COVID-19 infection less prevalent among newborns, lack of ACE-2 receptors in placenta may shield fetus, claims NIH study

Until the baby is born, the mother’s body not only takes care of her own body but also provides a protective shield to the baby in the form of the placenta. The placenta serves as the lungs, gut, kidneys and liver to the unborn baby. The amniotic sac is a water-filled cavity which protects the child against microbes that can try to intrude the sac. Even if the mother gets infected with a blood-borne disease, the cells of the placenta (trophoblast), syncytiotrophoblasts and cytotrophoblasts prevent the baby from getting the disease. However, there are some viruses such as the Rubella virus, herpesvirus, cytomegalovirus and Zika virus which can cross the placenta and infect the fetus. Recently, scientists from the National Institute of Health (NIH), US, stated that they have found the reason why there are only a few cases of fetal transmission of COVID-19 infection throughout the world. Studying the placental tissues In the study published in the journal elife on 14 July 2020, the scientists collected the samples of the placenta from two groups of patients after their delivery. The first group included the women who were diagnosed with placenta accreta at 18 weeks of gestation, which is a condition where the placenta attaches itself too deeply into the uterine wall. The other group included 32 patients who had different conditions at the third trimester. The scientists further processed these placental tissues to test their DNA sequence. Results of the study It is an established fact that the SARS-CoV-2 virus has an affinity for ACE-2 receptors which are present in different organs. Some studies have also concluded that another enzyme called the Transmembrane protease serine 2 (TMPRSS2) is equally responsible for the introduction of the SARS-CoV-2 virus in the body. On testing various placental tissues, scientists from the NIH found that in the first trimester of pregnancy there was a minimal presence of ACE-2 receptors in the placenta. However, in the second and third trimester, there were almost no traces of ACE2 and TMPRSS2 in the placenta and amniotic sac. The scientists concluded that the vertical transmission of SARS-CoV-2 virus is very unlikely as there is an absence of the required receptors in the placenta and amniotic sac, especially in the third trimester. However, the scientists stated that the fetus could be born with COVID-19 infection if any pathological infection simultaneously affecting the mother’s body breaches the placental barrier, thus letting the SARS-CoV-2 virus enter the amniotic cavity. They further added that the virus can also infect the fetus with the help of proteins which facilitate the entry of the virus. For instance, previous in vitro studies have shown that a protein called Basigin can provide an alternate entry to SARS-CoV-2 in the absence of ACE-2 and TMPRSS2 receptors. For more information, read our article on COVID-19 infection in infants. Health articles in Firstpost are written by myUpchar.com, India’s first and biggest resource for verified medical information. At myUpchar, researchers and journalists work with doctors to bring you information on all things health.