key: cord-0796169-7q2jd0mf
authors: Fox, Alisa; Marino, Jessica; Amanat, Fatima; Krammer, Florian; Hahn-Holbrook, Jennifer; Zolla-Pazner, Susan; Powell, Rebecca L.
title: Robust and specific secretory IgA against SARS-CoV-2 detected in human milk
date: 2020-10-26
journal: iScience
DOI: 10.1016/j.isci.2020.101735
sha: 78b5cc00c3ff67bf9708e8ba4230dc89b135b731
doc_id: 796169
cord_uid: 7q2jd0mf

The SARS-CoV-2 immune response in human milk has not yet been examined, though protecting infants and young children from COVID-19 is critical for limiting community transmission, and preventing serious illness and death. Here, milk samples from 8 COVID-19-recovered and 7 COVID-19-suspected donors were tested for antibody (Ab) binding to the SARS-CoV-2 Spike protein. All samples exhibited significant specific IgA reactivity to the full Spike, while 80% exhibited significant IgA and secretory (s)Ab binding to the receptor binding domain (RBD). Additionally, 67% of samples exhibited IgG and/or IgM binding to RBD. IgA and sAb titers were highly correlated, indicating most IgA to be sIgA. Overall, these data indicate that a robust sIgA-dominant SARS-CoV-2 Ab response in human milk after infection should be expected in a significant majority of individuals. Further research is highly warranted to determine Ab functionality, and the potential for exploiting extracted milk sIgA for therapeutic use.

infection is essential. One potential protective mechanism might be passive immunity via 45 breastfeeding from a previously-infected mother or milk donor. 

Milk samples were initially evaluated for IgA binding reactivity by human IgA-specific ELISA to the 88 full trimeric SARS-CoV-2 Spike (Fig. 1) . It was evident that all samples obtained from COVID-19-89 recovered donors (100%), in undiluted form, exhibited binding activity significantly above that of the 90 pre-pandemic control milk samples, which did exhibit some low-level non-specific or cross-reactive 91 activity (Fig. 1a) . Milk samples were titrated and endpoint titer values were determined. It was found 92 that all COVID-19-recovered samples exhibited endpoint titers significantly higher than control samples evident that most of the samples contained SARS-CoV-2-reactive IgA without necessarily containing 146 measurable IgG and/or IgM, which particularly in the case of IgG, would likely be derived in large part 147 from the serum. Notably, IgG and IgM reactivities in undiluted milk exhibited a moderate correlation. It 148 may also be that as total IgG and IgM are so much lower in milk than IgA, that this ELISA lacked the 149 sensitivity to pick up very low-titer responses. 

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