Diagnostic potential of new linear epitopes derived from the N-terminal domain of the SARS-CoV-2 Glycoprotein S.

Background And Objectives: The aim of this study was to assess the effectiveness of a new linear epitope from the N-terminal domain (NTD) of the SARS-CoV-2 S protein in the diagnosis of COVID-19.

Materials And Methods: Serum samples from patients were confirmed to have COVID-19 by means of RT-PCR. The linear epitope sequence of the NTD was amplified by RT-PCR, inserted into an expression vector, and produced in (DE3) pLysS. Subsequently, the recombinant proteins were purified and refolded. The interaction between the purified protein and the antibodies in COVID-19 patient sera was evaluated using ELISA.

Results: Sequencing verified that the N-terminal linear epitope was successfully cloned into the PET-22b vector with a 6His-tag at the C-terminal end. The presence of a 25 kDa band on SDS-PAGE indicated the successful purification of the recombinant protein using Ni-NTA chromatography. The results of ELISA showed that the NTD linear epitope had strong sensitivity (88%) and specificity (96%) for identifying viral infection in COVID-19 patients' blood samples.

Conclusion: The findings of this study demonstrated that the NTD linear epitopes of the SARS-CoV-2 spike protein exhibit significant sensitivity and specificity for the diagnosis of COVID-19 infection using serological techniques. However, further evaluations involving larger sample sizes across diverse ethnic populations is essential.