Breast milk stimulates infants' Covid-19 defences: a study in Jama
Breast milk and Covid-19: a study in collaboration with Policlinico Umberto I examined infants of SARS-CoV-2 positive mothers at delivery. Results published in JAMA Network Open
The possibility that a mother who is SARS-CoV-2 positive at the time of delivery transfers the infection to her newborn is very rare: clinical experience during these two years of pandemic has shown this.
But what are the mechanisms that defend the newborn? This is the question posed by researchers at the Bambino Gesù Children’s Hospital, who conducted a study in collaboration with the Policlinico Umberto I in Rome.
The study, published in JAMA Network Open, shows that thanks to the milk of mothers infected with the virus, these newborns are able to develop their own immune defences against Covid-19.
RESEARCH ON BREAST MILK AND ANTI-COVID-19 DEFENCES
The research just published has been promoted by the Immunological Diagnostic Research Unit of the Bambino Gesù Children’s Hospital, within the framework of Multimodal Laboratory Medicine and the Complex Operative Unit of Neonatology, Pathology and Neonatal Intensive Care of the Policlinico Umberto I.
The study involved 28 women – and their newborns – who gave birth at Policlinico Umberto I between November 2020 and May 2021.
All the women tested positive for SARS-CoV-2 at delivery following the hospital admission swab, although many were asymptomatic.
None of the women had been vaccinated against Covid-19 at the time. The researchers set out to ascertain whether and how this condition of the mother at the time of delivery affected the infant’s immunity.
ANTIBODY PROTECTION IN BREAST MILK
In general, the mother protects her baby in the first days and months of life by transferring her own antibodies through the placenta.
These are IgG antibodies (or immunoglobulins) produced in response to infection or vaccination and contained in the mother’s blood.
This mechanism provides the newborn baby with passive protection by allowing it to use its mother’s antibodies in the absence of its own.
If the mother breastfeeds, she also transfers to the baby another type of antibody (IgA), called mucosal antibodies, because they are produced by the mucous membranes of the mother’s respiratory tract (as well as the intestine) and because they help the newborn against mucosal infections, such as colds or flu.
The researchers studied how this protective mechanism worked in the case of coronavirus-positive mothers at the time of birth.
They looked for and measured the presence of specific immunoglobulins against SARS-CoV-2 in the blood and milk of mothers, as well as in the blood and saliva of newborns.
Saliva contains IgA antibodies that protect the mucous membranes and which the pandemic experience has shown to be generally very effective against SARS-CoV-2 infection.
The tests were carried out 48 hours after delivery and repeated after two months.
SPECIFIC ANTIBODIES IN NEWBORN SALIVA
The results of the tests showed that specific antibodies to the virus were present in the mothers’ blood two months after birth, but not at 48 hours.
This is a predictable result, because we know that the immune system needs two weeks to produce IgG immunoglobulins.
In milk, on the other hand, specific IgA antibodies were present as early as 48 hours after birth, showing that the mucosal response for antibody production is faster than the body’s systemic response.
Consistent with these findings, the infants did not have SARS-CoV-2 specific IgG in their blood at either 48 hours (because the mother could not transmit it through the placenta, as she did not have it before delivery) or two months after birth (because the infants had not been attacked by the virus and had not become infected).
In saliva, on the other hand, mucosal antibodies to the virus were present not only at 48 hours but also two months after birth, but only in the breastfed babies: 17 compared with 13 (including two sets of twins).
This is a surprising first result, because at the same time the presence of antibodies in the mothers’ milk was significantly reduced, as they were no longer positive for the coronavirus.
Something in children seems to go beyond the mechanism of mere passive protection.
MOTHER’S MILK AS A COVID VACCINE
After 48 hours, the breastfed babies had specific mucosal antibodies in their saliva against Covid-19 that the other infants did not have.
After two months, these antibodies continued to be present even though the mothers had stopped producing them.
For the researchers, this is proof that breast milk plays a fundamental role not only by offering passive protection, i.e. transferring the antibodies produced by the mother to the baby, but also by helping the baby to produce its own immune defences.
The mechanism seems to be similar to that of a vaccine.
The IgA produced by infected mothers binds to the Spike protein expressed on the surface of the virus, forming a molecule, called an immune complex, which will be transferred from the mother to the newborn through breastfeeding.
The IgA-Spike complex inherited from the mother proves to be immunogenic, i.e. it stimulates the immune system to produce antibodies against SARS-COV-2, so that the newborn is able to produce its own protective IgA.
This is the first time that this mechanism has been demonstrated,” says Dr Rita Carsetti, head of Immunology Diagnostics at Bambino Gesù.
We now know how mother’s milk can help the baby to develop its own immune defences.
The system could work in the same way for many other pathogens that are present in the mother during breastfeeding”.
Furthermore: ‘There are currently no vaccines for newborns.
Immuno-complexes could be an oral immunisation system that could protect the child in the first days of life.
The research, she explains, ‘will now be extended and expanded in two directions: on the one hand, mothers who have received the Covid-19 vaccine during pregnancy, and on the other, widespread infections such as Cytomegalovirus and Respiratory Syncytial Virus.
It should be remembered that vaccination during pregnancy remains the most effective tool for enhancing the mother’s ability to protect her newborn thanks to antibodies transferred across the placenta’.
The results of this research underline how “every effort must be made from an organisational and communicative point of view to encourage contact between mother and newborn in order to promote breastfeeding even in extreme situations such as the SARS-Cov2 infection” states Prof. Gianluca Terrin, Director of the Neonatology Unit of the Policlinico Umberto I.
The research “was carried out in a dimension of complete emergency, during the second and violent wave of spread of COVID-19” underlines Prof. Terrin, adding that “these important results show how the great assistance response of the Policlinico Umberto I was accompanied by the accurate study of the observed phenomena, which led to significant scientific progress regarding the knowledge of the mechanisms of the development of the immune response in the early stages of life that could also have implications in other areas of clinical practice”.