Diagnostic Accuracy of an Immunoassay Using Avidity-Enhanced Polymeric Peptides for SARS-CoV-2 Antibody Detection [Presentation for the 27th University of the Philippines College of Medicine Student Research Forum]

Conference InformationConference Title. 27th Student Research Forum Host Institution. University of the Philippines College of Medicine Conference Date. 3 March 2026 Conference Location. Manila, PhilippinesAbstractThere is a critical need for synthetic peptide-based serologic assays that exploit avidity to replace whole viral antigens and enable low-cost diagnostics suitable for resource-limited settings. This study evaluated the diagnostic accuracy of a polymeric peptide-based ELISA designated S559.The epitope was identified through Immune Epitope Database retrieval and synthesized using solid-phase peptide synthesis with LC-MS validation, followed by controlled polymerization to achieve homomultivalent presentation. The assay was validated using 1,222 clinical cases and 218 controls.Polymerized S559 demonstrated a 2.18-fold avidity gain relative to the depolymerized form, with Kdapp values of 29.26 nM⁻¹ versus 63.76 nM⁻¹. Using a post hoc threshold determined by Youden J, the assay achieved 95.01 percent sensitivity and 100.00 percent specificity. The area under the receiver operating characteristic curve was 96.59 percent.Homomultivalent epitope presentation using polymeric S559 enables a highly specific immunoassay suitable for infection diagnosis, vaccination confirmation, and population-level surveillance.