Evaluating Anti-SmD1-amino-acid 83-119 Peptide Reactivity in Children with Systemic Lupus Erythematosus and Other Immunological Diseases

Abstract

Background:SmD1-amino-acid 83-119 peptide (SmD183-119) is the major epitope of Smith (Sm) antigen, which is specific for adult systemic lupus erythematosus (SLE). The anti-SmD183-119 antibody has exhibited higher sensitivity and specificity than anti-Sm antibody in diagnosing adult SLE. However, the utility of anti-SmD183-119 antibodies remains unclear in children with SLE (cSLE). This study aimed to assess the characteristics of anti-SmD183-119 antibody in the diagnosis of cSLE.Methods:Samples from 242 children with different rheumatological and immunological disorders, including autoimmune diseases (SLE [n = 46] and ankylosing spondylitis [AS, n = 11]), nonautoimmune diseases (Henoch-Schonlein purpura [HSP, n = 60], idiopathic thrombocytopenia purpura [n = 27], hematuria [n = 59], and arthralgia [n = 39]) were collected from Shanghai Children's Medical Center from March 6, 2012 to February 27, 2014. Seventy age- and sex-matched patients were enrolled in this study as the negative controls. All the patients' sera were analyzed for the anti-SmD183-119, anti-Sm, anti-U1-nRNP, anti-double-stranded DNA (dsDNA), anti-nucleosome, anti-SSA/Ro60, anti-SSA/Ro52, anti-SSB, anti-Scl-70, and anti-histone antibodies using the immunoblotting assay. The differences in sensitivity and specificity between anti-SmD183-119 and anti-Sm antibodies were compared by Chi-square test. The correlations between anti-SmD183-119 and other auto-antibodies were analyzed using the Spearman's correlation analysis. A value of P < 0.05 was considered statistically significant.Results:Thirty-six out of 46 patients with cSLE were found to be positive for anti-SmD183-119, while 12 patients from the cSLE cohort were found to be positive for anti-Sm. Compared to cSLE, it has been shown that anti-SmD183-119 was only detected in 27.3% of patients with AS and 16.7% of patients with HSP. In comparison with anti-Sm, it has been demonstrated that anti-SmD183-119 had a higher sensitivity (78.3% vs. 26.1%, χ2 = 25.1, P < 0.05) and a lower specificity (90.8% vs. 100%, χ2 = 13.6, P < 0.05) in the diagnosis of cSLE. Further analysis revealed that anti-SmD183-119 antibodies were positively correlated with anti-dsDNA, anti-nucleosome, and anti-histone antibodies in cSLE. Moreover, it has been clearly shown that anti-SmD183-119 was more sensitive than anti-Sm in discriminating autoimmune diseases from nonautoimmune disorders in patients with arthralgia or hematuria.Conclusions:Measurement of anti-SmD183-119 in patients with cSLE has a higher sensitivity and a marginally lower specificity than anti-Sm. It has been suggested that inclusion of anti-SmD183-119 testing in the integrated laboratory diagnosis of cSLE may significantly improve the overall sensitivity in child populations.

Reaction of Human Monoclonal Antibodies to SARS-CoV-2 Proteins With Tissue Antigens: Implications for Autoimmune Diseases

“…Our study design did not specifically include analyses that would capture conformational or non-linear epitopes, but any of the tissue sequences that found matches with the viral sequences, especially the highly recurring ones, could possibly be conformational epitopes. Conformational epitopes are not only important in the production of monoclonal neutralizing antibodies, they could also be major targets of autoantibody production in autoimmune diseases ( 59 , 60 ). Other antigens among our list that had moderate reactions or greater with SARS-CoV-2 may also have sequences here and there in their structure that could potentially be triggers of autoimmunity, and likewise deserve additional attention and study.…”