Identification of a Novel Serological Marker in Seronegative Rheumatoid Arthritis Using the Peptide Library Approach

A study of the roles of some immunological biomarkers in the diagnosis of rheumatoid arthritis

Autoimmune rheumatoid arthritis (RA) is a systemic condition closely correlated with a variety of autoantibodies (Abs) that could be considered diagnostic and prognostic markers. The current research was designed to detect the diagnostic values for a number (n) of these auto-Abs in RA detection and to evaluate the accuracy of a combined diagnostic scheme. This prospective study was conducted between September 2021 and August 2022 and included 110 subjects with RA, 70 individuals with other autoimmune disorders as positive controls (PC), and 50 unrelated, apparently healthy individuals as healthy controls (HC). The eligibility criteria for all study groups were followed stringently. An enzyme-linked immunosorbent assay (ELISA) was employed to measure rheumatoid factors (RF), cyclic citrullinated peptide antibodies (CCP-Abs), mutated citrullinated vimentin antibodies (MCV-Abs), anti-perinuclear factor antibodies (APF-Abs), and anti-keratin antibodies (AKA). We calculated the specificity, sensitivity, and predictive values of all auto-Abs. Significantly higher levels of anti-CCP-Abs, anti-MCV-Abs, APF-Abs, and AKAs were reported in the RA patients compared to the HC and PC subjects. RF levels, however, were only statistically elevated when compared to the HC individuals. Anti-APF-Abs had a higher sensitivity rate (70.9%), and anti-CCP-Abs had a higher specificity rate (94.16%) compared to other auto-Abs, whereas the combined detection scheme revealed a higher sensitivity (81.81%) and excellent specificity (90.83%) compared to the two former auto-Abs. Anti-perinuclear factor-Ab was a highly sensitive test, and CCP-Ab was a surpassingly specific assay for identifying RA. Furthermore, the combined detection scheme is an essential serological approach for RA diagnosis and crucial in differentiating this disease from other autoimmune diseases, thus promoting early diagnosis and treatment.

A novel click chemistry-based peptide ELISA protocol: development and technical evaluation

ELISA is the current standard for (auto)antibody diagnostics. Once established, ELISA protocols can be easily adapted for novel antigens; however, peptide-based protocols are rarely available. Herein the authors describe the results of a technical investigation of an indirect ELISA protocol using peptides conjugated onto a protein carrier based on click chemistry and immobilized in standard plastics. The authors compared this approach with the common biotin-avidin system and obtained a slightly improved limit of detection for purified IgG of 25-100 ng/well compared with 25-1000 ng/well. Reproducibility and stability of the methodological approach were conducted for further technical characterization. Indirect ELISA using immunoreactive peptides conjugated to bovine serum albumin offers a reliable method that is complementary to standard plastics and plate readers.