Fig. 4.

Development of a prototype test cassette for measuring Nab against SARS-CoV-2. a. and b. A schematic and a photograph depicting our prototype lateral flow assay cartridge design. c. 6 representative healthy pre-COVID-19 samples and 6 representative COVID-19 patient samples as run on the prototype lateral flow cartridge. d. Conversion of stripe intensity from each sample to a % inhibition based on the formula % inhibition = (1 - sample intensity/ average intensity of COVID-19-ve samples) x100. n = 200 (COVID-19+) / 60 (Healthy controls) biological replicates. P-value <0.0001 from Mann-Whitney test. e. Readings from lateral flow strips were plotted against readings for same samples derived from virus microneutralisation assay. Semi-log regression with 95%CI (dashed lines), n = 126 biological replicates. f. 93 of the samples from e. where anti-RBD antibody levels were available were plotted against microneutralisation titres for the same samples. Semi-log regression with 95%CI (dashed lines). g. Samples from an individual that were collected from 3 to 10 weeks. Six COVID-19 -ve samples were also run for comparison. Results from patient C1 are plotted as % inhibition vs days from symptom onset. h. Pre- and post-infection samples from a symptomatic patient at indicated timepoints.