Comparative Studies on the Induction of Virus-Associated Nuclear Antigen and Early Antigen by Lymphocyte-Transforming (B95–8) and Nontransforming (P3HR-1) Strains of Epstein-Barr Virus

Abstract

The kinetics of the appearance of Epstein-Barr virus (EBV)-associated nuclear antigen (EBNA) and early antigen (EA) in different EBV-infected target cell systems was studied. In addition, attention was given to the effect of pokeweed mitogen (PWM) and phosphonoacetic acid (PAA) (an inhibitor of herpesvirus DNA replication in infected cells) on the expression of EBNA and EA in EBV genome-negative target cells. The results obtained show that both of the EBV strains used (B95–8 and P3HR-1) induce EBNA at different time periods in the EBV genome-negative BJA-B cells and that P3HR-1 EBV is unable to induce either EBNA or EA in human umbilical cord blood lymphocytes (CBL) even after prestimulating these cells with PWM. Thus, our data present additional evidence for biological differences between B95–8 and P3HR-1 strains of EBV. EBNA is indeed the very first EBV-induced intracellular antigen to appear in an EBV-infected cell, and it is possible that the blast state may play an important role in the early induction of EBNA in CBL (as compared to BJA-B cells). Our data also suggest that the resident EBV genome in Raji cells may contribute, through an unknown mechanism, to the early expression of EA following superinfection with P3HR-1 EBV. Furthermore, our results also indicate that PAA does not inhibit the expression of EBNA or EA in BJA-B cells. The importance of these findings in relation to EBV-lymphocyte interaction and particularly in relation to cell transformation by EBV is discussed.