Serum Neopterin Levels and IDO Activity as Possible Markers for Presence and Progression of Hepatitis B

Abstract Chronic Hepatitis B virus (HBV) is still one of the major reasons for liver related mortality and morbidity all around the world. This study aimed to investigate the possible relationship between the immune system activation and presence, as well as progression, of hepatitis B infection by monitoring the tryptophan degradation and serum neopterin levels in patients with HBV. 110 patients with HBV and 23 healthy subjects were included in the study. The patients had significantly higher neopterin levels and increased kynurenine to tryptophan ratios, which were most probably due to enhanced indoleamine 2,3-dioxygenase (IDO) activity compared to healthy control. A strong positive correlation was found between neopterin levels and IDO activity in patient group. Neopterin levels and IDO activity were markedly increased in patients with histological activity index (HAI) ≥4 compared to HAI<4, and a significant correlation was found between neopterin and HAI. Moreover, there was a significant correlation between albumin levels and IDO activity in HBV patients. These findings suggest that tryptophan degradation results from IFN-γ-induced IDO activation, likewise depletion of albumin synthesis in HBV patients may result from diminished tryptophan availability. In conclusion, based on the study results, serum neopterin levels and IDO activity could provide additional immunological information for monitoring liver histological activity and can be used as prognostic markers in HBV disease.