Development of rapid antigen test prototype for detection of SARS-CoV-2 in saliva samples

• Published in: Upsala journal of medical sciences 2022, Vol.127, p.e8207-9
• Main Authors: Kivrane, Agnija, Igumnova, Viktorija, Liepina, Elza Elizabete, Skrastina, Dace, Leonciks, Ainars, Rudevica, Zanna, Kistkins, Svjatoslavs, Reinis, Aigars, Zilde, Anna, Kazaks, Andris, Ranka, Renate
• Format: Article
• Language: English
• Subjects: Animals; Antibodies; Antibodies, Viral; antigen test; Antigens; Binding sites; Coronaviruses; COVID-19; COVID-19 - diagnosis; Disease transmission; elisa; Humans; Immunization; Infections; Laboratory animals; lateral flow assay; Medical personnel; Mice; Original; Pilot Projects; point-of-care testing; polyclonal antibodies; Proteins; R&D; Rabbits; Research & development; Saliva; SARS-CoV-2; Severe acute respiratory syndrome coronavirus 2; Spike Glycoprotein, Coronavirus
• ISSN: 0300-9734; 2000-1967
• DOI: 10.48101/ujms.v127.8207

The development of easy-to-perform diagnostic methods is highly important for detecting current coronavirus disease (COVID-19). This pilot study aimed at developing a lateral flow assay (LFA)-based test prototype to detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus in saliva samples. Mice were immunized using the recombinant receptor-binding domain (rRBD) of SARS-CoV-2 virus spike protein. The combinations of the obtained mouse anti-receptor-binding domain (RBD) polyclonal antibodies (PAbs) and several commercial antibodies directed against the SARS-CoV-2 spike protein were used for enzyme-linked immunosorbent assay (ELISA) to select antibody pairs for LFA. The antibody pairs were tested in a LFA format using saliva samples from individuals with early SARS-CoV-2 infection ( = 9). The diagnostic performance of the developed LFA was evaluated using saliva samples from hospitalized COVID-19 patients ( = 111); the median time from the onset of symptoms to sample collection was 10 days (0-24 days, interquartile range (IQR): 7-13). The reverse transcription-polymerase chain reaction (rRT-PCR) was used as a reference method. Based on ELISA and preliminary LFA results, a combination of mouse anti-RBD PAbs (capture antibody) and rabbit anti-spike PAbs (detection antibody) was chosen for clinical analysis of sample. When compared with rRT-PCR results, LFA exhibited 26.5% sensitivity, 58.1% specificity, 50.0% positive prediction value (PPV), 33.3% negative prediction value (NPV), and 38.7% diagnostic accuracy. However, there was a reasonable improvement in assay specificity (85.7%) and PPV (91.7%) when samples were stratified based on the sampling time. The developed LFA assay demonstrated a potential of SARS-CoV-2 detection in saliva samples. Further technical assay improvements should be made to enhance diagnostic performance followed by a validation study in a larger cohort of both asymptomatic and symptomatic patients in the early stage of infection.