Some factors affecting the expression of Epstein-Barr virus-associated membrane antigens

The effect of two factors, L-arginine concentration and phytohemagglutinin (PHA) stimulation, on the expression of Epstein-Barr virus (EBV)-associated membrane antigens (MA) was evaluated. An EBV-producer cell line, AV-1, was cultivated in Eagle's basal medium with Earle's salts, supplemented with various L-arginine concentrations ranging from 0.0 to 20.0 mM. In most of the L-arginine concentrations, the number of cells expressing MA decreased within the first 24 hours. This decrease was followed by a marked increase in MA-positive cells at 48 hours and a slight decrease between 48 and 72 hours. Statistical evaluation, however, revealed no significant differences in the level of MA expression among cells exposed to the various L-arginine concentrations. These findings were discussed in relation to the cell cycle dependence of L-arginine-deficient media as a virus-activating agent. AV-1 cell cultures were treated with PHA and observed at 24-hour intervals for 72 hours. Within the first 24 hours, the percentage of cells showing MA was markedly increased. This was followed by a rapid decline in percentage of MA-positive cells within the next 24 hours. Treatment of an EBV-nonproducer cell line, NC37, with PHA resulted in the production of MA in approximately 11% of the cells within the first 24 hours. The number of MA-positive cells gradually declined over the next 48 hours. No viral capsid antigens were detected in these cells. The data suggested either complete or partial activation of the latent EBV genome by PHA.