A HIGH-INCIDENCE OF SERUM IGG ANTIBODIES TO THE EPSTEIN-BARR-VIRUS REPLICATION ACTIVATOR PROTEIN IN NASOPHARYNGEAL CARCINOMA

The BamHI Z EBV replication activator (ZEBRA) protein is involved in t he switch from latency to productive cycle of Epstein-Barr virus. A re combinant ZEBRA protein was synthesized and assessed in enzyme-linked immunosorbent assay (ELISA) for serum IgG response in nasopharyngeal c arcinoma (NPC) patients. In 100 NPC serum samples that were positive f or IgA to the EBV viral capsid antigen (VCA), 75% had IgG anti-ZEBRA a ntibodies. In contrast, only 3/83 (3.6%) serum samples from healthy do nors and 2/50 (4%) from other cancers were positive for IgG to ZEBRA. Interestingly, in a selected group of 100 NPC sera negative for IgA to VCA, 25% contained IgG anti-ZEBRA antibodies. This suggests that the ELISA for IgG anti-ZEBRA may also identify earlier cases of NPC not de tected by the conventional immunofluorescence test for IgA to VCA.