Notably, HCMV infection had previously been reported to sensitize cells to TRAIL and induce DR expression (Sedger et al., 1999), but this can now be explained in those studies by the use of the high-passage AD169 strain, which encodes a defective UL36 and also lacks the entire UL/b′ genomic region (Skaletskaya et al., 2001a; Cha et al., 1996). This evidence concerns the gene TNFSF10 and cytomegalovirus infection.