Thread by @VikiLovesFACS

There are already lots of studies showing that antibodies pass into breastmilk after #COVID19 #vaccination. But this new preprint looks at the properties of those antibodies in more detail, as well as reporting for the first time on T cells... 💉🤱🏿🧵

medrxiv.org/content/10.110…

First - in agreement with the other studies - anti-Spike IgA and IgG are found in breast milk following vaccination.

(Milk shown in purple, plasma in orange). 2/

Next, they looked at what kind of IgA it was. Is it monomeric (M) like IgA in blood? Or oligomeric (O), suggesting it is produced at a mucosal surface?

The IgA in milk is mostly oligomeric, suggesting it is produced locally in the breast. 3/

Looking at the ability of IgA to neutralise virus, they found that IgA in breast milk is much less able to neutralise virus than that in blood. 4/

This is interesting, because IgA in breast milk following COVID infection *does* neutralise virus.

This might suggest that if we want good neutralising IgA at mucosal surfaces (and in breast milk!) we need a different vaccination strategy. 5/

ncbi.nlm.nih.gov/pmc/articles/P…

(For completeness, I will mention that this study did find some ability of IgA in breastmilk to block Spike binding to ACE2 following vaccination, but using a different and probably less good assay.) 6/

medrxiv.org/content/10.110…

Finally, what about those T cells? T cells do get into breast milk, and this study found that after dose 2, some of the T cells in breast milk are Spike-specific. 7/

There is some evidence that T cells survive the infant gut and seed tissues - especially in the 1st few weeks of life. So this could provide another route by which #COVID19 #vaccination of #breastfeeding ppl could protect their babies. 💉🤱🏻👶🏻🥳

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onlinelibrary.wiley.com/doi/full/10.11…