Figure 2.

Reactivity of prepandemic and COVID-19 naso-oropharyngeal swabs to coronaviruses spike and to SARS-CoV-2 pseudo-type.

(a) Enzyme-linked immunosorbent assay to SARS-CoV-2 spike antigen with prepandemic and pandemic nasopharyngeal swabs with SARS-CoV-2-positive reverse transcriptase-polymerase chain reaction result showing high cross-reactivity with no significant difference between the two sample sets. (b) Pseudotyped SARS-CoV-2 neutralization using the selected SARS-CoV-2 spike (S2) reactive IgA (n = 30) and nonreactive IgA (n = 15) samples are shown. There was neutralization with the S2-reactive samples, mean ID50 of 1:5.9 but no neutralization with nonreactive IgA (n = 15) samples. (c) There were also significantly higher responses of S2-reactive IgA samples than the S2-nonreactive IgA samples among the four endemic HCoV.

HCoV, human coronaviruses; Ig, immunoglobulin; ns, not significant; OD, optical density.