High prevalence of HHV-6 DNA in peripheral blood mononuclear cells of healthy individuals detected by nested-PCR.

The aim of the study was the evaluation of human herpesvirus-6 (HHV-6) infection rate and semiquantification of viremia in healthy people. Healthy blood donors were studied. Human herpesvirus-6 IgG and IgM antibody titers were measured by indirect immunofluorescence assay. Human herpesvirus-6 DNA amplification (nested-PCR) was performed in peripheral blood mononuclear cells (PBMC) and in serum. Seventeen of 50 (34 percent) individuals were positive for IgG anti-HHV-6 and the titers ranged from 1:40 to 1:160. None of 30 individuals was positive for IgM anti-HHV-6, suggesting no recent infection nor reactivation. Human herpesvirus-6 DNA was detected by nested-PCR amplification in peripheral blood mononuclear cells but not in sera. When 1 microgram DNA was amplified, HHV-6 DNA was detected in 8 of 20 individual (40%), but in 18 of 20 (90%) when 5 micrograms DNA were amplified. It is concluded that HHV-6 is present in a high proportion of the healthy population but in minimal amounts, and although it can be detected in 1.4 x 10(5) PBMC, 7 x 10(5) cells are necessary to detect most cases. No reactivation was observed in healthy people.