In all the discussion and research around covid-19 and its vaccines, pregnant women and children are more often than not missing. Whether it be the impact of the covid-19 vaccine in expecting women or the transmissibility of SARS-CoV-2 in breast milk—very little is known about this infection and how it impacts pregnancy or motherhood.
However, all is not lost on this front as researchers from Massachusetts General Hospital (MGH) have some news to share. And it’s not good! According to the investigators at the hospital, that the risk covid-19 poses in pregnant women and infants could be severe.
Their findings were published in the journal Cell. They reveal lower than the expected transfer of protective SARS-CoV-2 antibodies via the placenta from mothers who are infected in the third trimester. The cause may be alterations to these antibodies after they’re produced—a process called glycosylation.
The results expand on the team’s recent findings published in JAMA Network Open that pregnant women with covid-19 pass no SARS-CoV-2 virus, but also relatively low levels of antibodies against it, to newborns.
For this latest study, the scientists compared maternal antibodies against the flu (influenza), whooping cough (pertussis), and SARS-CoV-2, and how these antibodies transferred across the placenta. Influenza- and pertussis-specific antibodies were actively transferred in a relatively normal fashion.
In contrast, transfer of SARS-CoV-2-specific antibodies to the baby was not only significantly reduced, but the antibodies transferred were less functional than the antibodies against influenza. The reduced transfer was only observed in third-trimester infection.
The scientists found that altered attachments of carbohydrates to the SARS-CoV-2-specific antibodies—a process called glycosylation—may be to blame for this reduced transfer from mother to fetus in the third trimester.
The carbohydrate attachments on SARS-CoV-2-specific antibodies in maternal blood were different than those seen on influenza- and pertussis-specific antibodies. This carbohydrate pattern may cause the covid-specific antibodies to be “stuck” in the maternal circulation, rather than transferred across the placenta via placental antibody receptors.
Infection-induced increases in total maternal antibodies, as well as higher placental expression of an antibody receptor that attracts the carbohydrate pattern on the SARS-CoV-2-specific antibodies, helped to partially overcome the problem and facilitate the transfer of some functional antibodies from mother to fetus.
Interestingly, some of the antibodies that transferred the best were also the most functional, activating natural killer cells that could help the newborn fight the virus if exposed.
“Vaccine regimens able to drive high levels of the COVID-specific antibodies with glycosylation patterns favoured by the placenta for selective transfer to the fetus may lead to better neonatal and infant protection,” said co-senior author Andrea Edlow, MD, MSc, a maternal-fetal medicine specialist at MGH and an assistant professor of Obstetrics, Gynecology, and Reproductive Biology at Harvard Medical School.
“We are beginning to define the rules of placental antibody transfer of SARS-CoV-2 for the very first time—catalyzing our ability to rationally design vaccines to protect pregnant women and their newborns,” Co-senior author and Core Member at the Ragon Institute of MGH, MIT and Harvard, Galit Alter, PhD, said.
In addition, understanding how antibody transfer varies by trimester may point to critical windows in pregnancy that may be most desirable for vaccination to optimize protection for both the mother and her infant.
(With inputs from ANI)