Immunologic identification of Epstein-Barr virus early antigen in a P3HR-1 cell extract

We extracted the Epstein-Barr soluble antigen (EBSA) from the P3HR-1 human lymphoid cell line, which carries the Epstein-Barr virus (EBV), after P3HR-1 cells were activated with 5-iodo-2'-deoxyuridine. EBSA was identified as the early antigen (EA) complex by immunodiffusion and blocking immunofluorescence tests with high-titered human antiserum to EA. The identity of the EA complex was confirmed with antiserum to EA prepared in rabbits and adsorbed to assure its immunologic specificity. The EA was partially purified on Sephadex G-200. Further characterization by immunoelectrophoresis showed that the EBSA moved rapidly toward the anode. This indicated a highly negative charge. EBSA appeared to be distinct from the previously described complement-fixing S-antigen. It was demonstrable only in EA-producer lymphoid cell lines and reacted specifically with human antiserum to EA, whereas the S-antigen was found in all EBV-carrying lymphoid cell lines and reacted with all EBV antibody-positive human antisera.