Human herpesvirus 6 infection in autologous bone marrow transplant recipients: a prospective study

After primary infection in early life, human herpesvirus 6 (HHV-6) remains latent in the body and may reactivate in subjects with poor immune status. A 180-day longitudinal study of HHV-6 infection was carried out in 23 autologous bone marrow transplant recipients to evaluate reactivation of HHV-6; two of these patients underwent a double transplant. The patients were monitored prospectively for HHV-6 DNA in peripheral blood mononuclear cells (PBMC) by hot start nested PCR. Positive samples were typed by the enzymatic restriction protocol. Positive plasma samples were also tested for HHV-6 DNA. Antibodies against HHV-6 were measured by immunofluorescence. Five and two out of 23 patients had intermittent and persistent positivity to HHV-6 DNA in PBMCs, respectively; four patients carried variant B, and the other three patients both A and B. None of the respective plasma samples were positive. Two patients were positive for HHV-6 antibodies. Since the significance of HHV-6 DNA in PBMCs is unclear, these findings do not necessarily indicate active infection but may be due to mild immunosuppression in autologous BMT recipients.