SARS-CoV-2 assays to detect functional antibody responses that block ACE2 recognition in vaccinated animals and infected patients
clinical diagnostics immunology/immunity vaccines virology
Authors:Walker et al.
Link to paper:https://doi.org/10.1101/2020.06.17.158527
Tags: Immunology/Immunity, Clinical/ Diagnostics, Vaccines, Virology
Developed a competitive ELISA to test for antibodies which inhibit SARS-CoV-2 spike protein RBD interaction with ACE2, which has the potential to test for vaccine efficacy.
In mice, antibodies had greater ACE2 inhibition for S1+S2 compared to only S1 for SARS-CoV-2 spike protein.
The authors tested a competitive ELISA assay with bound SARS-CoV-2 spike protein, with competition between ACE2 and purified IgG or sera from vaccinated animal models (mice, rabbits, guinea pigs, rhesus macaques) and Covid-19 patients. The animals were vaccinated with the INO-4800 vaccine, and naive animals (mock saline vaccination) and Day 0 sera were used as negative controls. Healthy human pre-pandemic samples were used as a negative control. There was no blinding used in the study.
Impact for SARS-CoV2/COVID19 research efforts
Develop diagnostic tools for SARS-CoV2/COVID19
Others: Also suggests tool could be used to test efficacy of the vaccines
In vitro study
In vivo study (e.g. mouse, NHP)
Strengths and limitations of the paper
Novelty:New tool to detect antibodies from sera which inhibit RBD-ACE2 interaction of SARS-CoV-2
Standing in the field:Another antibody assay, ELISA-based
Appropriate statistics:Some statistics, but lacking and poorly explained
Viral model used:SARS-CoV-2 spike protein (S1+S2) and S1, SARS-CoV-2 pseudovirus
Translatability:Might be useful as an antibody test, including for vaccine efficacy investigation
No blinding of samples before experiments, and previous vaccine study in animal models which was referenced also had no blinding.
No descriptions of repeats, or mention of duplicates or triplicates for ELISAs
Low numbers of animals for each test
Barely anything done with SPR assay - did not use purified IgG or sera to validate assay
No rationale for the steps taken in the study and unclear descriptions and figures
No comparison between their competitive ELISA and a sandwich ELISA to show sera/purified IgG/ACE2 binding to SARS-CoV-2 RBD, matrix effects, and quantification.