CD4+ T Cells Coexpressing CD134 (OX40) Harbor Significantly Increased Levels of Human Herpesvirus 6B DNA Following Umbilical Cord Blood Transplantation.

Human herpesvirus 6B (HHV-6B) commonly reactivates after umbilical cord blood transplantation (UCBT) and is associated with delayed engraftment, fever, rash, and central nervous system dysfunction. Recently, CD134 (OX40) has been implicated as a potential viral entry receptor. We evaluated CD4+CD134+/neg-lo and CD8+CD134+/neg-lo cells at day 28 after UCBT in 20 subjects with previously documented HHV-6 reactivation and persistent viremia. Analysis of CD4+CD134+ cells as compared to CD4+CD134neg-lo cells showed 0.308 versus 0.129 copies of HHV-6B/cell (P = .0002). CD8+CD134+/neg-lo cells contained little to no HHV-6B copies. Following UCBT, CD4+CD134+ cells harbor significantly increased levels of HHV-6B, suggesting that CD134 (OX40) may facilitate viral entry.