P068 Impact of anti-HLA antibodies on early complications and outcome in unrelated hematopoietic stem cell transplantation

Aim To evaluate the clinical significance of anti-HLA antibodies (Abs) on early complications and outcome of unrelated donor hematopoietic stem cell transplantation (UD-HSCT). Methods From June 1, 2014 to March 20, 2016, 90 adult patients, who reached 6-month follow-up after their first UD-HSCT or died within this period, were recruited into this study. All donor-patient pairs were 10/10 or 9/10 matched at HLA-A, -B, -C, -DRB1, and -DQB1 loci. Additionally, HLA-DRB3,4,5 and -DPB1 loci were typed. Patients’ sera sample collection was scheduled before the start of conditioning treatment and at 1, 2, 3, and 6 months after UD-HSCT. Anti-HLA Abs were screened and identified by solid-phase immunoassays on the Luminex platform. HLAMatchmaker programs were used to perform structural HLA class I and class II matching at the eplet level. Results Patient’s median age was 56 years (range 19–74) and 47 of 90 patients (52.2%) were men. Seventy-four donor - patient pairs (82.2%) were 10/10 matched. Eighty-nine of 90 patients (98.8%) received peripheral blood stem cell graft. All patients achieved neutrophil engraftment and four patients (4.4%) had secondary graft failure. The overall prevalence of preformed anti-HLA Abs (no donor-specific antibodies were found) was 41.1% and 32 of 37 patients retained anti-HLA Abs after UD-HSCT. The presence of preformed anti-HLA Abs was found to be associated with the development of early grades III and IV acute graft-versus-host disease (aGVHD) post-transplant complications ( p  = 0.0446), higher transplant-related mortality ( p  = 0.011), and shorter overall survival ( p  = 0.021). The preformed anti-HLA Abs did not affect engraftment, incidence of relapse, graft failure, event free survival or development of non-aGVHD complications. Anti-HLA Abs detected after UD-HSCT (retained and de novo) had no impact on development of early complications and outcome of UD-HSCT. Nine patients developed de novo anti-HLA Abs after UD-HSCT. In the only case they were donor-specific and directed against mismatched DQA1*/DQB1* antigens. Conclusions Preformed anti-HLA Abs have impact on development of severe aGVHD, higher transplant related mortality and reduced overall survival after UD-HSCT. Therefore, routine testing for anti-HLA Abs may be considered in pre-transplant work-up of the recipients.