Specific IgA antibodies to recombinant early and nuclear antigens of Epstein-Barr virus in nasopharyngeal carcinoma

Nasopharyngeal carcinoma is a corm-non cancer in Taiwan. The Epstein-Barr v irus (EBV) is closely associated with nasopharyngeal carcinoma. The sera of patients with nasopharyngeal carcinoma have IgA antibodies to a variety of EBV latent and replicated antigens. Recently, an enzyme-linked immunosorbe nt assay (ELISA) kit, combining both the EBV early antigen (EA) and nuclear antigen (EBNA-1) became commercially available. The purpose of this study was to assess its clinical application. Serum IgA antibodies to the EBV EA and EBNA-1 were measured by using the ELISA kit in various group,; of subje cts. Fluorescence antibody (FA) tests against EBV viral capsid antigen (VCA ) and EA in the IgA and IgG classes were also studied for comparison. The D NA content analysis was also carried out to investigate the association wit h IgA antibody titres using ELISA. The sensitivity, specificity and accurac y of the ELISA test were 98.1%, 81.8% and 88.7% respectively. It was far be tter than any FA tests. The IgA antibody titres showed no association with DNA content analysis. Univariate analysis of various factors revealed that IgA antibody titres were statistically correlated to N stage (P=0.0291) and M status (P=0.001). However, there was no association with the age, sex, T stage and clinical stage. Multivariate analysis or various factors was fou nd to be statistically significant in patients with T4 (P=0.0133), N3 (P=0. 0244) or M1 (P=0.001) respectively. Serial testing of antibody titres in 22 previously untreated patients found a trend of decreasing I-A antibody tit res after initial treatment when the tumours disappeared (P=0.0358). The EL ISA kit to identify specific I-A antibodies with the combination of EBV EA and EBNA-1 recombinant antigens has high sensitivity and acceptable specifi city and accuracy in the diagnosis of nasopharyngeal carcinoma. This assay should be useful for early diagnosis and mass screening of patients.