This study investigates the use of virus-specific T cell lines (VSTs) to see if they are safe and can help control three specific viruses: Epstein-Barr Virus (EBV), Cytomegalovirus (CMV), and adenovirus. These viruses can cause infections in people who have had a stem cell transplant or those with a primary immunodeficiency disorder. A stem cell transplant is a procedure where healthy stem cells are transferred to a patient to replace damaged or diseased cells. Primary immunodeficiency disorder is a condition where the immune system is not working properly from birth.

Participants in the study will receive T cell lines that are closely matched to their own immune system. These T cells are taken from a bank of allogeneic, or donor, virus-specific T cells. The study will observe if these T cells can fight off the viruses in patients who have not responded to standard treatments. Standard treatments usually involve antiviral medications, but sometimes these do not work or cannot be tolerated by the patient.

• Who can participate: This study is for patients who have had an allogeneic stem cell transplant or have a primary immunodeficiency disorder. Participants must have infections with CMV, adenovirus, or EBV that have not improved with standard treatments. Those who have used certain immunosuppressive drugs within the last 28 days or have uncontrolled infections are not eligible.
• Study details: Participants will receive virus-specific T cells from a donor bank to see if these cells can control their viral infections. The study will test if this approach is safe and effective for patients who have not responded to usual treatments. A placebo, which is an inactive substance that looks like the investigational medicine but does not contain any medicine, is not used in this study.