Thus, we were interested to know whether activation of the specific ATR/Chk1-mediated pathway within 96 hours post EBV inoculation in vitro has any consequences for the subsequent transformation of TBCs, since the risk for PTLD in transplant recipients is highest following primary EBV infection but is also present in EBV carriers [22]. This evidence concerns the gene ATR and Epstein-Barr virus infection.