Human Adenovirus-specific T-cells can persist and augment impaired adenovirus immune response post allogeneic haematopoietic stem cell transplant, and reduce the requirement for antiviral therapy without toxicity or increasing the occurrence of Graft Versus Host Disease. This is a Phase I/IIa open-label safety study, assessing the effects of administering adenovirus-specific T-cells (Cytovir ADV) to paediatric patients post haematopoietic stem cell transplant.

Inclusion Criteria:

Patients:

1. Age 16 years or younger
2. Scheduled to undergo an allogeneic HSCT with an unrelated donor, mismatched unrelated donor, mismatched family donor or haplo identical donor
3. The subject (or legally acceptable representative) must give informed consent (and assent for subjects ≥ 12 years). All subjects will have a parent or guardian provide informed consent and the subject will provide witnessed verbal assent
4. Negative serology for HIV 1 + 2, HepB, HepC, Syphilis, hCG.

Donors

1. Meets requirements of Directive 2004/23/EC as amended and the UK statutory instruments pursuant therein
2. Negative serology for HIV 1 + 2, HepB, HepC, Syphilis, hCG
3. Passed medical assessment for stem cell donation
4. HdADV seropositive
5. Signed informed consent
6. Age 16 years or older

Exclusion Criteria:

Patients

1. Pregnant or lactating females
2. Co-existing medical problems that would place the patient at significant risk of death due to GVHD or its sequelae
3. Human Immunodeficiency Virus (HIV) infection

Donors

1. Pregnant or lactating females
2. (assessed prior to apheresis) Platelets < 50x109/L