Transmission electron microscopy of HHV-6–inoculated SAS413 and SAS527. Note that many HHV-6 particles are present in HHV-6A–inoculated SAS413 (A and B) and SAS527 (C and D), whereas no virus is detectable in HHV-6B–inoculated SAS413 (E) and SAS527 (F). The highly magnified boxed areas in (A) and (C) are shown in (B) and (D), respectively. HHV-6A–inoculated SAS413 cells were examined at day 6 of virus inoculation, and HHV-6B–inoculated SAS413, HHV-6A–inoculated SAS527, and HHV-6B–inoculated SAS527 cells were examined at day 240.