Figure 2. Antibody titers in human milk samples and their neutralization potential in Vero E6 cells and fetal intestinal monolayers.

(A) IgG and IgA titers against SARS-CoV-2 spike protein in human milk samples (1:10 dilution) collected from three lactating mothers participating in the COVID MILK study (van Keulen et al, 2020 Preprint), measured by ELISA. (B) Neutralization antibody titer of human milk measured by a neutralization assay on Vero E6 cells. Dotted lines represent the lower limit of detection. (C) Growth curves for SARS-CoV-2 replication under the different conditions. Each time point is a geometric mean of the values measured on three fetal-derived intestinal epithelial monolayers from three different fetal donors. SARS-CoV-2 RNA was measured by RT-qPCR analysis of the E gene in the culture medium collected at different time points. (D) Replication competent viral titers measured using a median tissue culture infectious dose (TCID50) assay. Legend: Milk+/+ was the human milk sample from a SARS-CoV-2 PCR–positive mother with SARS-CoV-2 spike-specific IgA and IgG in serum and human milk. Milk+/− was the human milk sample from a SARS-CoV-2 PCR–positive mother without SARS-CoV-2 spike-specific antibodies in serum and human milk. Milk−/− was the human milk sample from a mother negative for SARS-CoV-2 and negative for SARS-CoV-2 spike-specific antibodies in serum and human milk. Data information: In (A, B), data are presented as mean. In (C, D), data are presented as geometric mean ± SEM.