CD4 and infection: Identification of class II MHC epitopes has been an active area of research for characterization of antigen-specific HCV and HIV CD4+ T cell responses in infection and vaccination and for construction of epitope-driven vaccines (De Groot et al., 2004; El-Awady et al., 2013; Karpenko et al., 2014; Mishra et al., 2014; Takei et al., 2014).