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Introduction. Coronavirus Disease 2019 (COVID-19) has infected over 670 million and killed almost 6,8 million people. Common symptoms are cough, fever and fatigue but severe infections can cause death.

Aim. The aim of this study was to identify immune cell biomarkers that may contribute to severe SARS-CoV-2 infections and investigate their possible correlations with comorbidities.

Methods. Immunohistochemical stainings against SARS-CoV-2, CD3, CD25, CD56, CD68,CD127 and myeloperoxidase were performed on lung autopsy tissues from one upper andlower lobe from 23 COVID-19 patients, respectively. Heat induced antigen retrieval and blocking of endogenous enzymes were performed before antibody application and hematoxylin counter staining. The sections were observed in light microscope and expressionof biomarkers were graded positive or negative.

Results. In 22 out of 46 sections SARS-CoV-2 expression were positive. All sections were positive to CD3, while 41 were positive to CD25, 44 to MPO and 32 to CD127. All sections displayed only weak positive or completely negative CD56 expression. The statistical significance between high MPO expression and SARS positivity was 0,072 and 0,089 in the lower and upper lobe, respectively. Every patient had at least one comorbidity, commonlyhypertension and heart diseases. The statistical significance between having asthma and SARS positivity was 0,096.

Conclusion. No significant correlation between SARS-CoV-2 positivity and expression of investigated biomarkers or comorbidities could be demonstrated. However, there was anindication of high MPO expression and COVID-19 and between having asthma and COVID19. With a larger number of samples, a more evident result might be obtained.