Could donor cells beat a deadly brain virus?

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

* INCLUSION CRITERIA - PATIENT: * Clinically definite PML, defined as clinical signs and MRI compatible with active PML and the presence of JCV by PCR in CSF * Modified Rankin Scale 1-4, inclusive * Age 18 or older * Patient medically stable and able to tolerate travel to NIH * Available PyVST * Subjects of childbearing or child-fathering potential must be willing to use a medically acceptable form of birth control, which includes abstinence, while they are being treated on this study * Willing and able to participate in all aspects of trial design and follow-up * Able to provide informed consent at the time of study enrollment (not required for reinfusions). EXCLUSION CRITERIA - PATIENT: * Patients with human immunodeficiency virus (HIV infection) * Patients who have been treated with natalizumab * Patients with readily reversible immunosuppressive state * Patients receiving immunosuppressive or immunomodulatory therapies within 28 days of screening for enrollment that could interfere with PyVST function * Patients with other uncontrolled infections. For bacterial infections, patients must be receiving definitive therapy and have no signs of progressing infection for 72 hours prior to enrollment. For fungal infections, patients must be receiving definitive systemic anti-fungal therapy and have no signs of progressing infection for 1 week prior to enrollment. * Patients who have received donor lymphocyte infusion (DLI) within 28 days * Uncontrolled relapse of malignancy * Patients with any other associated CNS disease that might confound outcomes * Patients with contraindication to MRI (including cardiac pacemakers and some infusion pumps, other metallic implants, metallic foreign objects) * MRI findings consistent with immune system reconstitution inflammatory syndrome (IRIS) and determined to be mounting an adequate immune response to the infection * Patients with medical contraindication to LP * For subjects who have previously received PyVST infusions, any treatment-limiting toxicity (defined in Section 8.3) to previous infusions * Subjects with a positive pregnancy test or who are nursing. INCLUSION CRITERIA - DONOR: * Ability to provide informed consent at the time of enrollment * First degree relative of patient (sibling, parent/child) * Age 18 or older EXCLUSION CRITERIA - DONOR: * Sickling hemoglobinopathies including HbSS and HbSC by history and peripheral blood smear; donors with HbAS are acceptable * HbsAg, anti-HBc, anti-HCV, anti-HIV, anti-HTLV, and RPR * Cardiovascular instability, severe anemia, inadequate venous access, severe coagulation disorder or any other medical condition that the Principal Investigator or Apheresis Unit staff considers a contraindication to the apheresis procedure or research blood draw. * Positive pregnancy test