• All subjects (or their guardians) must have the ability to understand and the willingness to sign a written informed consent; age appropriate assent will be obtained per institutional guidelines; to allow non-English patients to participate in this study, bilingual health services will be provided in the appropriate language when feasible

• Participant must be willing to comply with study and/or follow-up procedures, including willingness to be followed for one year post-HCT

• Planned allogenic (allo)-HCT, with 9/10 or 10/10 (A, B, C, DRB1, DQB1) high/intermediate resolution HLA donor allele matching and with no T-cell depletion of graft

• Planned related HCT with molecular 3/6 HLA donor allele matching (haploidentical) (for phase I only)

• CMV seropositive at the time of HCT

• Conditioning and immunosuppressive regimens according to institutional guidelines are permitted

• Negative serum or urine beta-human chorionic gonadotropin (HCG) test (female patient of childbearing potential only) within two weeks of registration

• Seronegative for human immunodeficiency virus (HIV), hepatitis C virus (HCV); if hepatitis B virus (HBV) core seropositive, absence of HBV deoxyribonucleic acid (DNA) within 2 months of registration

• Agreement by females of childbearing potential and sexually active males to use an effective method of contraception (hormonal or barrier method of birth control or abstinence) prior to study entry and for up to 90 days post-HCT; should a woman become pregnant or suspect that she is pregnant while participating on the trial, she should inform her treating physician immediately