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Serology and Neutralization Assays for COVID-19


The global response to COVID-19 is leading to rapid advances in diagnostic, surveillance, and vaccine and therapeutic development. A critical measurement underpinning much of these efforts is a serological assay that helps to assess the complex patient responses to SARS-CoV-2. Specifically, reliable and rapid serological testing is needed to monitor the spread of the virus, patient immunity against the virus, and to determine the efficacy of vaccines and therapeutics. Yet, serology test results are highly variable for existing serologic tests, in part due to the lack of well characterized globally traceable reference materials needed for validation and assay control.  Leveraging our Flow Cytometry Quantitation Consortium and state-of-the-art facilities, we have developed a rapid, multiplexed, and sensitive flow cytometry-based serological assay as well as a BSL-3 sparing neutralization assays (surrogate bead-based neutralization assay and pseudo-virus neutralization assays).  This work has supported the development of the WHO Reference Panel: First WHO International Reference Panel for anti-SARS-CoV-2 immunoglubulin as well as the Human SARS-CoV-2 Serology Standard developed by NIH/NCI Serology Science Network (SeroNet) and FNLCR. These assays also enable the development of a robust measurement infrastructure for serological assays and associated critical reagents. 



Multiplexed bead-based SARS-CoV-2 serological assay

We have developed a validated multiplexed bead-based SARS-CoV-2 serological assay that measures different antibodies produced by a patient (IgG, IgM, IgA). In collaboration with the NIST Applied and Computational Mathematics Division, we have developed a new strategy to more confidently classify positive and negative samples. The validated assay was used to characterize the first WHO Serology Reference Panel through an inter-laboratory study as well as upcoming effort to develop Second WHO International Standard for SARS-CoV-2 Antibody and Variants of Concern (VOC) Panel.

BSL-3 sparing neutralization assays

We have developed surrogate bead-based neutralization assay via flow cytometry and pseudo-virus neutralization assays via live cell imaging and flow cytometry to assist SARS-CoV-2 vaccine and therapeutic development.  These assays will enable the functional assessment of the ability of serum antibodies to prevent cell binding, entry, or other effects of the virus on the cell in vitro. Data showed excellent correlation between our serology and bead-based neutralization assay results.

Live cell imaging
Live cell imaging is performed with transmitted light microscopy to identify all cells and fluorescence imaging with green fluorescence protein (GFP) to identify pseudovirus infected cells.

Interlaboratory study and reference materials to enable more quantitative serology assays

NIST and CDC are leading an effort to collect data through an interlaboratory study to

  • Determine the suitability of a mAb panel to be used in conjunction with the WHO International Standard to enable more quantitative serology assays
  • Develop a mAb panel to enable comparability and traceability of serological assay results collected over time as new variants emerge
  • Determine suitability of well characterized mAb as reference materials to correlate serological and neutralization assays


Towards Quantitative and Standardized Serological and Neutralization Assays for COVID-19

Created November 12, 2020, Updated June 1, 2022