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

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

Publication date: Mar 27, 2024

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 cD7 10 copies/ml vs. 0. 4 cD7 10 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.

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Concepts Keywords
Ct30 Biotin
Nanobodies Nanobodies
Pandemic Rapid test
Surgery Saliva
Viral SARS-CoV-2 S1


Type Source Name
drug DRUGBANK Biotin
disease MESH infectious diseases
disease MESH COVID-19 pandemic
disease VO LACK
drug DRUGBANK Gold
drug DRUGBANK Angiotensin II
disease MESH Middle East respiratory syndrome
drug DRUGBANK Tropicamide
disease MESH infection
disease VO effective
drug DRUGBANK Coenzyme M
disease VO organization
disease VO Glycoprotein
drug DRUGBANK Human Serum Albumin
drug DRUGBANK Sucrose
disease VO USA
drug DRUGBANK Water
disease MESH sore throat
disease MESH chest pain
disease VO mouth
disease IDO assay
disease VO manufacturer
disease VO protocol
disease VO volume
drug DRUGBANK Boric acid
disease VO efficiency
disease MESH Influenza
disease VO Viruses
disease VO storage
drug DRUGBANK Saquinavir
disease VO efficient
disease VO time
disease VO Optaflu
drug DRUGBANK Ciclosporin
disease IDO process
disease VO viable
disease MESH morbidity
drug DRUGBANK Medical air
drug DRUGBANK Oxygen
disease VO population
drug DRUGBANK Silicon dioxide
disease MESH schistosomiasis
disease MESH virus infections
drug DRUGBANK Fenamole
disease MESH respiratory infections

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