Abstract
The novel coronavirus, severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), is the causative agent of the 2020 worldwide coronavirus pandemic. Antibody testing is useful for diagnosing historic infections of a disease in a population. These tests are also a helpful epidemiological tool for predicting how the virus spreads in a community, relating antibody levels to immunity and for assessing herd immunity. In the present study, SARS-CoV-2 viral proteins were recombinantly produced and used to analyse serum from individuals previously exposed, or not, to SARS-CoV-2. The nucleocapsid (Npro) and spike subunit 2 (S2Frag) proteins were identified as highly immunogenic, although responses to the former were generally greater. These two proteins were used to develop two quantitative enzyme-linked immunosorbent assays (ELISAs) that when used in combination resulted in a highly reliable diagnostic test. Npro and S2Frag-ELISAs could detect at least 10% more true positive coronavirus disease-2019 (COVID-19) cases than the commercially available ARCHITECT test (Abbott). Moreover, our quantitative ELISAs also show that specific antibodies to SARS-CoV-2 proteins tend to wane rapidly even in patients who had developed severe disease. As antibody tests complement COVID-19 diagnosis and determine population-level surveillance during this pandemic, the alternative diagnostic we present in this study could play a role in controlling the spread of the virus.
Highlights
Severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) is a newly emerging member of the Coronaviridae (CoV) family, responsible for the coronavirus disease-2019 (COVID-19) pandemic
Recombinant proteins were successfully expressed in E. coli BL21 cells; spike protein and its various subunits were associated with insoluble inclusion bodies
Our results indicate that targeting the antibody response against both nucleocapsid protein (Npro) and S2Frag in serological diagnostic tests increases the sensitivity of detection of true positive severe acute respiratory syndrome (SARS)-CoV-2 infection and, represents an important strategy to improve COVID-19 diagnosis
Summary
Severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) is a newly emerging member of the Coronaviridae (CoV) family, responsible for the coronavirus disease-2019 (COVID-19) pandemic. Sixteen non-structural proteins (nsp) are co-translationally and post-translationally released from pp1a and pp1ab upon proteolytic activity of two virus proteases, the papain-like protease (PLpro) and the 3C-like protease. These proteins are responsible for the establishment of the viral replication and transcription complex (RTC), which is crucial for virus replication inside the cells [5]
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