Hepatitis C virus (HCV) specific immune responses in anti-HCV positive patients without hepatitis C viraemia

Background/Aims-Most patients infected with hepatitis C virus (HCV) develop chronic infection and persistent viraemia, The immune mechanisms responsib le for resolution of viraemia remain poorly understood. HCV specific humora l and cellular immune responses in patients with and without viraemia were investigated. Methods-In vitro T helper (T-H) lymphocyte responses to structural and nons tructural HCV proteins were determined by means of proliferative response a nd cytokine production in 35 anti-HCV positive/HCV RNA negative patients an d in 31 patients with chronic HCV infection and persistent viraemia. Humora l responses were determined by measuring Hcv specific antibody quantity and specificity. Results-A T-H response to two or HCV proteins was present in 18 of 35 patie nts with serological viral clearance compared with just one of 31 viraemic patients (p = 0.00001). HCV specific interferon-gamma production was increa sed only in the former group. In contrast, the antibody levels were signifi cantly lower and directed at fewer HCV antigens in patients with undetectab le HCV RNA. Conclusions-Patients without viraemia after HCV infection frequently have s trong T-H lymphocyte responses of the T(H)1 type to multiple HCV antigens m any years after the onset of infection, whereas antibody responses are less marked. These results suggest that control of HCV replication may depend o n effective T-H lymphocyte activation.