BONE-MARROW TRANSPLANT RECIPIENTS HARBOR THE B-VARIANT OF HUMAN HERPESVIRUS-6

Lymphotropic herpesviruses have recently been isolated from patients u ndergoing kidney, liver and bone marrow transplantation (BMT). We have molecularly characterized isolates of HHV-6 from children undergoing allogenic BMT. We show that viruses recovered from the BMT recipients correspond to the B variant of human herpesvirus 6, the etiological ag ent of exanthem subitum. HHV-6 B strains are known to be associated wi th infections in the majority of children in infancy or early childhoo d. Infection in the BMT recipients most likely reflects the reactivati on of these viruses during immunosuppressive treatment. Each of the re activated viruses has its own characteristic heterogeneous (het) seque nce. We show that the het sequence is stably unique for each HHV-6 str ain. We also show that prolonged viremia can be documented with some o f the patients, unlike the characteristic short duration febrile sickn ess in the exanthem subitum cases of infancy. The mechanism of HHV-6 B reactivation from latency is not known. Furthermore, the full clinica l outcome of HHV-6 B viremia in the BMT patients requires further inve stigation.