Lautenschlager, Irmeli

AbstractHuman herpesvirus 6 (HHV‐6A and HHV‐6B) can cause primary infection or reactivate from latency in liver transplant recipients, which can result in a variety of clinical syndromes, including fever, hepatitis, encephalitis and higher rates of graft dysfunction as well as indirect effects including increased risks of mortality, CMV disease, hepatitis C progression and greater fibrosis scores. Although HHV‐6 infection is currently diagnosed by quantifying viral DNA in plasma or blood, biopsy to demonstrate histopathological effects of HHV‐6 remains the gold standard for diagnosis of end‐organ disease. HHV‐6 reactivation may be restricted to the infected organ with no evidence of active infection in the blood. HHV‐6 infections in liver transplant patients are mostly asymptomatic, but clinically significant tissue‐invasive infections have been treated successfully with ganciclovir, foscarnet or cidofovir. Inherited chromosomally integrated HHV‐6 (ciHHV‐6), in either the recipient or the donor organ, may create confusion about systemic HHV‐6 infection. Recipients with inherited ciHHV‐6 may have an increased risk of opportunistic infection and graft rejection. This article reviews the current scientific data on the clinical effects, risk factors, pathogenesis, diagnosis and treatment of HHV‐6 infections in liver transplant recipients.

SUMMARY Chromosomally integrated human herpesvirus 6 (ciHHV‐6) is a condition in which the complete HHV‐6 genome is integrated into the host germ line genome and is vertically transmitted in a Mendelian manner. The condition is found in less than 1% of controls in the USA and UK, but has been found at a somewhat higher prevalence in transplant recipients and other patient populations in several small studies. HHV‐6 levels in whole blood that exceed 5.5 log10 copies/ml are strongly suggestive of ciHHV‐6. Monitoring DNA load in plasma and serum is unreliable, both for identifying and for monitoring subjects with ciHHV‐6 due to cell lysis and release of cellular DNA. High HHV‐6 DNA loads associated with ciHHV‐6 can lead to erroneous diagnosis of active infection. Transplant recipients with ciHHV‐6 may be at increased risk for bacterial infection and graft rejection. ciHHV‐6 can be induced to a state of active viral replication in vitro . It is not known whether ciHHV‐6 individuals are put at clinical risk by the use of drugs that have been associated with HHV‐6 reactivation in vivo or in vitro . Nonetheless, we urge careful observation when use of such drugs is indicated in individuals known to have ciHHV‐6. Little is known about whether individuals with ciHHV‐6 develop immune tolerance for viral proteins. Further research is needed to determine the role of ciHHV‐6 in disease. Copyright © 2011 John Wiley & Sons, Ltd.