Detection of human herpesvirus 6 DNA and chromosomal integration after allogeneic hematopoietic stem cell transplantation: A retrospective single center analysis.

Introduction: Human herpesvirus 6 (HHV-6) can reactivate after allogeneic hematopoietic stem cell transplantation (allo-HSCT) and may be associated with significant morbidity and mortality.
Methods: The epidemiology of HHV-6 infections and their impact on outcome after allo-HSCT were retrospectively analyzed in 689 adult allo-HSCT recipients (January 2015-December 2018). Chromosomal integration of HHV-6 (ciHHV-6) in the donor was retrospectively investigated to critically evaluate antiviral treatment strategies.
Results: HHV-6 DNA in any specimen was found in 89 patients. HHV-6 infections (encephalitis (one), gastroenteritis (44), dermatitis (two), hepatitis (one), or pneumonitis (five)) were diagnosed in 53/689 patients (7.7%). Elevated levels of HHV-6 DNA were found in 38 patients (5.5%). ciHHV-6, analyzed in patients with HHV-6 viral loads ≥10 ⁴  copies/ml, was identified in four patients (10/38 patients; 10.5%). Two of those displayed copy numbers of HHV-6 ranging from ≥2 × 10 ⁵ to 2.5 × 10 ⁶  copies/ml (HHV-6A). Here, ciHHV-6 was integrated into donor and not into the patients' cells. In this series of allo-HSCT recipients, 10.5% of patients with blood viral loads of HHV-6 showed ciHHV-6.
Conclusion: Screening of the donor for ciHHV-6 before initiation of antiviral therapy is recommended.
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