HHV-6 encephalitis in umbilical cord blood transplantation: a systematic review and meta-analysis

Reactivation of human herpesvirus-6 (HHV-6) frequently occurs following hematopoietic SCT (HSCT), and has been associated with clinical consequences in many patient populations. HHV-6 reactivation and HHV-6 encephalitis seem to occur more frequently in patients undergoing HSCT with cord blood (CB) as the stem cell source. We have conducted a systematic literature review and meta-analysis to investigate the clinical significance of this correlation. A systematic review of publications indexed in PubMed was performed for HSCT studies published over the past 10 years that fit inclusion criteria. Data on prevalences of HHV-6 reactivation and HHV-6 encephalitis post HSCT were abstracted from 19 papers. Meta-analyses were conducted to calculate combined prevalence estimates. The prevalences of HHV-6 reactivation and encephalitis were compared among CB vs non-CB HSCT. Prevalences of HHV-6 reactivation and HHV-6 encephalitis were significantly higher in patients receiving CB as the stem cell source than in patients receiving another stem cell source (72.0% vs 37.4%, P<0.0001; 8.3% vs 0.50%, P<0.0001, respectively). HHV-6 reactivation and HHV-6 encephalitis are significant complications in the post-HSCT setting, particularly in patients receiving CB as the stem cell source. Thus, patients undergoing umbilical CB transplantation should be closely monitored for HHV-6 reactivation. Bone Marrow Transplantation (2013) 48, 574-580; doi: 10.1038/bmt.2012.180; published online 24 September 2012