Assessment of neopterin and indoleamine 2,3‐dioxygenase activity in patients with seasonal influenza: A pilot study

Abstract

BackgroundSeasonal influenza is an important cause of morbidity and mortality worldwide. Immune activation after stimulation with interferon‐gamma leads to increased production of neopterin but also results in increased tryptophan catabolism through indoleamine 2,3‐dioxygenase (IDO). Our pilot study determined neopterin serum levels and IDO activity in patients with influenza infection and investigated whether neopterin is linked to clinical outcome parameters (mortality ≤30 days, acute cardiac events (ACE) length of hospitalization, ICU admission).MethodsNeopterin concentrations were analyzed in serum samples of 40 patients with a confirmed diagnosis of influenza infection and in‐hospital treatment for >24 hours. Data were compared to values of 100 healthy blood donors and 48 age‐matched pneumonia patients. In a subgroup of 14 patients, tryptophan and kynurenine concentrations, as well as kynurenine‐to‐tryptophan ratio, were analyzed.ResultsIn all influenza patients, neopterin concentrations were increased and significantly higher compared to those determined in patients with pneumonia and healthy controls. Positive correlations between the duration of hospitalization and neopterin were found. Significantly higher levels of kynurenine, kynurenine‐to‐tryptophan ratio, and lower levels of tryptophan were seen in influenza patients compared to healthy controls.ConclusionsNeopterin seems to be related to the course of the disease and could be a valuable biomarker to identify patients at an elevated risk of a worsened outcome; however, further prospective validation studies are needed to support the here presented preliminary results.

The prognostic role of neopterin in COVID‐19 patients

“…There are several studies focused on the prognostic value of neopterin in various viral infections. Pizzini et al 12 showed that a higher level of neopterin was associated with the lengthened hospitalization and increased risk of acute cardiac events in seasonal influenza patients. In HIV infected population, serum neopterin levels were correlated with increased viral load and mortality 14,19,20 .…”

“…The level of serum neopterin reflects the stage of activation of the cellular immune system, which is important in the pathogenesis and progression of various diseases 11 . In previous studies, the relationship between neopterin serum levels and prognosis has been shown in some viral infections such as influenza, human immunodeficiency viruses, hepatitis C virus, dengue fever virus 12–14 . In severe acute respiratory syndrome (SARS) patients, serum neopterin has been reported to be a useful marker in the early assessment of disease severity 15 …”

Increased kynurenine-to-tryptophan ratio in the serum of patients infected with SARS-CoV2: An observational cohort study.

“…The Kyn:Trp ratio, measured in blood, is a valuable clinical benchmark of IDO-1 activation, and reflects the state of immune activation or tolerance in cancer immunity, autoimmunity, infection and other disorders. Changes in Kyn:Trp ratio have been associated with viral infections, such as HIV and HIV-human herpes virus co-infection [ 14 ], seasonal influenza [ 15 ], Dengue virus [ 16 ], and HBV [ 17 ].…”

The potential role of neopterin in Covid-19: a new perspective

“…Indeed, various types of viral infections are able to activate the formation and release of INF-γ from infected cells, where INF-γ stimulates macrophages to produce and release of NPT. Therefore, NPT concentrations reflect an underlying cell-mediated immune activation [ 18 ].…”