Breakthrough reactivation of HHV-6 occurs with liver transplantation in spite of valganciclovir preemptive therapy for CMV

High-grade HHV-6 viremia is independently associated with rejection of liver transplants within 12 months.

Antiviral prophylaxis directed at CMV in transplant patients also may inhibit reactivation of HHV-6. Singh et al. of the University of Pittsburgh and collaborators at multiple institutions examined the effect on HHV-6 reactivation of preemptive vanganciclovir therapy given to people at high risk for CMV reactivation during liver transplantation. The patients were at high risk because the donors were CMV seropositive while the recipients were CMV seronegative (D+R- transplant patients).

 HHV-6 and CMV viral loads (but not viral loads of other herpesviruses) using quantitative PCR were measured weekly over many weeks following transplantation in 96 patients. HHV-6 viremia developed in 44/96 patients, or 42%: 5 had only HHV-6 viremia, 35 had both HHV-6 and CMV viremia, and 44 had CMV viremia, alone.

The median viral load in HHV-6 viremic patients was 100 copies/mL. Only one patient had > 1000 copies/mL, other than one patient who had inherited chromosomally integrated HHV-6 (iciHHV-6).

Of the 35 patients who developed HHV-6 viremia and received valganciclovir, 19 received the antiviral after the onset of viremia, 10 were on the antiviral at the onset of viremia and 6 had completed the course of antivirals at the onset of viremia.

HHV-6 viremia was associated with increased age, and with critical illness requiring intensive care. People with higher peak viral loads of HHV-6, or with more persistent viremia, or with early onset of viremia, were also more likely to experience CMV reactivation.

High-grade HHV-6 viremia was significantly associated with allograft rejection within 100 days and 12 months.

Read the full article: Singh 2021