Spike-specific T cells are enriched in breastmilk following SARS-CoV-2 mRNA vaccination

Abstract

We compared the phenotype, diversity, and antigen specificity of T cells in the breastmilk and peripheral blood of lactating individuals who received SARS-CoV-2 mRNA vaccination. Relative to blood, breastmilk contained higher frequencies of T effector and central memory populations that expressed mucosal-homing markers. T cell receptor (TCR) sequence overlap was limited between blood and breastmilk. Overabundant breastmilk clones were observed in all individuals, were structurally diverse, and contained CDR3 sequences with known epitope specificity including to SARS-CoV-2 Spike. Spike-specific TCRs were more frequent in breastmilk compared to blood and expanded in breastmilk following a third mRNA vaccine dose. Our observations indicate that the lactating breast contains a distinct T cell population that can be modulated by maternal vaccination with potential implications for infant passive protection.SummaryThe breastmilk T cell repertoire is distinct and enriched for SARS-CoV-2 Spike-specificity after maternal mRNA vaccination.

Maternal immune protection against infectious diseases

“…These T cells were uniformly effector memory T cells and expressed increased levels of mucosal homing markers CCR9 and CD103 when compared to circulating T cells. Interestingly, the expression of CCR9 increased in relation to time since delivery and time since 2 nd vaccine dose further supporting that the mammary gland is a mucosal site where local T cells are stimulated and mature overtime (Armistead et al, 2021).…”

“…CMV (Moylan et al, 2017), EBV (Sabbaj et al, 2005), HIV (Sabbaj et al, 2002) and influenza-specific (Ruben et al, 1982) T cells are detected in breast milk, are at higher frequencies than in peripheral blood, and expand during maternal or infant infection (Hassiotou et al, 2013a;Hassiotou et al, 2013b). In a recent report authors found spike-specific T cells after SARS-CoV-2 mRNA vaccination in lactating mothers (Armistead et al, 2021). These T cells were uniformly effector memory T cells and expressed increased levels of mucosal homing markers CCR9 and CD103 when compared to circulating T cells.…”

Vaccine Protection Through Placenta and Breastfeeding: The Unmet Topic in COVID-19 Pandemic

“…Although studies about memory T cells against SARS-CoV-2 in human milk are scarce, Armistead et al observed that the lactating breast contains a distinct T-cell population that can be modulated by maternal vaccination with potential implications for infant passive protection. These researchers have identified SARS-CoV-2 spikespecific T cells in mRNA vaccinated in lactating women (89). Another study conducted by Goncalves et al involving lactating women who received mRNA vaccination found a combination of spike-reactive T cells and anti-SARS-CoV-2 secreted IgA in their milk, which shows that immune transfer to the infant could linger even after weaning, especially because of long-lived memory T cells transferred (64).…”

Effects of Vaccination Against Influenza, Pertussis, and COVID-19 on Human Milk Antibodies: Current Evidence and Implications for Health Equity

“…Using animal models, it was shown that cells from milk can survive the digestive tract and can traffic into infant organs ( 112 , 113 ). Interestingly two recent studies have demonstrated the presence of SARS-CoV-2 specific Spike-reactive T cells in human milk after vaccination ( 111 , 114 ). However, it is unknown if human milk cells provide immune protection to the respiratory tract or gastrointestinal tract of human infants or if they are taken up in the infant gut into systemic circulation.…”