tokens: The only exception is represented by the P3HR1 cells , in which , however , the infection by the variant B does not determine induction of EBV antigens ; ( 2 ) the presence of the EBV genome contributes to the susceptibility of the B cell lines to HHV-6 infection , increasing the binding sites and the percentage of infectable cells , as detected by immunoelectron microscopy ; and ( 3 ) HHV-6 infected T cells , transfected with plasmids bearing the promoter regions of the EBV early genes BZLF1 and BMRF1 , show a strong transactivation of these promoters .