Immunological Analysis During Interferon-Free Therapy for Chronic Hepatitis C Virus Infection Reveals Modulation of the Natural Killer Cell Compartment

Background. Chronic hepatitis C virus (HCV) infection is a global health problem, resulting in liver failure, hepatocellular carcinoma, and liver-related death. Natural killer (NK) cells are innate immune cells, and their activity is known to correlate to viral treatment response of HCV. In this study, we investigate the immune effects of viral load decline with direct-acting antivirals (DAAs) in blood. Methods. Twelve patients with chronic HCV were treated with asunaprevir and daclatasvir, and peripheral blood was analyzed at various time points during therapy. Results. In line with previous studies, we confirmed restoration of HCV-specific T-cell frequency upon viral load decline. In addition, we show that serum interferon (IFN)-gamma inducible-protein 10, interleukin (IL)-12p40, and IL-18 levels decreased early after start of therapy. Surface expression of activation receptors NKp30, NKp46, and inhibitory receptor NKG2A on blood NK cells reduced during therapy. In addition, the expression of TRAIL on NK cells was reduced during IFN-free therapy, suggesting a decrease in TRAIL-mediated killing by NK cells. Conclusions. We show that viral load decline as a consequence of treatment with novel DAAs in chronic HCV patients reduces serum levels of NK cell-stimulating cytokines and causes correction of the altered NK cell phenotype observed in chronic HCV patients.