Quantitative analysis of SARS-CoV-2 viral load in the lungs of COVID-19 deceased patients [Количественный анализ уровня вирусной нагрузки SARS-CoV-2 в легких умерших пациентов с COVID-19]

The objective: to perform quantitative analysis of SARS-CoV-2 viral load (VL) levels in lung tissues in deceased patients with COVID-19 and to evaluate its association with the nature of histological changes in the lungs and the duration of stay in ICU till the lethal outcome. Subjects and Methods. Sections of formalin-fixed and paraffin-embedded lung tissues of 36 deceased patients with COVID-19 were used. The SARS-CoV-2 viral load was quantitatively assessed using the original qPCR. VL was calculated using the following formula: copies SARS-CoV-2/copies ABL1 × 100, expressed as the ratio of the true number of SARS-CoV-2 cDNA copies per 100 copies of ABL1 gene cDNA. Results. In cases with no histological changes typical of diffuse alveolar lung injury (DAI), the detection rate of SARS-CoV-2 RNA and the average level of the SARS-CoV-2 viral load were 62.5% (5 out of 8 observations) and 104.75 (range 0-313) copies of SARS-CoV-2 cDNA per 100 copies of human ABL1 gene cDNA. The average level of the SARS-CoV-2 viral load in the lungs with prevailing histological changes characteristic of the proliferative and exudative phases of DAI differed by 60 times and amounted to 909 (18-2,657) and 54,924 (834-250,281) copies of SARS-CoV-2 cDNA per 100 copies of human ABL1 cDNA, respectively. The average duration of stay in the intensive care unit in the group of patients with exudative and proliferative phases of DAI was 10.64 (1-22) and 8.14 (1-21) bed-days, respectively. The detection rate of the SARS-CoV-2 RNA in patients with diffuse alveolar lung injury was 100%. © 2021 New Terra Publishing House. All rights reserved.