CD69 and infection: Following tertiary exposure to the HCV NS3 antigen, through challenge with the MHV-68-NS3 recombinant virus, we observed expansion of HCV-specific cells in response to infection in all immunized groups but MVA boosted mice showed consistently higher levels of cells expressing CD69, Ki67 or Granzyme B, markers that are commonly identified with functional T-cell activation in response to antigens.