Maintenance of Th1 hepatitis C virus (HCV)-specific responses in individuals with acute HCV who achieve sustained virological clearance after treatment

Background and Aim: T-cell responses against hepatitis C are believed to be critical in achieving both natural and treatment-induced clearance. However, rapid clearance of antigen with early treatment of primary infection may result in reduced or poorly sustained cellular immunity. This study longitudinally examined Th1 and Th2 hepatitis C virus (HCV)-specific cytokine production and T-cell effector function from subjects enrolled in the Australian Trial in Acute Hepatitis C comparing three groups: treatment-induced clearance (sustained virological response [SVR]), treatment non-response, and untreated spontaneous clearance. Methods: HCV-specific T-cell responses were characterized by HCV peptide ELISpot, in vitro cytokine production, and T-cell flow cytometry assays. Results: Treated subjects with a sustained virological response (SVR) displayed a better maintenance of HCV-specific Th1 responses compared to treatment non-responders (higher interferon [IFN]-gamma and interleukin (IL)-2 magnitude at week 24, broader IFN-gamma responses at weeks 24 and 48, P < 0.05) and significantly increased IFN-gamma responses between screening and week 48 (magnitude P = 0.026, breadth P = 0.009). Treatment-induced viral clearance was also associated with a trend toward decreased IL-10 responses (screening to week 48, P = 0.070), higher expression of CD45RO (P = 0.042) and CD38 (P = 0.088) on CD4(+) T cells, and higher IFN-gamma R expression (CD56(+)IFN-gamma R+ P = 0.033) compared to treatment non-responders. Untreated subjects with viral clearance also displayed high magnitude and broad HCV-specific IFN-g and IL-2 responses early in infection; however, IFN-gamma responses were not as well maintained compared to treated subjects with a SVR (week 48 magnitude, breadth P = 0.064). Conclusion: Treatment-induced viral clearance of recent HCV infection is associated with maintenance of HCV-specific Th1 responses.