Understanding Immune Suppression in Patients with Chronic Hepatitis C Virus Infections

Abstract

Hepatitis C Virus (HCV) is a small RNA virus that progresses to chronicity in 50-80% of infected individuals. Direct-acting antivirals (DAAs) are revolutionary treatments for HCV with 90-98% cure rates. However, over time, chronic HCV infections can result in advanced liver disease, including cirrhosis. Patients with advanced fibrosis experience a poor response to vaccination, recurrent infections and increased risk for hepatocellular carcinoma (HCC). These outcomes are, in part, a consequence of immune dysfunction. Increased inhibitory receptor and Galectin-9 (GAL-9) expression is a possible mechanism promoting lymphocyte dysfunction. In this study, blood samples were collected from chronic HCV patients with different degrees of liver fibrosis. I conducted a 13-parameter flow stain on the peripheral blood mononuclear cells (PBMC) of these patients. Next, I measured the expression of inhibitory receptors (PD-1, CTLA-4, LAG-3, TIGIT and TIM-3) and GAL-9 on bulk T cell and NK cells of 15 chronic HCV patients with no to moderate fibrosis (F0-F2) and 15 with advanced fibrosis (F3-F4). To analyze receptor co-expression, I employed t-distributed stochastic neighbor embedding (t-SNE) analysis to dimensionally reduce the multi-parametric data. Notably, I found that F3-F4 patients had higher frequencies of >3 inhibitory receptor co-expression on NK cells. Moreover, t-SNE analysis of bulk T cells revealed that F3-F4 patients manifest a higher frequency of cells in the clusters with CD25+TIGITmed-hi CD4+ T cells and PD-1medLAG-3med-hiGAL-9med-hi CD4+ T cells. t-SNE analysis of NK cells also showed that F3-F4 patients manifest a higher frequency of cells in the cluster with CD25+TIGITmed-hiTIM-3med-hi CD56Dim NK cells and CCR7+ PD-1medLAG-3med-hiGAL-9med-hi CD56Dim NK cells. Lastly, the frequency of cells in these clusters was found to positively correlate with patient’s extent of liver damage. In conclusion, I identified phenotypes of immune dysregulation that could explain the increased susceptibility to infection and HCC in chronic HCV patients with advanced fibrosis. These phenotypes could identify targets for combinatorial checkpoint blockade therapy to potentially improve immune function in these patients.