Q: So you want what are called T cells to go after the virus in question. How do you do that?
A: When a virus infects a cell, it takes over the cell's protein-making machinery. That infected cell starts churning out viral proteins. Pieces of those proteins sort of decorate the outside of that cell. Those decorations are things the T cells can recognize and [identify as] a foreign protein. So [T cells] kill the cells that have some foreign proteins.