A high-throughput neutralizing antibody assay for COVID-19 diagnosis and vaccine evaluation

Authors: Muruato et al.

Link to paper: https://doi.org/10.1101/2020.05.21.109546

Journal/ Pre-Print: BioRxiv

Tags: Clinical, Diagnostics

Research Highlights 

1. Development of a high-throughput SARS-CoV-2 antibody neutralization assay suitable for rapid functional serodiagnosis

2. Reporter virus assay produces results which are comparable to the plaque reduction neutralization test (PRNT).

Summary

This study describes the development of a high-throughput fluorescent-based neutralizing antibody assay against SARS-CoV-2. 40 sera from RT-PCR confirmed Covid-19 patients and 10 sera from before Covid-19 emergence were used to verify the accuracy of the assay, using serum dilutions to measure NT50 values. NT50 values were found to be comparable to PRNT with the same set of patient specimens. Specificity testing of their assay using sera with possible interfering antigens, or antibodies against different microbes, found no cross reactivity. This included four common cold coronaviruses. The authors also report the neutralization test has a shortened turnaround time by days compared to PRNT.

Impact for SARS-CoV2/COVID19 research efforts

Develop diagnostic tools for SARS-CoV2/COVID19

Other: Neutralizing antibody detection/activity against SARS-CoV-2/COVID19

Study Type

· In vitro study

Strengths and limitations of the paper

Novelty: Development of a novel high-throughput antibody neutralization assay for SARS-CoV-2 serodiagnosis

Standing in the field: Literature supports claims made in the paper

Appropriate statistics: Statistics were appropriate, would have been nice to have some calculated errors for the NT50 values

Viral model used: Sera of COVID-19 confirmed patients, assay uses mNeonGreen SARS-CoV-2 (ORF7 of viral genome replaced with mNeonGreen gene)

Translatability:

● Assay has the potential to be used in the clinic as a rapid means of assessing the presence of neutralizing antibodies, which is important for diagnostics and vaccine development.

● By measuring functional SARS-CoV-2 neutralizing activity in the samples the assay may offer an advantage over conventional ELISA assay.

Main limitations:

● Would have been good to have seen more of the dose-response plots from their data.

● More specimens needed to show there is low cross reactivity of the assay (only 1 to 14 samples per type of interfering sera). Would have been good to also have included specimens from SARS-CoV-1 and MERS-CoV infections.

● Would have been interesting if the NT50 values from Covid-19 patient sera had been correlated to the patient disease progression/severity.

● Unclear whether it is better than a SARS-CoV-2 S-pseudovirus assay that is also fast turnaround and can be used in containment level-2.