Utility of autoantibody against an UCH-L1 epitope as a serum diagnostic marker for neuropsychiatric systemic lupus erythematosus

Objective Neuropsychiatric systemic lupus erythematosus (NPSLE) is one of the most serious complications of systemic lupus erythematosus (SLE), lacking efficient diagnostic biomarkers. Previous studies have shown that anti-ubiquitin carboxyl hydrolase L1(UCH-L1) autoantibody is a promising cerebrospinal fluid (CSF) biomarker for NPSLE diagnosis. The purpose of this study is to explore the serum autoantibodies against different UCH-L1 epitopes and investigate the potential diagnostic value of serum autoantibodies against different UCH-L1 epitopes in NPSLE. Methods The epitopes of UCH-L1 protein were predicted in DNAStar software. The serum levels of different UCH-L1 epitope autoantibodies in 40 NPSLE patients, 32 SLE patients without neuropsychiatric symptoms and 21 healthy controls were determined by enzyme-linked immunosorbent assay (ELISA). Data were analysed using Pearson correlation analysis, ROC curve analysis, nonparametric Mann-Whitney test, t-test and chi 2 test.Results We screened three candidate epitopes of UCH-L1 protein. The autoantibody against amino acid 58 to 69 of UCH-L1 (UCH58-69) showed highest diagnostic power in distinguishing NPSLE patients from SLE patients without neuro-psychiatric symptoms (p=0.0038). The ROC analysis showed that the specificity and sensitivity of anti-UCH58-69 were 92.3% and 37.5%, respectively. In addition, increased serum anti-UCH58-69 levels were associated with increased SLEDAI, CSF microprotein, CSF leukocyte count, ESR, AnuA, anti-dsDNA, IgG and IgM but with decrease of C3 in SLE patients.Conclusion The serum levels of anti-UCH58-69 significantly increased in NPSLE patients compared with SLE patients without neuropsychiatric symptoms and were correlated with disease severity. Anti-UCH58-69 autoantibody may become a novel serum biomarker for NPSLE non-invasive diagnosis, which might be applicable for NPSLE early screening and diagnosis.

Automated summary

This study investigates the diagnostic potential of serum autoantibodies against different UCH-L1 epitopes in NPSLE. The results show that the autoantibody against amino acid 58 to 69 of UCH-L1 (UCH58-69) has the highest diagnostic power in distinguishing NPSLE patients from SLE patients without neuro-psychiatric symptoms. Moreover, increased serum anti-UCH58-69 levels are associated with disease severity in SLE patients.