Inclusion Criteria:  Adult or paediatric patients (> 2 months of age) after allogeneic stem cell transplantation (SCT) (no time restrictions apply) suffering from new or reactivated CMV or EBV or AdV infection refractory to standard antiviral treatment for two weeks (defined as no decrease or insignificant decrease of less than 1log in viral load over two weeks) as confirmed by quantitative blood PCR analysis. Original HSCT-donor available with an immune response at least to the virus causing the therapy-refractory infection. Written informed consent given (patient or legal representative) prior to any study-related procedures.  Exclusion Criteria:  Patient with acute GvHD > grade II or extensive chronic GvHD at the time of T-cell transfer Patient receiving steroids (>1 mg/kg BW Prednisone equivalent) at Screening. Therapeutic donor lymphocyte infusion (DLI) from 4 weeks prior to IMP infusion until 8 weeks post IMP infusion. Prescheduled prophylactic DLI ≤3x105 T cells/kg BW in case of T-cell depleted HSCT is not considered an exclusion criterion. Patient with organ dysfunction or failure as determined by Karnofsky (patients >16 years) or Lansky (patients ≤16 years) score ≤30% Concomitant enrolment in another clinical trial interfering with the endpoints of this study Any medical condition which could compromise participation in the study according to the investigator's assessment Progression of underlying disease (disease that has led to the indication of HSCT, e.g. leukaemia) that will limit the life expectance below the duration of the study Second line or experimental antiviral treatment other than Ganciclovir/Valganciclovir, Foscarnet, Cidofovir and Rituximab until 8 weeks after IMP study. Known HIV infection. In case patients do not have a negative HIV test performed within 6 months before enrolment in the study, HIV negativity has to be confirmed by a negative laboratory test.  Female patient who is pregnant or breast-feeding. Female patient of child-bearing potential (i.e. post menarche and not surgically sterilized) or male patient of reproductive potential not willing to use an effective method of birth control from Screening until the last follow-up visit (FU6, Visit 8).  Note: Women of childbearing potential must have a negative serum pregnancy test at study entry ≤7 days before IMP administration on Day 0. Acceptable birth control methods are hormonal oral contraceptive ('pill'), contraceptive injection or patch, intrauterine pessar or the combination of two barrier methods. The combination of female and male condomes is NOT acceptable. If the male partner is sterilized, no further contraceptive is required. Women of post-menopausal status (no menses for 12 months without an alternative medical cause) are also not required to use contraceptives during the study.  Known hypersensitivity to iron dextran Patients unwilling or unable to comply with the protocol or unable to give informed consent.