Anti-HLA class I donor-specific antibodies are associated with lower overall and event-free survival and late mortality in outpatient haploidentical-related stem cell transplantation from the peripheral blood

Background: Donor-specific (DSA) anti-HLA antibodies can adversely influence outcomes of haploidentical hematopoietic stem cell transplantation (haplo-HSCT). Methods: Patients who received a haplo-HSCT from a sibling after reduced-intensity conditioning (RIC) and had a virtual cross match against donor's HLA typing performed and a positive single-antigen microspherebased immunoassay test were studied. DSA were considered positive with a mean fluorescence intensity (MFI) >= 1000. Results: Anti-HLA DSA >= 1000, median 2623 (range 1000-13,235) MFI were documented in 27/65 (42 %) patients. In 14 (21.5 %) patients, antibodies were anti-HLA class I, in 18 (27.7 %) anti-HLA class II, and in 6 (9.2 %) against both. Overall (OS) and event-free survival (EFS) were lower in patients with anti-HLA Class I DSA (p = 0.026 and p = 0.037, respectively). One-year mortality was higher with anti-HLA DSA of any class (p = 0.009). Nine (64.3 %) of 14 patients with DSA anti-HLA class I died, vs. 11/18 (61 %) with class II DSA (p = 0.238). Anti-HLA DSA were not associated with graft failure (GF) in the cohort. There was no difference in relapse or acute or chronic GVHD in patients with and without DSA. Conclusion: Anti-HLA Class I DSA > 1000 MFI after haplo-HSCT was associated with lower OS and EFS and higher one-year mortality, but no with GF, acute or chronic GVHD, or relapse.