Determination of Indoleamine 2,3 Dioxygenase Enzyme (IDO-1) Activity Levels in COVID-19 Patients According to Disease Severity, and Relationship with Inflammatory Markers

Introduction:The novel coronavirus (COVID-19) infection continues to impact the world, and its full effects on the immune system remain unknown.According to recent research, indoleamine dioxygenase (IDO) is crucial for viral infections such hepatitis B, C, HIV, and influenza.This study measured IDO-1 activity levels in COVID-19 patients to evaluate the influence of acute phase reactants and IDO-1 activity on disease severity. Materials and Methods:The study is a prospective cross-sectional study.Between 15 March 2020 and 5 April 2020, adult patients who were hospitalised in the infectious diseases clinic of the hospital and diagnosed with COVID-19 infection with SARS-CoV-2 PCR test positivity were included in the study.Patients were categorised according to World Health Organization COVID-19 disease severity.On the first day of hospitalisation, C-reactive protein (CRP), D-dimer, ferritin, fibrinogen, procalcitonin, leukocyte and IDO-1 levels were analysed.Results: The group with severe-critical pneumonia was older and had significantly higher levels of D-dimer, ferritin, and CRP (p< 0.001, p= 0.039, p= 0.008, and p< 0.001, respectively).IDO-1 levels were detected in both groups.The group with mild-moderate pneumonia had a higher mean IDO-1 level, although the difference was not statistically significant.Conclusion: Although no statistically significant difference was found, elevated IDO-1 levels were observed in the serum of patients with mild to moderate COVID-19 pneumonia.This is consistent with findings from other studies that reported high IDO-1 levels at the histopathological level in patients with mild to moderate COVID-19 pneumonia.