A POSSIBLE PROGNOSTIC ROLE OF IMMUNOGLOBULIN-G ANTIBODY AGAINST RECOMBINANT EPSTEIN-BARR-VIRUS BZLF-1 TRANSACTIVATOR PROTEIN ZEBRA IN PATIENTS WITH NASOPHARYNGEAL CARCINOMA

Background. Epstein-Barr virus BZLF-1 replication activator (ZEBRA) is involved in the switch from viral latency to a productive cycle. Prev ious immunofluorescent study has shown that patients with nasopharynge al carcinoma (NPC) have elevated immunoglobulin-G (IgG) antibody titre s against recombinant ZEBRA protein (ZEBRA/IgG). Methods. The prognost ic role of ZEBRA/IgG was further investigated by enzyme-linked immunos orbent assay (ELISA) in 110 NPC patients under long period of clinical follow-up. Results. Ninety-seven percent (85 of 88) of the patients w ith NPC had significantly higher ZEBRA/IgG titres (geometrical mean ti tre, i.e., GMT = 8397) than normal Chinese individuals (GMT = 233 and P < 0.0001). Based on Kaplan-Meier analysis, the actuarial survival in patients with high ZEBRA/IgG titres (25%) after radiotherapy was sign ificantly lower than that of those with low (76%; P = 0.0008) or inter mediate titres (62%; P = 0.0036), although the titres taken before tre atment did not bear such a relationship. Subdividing the patients into either individual UICC or Ho's stages, those with late-stage disease (UICC Stage 4 and Ho's Stages 3 and 4) and with high ZEBRA/IgG titres also had poorer prognosis than those with disease of the same stages b ut who had low titres. Poor prognosis in those with high titres could be associated with a high risk of distant metastasis because consisten t titre increase was found in the majority of patients who later devel oped distant metastasis either in the lung or liver. Only a minimal in crease was found in patients with recurrence in the cervical lymph nod es. No consistent increase was observed, however, in patients whose di sease was in remission or the majority of those with bone metastasis o r local recurrence in the nasopharynx. Conclusion. The postradiotherap y ZEBRA/IgG titre could be a potentially useful marker for differentia ting NPC patients with poor prognosis from those at high risk for the development of distant metastasis to the lung or liver.