Immune cells take on BK virus in vulnerable transplant patients

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: Patient Eligibility * Patients with symptoms of cystitis and elevated BK virus DNA by screening PCR as above (section 4) post allogeneic HSCT, post chemotherapy 1. Symptoms of cystitis may include: hematuria (microscopic or gross), pain with urination, frequency, bladder spasms. 2. Patient may be otherwise treated for cystitis as per local institutional standards. Such treatments may include hydration, antiviral medications, or surgical intervention as deemed appropriate by treating physician. * Consent: Written informed consent given (by patient or legal representative) prior to any study-related procedures. * Performance Status \> 30% (Lansky \< 16 yrs and Karnofsky \> 16 yrs) * Age: 0.1 to 25 years * Females of childbearing potential with a negative urine pregnancy test. Donor Eligibility * Related donor available with a T-cell response to the BK-virus MACS® PepTivator® antigen(s). 1. Original allogeneic donor if available, IgG positive for BKV or confirmatory testing to respond to BKV MACS Peptivator®. 2. Third Party Allogeneic Donor: If original donor is not available or does not have a T-cell response: third party allogeneic donor (family donor \> 1 HLA A, B, DR match to recipient) with a T-cell response to the BK MACS® PepTivator. AND * Allogeneic donor disease screening is complete similar to hematopoietic stem cell donors (Appendix 1). AND • Obtained informed consents by donor or donor legally authorized representative prior to donor collection. Exclusion Criteria: Patient exclusion criteria: A patient meeting any of the following criteria is not eligible for the present study: * Patient with acute GVHD \> grade 2 or extensive chronic GVHD at the time of BK Virus CTL infusion * Patient receiving steroids (\>0.5 mg/kg prednisone equivalent) at the time of BK Virus CTL infusion or within 3 days of planned infusion. * Thymoglobulin (ATG), campath or T cell immunosuppressive monoclonal antibodies within 30 days * Patient with poor performance status determined by Karnofsky (patients \>16 years) or Lansky (patients ≤16 years) score ≤30% * Concomitant enrollment in another experimental clinical trial investigating the treatment of refractory BK virus infection. * Any medical condition which could compromise participation in the study according to the investigator's assessment * Known HIV infection * Female patient of childbearing age who is pregnant or breast-feeding or not willing to use an effective method of birth control during study treatment. * Known hypersensitivity to iron dextran * Patients unwilling or unable to comply with the protocol or unable to give informed consent. * Known human anti-mouse antibodies