SARS-CoV-2 serological testing using electrochemiluminescence reveals a rapid onset of seroconversion in severe COVID-19 patients
clinical diagnostics immunology/immunity
Authors:Munitz et al
Link to paper: https://doi.org/10.1101/2020.06.28.20141838
Tags: Immunology/Immunity, Clinical/ Diagnostics
1. Adapted an electrochemiluminescence-based ELISA assay for detecting IgM, IgG and IgA against SARS-CoV-2 RBD and NP antigens which was observed to have higher sensitivities and a broader dynamic range than the standard ELISA assay.
2. Antibody responses were observed to develop more rapidly against the RBD antigen compared to the NP antigen in patients.
3. Moderate/severe patients were observed to have a more rapid antibody response (anti-RBD IgM, IgG and IgA, and anti-NP IgG and IgA) compared to mild patients, but final antibody levels were similar in both groups.
The authors adapted an electrochemiluminescence-based ELISA assay to detect IgM, IgG and IgA against SARS-CoV-2 RBD and NP antigens. Higher sensitivities were seen in side-by-side comparison with standard ELISA assay. Their assays were validated using sera from COVID-19 patients and recovered individuals (n=96) and 195 pre-pandemic controls. All antibody classes against RBD were developed rapidly. IgG and IgA anti-NP developed much slower and IgM did not develop significantly. Moderate/severe patients had a more rapid antibody response for IgG and IgA against RBD and NP, and IgM against RBD compared to mild patients. Final antibody levels were similar in both groups.
Impact for SARS-CoV2/COVID19 research efforts
Understand the immune response to SARS-CoV2/COVID19
Develop diagnostic tools for SARS-CoV2/COVID19
Others: Multiplexed assay design could be used for serological studies in vaccine development and further patient and/or diagnostic studies
In vitro study
Strengths and limitations of the paper
Novelty: Multiplexed electrochemiluminescence serological assay with broader dynamic range and sensitivity than the standard ELISA
Standing in the field:Building on well-established knowledge and technology
Appropriate statistics:Statistics are appropriate and accurate
Viral model used:RBD and NP SARS-CoV-2 antigens
Translatability:Possible use in diagnostics and further serological studies
Did a side-by-side comparison between standard ELISA assay and the electrochemiluminescence-based ELISA assay for IgG and IgM, but did not include IgA. Comparison was also only made using SARS-CoV-2 RBD antigen and did not include NP.
Not clear when homemade RBD or company-bought RBD was used in ELISA assay comparison and in further serological assays. Integrity of homemade RBD compared to the company-bought was not analysed.
Only 29 mild patients and 28 moderate/severe patients used in antibody response analysis, and no breakdown of the number of moderate and severe patients in the latter group.
Would have been useful to have included viral load measurements
Data includes both recovered and moderate/severe individuals in the same group for > 28DPS to analyse long term antibody response, when these could differ greatly between the groups and skew data.
Figures using violin plots are difficult to interpret as are the conclusions made from them.
No description of replicates, and samples are not distinguished into unique samples and those with multiple time points.