Cellular and Growth-Factor Requirements for the Replication of Human Herpesvirus 6 in Primary Lymphocyte Cultures

Abstract

Human herpesvirus 6 (HHV-6) was first isolated in 1986 from peripheral blood of AIDS patients and patients with lymphoproliferative disorders (1). Yamanishi and coworkers (2, 3) have further shown that HHV-6 is the causative agent of exanthem subitum (roseola infantum), a common childhood disease characterized by high fever and skin rash. Analyses of HHV-6 cell tropism have yielded complex results. The GS strain isolated by Salahuddin et al. (1) was shown to replicate in a variety of established cell lines including B cells positive for Epstein-Barr virus, continuous T-cell lines, megakaryocytes, and glioblastoma cells (4). Other HHV-6 strains were reported to replicate in continuous T-cell lines (5, 6). In contrast, the Z29 strain does not readily replicate in these cells (7, 8). While more quantitative studies are needed to evaluate the relative efficiencies of virus replication in different cell types, it is commonly accepted that HHV-6 isolates readily replicate in T cells (5–7, 9). Moreover, Takahashi et al. (10) reported that HHV-6 isolates infect predominantly CD4⁺ T cells in the peripheral-blood lymphocytes (PBL) of exanthem subitum patients.