COVID-19 and human milk: SARS-CoV-2, antibodies, and neutralizing capacity

Abstract

Background: It is not known whether SARS-CoV-2 can be transmitted from mother to infant during breastfeeding, and if so whether the benefits of breastfeeding outweigh this risk. This study was designed to evaluate 1) if SARS-CoV-2 RNA can be detected in milk and on the breast of infected women, 2) concentrations of milk-borne anti-SARS-CoV-2 antibodies, and 3) the capacity of milk to neutralize SARS-CoV-2 infectivity. Methods: We collected 37 milk samples and 70 breast swabs (before and after breast washing) from 18 women recently diagnosed with COVID-19. Samples were analyzed for SARS-CoV-2 RNA using RT-qPCR. Milk was also analyzed for IgA and IgG specific for the nucleocapsid protein, receptor binding domain (RBD), S2 subunit of the spike protein of SARS-CoV-2, as well as 2 seasonal coronaviruses using ELISA; and for its ability to neutralize SARS-CoV-2. Results: We did not detect SARS-CoV-2 RNA in any milk sample. In contrast, SARS-CoV-2 RNA was detected on several breast swabs, although only one was considered conclusive. All milk contained SARS-CoV-2-specific IgA and IgG, and levels of anti-RBD IgA correlated with SARS-CoV-2 neutralization. Strong correlations between levels of IgA and IgG to SARS-CoV-2 and seasonal coronaviruses were noted. Conclusions: Our data do not support maternal-to-child transmission of SARS-CoV-2 via milk; however, risk of transmission via breast skin should be further evaluated. Importantly, milk produced by infected mothers is a source of anti-SARS-CoV-2 IgA and IgG and neutralizes SARS-CoV-2 activity. These results support recommendations to continue breastfeeding during mild-to-moderate maternal COVID-19 illness.

Humoral and cell-mediated response in colostrum after exposure to severe acute respiratory syndrome coronavirus 2

“…Our results provide a snapshot of the dynamic immune response in colostrum following SARS-CoV-2 infection, confirming recent findings on the presence of SARS-CoV-2-specific antibodies in milk from infected women4,5 , and describing for the first time, the associated cytokine profile. Colostrum samples archived before the pandemic together with analysis of bilateral samples provide important controls for this study, and the similarities between resultsfrom the spot card and the liquid colostrum demonstrate the value of the spot card collection method.…”

Detection of breastmilk antibodies targeting SARS-CoV-2 nucleocapsid, spike and receptor-binding-domain antigens

“…A small number of reports have shown that antibodies against SARS-CoV-2 can be detected in the breastmilk of breastfeeding women who have recovered from documented SARS-CoV-2 infection [ 4-6 ]. The largest of these reports investigated 37 breastfeeding women with recent documented SARS-CoV-2 infection finding that all (100%) had detectable SARS-CoV-2 IgA and IgG [ 7 ], while another investigating 15 breastfeeding women found that 12/15 (80%) had detectable IgA and IgG reactive to the SARS-COV-2 RBD-antigen [ 4 ]. Two other reports describe two individual patients: a pregnant woman with active SARS-CoV-2 infection who delivered an infant who had detectable IgA and IgG in her breastmilk [ 5 ], and a breastfeeding woman found to have SARS-CoV-2 IgG and IgM in her breastmilk (IgA was not tested) [ 6 ].…”

Breastfeeding, Human Milk and COVID-19—What Does the Evidence Say?

“…In addition to the already well-known and documented benefits of breastfeeding (3), recent research has shown specific benefits relevant to the COVID-19 situation. For example, antibodies to SARS-CoV-2 have recently been isolated in human milk (34)(35)(36) and have shown strong SARS-CoV-2 neutralizing capabilities (18,37). Whilst these data show a robust immunological response by human milk against the virus they also suggest that human milk provides an active form of protection against the virus, a form of protection that cannot be provided to the infant via artificial formula, thus further supporting the need for the protection and promotion of breastfeeding.…”