Secretory IgA and T cells targeting SARS-CoV-2 spike protein are transferred to the breastmilk upon mRNA vaccination

Juliana Gonçalves,A Margarida Juliano,Nádia Charepe,Marta Alenquer,Diogo Athayde,Filipe Ferreira,Margarida Archer,Maria João Amorim,Fátima Serrano,Helena Soares

doi:10.1016/j.xcrm.2021.100468

Abstract

SummaryIn view of the scarcity of data to guide decision making, we evaluated how BNT162b2 and mRNA-1273 vaccines affect the immune response in lactating women and the protective profile of breastmilk. Compared with controls, lactating women had a higher frequency of circulating RBD memory B cells and higher anti-RBD antibody titers but similar neutralizing capacity. We show that upon vaccination, immune transfer to breastmilk occurs through a combination of anti-spike secretory IgA (SIgA) antibodies and spike-reactive T cells. Although we found that the concentration of anti-spike IgA in breastmilk might not be sufficient to directly neutralize SARS-CoV-2, our data suggest that cumulative transfer of IgA might provide the infant with effective neutralization capacity. Our findings put forward the possibility that breastmilk might convey both immediate (through anti-spike SIgA) and long-lived (via spike-reactive T cells) immune protection to the infant. Further studies are needed to address this possibility and to determine the functional profile of spike T cells.

Highlights

Clinical trials of coronavirus disease 2019 (COVID-19) mRNA vaccines excluded lactating women, causing a dearth of data to guide vaccine decision making by health authorities.[1]. This is especially worrisome because infants are the group of children most affected by COVID-19.2,3 In view of the physiological alterations observed in lactating women and of the crucial role of breastmilk in providing immunity to the suckling infant, there is a pressing need to determine how mRNA vaccines affect immune responses in lactating mothers and to uncover the effector profile of breastmilk-transferred immune protection
We looked at humoral response in breastmilk and blood $10 days after first vaccine dose, when protection conferred by mRNA vaccines is starting.[35,36]
As mRNA vaccines are better suited to inducing systemic monomeric IgA than polymeric mucosal secretory IgA (SIgA), we sought to identify the source of IgA in the breastmilk through detection of SIgA reactive against spike and its RBD domain

Summary

Introduction

Clinical trials of coronavirus disease 2019 (COVID-19) mRNA vaccines excluded lactating women, causing a dearth of data to guide vaccine decision making by health authorities.[1]. Whether mucosal immunity is elicited or not by vaccination depends to a great extent on the vaccination route, with intramuscular inoculation favoring a systemic immune response and intranasal or oral vaccination inducing mucosal immunity.[12,13]

Methods

Results

Discussion

Conclusion