Peripheral blood CD8 T cells in chronic HCV infection with cirrhosis exhibit lasting alterations in gene expression changes, with insights into the role of Hedgehog signaling
The impact of chronic hepatic infection on antigen non-specific immune cells, especially in association with liver fibrosis severity, remains poorly described. We previously reported lasting hyperfunction of bulk peripheral blood CD8 T cells in HCV-infected individuals with cirrhosis. RNA sequencing of blood CD8 T cells from HCV-infected individuals with minimal (Metavir F0-1, Fibroscan liver stiffness = 7.0 kPa) or advanced fibrosis or cirrhosis (F4 = 12.5 kPa), before and after direct-acting antiviral therapy, was performed. Principal component analyses determined robust differences in 362 genes expressed by CD8 T cells from HCV-infected individuals with minimal or advanced fibrosis and data suggests this remains relatively stable after viral clearance. Gene ontology analyses identified differential gene expression related to cellular metabolism, including upregulated phospholipase, phosphatidyl-choline/inositol activity and second-messenger-mediated signaling, while genes in pathways associated with nuclear processes, RNA transport and cytoskeletal dynamics were reduced. Gene Set Enrichment Analysis identified decreased expression of genes regulated by the cMyc and E2F transcription factors in cirrhotics, compared to the minimal fibrosis group, as well as reduced expression of genes linked to oxidative phosphorylation, mTOR signaling, and more. Upregulated gene sets in cirrhotics included IFN-a, -?, TGF-ß response genes, apoptosis, and apical surface pathways, among others. The Hedgehog (Hh) signaling pathway was the top featured gene set upregulated in cirrhotics, wherein hallmark genes GLI1 and PTCH1 ranked highly. This analysis of bulk CD8 T cell gene expression in chronic HCV infection suggests considerable reprogramming of the CD8 T cell pool in liver cirrhosis. Increased Hh signaling in cirrhosis may contribute to generalized CD8 T cell hyperfunction observed in chronic HCV infection. Understanding the lasting nature of immune cell dysfunction may help mitigate remaining clinical challenges after HCV clearance and more generally, improve long term outcomes for individuals with severe liver disease. Overall design: Study participants were chronically infected HCV patients (>6 months HCV RNA+), before direct-acting antiviral (DAA) treatment (pre-DAA) or 24 weeks after sustained virologic response (24W post-SVR). PBMCs of participants were isolated by density gradient centrifugation. CD8 T cells were isolated by magnetic bead positive selection, and stimulated with 0.5 µg/ml phytohemaglutanin-L for 18h. Total RNA was isolated using TRIzol Reagent prior to RNA-sequencing.