Human Herpesvirus 6 Infection After Allogeneic Stem Cell Transplantation: Incidence, Outcome, and Factors Associated with HHV-6 Reactivation

Background: Human herpesvirus 6 (HHV-6) is susceptible to latency and reactivation in hematopoietic stem cell transplant (HSCT) recipients. We investigated the incidence of HHV-6 DNAemia and factors related to HHV-6 DNAemia and death after allogeneic stem cell transplantations. We also explored the relationship between HHV-6 viral load and the presence of clinical signs.

Methods: Data concerning age, sex, transplantation conditions, graft-versus-host disease (GVHD), treatments, clinical signs, outcome, HHV-6, and other infections were collected for a historical cohort of 390 HSCT performed between 1999 and 2008 in the Transplant Unit of Nancy University Hospital Center. Univariate analysis was used to evaluate influences between the different parameters.

Results: The study included 220 of the 390 allogeneic HSCTs. For the analyzed period, 44 patients (n=44/220, 20%) presented HHV-6 DNAemia in whole blood, including three integrated forms. Fifteen percent (7/41) of HHV-6-positive patients presented clinical signs not related to higher viral load (P=0.164). The factors associated with HHV-6 DNAemia were as follows: cord blood transplantation (P<0.001), conditioning regimen (P=0.030), acute GVHD (P=0.003), and the type of prophylactic treatment for GVHD (P=0.001). HHV-6 DNAemia was not significantly associated with cytomegalovirus infection (P=0.937). HHV-6 DNAemia was not associated with death (P=0.151).

Conclusions: HHV-6 DNAemia was not so frequent after allogeneic transplantation. Factors associated with HHV-6 DNAemia were similar to those for other infections. No abnormally high death rate was observed in the HHV-6 positive population. The presence of clinical signs did not appear to be statistically related to HHV-6 viral load.