Effect of HLA Mismatch on Post-Transplant Infections in Allogeneic Hematopoietic Stem Cell Transplantation with PTCy-Based GvHD Prophylaxis

Abstract

The aim of the study was to assess the risk of infections in the first 100 days in patients grafted from haploidentical donors (HAPLO) (n=116) or HLA-matched donors (MATCHED) (Related, n=29; unrelated n=39): all patients received graft-versus-host disease (GvHD) prophylaxis with post-transplant cyclophosphamide (PTCy), mycophenolate, and cyclosporine. The two groups had comparable age, intensity of conditioning, and disease status; the stem cell source was bone marrow for HAPLO and peripheral blood for MATCHED transplants. HAPLO patients had an increased risk of bloodstream infections (BSI) (HR 2.54; 95% CI 1.39-4.62; p=0.002), in particular gram-positive BSI (HR 4.42; 95% CI 1.57-12.5; p=0.005). HAPLO patients also had increased CMV infection/reactivation (HR 3.51; 95% CI 1.79-6.87; p<0.001) and a trend for increased invasive fungal infections (HR 1.80; 95% CI 0.90-3.57; p=0.10) and EBV infection/reactivation (HR 2.07; 95% CI 0.44-9.70; p=0.35). Overall, post-transplant infections were more likely to result in infection-related mortality in HAPLO grafts (p=0.03). In this single-center study, patients with HAPLO grafts had an increased risk of BSI and CMV infection/reactivation and a trend for increased IFI and EBV infection/reactivation, compared with MATCHED grafts. These findings call for diligent monitoring of infections in patients undergoing a HAPLO transplant.