Impact of Human Herpesvirus-6 Reactivation on Outcomes of Allogeneic Hematopoietic Stem Cell Transplantation

Human herpesvirus-6 (HHV-6) is known to reactivate after allogeneic hematopoietic stem cell transplantation (allo-HSCT) and may be associated with development of acute graft-versus-host disease (GVHD) and nonrelapse mortality (NRM). However, the clinical significance of HHV-6 reactivation after allo-HSCT remains unclear. Therefore, we conducted a retrospective analysis to elucidate the impact of HHV-6 reactivation on transplantation outcomes. Of 236 patients who underwent allo-HSCT, 138 (58.5%) developed HHV-6 reactivation and 98 (41.5%) did not. Univariate analysis indicated that at 3 years, patients with HHV-6 reactivation had significantly higher NRM (27.7% versus 13.7%, P = .003) and worse overall survival (42.1% versus 59.0%, P = .008) than those without reactivation. In multivariate analysis, HHV-6 reactivation was associated with higher incidence of acute GVHD (hazard ratio [HR], 1.87; P = .01), cytomegalovirus reactivation (HR, 2.24; P < .001), and NRM (HR, 2.73; P = .007). Subgroup analysis stratified according to conditioning intensity indicated that a significant impact of HHV-6 reactivation on acute GVHD was observed only in patients who received myeloablative conditioning (MAC). These results indicate that HHV-6 reactivation was associated with development of acute GVHD, cytomegalovirus reactivation, and NRM. Furthermore, adverse impact of HHV-6 reactivation on transplantation outcomes was prominent in the setting of MAC.