Peptide-Integrated Superparamagnetic Nanoparticles for the Identification of Epitopes from SARS-CoV-2 Spike and Nucleocapsid Proteins

Abstract

The COVID-19 pandemic, caused by the fast transmission and spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is currently considered a serious health problem, requiring an effective strategy to contain SARS-CoV-2 dissemination. For this purpose, epitopes of the SARS-CoV-2 spike (S) and sucleocapsid (N) proteins were identified by bioinformatics tools, and peptides that mimic these epitopes were chemically synthesized and then conjugated to superparamagnetic nanoparticles (SPMNPs). Three peptides from S protein and three from N protein were used as antigens in a conventional enzyme-linked immunosorbent assay (ELISA) against serum samples from COVID-19-positive patients, or from healthy donors, collected before the pandemic. Three peptides were effective as antigens in conventional peptide-based ELISA, achieving 100% sensitivity and specificity, with high accuracy. The best-performing peptides, p2pS, p1pN, and p3pN, were associated with superparamagnetic nanoparticles (SPMNPs) and were used to perform nanomagnetic peptide-based ELISA. The p2pS–SPMNP conjugate presented 100% sensitivity and specificity and excellent accuracy (area under the curve (AUC) = 1.0). However, p1pN and p3pN peptides, when conjugated to SPMNPs, did not preserve the capacity to differentiate positive sera from negative sera in all tested samples, yet both presented sensitivity and specificity above 80% and high accuracy, AUC > 0.9. We obtained three peptides as advantageous antigens for serodiagnosis. These peptides, especially p2pS, showed promising results in a nanomagnetic peptide-based ELISA and may be suitable as a precoated antigen for commercial purposes, which would accelerate the diagnosis process.

B-Cell Epitopes-Based Chimeric Protein from SARS-CoV-2 N and S Proteins Is Recognized by Specific Antibodies in Serum and Urine Samples from Patients

“…Bioinformatic tools to predict antigenic epitopes that are specific for the pathogens have been advancing the development of new diagnostics. Many epitopes have been identified by immunoinformatics prediction or immunoassays and the peptides validated by serological assays, such as ELISA [ 22 , 23 , 24 , 25 ]. Epitope-based chimeric proteins have been then proposed as recombinant proteins for the development of new COVID-19 vaccines or diagnostics, showing stronger immunogenicity with the possibility to express proteins in a simpler prokaryotic system [ 13 , 14 ].…”

Multiplex and Ultrasensitive Detection of Severe Acute Respiratory Syndrome Coronavirus 2 and Influenza A/B Nucleocapsid Proteins Based on Nanometer-Sized Core–Shell Superparamagnetic Antifouling Probes

“…However, fluorescence detection based on fluorescent materials is constrained by significant background noise and fluorescence quenching, whereas colloidal gold exhibits low sensitivity and a narrow dynamic range . Magnetic particles (MNPs) exhibit superior biocompatibility, stability, and ease of collection under external magnetic fields and are frequently employed in the enrichment of proteins, , nucleic acids, , rare cells, and ICTs. , The MNP-based immunochromatographic test (MICT) has been successfully employed in the quantitative detection of viruses, bacteria, and cancer biomarkers because of the high signal to noise ratio and wide linear dynamic detection range of MNPs. However, a lot of core-shell MNPs from commercial often agglomerate during an immunochromatographic test.…”

SARS-CoV-2 peptides/epitopes for specific and sensitive diagnosis

“…Compared to traditional ELISA, the B-cell epitope-based QD biosensor exhibited higher sensitivity (92.3–98.1% positive rates in 207 COVID-19 patient sera) while requiring less time (5 min) and labor. Scussel et al conducted a nanomagnetic peptide-based ELISA that employed superparamagnetic nanoparticles (SPMNPs) conjugated with peptides/epitopes of the S and N proteins for detecting COVID-19 [ 15 ]. Among the peptides tested, the p2pS mimotope exhibited optimal performance, achieving excellent sensitivity and specificity.…”