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Confirmatory evidence of the visualization of severe acute respiratory syndrome coronavirus 2 invading the human placenta using electron microscopy

Published:August 27, 2020DOI:https://doi.org/10.1016/j.ajog.2020.08.106
      To the Editors:
      In May 2020, our article reporting on the visualization of the invasion of the human placenta by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) using electron microscopy, was published online in the American Journal of Obstetrics and Gynecology.
      • Algarroba G.N.
      • Rekawek P.
      • Vahanian S.A.
      • et al.
      Visualization of severe acute respiratory syndrome coronavirus 2 invading the human placenta using electron microscopy.
      In a subsequent Reply to a Letter to the Editors, we provided further evidence to support the findings of our original article, proving that it was indeed SARS-CoV-2 virions that were visualized.
      • Algarroba G.N.
      • Rekawek P.
      • Vahanian S.A.
      • et al.
      Reply.
      The evidence we have presented includes the following: (1) the virus was visualized with transmission electron microscopy showing that the extracellular structures that were visualized were identical to those seen within the cells, thus indicating that these were not clathrin-coated vesicles; (2) immunohistochemical analysis of the placental samples was positive for SARS-CoV-2 glycoprotein using a specific antibody in conjunction with positive and negative controls; (3) the virus was immunolocalized using immunogold electron microscopy; and (4) the virus was detected in the placenta using real-time polymerase chain reaction (RT-PCR)–specific primers. Our aforementioned findings are very consistent with subsequent reports that also documented the visualization of SARS-CoV-2.
      • Hosier H.
      • Farhadian S.F.
      • Morotti R.A.
      • et al.
      SARS-CoV-2 infection of the placenta.
      ,
      • Bradley B.T.
      • Maioli H.
      • Johnston R.
      • et al.
      Histopathology and ultrastructural findings of fatal COVID-19 infections in Washington State: a case series.
      With the current letter, we would like to provide additional information regarding the detection of the virus in our placental sample. A fresh piece of the placenta from our case was tested for SARS-CoV-2 by RT-PCR by our neonatal research team, led by Dr. Nazeeh Hanna, who is also conducting coronavirus disease 2019 related research, funded by the National Institute of Child Health and Human Development (NICHD), R01 HD098258-01A1. Fresh placental tissues were collected immediately after birth. The total RNA was isolated with a miRNeasy mini kit (QIAGEN Sciences Inc, Germantown, MD). The SARS-CoV-2 nucleocapsid (N) 1 and N2 genes were assayed for by a 2-step RT-PCR test. Reverse transcription was carried out using the High-Capacity cDNA Reverse Transcription Kit (Applied Biosystems, Foster City, CA), with primers specific for the N1, N2, and RNase P genes.
      US Department of Health and Human Services
      2019-Novel coronavirus (2019-nCoV) real-time rRT-PCR panel primers and probes. 2020.
      The presence of the viral RNA was assayed for using a 2019-nCoV RUO Kit (Integrated DNA Technologies, Coralville, IA) and a sample with a cycle threshold value less than 40 was considered positive. The results were positive for the presence of viral RNA in the placenta of our case report.
      • Algarroba G.N.
      • Rekawek P.
      • Vahanian S.A.
      • et al.
      Visualization of severe acute respiratory syndrome coronavirus 2 invading the human placenta using electron microscopy.
      In conclusion, we want to emphasize that literature published after our case report
      • Algarroba G.N.
      • Rekawek P.
      • Vahanian S.A.
      • et al.
      Visualization of severe acute respiratory syndrome coronavirus 2 invading the human placenta using electron microscopy.
      has shown unequivocally that there is scientific and clinical evidence that placental invasion by SARS-CoV-2 is valid.
      • Hosier H.
      • Farhadian S.F.
      • Morotti R.A.
      • et al.
      SARS-CoV-2 infection of the placenta.
      ,
      • Hecht J.L.
      • Quade B.
      • Deshpande V.
      • et al.
      SARS-CoV-2 can infect the placenta and is not associated with specific placental histopathology: a series of 19 placentas from COVID-19-positive mothers.
      • Penfield C.A.
      • Brubaker S.G.
      • Limaye M.A.
      • et al.
      Detection of severe acute respiratory coronavirus 2 in placental and fetal membrane samples.
      • Vivanti A.J.
      • Vauloup-Fellous C.
      • Prevot S.
      • et al.
      Transplacental transmission of SARS-CoV-2 infection.
      As a matter of fact, when vertical transplacental transmission occurs, the viral load in the placenta is severalfold higher than in the other maternal and fetal compartments.
      • Vivanti A.J.
      • Vauloup-Fellous C.
      • Prevot S.
      • et al.
      Transplacental transmission of SARS-CoV-2 infection.
      For all the reasons outlined in this letter, we are convinced that we have successfully reported on the visualization of SARS-CoV-2 in the human placenta.
      • Algarroba G.N.
      • Rekawek P.
      • Vahanian S.A.
      • et al.
      Visualization of severe acute respiratory syndrome coronavirus 2 invading the human placenta using electron microscopy.

      References

        • Algarroba G.N.
        • Rekawek P.
        • Vahanian S.A.
        • et al.
        Visualization of severe acute respiratory syndrome coronavirus 2 invading the human placenta using electron microscopy.
        Am J Obstet Gynecol. 2020; 223: 275-278
        • Algarroba G.N.
        • Rekawek P.
        • Vahanian S.A.
        • et al.
        Reply.
        Am J Obstet Gynecol. 2020; ([Epub ahead of print])
        • Hosier H.
        • Farhadian S.F.
        • Morotti R.A.
        • et al.
        SARS-CoV-2 infection of the placenta.
        J Clin Invest. 2020; ([Epub ahead of print])
        • Bradley B.T.
        • Maioli H.
        • Johnston R.
        • et al.
        Histopathology and ultrastructural findings of fatal COVID-19 infections in Washington State: a case series.
        Lancet. 2020; 396: 320-332
        • US Department of Health and Human Services
        2019-Novel coronavirus (2019-nCoV) real-time rRT-PCR panel primers and probes. 2020.
        (Available at:)
        • Hecht J.L.
        • Quade B.
        • Deshpande V.
        • et al.
        SARS-CoV-2 can infect the placenta and is not associated with specific placental histopathology: a series of 19 placentas from COVID-19-positive mothers.
        Mod Pathol. 2020; ([Epub ahead of print])
        • Penfield C.A.
        • Brubaker S.G.
        • Limaye M.A.
        • et al.
        Detection of severe acute respiratory coronavirus 2 in placental and fetal membrane samples.
        Am J Obstet Gynecol MFM. 2020; 2: 100133
        • Vivanti A.J.
        • Vauloup-Fellous C.
        • Prevot S.
        • et al.
        Transplacental transmission of SARS-CoV-2 infection.
        Nat Commun. 2020; 11: 3572

      Linked Article

      • Visualization of severe acute respiratory syndrome coronavirus 2 invading the human placenta using electron microscopy
        American Journal of Obstetrics & GynecologyVol. 223Issue 2
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          The outbreak of the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which results in the development of coronavirus disease 2019 (COVID-19), has been associated with significant morbidity and mortality. The risk of vertical transmission from infected pregnant women to their fetuses is controversial. Recent studies have revealed the possibility of vertical transmission,1,2 contrary to previous reports of no evidence of vertical transmission of SARS-CoV-2.3 Whether vertical transmission occurs and if so, at what frequency, remains unknown.
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