Sialylation profile in placentas of pregnancies affected by SARS-CoV-2 infection

Recent investigations have indicated the potential negative consequences of SARS-CoV-2 infection on pregnant women and pregnancy outcomes. Studies have described pathological changes in the placental tissue of SARS-CoV-2-positive mothers, which may or may not be associated with infection severity or the trimester of infection [1]. Among the various molecules involved in the normal structure and functioning of the placenta, sialic acids (Sias) appear to play a signifi cant role. Th erefore, our objective was to examine potential alterations in the distribution and levels of Sias with diff erent glycosidic linkages, specifi cally α2,3 and α2,6 Galactose- or N-acetyl-Galactosamine-linked Sias, as well as polymeric Sia (PolySia), in placentas from pregnant women infected with SARS-CoV-2 during diff erent trimesters of pregnancy [2, 3]. We employed lectin histochemistry, utilizing Maackia amurensis agglutinin (MAA) and Sambucus nigra agglutinin (SNA) for the evaluation of α2,3 and α2,6 Galactose-linked Sias, respectively. Immunohistochemistry was employed for the detection of PolySia. Th e data revealed decreased levels of α2,3 Galactoselinked Sias in the trophoblast and underlying basement membrane/basal plasma membrane in placentas from women infected during the second and third trimesters, in comparison to uninfected cases and those infected during the fi rst trimester. Conversely, higher levels of PolySia were observed in the trophoblast during the second and third trimesters of infection. Our fi ndings suggest that alterations in the sialylation status of the trophoblast and its basement membrane/ basal plasma membrane, in conjunction with other concurrent factors, could underlie the most common placental histopathological changes and gestational complications found particularly in pregnancies with SARSCoV- 2 infection during the second and third trimesters.