified Luminescence Proximity Homogeneous Assay) To evaluate the serum antibody levels, AlphaLISA was used.
Results After the initial screening using protein array, we identified 67 antigens in sera of patients with SLE. In the second screening, 170 peptides derived from amino acid sequences of 67 antigens were synthesized and used as antigens for analysis of serum antibody levels by AlphaLISA. The antibody levels for ten peptides were significantly higher in the sera of patients with SLE than in those of healthy donors. Further AlphaLISA analysis of sera of patients with CI, CVD or DM revealed that the serum antibody levels for four peptides derived from SOSTDC1, CTNND1, CLDND1 and CCNG2 were elevated in patients as compared to those of healthy donors.
Conclusions Serum antibody levels against peptide antigens of SOSTDC1, CTNND1, CLDND1 and CCNG2 are useful markers for diagnosis of the progression of CI, CVD and/or DM.
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Acknowledgements This work was partly supported by Grants-in-Aid of Japan Science and Technology Agency
(Exploratory Research No. 14657335) and Ministry of Health, Labour and Welfare, and a grant from
SEISHIN Medical Research Foundation.
Disclosure of Interest None declared