Modified streptavidin–biotin based lateral flow test strip for rapid detection of SARS-CoV-2 S1 antigen in saliva samples

Theodor Bilharz Research Institute

Bibliographic Information

Authors: Kamel M.; Atta S.; Maher S.; Abd Elaziz H.; Demerdash Z.

Journal: Scientific Reports

Publisher: Nature Research

Publication Date: 27 March 2024

Volume / Issue: Volume 14 / Issue 1

Article No.: 7319

ISSN: 20452322

DOI: 10.1038/s41598-024-57230-8

Scopus: View on Scopus

PubMed: 38538635

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, Egypt; Atta S., Immunology Department, Theodor Bilharz Research Institute, Giza, Egypt; Maher S., Immunology Department, Theodor Bilharz Research Institute, Giza, Egypt; Abd Elaziz H., Surgery Department, Theodor Bilharz Research Institute, Giza, Egypt; Demerdash Z., Immunology Department, Theodor Bilharz Research Institute, Giza, Egypt

Abstract

Compared to other infectious diseases, for which LFT development can take years, SARS-CoV-2 antigen LFTS were developed and deployed within months. LFTS for antigen detection were adopted on an unprecedented scale during the COVID-19 pandemic, but many of them lack the sensitivity especially for samples with low viral load. In our previous work, we developed an enhanced signal strip for detection of SARS CoV-2 SI antigens in saliva. Here we introduce some modification to improve the sensitivity, and specificity, and to lower the cost of the strip, by using biotin streptavidin (BS) system. In the modified BS strip, gold-streptavidin and biotinylated Nanobodies (Nbs) against S1 antigen were externally mixed with the tested samples (saliva or nasopharyngeal swab) before their application on the sample pad of the test strip containing angiotensin converting enzyme (ACE-2), as the capturing probe. The study included 320 individuals, with 180 being positively confirmed by RT-PCR and 140 confirmed negative, as well as, 45 health care workers, who were responsible for screening and handling of surgical cases in General Surgery Department and COVID clinic of TBRI. Our results proved that modified BS strip improved the overall sensitivity and specificity of S1antigen detection in saliva samples (95.21% and 99.29% respectively) compared to our previously developed enhanced LFTS (91.66% and 98.57% respectively). Also, the sensitivity of cases with Ct ≤ 30, Ct ≤ 35, and Ct ≤ 40 using the modified BS strip showed higher values (98.54%, 95.38%, and 88.89% respectively), compared to the corresponding results of our previously developed enhanced LFTS (95.86%, 92.31%, and 82.22% respectively). There were no cross-reactions with either Middle East respiratory syndrome corona virus MERS-CoV or SARS-CoV antigens. Furthermore, we found that the lower viral detection limit (LVD) of BS strip was obviously lower than our previous LVD limit of the enhanced LFTS (0.2 × 104 copies/ml vs. 0.4 × 104 copies/ml, respectively). Our developed BS strip showed that saliva samples gave better results than nasopharyngeal swabs of the same patients. The fact of using smaller amounts of Nbs, and ACE2, as well as the dispensing off of conjugate pad when applying BS strip modifications, justified the expected reduction in the costs of the strip. The implementation of BS strips on saliva samples of 45 health co-workers, who were tested 4 and 6 days after exposure to infection, showed an increase in the sensitivity, starting from the 4th day and reaching its highest level on the 6th day in both high risk and paramedic groups (90.9%, and 80.0%, respectively). This study provides evidence that employment of the modified BS system could increase the sensitivity of the strips, lower their cost, and render them an effective screening tool for early detection of the virus in saliva of suspected Covid-19 patients. © The Author(s) 2024.

Keywords

Biotin; Nanobodies; Rapid test; Saliva; SARS-CoV-2 S1; Streptavidin; Antigens, Viral; COVID-19; Humans; Nasopharynx; Neoplasm Proteins; Pandemics; SARS-CoV-2; Specimen Handling; sarcoma-associated antigen S1; tumor protein; virus antigen; coronavirus disease 2019; human; pandemic; Severe acute respiratory syndrome coronavirus 2

Citation Information

Scopus Citations: 11

For comprehensive information about the Theodor Bilharz Research Institute (TBRI), its institutional activities, scientific and research achievements, clinical and hospital services, and the diverse expertise offered through its 22 specialized research and clinical departments, as well as opportunities for professional training, specialized workshops, and scientific conferences, readers are invited to visit the Institute’s official website.

The website provides regularly updated information on the Institute’s latest news, research activities, scientific initiatives, clinical services, institutional programs, and academic and professional opportunities.

English Website: https://www.tbri.sci.eg/en/

Arabic Website: https://www.tbri.sci.eg/ar/

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