Fig 4. Extracted milk IgA from COVID-19-recovered donors exhibits SARS-CoV-2 Spike-targeted neutralization potency that is highly correlated with IgA binding activity.

(A) Total IgA was purified from 8 COVID-19 and 8 control milk samples by conventional means using peptide M agarose. IgA was titrated and tested in a VSV-based SARS-CoV-2 pseudovirus neutralization assay. NEG/segmented lines: pre-pandemic controls. COV/solid lines: COVID-19-recovered milk samples. Segmented line: 50% neutralization cutoff value. (B) Percent neutralization achieved using 50ug/mL of total extracted milk IgA. Mean values with SEM are shown. **p = 0.0064. Mann-Whitney U test (2-tailed) was used to compare grouped data with significance level set at p < 0.05. (C) Neutralization IC50 values determined from IgA titration curves. (D) Endpoint titer values determined in Fig 1 and IC50 values were used in a 2-tailed Spearman correlation test.