Outcomes of Hematopoietic Stem Cell Transplantation in Patients With Thalassemia Major: How Do Anti-HLA Antibodies Impact?: The Impact of Anti-HLA Antibodies on Transplantation Outcomes in Thalassemia Major.

Aim: To investigate the effects of anti-human Leucocyte Antigen (HLA) antibody positivity on early hematopoietic stem cell transplantation (HSCT) results in patients with thalassemia major (TM).

Methods: One hundred and twenty-four HLA-matched HSCTs were performed in patients with TM between 2015 and 2022. Ninety-one patients were screened for anti-HLA antibodies by testing panel reactive antigens (PRA). Demographic and transplantation characteristics of patients were recorded. The presence of PRA was tested with the Antibody Testing Assay (Luminex LIFECODES HLA Antibody Identification System).

Results: The number of PRA-positive patients was 54. There was no relationship between acute graft versus host disease (GVHD), chronic GVHD, grade of GVHD, and viral reactivation of the patients. However, platelet engraftment took around 3 days longer in the PRA-positive group (p = 0.05). The median number of erythrocyte transfusions was significantly higher in PRA-positive patients in the post-transplant period (p = 0.003), as was the median number of platelet transfusions (p = 0.003). Treosulfan conditioning increased the stable mixed chimerism (MC) rate by 3.8-fold (p = 0.011). In contrast, reduced rates of MC were found in patients who received matched unrelated donor cells or peripherally derived stem cells (p = 0.011 and p = 0.039, respectively) in the posttransplantation period in TM patients. PRA-positivity did not affect MC (p = 0.478). However, 80% of patients who had primary graft failure (n = 5; p = 0.59) and 75% of patients who died (n = 4) were PRA positive (p = 0.64), but these results were statistically insignificant due to the low number of patients.

Conclusion: Anti-HLA antibodies primarily delayed platelet engraftment in TM patients and increased the erythrocyte and thrombocyte transfusion requirements. Although PRA positivity was more common in patients with primary graft failure or who died, there was no statistically significant impact of PRA positivity on chimerism, acute or chronic GVHD, viral activation, or mortality rates.