A Highly Sensitive Immunoassay for Determination of Immune Response to SARS-CoV-2 in Capillary Blood Samples
Belén G. Sánchez,
Alicia Bort,
José María Mora-Rodríguez,
Alba Díaz-Yuste,
José Manuel Gasalla,
Manuel Sánchez-Chapado,
Alba Sebastián-Martín,
Inés Díaz-Laviada
Affiliations
Belén G. Sánchez
Biochemistry and Molecular Biology Unit, Department of Systems Biology, School of Medicine and Health Sciences, University of Alcalá, 28871 Alcalá de Henares, Madrid, Spain
Alicia Bort
Department of Comparative Medicine, School of Medicine, Yale University, New Haven, CT 06519, USA
José María Mora-Rodríguez
Biochemistry and Molecular Biology Unit, Department of Systems Biology, School of Medicine and Health Sciences, University of Alcalá, 28871 Alcalá de Henares, Madrid, Spain
Alba Díaz-Yuste
Biochemistry and Molecular Biology Unit, Department of Systems Biology, School of Medicine and Health Sciences, University of Alcalá, 28871 Alcalá de Henares, Madrid, Spain
José Manuel Gasalla
Biochemistry and Molecular Biology Unit, Department of Systems Biology, School of Medicine and Health Sciences, University of Alcalá, 28871 Alcalá de Henares, Madrid, Spain
Manuel Sánchez-Chapado
Department of Urology, Príncipe de Asturias Hospital, 28805 Alcalá de Henares, Madrid, Spain
Alba Sebastián-Martín
Biochemistry and Molecular Biology Unit, Department of Systems Biology, School of Medicine and Health Sciences, University of Alcalá, 28871 Alcalá de Henares, Madrid, Spain
Inés Díaz-Laviada
Biochemistry and Molecular Biology Unit, Department of Systems Biology, School of Medicine and Health Sciences, University of Alcalá, 28871 Alcalá de Henares, Madrid, Spain
Throughout the pandemic, serological assays have been revealed as crucial for detecting previous exposures to the virus and determining the timing of antibody maintenance after vaccination or natural infection. This study aimed to develop an optimized enzyme-linked immunosorbent assay (ELISA)-based serology, which could be used in case of reagent shortages, such as that occurred in the beginning of this health emergency. As a result, we present a high-sensitive immunoassay for the determination of IgG levels in venous serum samples, using 2 μg/mL antigen (receptor-binding domain of the spike protein S1) for coating the plate and utilizing human samples at a dilution 1:1000. This method showed non-inferiority features versus a commercial kit, is less expensive, and has a higher spectrophotometric range that allows for a better quantification of the antibody titers. The optical density values before and after heating venous serum samples at 56 °C during 30 min was quite similar, showing that heat inactivation can be used to reduce the biohazardous risks while handling samples. Furthermore, we show that finger-stick capillary blood samples can also serve as a suitable source for IgG detection, bypassing the need for serum isolation and being suitable for point-of-care application (Pearson’s coefficient correlation with capillary serum was 0.95, being statistically significant).
