Serological antibody testing in the COVID-19 pandemic: their molecular basis and applications

Abstract

The ongoing COVID-19 pandemic has placed an overwhelming burden on the healthcare system, and caused major disruption to the world economy. COVID-19 is caused by SARS-CoV-2, a novel coronavirus that leads to a variety of symptoms in humans, including cough, fever and respiratory failure. SARS-CoV-2 infection can trigger extensive immune responses, including the production of antibodies. The detection of antibody response by serological testing provides a supplementary diagnostic tool to molecular tests. We hereby present a succinct yet comprehensive review on the antibody response to SARS-CoV-2 infection, as well as molecular mechanisms behind the strengths and limitations of serological antibody tests. The presence of antibodies can be detected in patient sera within days post symptom onset. Serological tests demonstrate superior sensitivity to molecular tests in some periods of time during disease development. Compared with the molecular tests, serological tests can be used for point-of-care testing, providing faster results at a lower cost. Commercially available serological tests show variable sensitivity and specificity, and the molecular basis of these variabilities are analysed. We discuss assays of different complexities that are used to specifically quantitate neutralising antibodies against SARS-CoV-2, which has important implications for vaccine development and herd immunity. Furthermore, we discuss examples of successful applications of serological tests to contact tracing and community-level sero-surveying, which provide invaluable information for pandemic management and assessment.

Feasibility of large-scale population testing for SARS-CoV-2 detection by self-testing at home

“…Recently, point-of-care rapid tests have been developed with a high diagnostic accuracy 4 – 7 . Rapid antibody tests, using capillary blood, can identify ongoing, recovering, or previous SARS-CoV2 infection, which is important to develop vaccination programs since vaccine doses could be saved in seropositive subjects at a time when the speed of vaccination is slow and vaccine availability limited 8 , 9 . Rapid antigen tests detect the presence of viral proteins expressed by SARS-CoV2 in samples from nasopharyngeal swabs identifying subjects with an acute infection 7 .…”

Longitudinal determination of mRNA-vaccination induced strongly binding SARS-CoV-2 IgG antibodies in a cohort of Romanian healthcare workers

“…1 Immunoglobulin G (IgG) is a good biomarker in blood for detecting long-term immune response due to infections. 2,3 Infected individuals mount very different immune responses, and the antibody levels that can be measured postinfection have a large variation. [4][5][6][7] SARS-CoV-2 IgG antibody levels were found to correlate with disease severity.…”

Estimating the risk of incident SARS-CoV-2 infection among healthcare workers in quarantine hospitals: the Egyptian example

“…However, the Egyptian public health authorities’ choice of a protocol relying on serological tests before working shifts was mainly driven by material constraints. Indeed, the use of rapid serological tests as a diagnostic tool was and remains of particular interest in limited-resource contexts due to their lower cost, the minimal equipment required, and faster results, as compared with RT-PCR tests [18]. Second, the assumption of a constant overall risk of infection among HCWs disregards dynamic fluctuations in risk driven by variation in the number of HCWs and/or patients in the hospitals, as well as the frequency and nature of HCWs’ contacts during their working shifts.…”