Human CD134 (OX40) expressed on T cells plays a key role for human herpesvirus 6B replication after allogeneic hematopoietic stem cell transplantation

Abstract Background CD134(OX40), which is a cellular receptor for human herpesvirus-6B(HHV-6B) and expresses on activated T cells, may play a key role for HHV-6B replication after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Objectives Therefore, we examined the CD134expression on T cells and HHV-6B replication after allo-HSCT, and analyzed the correlation between them. Study design Twenty-three patients after allo-HSCT were enrolled. The percentages of CD134-positive cells within the CD4 + and CD8 + cell populations were measured by flow cytometry, and the viral copy number of HHV-6B was simultaneously quantified by real-time PCR. The correlation between CD134and HHV-6B viral loadwas then statistically analyzed. Results HHV-6B reactivation occurred in 11 of 23 patients (47.8%). CD134expression was seen on T cells and was coincident with the time of peak viral load. The percentage of CD134-positive cells decreased significantly when HHV-6B DNA disappeared (p = .005 in CD4 + T cells, p = .02 in CD8 + T cells). In the 4 patients who underwent umbilical cord blood transplantation (UCBT), the viral loadvaried with the percentage of CD134-positive cells. In the comparison between the HHV-6B reactivation group and non-reactivation group, maximum percentages of CD134-positive cells among CD4 + T cells in reactivation group were significantly higher than those in non-reactivation group (p = .04). Conclusions This is the first study to show that a correlation of CD134expression on T cells with HHV-6B replication after allo-HSCT, especially in UCBT. The results possibly indicate that CD134on T cells plays a key role for HHV-6B replication after allo-HSCT.