Evidence of a significant secretory-IgA-dominant SARS-CoV-2 immune response in human milk following recovery from COVID-19

Authors: Fox et al.

Link to paper: https://doi.org/10.1101/2020.05.04.20089995

Journal/ Pre-Print: MedRxiv

Tags: Immunology/Immunity, Therapeutics 

Research Highlights 

1. 12/15 milk samples of previously SARS-CoV-2 infected participants contained IgA reactive to the receptor binding domain (RBD) of the SARS-CoV-2 spike protein as well as the secretory type Ab reactive to RBD

2. Of these 12 milk samples additional Ig reactivity to RBD was detected (4 samples positive for IgG and IgM reactivity, 2 samples positive for only IgG reactivity, 1 sample positive for only IgM reactivity and 1 sample showed only positive IgG reactivity)

3. IgA as well as secretory Abs could be used as therapeutics

Summary 

To investigate the reactivity of different immunoglobulins to the receptor binding domain (RBD) of the SARS-CoV-2 spike protein, the authors tested 15 milk samples from previously SARS-CoV-2 infected participants. They found that 80% of the samples contained IgA as well as secretory antibodies reactive to the RBD. This could be important for passive immunisation of infants as well as of potential use as a COVID-19 therapeutic. The report highlights the preliminary data of 15 participants of a larger study which recruited over 1000 lactating participants.

Impact for SARS-CoV2/COVID19 research efforts

Understand the immune response to SARS-CoV2/COVID19

Treat of SARS-CoV2/COVID19 positive individuals

Study Type

· Patient Case study

· In vitro study

Strengths and limitations of the paper

Novelty: Detection of IgA and secretory antibodies in milk of SARS-CoV-2 recovered participants

Standing in the field: To our knowledge one of the first studies in this research area

Appropriate statistics: Appropriate, detailed description of technical and biological replicates and statistical analysis used

Viral model used: used milk samples of previously SARS-CoV-2 infected participants

Translatability: Potential use of secretory IgA for therapeutics, as they are more stable and lower dose is needed when administered via the respiratory tract

Main limitations:

1. Study includes 15 participants, which had either a laboratory confirmed COVID-19 infection or a highly likely infection, virus titres of participants would be valuable to compare viral load to Ig production in the milk

2. Study includes 15 participants, while the authors state that these are part of a much larger cohort (around 1000 participants) at the current state the analysis is lacking power

3. Milk was obtained around 14-30 after symptoms have stopped, the variation in the time passed after symptoms have stopped might be mirrored in the antibody response

4. More details about the health status of the participants would help to interpret the antibody production in the milk (e.g. virus titre, previous disease severity or comorbidities)