Reported Consequences of HHV-6 Reactivation Following Transplantation

HHV-6 & Stem Cell Transplantation

HHV-6 Encephalitis
HHV-6 encephalitis is a significant concern in the post-transplant setting, particularly in the setting of cord blood transplantation. A 2012 review indicated that nearly 10% of all cord blood transplant recipients develop HHV-6 encephalitis, compared to only 1% of patients receiving traditional SCT (Scheurer 2012). For more information, please visit the HHV-6 Foundation’s webpage on HHV-6 Encephalitis.

Risk Factors for the Development of HHV-6 Encephalitis in Transplantation:
1. Use of umbilical cord blood (Scheurer 2012)
Alemtuzumab (Vu 2007)
Thymoglobulin conditioning (Hill 2011)
Steroid administration (Ogata 2010)
Unrelated donors (Betts 2011)
6. Two or more HSCT (Mori 2010)

HHV-6 and Cognitive Dysfunction
HHV-6 reactivation is the most common cause of mental confusion among post-transplant patients (Zerr 2011). HHV-6-associated encephalitis also presents as retrograde and anterograde amnesia.

HHV-6 and GVHD
HHV-6 reactivation has been increasingly associated with acute graft-versus-host disease (aGVHD) and allograft rejections in the transplant setting. A recent survey of 235 allogeneic stem cell transplant patients indicated that post-transplant HHV-6 reactivation is strongly associated with delayed platelet engraftment, early post-transplantation mortality, and the development of acute GVHD (Dulery 2011). To view the latest research on this relationship, download the HHV-6 Foundation’s IDWeek 2012 handout on HHV-6 & GVHD.

HHV-6 & Solid Organ Transplantation

In kidney transplant patients, HHV-6 has been associated with the development of chronic allograft nephropathy (Chapenko 2009) and GVHD (Caiola 2012). Consequences of HHV-6 reactivation in liver transplant patients include bone marrow suppression, central nervous system dysfunction, pneumonitis, hepatitis, increased severity of graft host disease, increased incidence of fungal infections and higher incidence of allograft rejection (Abdel Massih 2009). A recent publication indicates that high intrahepatic HHV-6 loads, but neither CMV nor EBV, are associated with decreased graft survival following diagnosis of graft hepatitis (Pischke 2012). In 2012, Drs. Irmeli Lautenschlager and Raymund Razonable, renowned SOT experts, wrote a comprehensive review of HHV-6 in the setting of SOT.