Two serological approaches for detection of antibodies to SARS-CoV-2 in different scenarios: a screening tool and a point-of-care test

Abstract

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has infected more than 8 million people worldwide, becoming a pandemic. Detecting antibodies against SARS-CoV-2 is of utmost importance and a good indicator of exposure and circulation of the virus within the general population. Two serological tools based on a double recognition assay [enzyme-linked immunosorbent assay (DR-ELISA) and lateral flow assay (DR-LFA)] to detect total antibodies to SARS-CoV-2 have been developed based on the recombinant nucleocapsid protein. A total of 1065 serum samples, including positive for COVID-19 and negative samples from healthy donors or infected with other respiratory pathogens, were analyzed. The results showed values of sensitivity between 91.2% and 100%, and specificity of 100% and 98.2% for DR-LFA and DR-ELISA, respectively. No cross-reactivity against seasonal coronavirus (HCoV-NL63, HCoV-229E, HCoV-HKU1, HCoV-OC43) was found. These results demonstrate the importance of serology as a complementary tool to polymerase chain reaction for follow-up of recovered patients and identification of asymptomatic individuals.

Keywords: COVID-19; Diagnosis; ELISA; LFA; SARS-CoV-2; Serology.

Fig. 1

Polyacrylamide gel electrophoresis of SARS-CoV-2 N protein expressed and purified from bacterial cultures, and visualized following staining with Coomassie brilliant blue. From left to right: uninduced culture (lane 1), induced culture (lane 2), N protein before purification (lane 3), and N protein after purification by immobilized metal affinity chromatography (lane 4, MW: 46.5 kDa).

Fig. 2

Validation of the DR-ELISA and DR-LFA. Dot plot diagrams where each dot represents an individual sample: results obtained for DR-ELISA (A) and DR-LFA (B). The horizontal solid line corresponds to the cutoff values in each assay, according to the MedCalc® 10 software. X-axis shows the positive (1) or negative (0) classification of samples according to the PCR and serological assay, and Y-axis shows S/P ratio and intensity obtained in the DR-ELISA and DR-LFA, respectively.