Study shows cell surface proteins in placental tissue prevent COVID-19 transmission

Scientists from the Maxwell Finland Laboratory for Infectious Diseases at Boston Medical Center have discovered properties in the placental tissue that may play a significant role in inhibiting the transmission of COVID-19 infection from a mother, who has the novel coronavirus, to her fetus.

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The results of the new study show that the novel coronavirus universally enters the placenta in cases with and without the proof of fetal infection, underscoring the protection that could be provided by the placenta against the COVID-19 infection. This is in line with the present-day data that indicates a COVID-19 transmission rate of less than 5% in newborns from their mothers.

These results, published in the Placenta journal, underline the significance of applying placental tissue in COVID-19 research studies targeted at developing new ways of diagnosing, treating, and preventing the transmission of COVID-19 virus.

For this study, the research team analyzed the placental tissue, which shares several physiological and developmental similarities with the lung and the immune response of the large and small intestines, rendering it a crucial source of human tissues that can be used for the current COVID-19 studies.

The placental tissue also features a special expression pattern of COVID-19 receptors that is quite different from other organs, and this fact could help develop COVID-19 treatments.

The results of this study provide evidence for ongoing research of COVID-19 infection at the maternal-fetal interface as means to better understand virus transmission and infection in other human tissues. Previous research has shown that the placenta protects the fetus from various types of infection, and exploring the particular ways in which it protects the fetus from COVID-19 transmission may help identify new targets of COVID-19 prevention and treatment.”

Elisha Wachman, MD, Study Principal Investigator and Associate Professor of Pediatrics, Boston University School of Medicine

Dr. Wachman is also a neonatologist at the Boston Medical Center.

From April to May 2020, the researchers collected samples from 15 COVID-19 positive maternal-fetal dyads for this research work, of which five cases had proof of fetal transmission. They examined and compared the placental tissue of the positive cases with 10 COVID-19 negative controls. The team detected the presence of COVID-19 virus in the placental tissues in cases with and without the proof of fetal infection.

The researchers also noted that the placenta contains a special pattern of cell surface proteins (ACE2 and TMPRSS2) that is significant for the entry of the COVID-19 virus, which is different from other types of cells. They also examined the demographics of mother-baby dyads and did not find any major differences. This shows that fetal transmission does not discriminate.

Determining how the placenta could be preventing COVID-19 infections during pregnancy can help provide clues on how to prevent infection in other organs, such as the lungs and gut. As a readily available tissue for research, the placenta can be a valuable source of scientific study for a variety of human diseases in pregnancy and beyond.”

Elizabeth Taglauer, MD, PhD, Neonatologist and Placental Biologist, Boston Children’s Hospital