High level of RNA HAS2-AS1 in the buffy coat of a patient blood sample is a more informative prognostic marker of COVID-19 clinical course compared to the level of hyaluronic acid in plasma

Numerous studies have confirmed the association of COVID-19 clinical course with the blood levels of hyaluronic acid and long non-coding RNA HAS2-AS1 as a positive regulator of hyaluronan synthase. We aimed to estimate both the level of hyaluronic acid in plasma and the level of RNA HAS2-AS1 in leukocytes (buffy coat) from the same blood sample at the time of patient admission to the hospital and to analyze the specificity of these indicators as biomarkers of COVID-19 severity. The study involved 78 patients with confirmed COVID-19 who underwent treatment between 2020 and 2021 at the Kyiv City Clinical Hospital N 4. The patients were divided into three groups based on the severity of the disease and classified as mild (n = 12), moderate (n = 36), and severe (n = 30). The level of hyaluronic acid in plasma was determined using the Hyaluronic Acid ELISA kit “Abcam” (USA). The buffy coat was isolated by centrifugation of the blood stabilized with EDTA-K and further aspiration of the leukocyte “cloud”. The expression level of HAS2-AS1 in buffy coat leukocytes was estimated using reverse transcription and real-time PCR. According to the obtained data, the level of hyaluronic acid in the plasma of patients with moderate and severe illness was 1.5 and 2.2 times higher compared to the mild illness group, respectively. Meanwhile, the level of RNA HAS2-AS1 in blood lymphocytes (buffy coat) of patient with moderate and severe illness was increased by 7.7 and 22.6 times compared to patients with mild illness. The results of our study demonstrate that, unlike the level of hyaluronic acid in plasma, the level of HAS2-AS1 in a buffy coat is a more reliable prognostic criterion for severe COVID-19 and allows distinguishing patients with varying clinical severity during hospitalization. Keywords: buffy coat, COVID-19, hyaluronic acid, leukocytes, plasma, RNA HAS2-AS1