Viral complications - Inverse relationship between human herpesvirus-6 and-7 detection after allogeneic and autologous stem cell transplantation

Human herpesvirus-6 (HHV-6) and -7 were analyzed in 25 and 18 patients with allogeneic (allo) and autologous (auto) stem cell transplantation (SCT), respectively, by weekly examination of viral DNA in peripheral mononuclear cells using semiquantitative PCR and serologic tests up to 12 weeks after SCT, HHV-6 DNA was detected in 29.6% and 27.9% of samples after allo- and auto-SCT, respectively. The proportions of HHV-6-DNA-positive samples increased in week 3 and 4 after allo-SCT, and in week 1 to 3 after auto-SCT, The frequency of HHV-7 DNA detection, however, was higher after auto-SCT (24.7%) than allo-SCT (12.8%) (P < 0.01). Antibody titer elevation was accompanied by HHV-6 infection in eight of 10 patients. That for HHV-7 was also frequently observed, but not associated with infection in the majority of patients. Five of six patients with > 10(2) copies of HHV-6 DNA (/10(5) cells) on two consecutive occasions were allo-SCT recipients and three showed clinical episodes. Conversely, three of five patients with continuous reactivation of HHV-7 were auto-SCT recipients. Thus, the frequencies of HHV-6 and -7 DNA detection showed an inverse relationship comparing allo- and auto-SCT, suggesting a different mechanism may regulate HHV-6 and -7 reactivation.