Pre-emptive immunotherapy of hCMV reactivation by ACT with virus-specific CD8+ T cells is an option to prevent CMV organ disease in HCT recipients who are latently infected (constellation D-R+), who receive an HC transplant derived from a latently infected donor (constellation D+R-), or who combine both risk factors (constellation D+R+). The gene discussed is CD8A; the disease is glycogen storage disease VI.