Background: Molecular studies have provided strong evidence for the association of human herpesvirus 8 (HHV-8) with Kaposi's sarcoma. These data have been supported by serological studies, which have also suggested that HHV-8 can be found in the healthy population. We report the presence of infectious HHV-8 in a healthy donor to a North American blood bank. Methods: We examined the peripheral blood mononuclear cells or CD19 cells of blood donors by PCR for evidence of HHV-8 infection. The CD19 cells were separated from peripheral blood mononuclear cells by immunomagnetic-bead selection. To enhance detection of HHV-8, the CD19 cells from eleven unsystematically selected blood donors were activated with phorbol ester and recombinant interleukin-6; the culture fluid was filtered and inoculated onto HHV-8-negative target CD19 cells that had been prepared from phytohaemagglutinin-stimulated peripheral blood mononuclear cells. These inoculated target cells were cultured for 3 days and then analysed for HHV-8 sequences by PCR. Serum samples were tested for antibodies to HHV-8 by an indirect immunofluorescence assay. Findings: One blood donor was consistently found to be infected with HHV-8 by PCR after the cell-culture activation procedure. He was seropositive for the virus. The HHV-8 recovered was infectious, as shown by a reverse-transcription-PCR technique that detected HHV-8 RNA in the inoculated target cells. Interpretation: These data provide the first indication that HHV-8 can be recovered from the blood of a healthy individual, a blood donor, and that the virus is infectious. This observation suggests that HHV-8 could be transmitted by blood transfusion, a possibility that merits further study.
We thank Sue Fujimura for flow cytometric analyses, Michael Busch for critical reading of the manuscript, and Christine Beglinger and Ann Murai for help in preparation of the manuscript.
DJB was supported by the University of California Universitywide AIDS Research Program (UARP) (F94-SF-008). The study was supported by UARP grant number R95-SF-088.