T cell dysfunction and metabolic disruption in chronic hepatitis C virus infection

Hepatitis C virus (HCV) infection remains a major global health burden and a leading cause of chronic liver disease, cirrhosis, and hepatocellular carcinoma. Despite the availability of highly effective direct-acting antivirals, sustained immune dysfunction and long-term complications continue to challenge disease management. Chronic HCV infection is facilitated by multiple viral evasion mechanisms, including rapid sequence variation, disruption of innate antiviral signaling, and altered natural killer cell function. A key feature of disease progression is the dysfunction of virus-specific CD4⁺ and CD8⁺ T cells caused by prolonged antigen exposure. These cells gradually develop an exhausted phenotype marked by reduced proliferation, impaired cytokine production, and increased expression of inhibitory receptors such as PD-1, CTLA-4, TIM-3, and TIGIT. At the same time, intrahepatic accumulation of regulatory T cells further suppresses antiviral immune responses and promotes viral persistence. Recent studies also show that chronic HCV infection induces significant metabolic and mitochondrial dysfunction including oxidative stress, impaired bioenergetics, and altered glycolytic adaptation, all of which contribute to defective T cell responses and disease progression. Notably, some of these immune defects persist even after viral eradication because of stable transcriptional and epigenetic changes in exhausted T cells. This review summarizes current understanding of how T cell dysfunction, epigenetic programming, and metabolic disruption interact in chronic HCV infection. Understanding these interconnected mechanisms may guide the development of novel therapeutic strategies that combine antiviral, immunomodulatory, and metabolic interventions to achieve durable immune restoration and improved clinical outcomes.