Replication Data for: Diagnostic Accuracy of an Immunoassay Using Avidity-Enhanced Polymeric Peptides for SARS-CoV-2 Antibody Detection

Diagnostic Accuracy of an Immunoassay Using Avidity-Enhanced Polymeric Peptides for SARS-CoV-2 Antibody Detection Background: There is a need for synthetic peptide-based serologic assays that exploit avidity to replace whole antigens while enabling low-cost diagnostics in resource-limited settings. Objective: To evaluate the diagnostic accuracy of a polymeric peptide-based ELISA leveraging avidity to enhance signal strength. Method: A 15-member SARS-CoV-2 peptide library corresponding to multiple epitope clusters and proteins was screened by indirect ELISA using pooled sera from RT-PCR-confirmed patients. The lead peptide candidate, S559, was identified and modified by terminal cysteine-substitution to enable disulfide-linked polymerization. Avidity gain was quantified by comparing the apparent dissociation constant (KDapp) of the polymerized vs. depolymerized forms, the latter achieved using N-acetylcysteine. An optimized ELISA based on S559 was evaluated on: 1,222 prospectively collected COVID-19 serum samples 218 biobanked negative controls Results: Polymeric S559 exhibited a 218% avidity gain relative to its depolymerized form, with a KDapp of 29.26 nM-1. Diagnostic performance of the optimized ELISA was: Sensitivity: 83.39% (95% CI: 81.18%–85.43%) Specificity: 96.79% (95% CI: 93.50%–98.70%) Using post hoc thresholds derived via the Youden Index: Sensitivity: 95.01% (95% CI: 93.63%–96.16%) Specificity: 100.00% (95% CI: 98.32%–100.00%) Conclusion: Homomultivalent epitope presentation using polymeric S559 enables a highly specific and sensitive immunoassay for detecting anti-SARS-CoV-2 antibodies. This method has potential utility in infection diagnosis, vaccine response monitoring, and seroepidemiologic surveillance. Contact: [e-mail]