Non-Invasive Detection of SARS-CoV-2 Antigen in Saliva versus Nasopharyngeal Swabs Using Nanobodies Conjugated Gold Nanoparticles

Theodor Bilharz Research Institute

Bibliographic Information

Authors: Kamel M.; Maher S.; El-Baz H.; Salah F.; Sayyouh O.; Demerdash Z.

Journal: Tropical Medicine and Infectious Disease

Publisher: MDPI

Publication Date: 13 June 2022

Volume / Issue: Volume 7 / Issue 6

Article No.: 102

ISSN: 24146366

DOI: 10.3390/tropicalmed7060102

Scopus: View on Scopus

Document Type: Article

Access: All Open Access; Gold Open Access; Green Open Access

Authors and Affiliations

Kamel M., Immunology Department, Theodor Bilharz Research Institute, Giza, 12411, Egypt; Maher S., Immunology Department, Theodor Bilharz Research Institute, Giza, 12411, Egypt; El-Baz H., Immunology Department, Theodor Bilharz Research Institute, Giza, 12411, Egypt; Salah F., Immunology Department, Theodor Bilharz Research Institute, Giza, 12411, Egypt; Sayyouh O., Infection Control Department, Theodor Bilharz Research Institute, Giza, 12411, Egypt; Demerdash Z., Immunology Department, Theodor Bilharz Research Institute, Giza, 12411, Egypt

Abstract

The development of sensitive, non-invasive tests for the detection of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) antigens is imperative, and it is still challenging to manage the extent of infection throughout the population. Here, we designed and optimized a sandwich enzyme-linked immunosorbent assay (ELISA) protocol for SARS-CoV-2 S1 antigen detection in saliva. Both saliva samples and nasopharyngeal swabs were collected from 220 real-time quantitative polymerase chain reaction (RT-qPCR)-confirmed positive and negative cases. S1 protein receptorbinding domain (RBD) nanobodies were efficiently conjugated with 40 nm gold nanoparticles (AuNPs) and employed as antigen detection probes in the developed system, while recombinant S1 monoclonal antibodies (S1mAbs) were employed as antigen capture probes. After checkerboard assays and system optimization, the clinical samples were tested. In saliva, the developed ELISA system showed the highest sensitivity (93.3) for samples with cycle threshold (Ct) values ≤ 30; interestingly, high sensitivity (87.5 and 86%) was also achieved for samples with Ct values ≤35 and ≤40, respectively, compared with 90, 80 and 88% sensitivity rates for nasopharyngeal swabs with the same categorized Ct values. However, the specificity was 100%, and no cross-reactions were detected with Middle East respiratory syndrome coronavirus (MERS-CoV) or SARS-CoV antigens. These results reveal that our protocol could be established as an efficient and sensitive, non-invasive diagnostic tool for the early detection of SARS-CoV-2 infection using easily collectable saliva samples. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

Keywords

diagnosis; ELISA; nanobodies; saliva; SARS-CoV-2; coronavirus protein; gold nanoparticle; monoclonal antibody; rbd nanobody conjugated gold nanoparticle; S1 monoclonal antibody; S1 protein; unclassified drug; adult; aged; antigen detection; Article; controlled study; coronavirus disease 2019; cycle threshold value; diagnostic test accuracy study; female; human; intermethod comparison; male; Middle East respiratory syndrome coronavirus; nasopharyngeal swab; non invasive measurement; nonhuman; real time reverse transcription polymerase chain reaction; sandwich ELISA; sensitivity and specificity; Severe acute respiratory syndrome coronavirus 2

Citation Information

Scopus Citations: 11

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