HHV-6A and HHV-6B in Solid Organ Transplantation

Human herpes virus 6 (HHV-6) infection, mostly due to HHV-6B, is frequently recorded after solid organ transplantation, but symptomatic infections are not common. Only 1 to 6.7% of transplant recipients have been reported to develop clinical illness or allograft dysfunction associated with HHV-6. Fever, myelosuppression, hepatitis, colitis, and encephalitis have been observed. HHV-6 has also been associated with indirect effects, such as acute and chronic allograft rejection, and increased risk of cytomegalovirus (CMV) disease, fungal infections, and other opportunistic infections. HHV-6 has an ability to integrate into the host chromosome, but the clinical significance of chromosomally integrated HHV-6 in transplant patients is not yet clear. The laboratory diagnosis of HHV-6 infection is complex due to the common asymptomatic reactivations. Laboratory diagnostics are primarily based on quantitative nucleic acid amplification tests of blood, plasma, or serum samples. HHV-6 antigens may also be demonstrated in clinical specimens by immunohistochemistry. Antiviral treatment of HHV-6 is indicated in encephalitis or other severe end-organ disease. Foscarnet, ganciclovir, and cidofovir are the drugs used for treatment.