The effects of mitogens on the expression of Epstein-Barr virus antigens in human lymphoid cell lines

Treatment of human lymphoblastoid cells with either phytohemagglutinin (PHA), concanavalin A, Staphylococcus protein A, or polyinosinic acid-polycytidylic acid, in combination with 5-iodo-2' deoxyuridine (IUdR) markedly increased the expression of Epstein-Barr virus (EBV) early antigen (EA) relative to IUdR alone. Such treatment did not, however, modify the production of virus capsid antigen in any of the lymphoid cell lines tested. The effect of PHA on EA induction in Raji cells was not accompanied by changes in the incorporation of labeled precursors into cellular DNA, or in the intracellular concentration of either adenosine 3'5' cyclic monophosphate or guanosine 3'5' cyclic monophosphate. However, those mitogens that stimulated EA expression in Raji cells also increased the fluorescence polarization of 1,6 diphenyl 1,3,5-hexatriene-labeled Raji cells. The possible role of cell surface changes in the mitogen activation of latent EBV in human lymphoblastoid cells is discussed.