Evaluation of lung cell populations in severe COVID-19 pneumonia

ABSTRACT

Introduction/Aim: Coronavirus disease 2019 (COVID-19) is a novel viral infection that can cause severe pneumonia and acute respiratory failure;however, the mechanism of disease progression is still unclear. The aim of this study is to evaluate inflammatory cells in the lung by analysing cell populations of bronchial aspirates of COVID-19 pneumonia. Method(s) Eligible cases were diagnosed as COVID-19, confirmed by SARS-CoV-2 PCR. All cases had developed severe COVID-19 pneumonia and undergone invasive positive pressure ventilation for the treatment of respiratory failure. Bronchial aspirates were collected during endotracheal intubation, and SARS-CoV-2 PCR was done. The populations of obtained cells from bronchial aspirates were examined by Giemsa staining and immunohistochemical staining of CD3, CD4, CD8, CD20 and CD68 antigens. Bronchial aspirates were cultured to confirm respiratory bacterial co-infections. Result(s) A total of 14 cases (median age 70;eleven male and three female) were enrolled in this study. Their bronchial aspirates were all positive for SARS-CoV-2 PCR. Bacterial co-infections were developed in 10 cases, including 6 cases of pneumonia/respiratory tract infection, 2 cases of sepsis, and 2 cases of urinary tract infection. Cell populations of bronchial aspirates with or without bacterial co-infections were as follows neutrophils 33.0% vs. 21.5%;CD3+ mononuclear cells (MNCs) 2.5% vs. 5.8%;CD4+ MNCs 4.6% vs. 3.4%;CD8+ MNCs 3.5% vs. 5.2%;CD20+ MNCs 0.2% vs. 0.1%;CD68+ MNCs 39.7% vs. 38.8%, respectively. Conclusion(s) CD68 antigen is mainly expressed in monocytes/macrophages. CD68+ MNCs were dominant in bronchial aspirates of the cases with severe COVID-19 pneumonia. Our data suggests that CD68+ MNCs, presumably macrophages, would play an essential role during the innate immune response to acute SARS-CoV-2 infection in the lung.