CD45RA-depleted DLI for the Prevention of Viral Infections in High-risk Patients After Haploidentical Transplantation

The goal of this clinical trial is to learn whether giving patients a special type of donor immune cells (called CD45RA Depleted DLI) can help prevent viral infections after a stem cell transplant. It will also learn about the safety of this treatment. The main questions it aims to answer are: Does this treatment lower the chance of getting serious viral infections after transplant? What medical problems do patients have when receiving this treatment?

Inclusion Criteria: Participants must meet all of the following criteria: * Patients undergoing allogeneic hematopoietic stem cell transplantation (any conditioning regimen or graft source is allowed). * Presence of at least one high-risk factor for post-transplant viral infection (any of the following): * Age ≥50 years or ≤14 years * Non-sibling matched transplantation * In vivo or ex vivo T-cell depletion * Myeloablative conditioning * Conditioning containing radiotherapy * Second transplantation * CMV IgG or EBV IgG donor/recipient mismatch (donor positive, recipient negative) * History of grade II or higher acute graft-versus-host disease (aGVHD) after transplantation and use of high-dose corticosteroids (prednisone equivalent ≥1 mg/kg/day) * Availability of a suitable lymphocyte donor (see "Donor Selection Criteria"). * Adequate organ function meeting the following laboratory criteria: * Liver function: ALT and AST ≤10× upper limit of normal (ULN); total bilirubin ≤5× ULN * Renal function: BUN and creatinine ≤1.25× ULN * No cardiac dysfunction on electrocardiogram or echocardiogram * Pulmonary function: oxygen saturation \>90% without supplemental oxygen * The patient or legal guardian has the desire and request to receive treatment, signs the informed consent form before treatment, and is willing to comply with the treatment plan, follow-up schedule, and laboratory tests. Exclusion Criteria: Patients meeting any of the following criteria will be excluded from this study: * Active grade II-IV acute graft-versus-host disease (aGVHD) * Active aGVHD requiring prednisone or equivalent corticosteroid \>0.5 mg/kg/day * Active viral infection * Uncontrolled or relapsed malignancy * Other serious acute or chronic physical or psychiatric conditions, or laboratory abnormalities, that may compromise patient safety or compliance, or affect informed consent, study participation, follow-up, or interpretation of results.