The Impact of Cytomegalovirus Reactivation on Cytomegalovirus-Specific Immune Reconstitution in Hematopoietic Stem Cell Transplant Recipients Receiving LMV Prophylaxis

Background Cytomegalovirus (CMV) remains the most common viral infection after hematopoietic stem cell transplantation (HSCT).The clinical significance of different CMV DNA forms remains unclear, particularly regarding CMV-specific immune reconstitution. Methods A total of 76 HSCT recipients were enrolled. A quantitative DNase I–resistant CMV-DNA assay was performed to distinguish infectious from non-infectious CMV DNA. Based on DNase treatment results, patients were divided into three groups: (1) Negative DNAemia (ND, n = 25): with no detectable CMV DNA; (2) DNase-sensitive DNAemia (DSD, n = 26): with only DNase-sensitive CMV DNA detected; (3) DNase-resistant DNAemia (DRD, n = 25): with at least one episode of DNase-resistant CMV DNAemia within 100 days post-transplant. CMV-specific T-cell responses were evaluated by multiparameter flow cytometry, and cytokine polyfunctionality was quantified using COMPASS analysis. Results Early CMV reactivation was associated with stronger CD8+ than CD4+ T-cell responses. DRD patients exhibited significantly enhanced polyfunctional CD8+ T-cell responses compared with ND patients, while DSD patients did not. Among patients with detectable CMV DNA, stronger CD8+ T-cell responses correlated with higher peak viral loads and greater viral shedding. Elevated CMV-specific CD4+ T-cell responses were associated with higher peak CMV-DNA loads and reduced risk of CMV reactivation after day 100 post-transplant. In multivariable analysis, acute graft-versus-host disease (aGvHD) was an independent risk factor for CMV reactivation. Conclusions CMV-specific immune reconstitution appears delayed in DSD compared with DRD patients, potentially reflecting limited exposure to replication-competent virus. Assessment of CMV-specific T-cell polyfunctionality may help identify HSCT recipients at increased risk for late CMV reactivation.