Recent Trends in the Immune Response against Hepatitis C Virus

Hepatitis C Virus (HCV) represents a viral pandemic infecting 170 million people worldwide, 80% of whom develop persistent infection and approximately 20% cirrhosis. HCV is present in numerous quasispecies in each individual patient, caused by its very high mutation rate. The development of quasispecies has, as a consequence, the development of escape mutants to humoral immunity. Cellular immunity, on the other hand, is believed to be the immune system's effector arm that is utilized the most in the fight against HCV. Recent data suggest that a vigorous, polyclonal and multispecific proliferative CD4+ T-cell response, and especially a Th1 shift in the cytokine profile of peripheral blood is associated with viral clearance. CD4+ Th1 immune responses are needed to prime and maintain the CD8+ cytotoxic T lymphocytes (CTL) response which is responsible for eliminating infected cells. Unfortunately, the response of cytotoxic T lymphocyte in persons with chronic hepatitis C infection seems to be insufficient to contain viremia but sufficient to cause collateral damage through the elaboration of inflammatory cytokines in the liver. A better understanding of the immunity in conjunction with the assessment of viral replication may facilitate further immunotherapeutic and vaccine strategies against HCV infection.