Latent human herpesvirus-6 DNA is sparsely distributed in peripheral blood lymphocytes of healthy adults and patients with lymphocytic disorders.

Human herpesvirus-6 (HHV-6) can be regularly isolated from peripheral blood mononuclear cells (PBMC) of children suffering from exanthema subitum, but only rarely from PBMC of adults. Although the high prevalence of HHV-6 infection in early childhood seems to result from cell-free infectious virus shedded in saliva of healthy adults, latent HHV-6 infection is supposed to occur in lymphocytes. Therefore, we performed polymerase chain reaction (PCR) with DNA from PBMC of 44 healthy adults, 31 HIV-seropositive individuals and 33 patients with leukaemia or lymphoproliferative disorders. As positive control served PBMC from 11 children with exanthema subitum and as negative control PBMC from 20 newborns. Whereas HHV-6-specific sequences were detected in PBMC from all children with exanthema subitum and never in PBMC from newborns, they were found in PBMC of 9% of healthy adults and HIV-seropositive individuals and in 16% of the patients with lymphoproliferative disorders. Apparently detection of HHV-6 DNA in PBMC was neither limited by low sensitivity of the HHV-6 PCR assay, which detected less than ten copies of cloned HHV-6 DNA, nor by a low rate of latently infected individuals, but was limited by the number of lymphocytes subjected to PCR. It is supposed that the presence of latent HHV-6 DNA in lymphocytes is common, but that infected lymphocytes are rare (less than or equal to 1 infected cell in 10(5) lymphocytes).(ABSTRACT TRUNCATED AT 250 WORDS)