Antibodies to the Epstein-Barr virus thymidine kinase: A characteristic marker for the serological detection of nasopharyngeal carcinoma

Patients suffering from nasopharyngeal carcinoma (NPC) generally exhibit elevated serum IgA antibody titres to Epstein-Barr virus (EBV) early antigen (EA) and virus capsid antigen (VCA). This property is frequently used as a diagnostic aid. Preliminary experiments suggested that an ELISA for IgA antibodies against the EBV-encoded thymidine kinase (TK) could form the basis of a more reliable diagnostic test. Here, we describe the construction of a recombinant baculovirus that expresses the EBV TK and present a full analysis of its use in serological surveys of NPC patients. Baculovirus-derived TK was used to develop a simple ELISA for serum IgA against this antigen. ELISA reactivity was strongly associated with NPC compared with an EBV-positive, normal control population. Comparison with the existing IgA-VCA and EA assays showed that the TK ELISA had higher sensitivity whilst the specificity was similar or higher. We conclude that the TK ELISA presents a strong predictor of NPC and, in its refined form, has improved pickup rates. In addition, results from patients with chronic nasopharyngitis (CNP) suggest that individuals with both symptoms of CNP and an elevated TK ELISA value may be at increased risk for the development of head-and-neck cancer.