Increased Infections and Delayed CD4+ T Cell but Faster B Cell Immune Reconstitution after Post-Transplantation Cyclophosphamide Compared to Conventional GVHD Prophylaxis in Allogeneic Transplantation

Post-transplantation cyclophosphamide (PTCy) is being increasingly used for graft-versus-host disease (GVHD) prophylaxis after allogeneic hematopoietic cell transplantation (allo-HCT) across various donor types. However, immune reconstitution and infection incidence after PTCy-based versus conventional GVHD prophylaxis has not been well studied. We evaluated the infection density and immune reconstitution (ie, absolute CD4+ T cell, CD8+ T cell, natural killer cell, and B cell counts) at 3 months, 6 months, and 1 year post-HCT in 583 consecutive adult patients undergoing allo-HCT with myeloablative (n = 223) or reduced-intensity (n = 360) conditioning between 2012 and 2018. Haploidentical (haplo; n = 75) and 8/8 HLA-matched unrelated (MUD; n = 08) donor types were included. GVHD prophylaxis was PTCy-based in all haplo (n = 75) and in 38 MUD allo-HCT recipients, whereas tacrolimus/methotrexate (Tac/MTX) was used in 89 and Tac/Sirolimus (Tac/Sir) was used in 381MUD allo-HCT recipients. Clinical outcomes, including infections, nonrelapse mortality (NRM), relapse, and overall survival (OS), were compared across the 4 treatment groups. The recovery of absolute total CD4+ T-cell count was significantly lower in the haplo-PTCy and MUD-PTCy groups compared with the Tac/ MTX and Tac/Sir groups throughout 1 year post-allo-HCT (P =.025). In contrast, CD19+ B-cell counts at 6 months and thereafter were higher in the haplo-PTCy and MUD-PTCy groups compared with the Tac/MTX and Tac/Sir groups (P <.001). Total CD8+ T cell and NK cell recovery was not significantly different among the groups. Infection density analysis showed a significantly higher frequency of total infections in the haplo-PTCy and MUD-PTCy groups compared with the Tac/MTX and Tac/Sir groups (5.0 and 5.0 vs 1.8 and 2.6 per 1000-person days; P <.01) within 1 year of allo-HCT. The cumulative incidence of cytomegalovirus reactivation/infection at 1 year post-allo-HCT was higher in the haplo-PTCy group (51%) compared with the MUD-PTCy (26%), Tac/MTX (26%), or Tac/Sir (13%) groups (P <.001). The incidence of BK, human herpesvirus 6, and other viruses were also higher in the PTCy-based groups. Overall, the treatment groups had similar 2 year NRM (P =.27) andOS (P =.78) outcomes. Our data show that PTCy-based GVHD prophylaxis is associated with delayed CD4+ T cell but faster B cell immune reconstitution and a higher frequency of infections compared with conventional GVHD prophylaxis but has no impact on nonrelapsemortality or overall survival. (C) 2021 The American Society for Transplantation and Cellular Therapy. Published by Elsevier Inc. All rights reserved.