Just seeing is not enough for believing : immunolabelling as indisputable proof of SARS-CoV-2 virions in infected tissue

Erman, Andreja (author), Wechtersbach, Karmen (author), Velkavrh, Dane (author), Pleško, Jerica (author), Frelih, Maja (author), Kojc, Nika (author)

Background: There is increasing evidence that identification of SARS-CoV-2 virions by transmission electron microscopy could be misleading due to the similar morphology of virions and ubiquitous cell structures. This study thus aimed to establish methods for indisputable proof of the presence of SARS-CoV-2 virions in the observed tissue. Methods: We developed a variant of the correlative microscopy approach for SARS-CoV-2 protein identification using immunohistochemical labelling of SARS-CoV-2 proteins on light and electron microscopy levels. We also performed immunogold labelling of SARS-CoV-2 virions. Results: Immunohistochemistry (IHC) of SARS-CoV-2 nucleocapsid proteins and subsequent correlative microscopy undoubtedly proved the presence of SARS-CoV-2 virions in the analysed human nasopharyngeal tissue. The presence of SARS-CoV-2 virions was also confirmed by immunogold labelling for the first time. Conclusions: Immunoelectron microscopy is the most reliable method for distinguishing intracellular viral particles from normal cell structures of similar morphology and size as virions. Furthermore, we developed a variant of correlative microscopy that allows pathologists to check the results of IHC performed first on routinely used paraffin-embedded samples, followed by semithin, and finally by ultrathin sections. Both methodological approaches indisputably proved the presence of SARS-CoV-2 virions in cells.

• Language: English
• Keywords: SARS-CoV-2, immunolabelling, microscopy, light microscopy, electron microscopy, correlative microscopy
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: MF - Faculty of Medicine
• Publication status: Published
• Publication version: Version of Record
• Year: 2021
• Number of pages: 9 str.
• Numbering: Vol. 13, iss. 9, art. 1816
• PID: 20.500.12556/RUL-136194
• UDC: 616.9
• ISSN on article: 1999-4915
• DOI: 10.3390/v13091816
• COBISS.SI-ID: 76924931
• Publication date in RUL: 19.04.2022

Record is a part of a journal

• Title: Viruses
• Shortened title: Viruses
• Publisher: MDPI
• ISSN: 1999-4915
• COBISS.SI-ID: 517597977

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.
• Licensing start date: 13.09.2021

Secondary language

• Language: Slovenian
• Keywords: SARS-CoV-2, imunooznačevanje, mikroskopija