Early and late components of Epstein-Barr virus-associated membrane antigen in superinfected Daudi cells and their reactivity with sera from nasopharyngeal carcinoma patients.

Investigations were carried out on newly synthesized MA, VCA and EA in Daudi cells superinfected with the P3HR-1 strain of EBV and treated with trypsin to remove previously adsorbed MA-positive material from the cell surface. Synthesis of MA, VCA and EA was completely blocked by puromycin. A marked reduction in the frequency of MA-positive cells was observed in the infected cell cultures in the presence of either Ara-C or PA, but a fraction of the MA-positive cells was insensitive to the inhibitors. Differential absorption of an EBV antibody-positive human serum with Ara-C-treated or -untreated infected cells revealed two antigenically different components of MA: early (Ara-C-insensitive) and late (Ara-C-sensitive) MA. Three of five sera from patients with NPC, but none of five sera from normal adults, showed an apparent 'prozone' phenomenon in their reactivity against late but not early MA.