Figure 2
Neutralising capacity of serum against SARS-CoV-2 spike is not significantly affected by storage on filter paper at room temperature for up to 28 days. Single-round infectious pseudo-virus particles (PVP) expressing SARS-CoV-2 spike were used to measure the neutralisation capacity of 7 human sera samples (squares-CCP-UK01, downwards traiangles-CCP-UK10a, upwards triangles CCP-UK10b, circles-CCP-UK05, diamonds-CCP-UK16, hexagons-CCP-UK17 and stars-CCP-UK31). Sera were stored on filter paper kept at room temperature (RT) as dried serum spots (DSS) for 0–28 days before elution and compared to sera stored as direct aliquots at − 80 °C (serum). Due to availability of sera only 4 out of 7 had DSS left at RT for 28 days. Bar charts a-f show neutralisation activity on the y-axes defined as the serum dilution that reduced PVP infectivity by 50% (a and d), 70% (b and e) and by 90% (c and f) (IC50, IC70 or IC90, respectively). Error bars represent standard deviation from the mean. Wilcoxon t-tests were run, and no significant differences (ns) were found between the mean IC values for serum controls and the mean IC values for DSS stored at RT from 2 to 28 days (p > 0.05).
