CD4 and infection: In acute HCV infection, after a 4–12 week incubation period of high-level viral replication, the appearance of highly functional and broadly reactive CD4+ T helper cells [17,18] and CD8+ cytotoxic T cells [19,20,21] targeting primarily nonstructural proteins of HCV (NS3-NS5) in the peripheral blood correlates with rapid reductions in viral load in subjects that go on to resolve infection [22,23].