Abstract
BackgroundRapid and simple serological assays for characterizing antibody responses are important in the current COVID-19 pandemic caused by SARS-CoV-2. Multiplex immunoblot (IB) assays termed COVID-19 IB assays were developed for detecting IgG and IgM antibodies to SARS-CoV-2 virus proteins in COVID-19 patients.MethodsRecombinant nucleocapsid protein and the S1, S2 and receptor binding domain (RBD) of the spike protein of SARS-CoV-2 were used as target antigens in the COVID-19 IBs. Specificity of the IB assay was established with 231 sera from persons with allergy, unrelated viral infections, autoimmune conditions and suspected tick-borne diseases, and 32 goat antisera to human influenza proteins. IgG and IgM COVID-19 IBs assays were performed on 84 sera obtained at different times after a positive RT-qPCR test from 37 COVID-19 patients with mild symptoms.ResultsCriteria for determining overall IgG and IgM antibody positivity using the four SARS-CoV-2 proteins were developed by optimizing specificity and sensitivity in the COVID-19 IgG and IgM IB assays. The estimated sensitivities and specificities of the COVID-19 IgG and IgM IBs for IgG and IgM antibodies individually or for either IgG or IgM antibodies meet the US recommendations for laboratory serological diagnostic tests. The proportion of IgM-positive sera from the COVID-19 patients following an RT-qPCR positive test was maximal at 83% before 10 days and decreased to 0% after 100 days, while the proportions of IgG-positive sera tended to plateau between days 11 and 65 at 78–100% and fall to 44% after 100 days. Detection of either IgG or IgM antibodies was better than IgG or IgM alone for assessing seroconversion in COVID-19. Both IgG and IgM antibodies detected RBD less frequently than S1, S2 and N proteins.ConclusionsThe multiplex COVID-19 IB assays offer many advantages for simultaneously evaluating antibody responses to different SARS-CoV-2 proteins in COVID-19 patients.
Highlights
Rapid and simple serological assays for characterizing antibody responses are important in the current COVID-19 pandemic caused by SARS-CoV-2
Coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARSCoV-2), first detected in Wuhan, China in December 2019 has become a global pandemic with approximately 108.2 million infections and 2.4 million deaths worldwide on 13 February 2021 [1]
Infection is most commonly diagnosed by nucleic acid amplification tests (NAATs), often RTqPCR, performed on nasopharyngeal and mid-turbinate swabs [2]
Summary
Rapid and simple serological assays for characterizing antibody responses are important in the current COVID-19 pandemic caused by SARS-CoV-2. Multiplex immunoblot (IB) assays termed COVID-19 IB assays were developed for detecting IgG and IgM antibodies to SARS-CoV-2 virus proteins in COVID-19 patients. Detection of antibodies to SARS-CoV-2 is important for several purposes including: (i) confirming present or past infection, (ii) evaluating patients with negative NAATs who show characteristic COVID-19 symptoms, (iii) sero-epidemiological studies on COVID-19, (iv) assessing the development of antibody-mediated protective immunity, and (v) investigating immune response and immunopathology in COVID-19 [3, 4]. The spike (S) and nucleocapsid (N) proteins of SARS-CoV-2 are commonly used target antigens in COVID-19 serological assays. S is composed of a N-terminal S1 region containing a receptor binding domain (RBD) which binds to the angiotensin-converting enzyme 2 receptor on host cells, and a C-terminal S2 region that subsequently mediates fusion between the viral and host cell membranes to allow the entry of viral RNA into the cell [5]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
