According to a new study published in Science Translational Medicine, women who contract COVID-19 during pregnancy transfer fewer antibodies to SARS-CoV-2 to their fetus if the fetus is male rather than female, which could explain the greater vulnerability of newborns and young male children facing infectious pathogens, including SARS-CoV-2. A second study also appeared in Science highlights the fact that pregnant women absolutely need a second dose of messenger RNA (mRNA) vaccine to develop adequate protection against COVID-19.
It was known that the risk of mortality and morbidity during the perinatal period and childhood is greater in boys than in girls. Presumably because of this greater perinatal vulnerability of boys, newborns and male children fare less well with COVID-19, in particular they are more likely than young female children to develop the disease. SARS-CoV-2 multisystem inflammatory syndrome. Several epidemiological studies have also shown that, even in adulthood, men with COVID-19 are three times more likely to end up in an intensive care unit than women and are at greater risk of dying from it. .
Given the immaturity of the immune system of newborns, the latter relies heavily on the transfer of antibodies from mother to fetus through the placenta and breast milk to cope with infectious pathogens early in their life. life. In an effort to assess the impact of COVID-19 on maternal and fetal immunity, researchers at Harvard Medical School in Boston examined the immune response in maternal blood, placenta and umbilical cord blood from 68 pregnant women who were infected with SARS-CoV-2 during pregnancy, 34 of whom carried a male fetus and the other half a female fetus.
Andrea Edlow, Evan Bordt and their colleagues thus measured lower amounts of antibodies against SARS-CoV-2 in mothers with a male fetus than in those with a female fetus. However, such a discrepancy has not been observed with regard to antibodies against influenza and pertussis.
“These reduced amounts of antibodies against SARS-CoV-2 in mothers pregnant with a boy undoubtedly contributed to the transfer of fewer antibodies across the placenta to male fetuses,” say the researchers in the discussion of their article published in Science Translational Medicine. These point out that the severity of the infection, the time of infection during pregnancy, the baby’s birth weight and gestational age did not appear to have had an impact on these results. They point out, however, that weaker transfer of antibodies to male fetuses had previously been observed in non-human primate females subjected to stress during pregnancy.
The researchers also specify that it is currently impossible to know whether this deficit in the transfer of antibodies makes male babies more vulnerable to COVID-19 early in their life, “because we do not know the amount of ‘antibody required to provide good protection against this infection,’ they write.
These scientists also noted that the male placentas – because it must be remembered that the placenta is a structure that develops from the cells of the embryo, it can therefore be of male or female origin – exhibited greater activation of the cells. signaling pathways of interferon, which is a powerful antiviral molecule that participates in the immediate immune response – known as innate – when the mother contracted COVID-19. “This activation would perhaps help prevent viruses from infecting the placenta and the fetus,” say the researchers, who stress the importance of monitoring the development of these children given the important changes that occur in the environment within. -uterine when the mother gets an infection during her pregnancy.
Pregnancy and immunity
In a second article also published in Science Translational Medicine, other researchers from the same institution analyzed the immune response induced by Pfizer’s and Moderna’s mRNA vaccines against COVID-19 in 84 pregnant women – this category of women had been excluded from clinical trials -, 31 women who were breastfeeding and 16 women who were not pregnant.
From the outset, these researchers remind us that important immunological changes occur in pregnant women during their pregnancy so that their immune system does not reject the fetus and that it allows its growth, while continuing to protect them all. both against pathogens. “The subtle balance between tolerance and immunity, combined with physiological and hormonal changes, contributes to the increased vulnerability of pregnant women to infections, such as influenza and COVID-19”, they point out, while indicating that pregnant women and who are breastfeeding are strongly encouraged to be vaccinated against influenza and COVID-19, which can be much more serious in them.
The researchers noted that the first dose of the COVID-19 vaccine elicited a significantly less protective response in pregnant and lactating women than in those who were not pregnant since they had produced significantly fewer antibodies and the ability to Fc receptors to bind to antibodies, and thus allow the latter to cross the placenta, was markedly lower. The second dose of vaccine, however, smoothed out these differences.
This poor response to a single dose of vaccine underscores the importance of administering a second dose of vaccine to pregnant and breastfeeding women in order to adequately protect them and their offspring. “Vaccination during pregnancy increases the protection of newborns, who are at high risk of suffering from a severe infection of the disease when they contract one due to the immaturity of their immune system,” they recall. They also state that “the antibodies present in breast milk also depend a lot on the second dose to stimulate their transfer into a functional form”.