We then examined the relationship between HCV-specific IL-17A and IL-21 production and plasma HCV RNA levels in individuals sampled during chronic HCV mono- and chronic HIV/HCV coinfection and saw no correlation between HCV-specific IL-21 or IL-17A responses and plasma HCV RNA levels (S1A–S1D Fig) suggesting that in chronic infection, there may be a defect in the ability of IL-21 to activate HCV-specific CD8+ T cells. The gene discussed is IL21; the disease is coinfection.