CALPROTECTIN KINETICS IN NORWEGIAN, HOSPITALIZED COVID-19 PATIENTS

Abstract

Intro: Activated neutrophils are proposedly linked to lung microcirculation damage in COVID-19 and increased neutrophil count is a risk factor for intensive care need and respiratory failure. Calprotectin and neutrophil extracellular traps (NETs) are neutrophil-derived, key inflammatory markers with pathophysiological effects that have been found in elevated levels in COVID patients. DNase may disrupt NETs by degrading their DNA content. The aim of this study was to investigate the kinetics of calprotectin and NETs at different timepoints during hospitalization and after recovery (3 and 12 months control) in a cohort of COVID-19 patients. Also, we wanted to examine whether such inflammatory responses were associated with relevant clinical parameters, such as length of hospitalization, time in the intensive care unit, respiratory failure and death. Methods: Totally 284 hospitalized COVID-19 patients, mostly from South-Eastern Norway, were included, and 66 of these patients were available for follow-up after 12 months. This ethically approved, participant consented project was organized by the Norwegian COVID cohort study group. Sera from the patients and healthy blood donors (controls) were examined by novel ELISA tests for Calprotectin (mixed monoclonal test, MiMo) and NETs (H3- or A12-NETs). Findings: Main finding was increased levels of calprotectin in COVID-19 patients during hospitalization and recovery, but normal levels of NETs in these patients. However, patient sera contained elevated levels of DNase. Discussion: The kinetics of calprotectin in association with clinical parameters will be discussed. Since calprotectin is contained in NETs, it is surprising that enhanced NETs remnants were not found in the COVID patients. However, the increased levels of DNase that were found in the patient sera could indicate increased digestion of NETs. Conclusion: We find that calprotectin, but not NETs levels, are enhanced during hospitalization and recovery in a cohort of Norwegian COVID-19 patients. The NETs levels may be normal due to increased levels of DNAse.