Interleukin 21, Essential to Control Chronic Viral Infections

HIV and hepatitis C (HCV) infections are two ofthe most relevant human chronic viral infectionsworldwide. They often coexist within the same host.Immune responses mediated by T lymphocytes aregenerally associated with control of viral replication.However, an impaired specific T-cell response is ahallmark of both HIV and HCV persistence. CD4+T-cell responses are required to sustain virus-specificCD8+ T-cell functions during chronic viral infections.Therefore, the loss of expression of cytokinesby virus-specific CD4+ T-cells could be an importantfactor underlying the failure of CD8+ T-cells to controlthese viral infections.