To make the CTLs, subject's donors' cells were mixed with small pieces of proteins, called peptides that come from adenovirus, CMV, EBV, BKV and HHV6. These peptides stimulate donor T cells that react against the viruses to grow and train the donor T cells to kill cells that are infected with CMV, EBV, adenovirus, BKV and HHV6. Once sufficient numbers of T cells were made, they were tested to make sure they would target the cells infected with these viruses but not the normal cells. Then the cells were frozen.