Abstract
Background
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has infected millions of people globally. Virus infection requires the receptor-binding domain (RBD) of the spike ...protein. Although studies have demonstrated anti-spike and -RBD antibodies to be protective in animal models, and convalescent plasma as a promising therapeutic option, little is known about immunoglobulin isotypes capable of blocking infection.
Methods
We studied spike- and RBD-specific immunoglobulin isotypes in convalescent and acute plasma/serum samples using a multiplex bead assay. We also determined virus neutralization activities in plasma and serum samples, and purified immunoglobulin fractions using a vesicular stomatitis pseudovirus assay.
Results
Spike- and RBD-specific immunoglobulin (Ig) M, IgG1, and IgA1 were produced by all or nearly all subjects at variable levels and detected early after infection. All samples displayed neutralizing activity. Regression analyses revealed that IgM and IgG1 contributed most to neutralization, consistent with IgM and IgG fractions’ neutralization potency. IgA also exhibited neutralizing activity, but with lower potency.
Conclusion
IgG, IgM, and IgA are critical components of convalescent plasma used for treatment of coronavirus disease 2019 (COVID-19).
Immunoglobulin (Ig) M, IgG1, and IgA1 antibodies against severe acute respiratory syndrome coronavirus 2 spike glycoprotein and its receptor-binding domain are present in plasma from patients with convalescent coronavirus disease 2019 (COVID-19). IgG, IgM, and IgA contribute to virus neutralization, providing the basis for optimal selection of convalescent plasma for COVID-19 treatment.
Abstract
More than 24 million infections with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) were confirmed globally by September 2020. While polymerase chain reaction–based assays ...are used for diagnosis, there is a need for high-throughput, rapid serologic methods. A Luminex binding assay was developed and used to assess simultaneously the presence of coronavirus disease 2019 (COVID-19)–specific antibodies in human serum and plasma. Clear differentiation was achieved between specimens from infected and uninfected subjects, and a wide range of serum/plasma antibody levels was delineated in infected subjects. All 25 specimens from 18 patients with COVID-19 were positive in the assays with both the trimeric spike and the receptor-binding domain proteins. None of the 13 specimens from uninfected subjects displayed antibodies to either antigen. There was a highly statistically significant difference between the antibody levels of COVID-19–infected and –uninfected specimens (P < .0001). This high-throughput antibody assay is accurate, requires only 2.5 hours, and uses 5 ng of antigen per test.
Rapid serologic assays are needed to detect antibodies in individuals infected with or recovering from severe acute respiratory syndrome coronavirus 2. The assay described is advantageous in that it is highly accurate, requires only 2.5 hours, uses little antigen/test, and constitutes a high-throughput platform.
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