Relationship between nasopharyngeal carcinoma and high antibody titers to Epstein-Barr virus-specific thymidine kinase.

Epstein-Barr virus (EBV) has long been implicated in nasopharyngeal carcinoma (NPC). Recent studies in our and other laboratories have shown a correlation between the disease and high antibody titers to EBV-specific DNase. These data led us to also examine serial sera from healthy adults and patients with infectious mononucleosis or NPC, for their capacity to neutralize the EBV-specific thymidine kinase (TK) activity from chemically induced EBV-carrying human lymphoblastoid cells. Our results were the following: (i) sera were found that efficiently blocked the EBV-specific TK activity of induced-Raji TK- cell extracts, but not the host-cell TK activity from EBV-negative BJAB cells; (ii) a relationship appeared between high levels of EBV-specific TK-neutralizing activity in sera and NPC pathology, even though in this preliminary study the degrees of EBV-induced TK-blocking activity detected in sera were not significantly correlated with EBV-specific antibody titers; (iii) the EBV-induced TK-neutralizing activity was found in the main IgG fraction derived from NPC sera. These data must be compared with other known antibody responses to EBV for their clinical interest in NPC control.