Detection of SARS-CoV-2 proteins by immunohistochemistry in human tissues Pathology collaborative analysis

Introduction: The COVID-19 (coronavirus disease 2019) caused by SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) is associated with high mortality rates worldwide. Polymerase chain reaction (PCR) is extensively used for virus detection in both infected patients and deceased persons. PCR, however, gives no information about the localization of the virus in cells and tissues. Detection of spike and nucleocapsid proteins and viral ribonucleic acid (RNA) of the SARS-CoV-2 in situ might provide more information and aid in the discovery of the pathomechanism of cellular damage. There are several commercially available anti-spike and anti-nucleocapsid antibodies used to detect immunohistochemical reactions, though each gives different results. Objective: The goal of the present study was to compare the intensity and specificity of several anti-spike and antinucleocapsid antibodies in different dilutions in four Hungarian university departments. Method: Immunohistochemical reactions were performed on coded slides taken from infected lungs of 3 deceased and placenta samples with appropriate negative controls of formalin-fixed paraffin-embedded tissues, scanned, evaluated unanimously and analysed statistically by the assessors. Results: By comparing the intensity, dilution, background and reproducibility of the different primary antibodies, it was possible to select the antibodies with the best results. Conclusion: The antibodies selected with established dilutions can be used in further studies to detect SARS-CoV-2 proteins in surgical materials and in samples obtained during autopsy.