Survival of Vaccine-Induced Human Milk SARS-CoV-2 IgG, IgA and SIgA Immunoglobulins across Simulated Human Infant Gastrointestinal Digestion

Abstract

Breastfeeding can be a vital way of acquiring passive immunity via the transfer of antibodies from the mother to the breastfeeding infant. Recent evidence points to the fact that human milk contains immunoglobulins (Ig) against the SARS-CoV-2 virus, either after natural infection or vaccination, but whether these antibodies can resist enzymatic degradation during digestion in the infant gastrointestinal (GI) tract or indeed protect the consumers remains inconclusive. Herein, we evaluated the levels of IgG, IgA, and secretory IgA (SIgA) antibodies against the spike protein of SARS-CoV-2 in 43 lactating mothers who received at least two doses of either an mRNA-based vaccine (Pfizer/BioNTech, Moderna; n = 34) or an adenovirus-based vaccine (AstraZeneca; n = 9). We also accessed the potential persistence of SARS-CoV-2 IgA, IgG, and secretory IgA (SIgA) antibodies from vaccinated women in the GI tract of the infants by means of a static in vitro digestion protocol. Our data depict that, although slightly reduced, the IgA antibodies produced after vaccination resist both the gastric and intestinal phases of infant digestion, whereas the IgGs are more prone to degradation in both phases of digestion. Additionally, SIgA antibodies were found to greatly resist the gastric phase of digestion albeit showing some reduction during the intestinal phase. The evaluation of the vaccine induced Ig profile of breastmilk, and the extent to which these antibodies can resist digestion in the infant GI tract provide important information about the potential protective role of this form of passive immunity that could help decision making during the COVID-19 pandemic and beyond.

Establishment of a measurement system to evaluate breast milk transfer of biological agents using dry filter paper: A multi‐institutional study

“…A study evaluating IgG, IgA and secretory IgA antibody levels of SARS‐CoV‐2 in nursing mothers who received at least two doses of either mRNA‐based or adenovirus‐based vaccine showed that IgG of SARS‐CoV‐2 was degraded in the digestive tract of infants. The study also showed that IgG of SARS‐CoV‐2 was easily degraded in the gastrointestinal tract of infants 32 . Similarly, a study of breast milk samples from nursing mothers who received mRNA vaccination against SARS‐CoV‐2 reported that gastrointestinal digestion of infants significantly decreased the levels of anti‐SARS‐CoV‐2 IgA and IgG 33 .…”

“…The study also showed that IgG of SARS-CoV-2 was easily degraded in the gastrointestinal tract of infants. 32 Similarly, a study of breast milk samples from nursing mothers who received mRNA vaccination against SARS-CoV-2 reported that gastrointestinal digestion of infants significantly decreased the levels of anti-SARS-CoV-2 IgA and IgG. 33 Additionally, a study examining the breakdown of antiphlogistic syncytial virus sIgA/IgA and IgG in human milk from four donors reported a reduction to 33% in the intestinal stage of simulated digestion.…”

Safety and Efficacy of Coronavirus Disease 2019 (COVID-19) mRNA Vaccines During Lactation

“…Breast-milk-derived SARS-CoV-2-specific antibodies have been detected in significant amounts in the breastfeeding infants' saliva and stool, 64,65,68 and studies performed in vitro support the capability of breast-milk-derived anti-SARS-CoV-2 IgG and secretory IgA to resist degradation in the infant gut. 69,70 Importantly, however, anti-SARS-CoV-2 antibodies have not been detected in the blood of infants whose mothers were vaccinated during lactation only, 29,68 suggesting that maternally derived antibodies from breast milk likely do not cross the gut mucosal barrier in detectable quantities. This stands in contrast to antibodies that are transplacentally transferred from mothers vaccinated during pregnancy, which are detectable in the infant's circulation for up to 6 months in the majority of cases.…”

Breastfeeding provides a protective hug and the benefits have outweighed the risks during the COVID‐19 pandemic

“…In this respect, secretory (s)IgA increased at the second dose and 3 weeks after the second dose and decreased at 6 months thereafter, while sIgG levels increased during the second dose and 3 weeks afterwards with maximum levels (peak) at 6 months after the first dose. Additionally, Pieri et al 26 have shown that after maternal vaccination, across simulated human infant gastrointestinal digestion, breastmilk IgA immunoglobulins are resistant to degradation in both the gastric and intestinal phase of the infant digestion, that IgG immunoglobulins are prone to degradation in both phases and that sIgA ones are highly resistant to the gastric phase, although they decline somewhat during the intestinal phase.…”