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

Nasopharyngeal carcinoma is a common cancer in Taiwan. The Epstein-Barr virus (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 immunosorbent 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 groups of subjects. Fluorescence antibody (FA) tests against EBV viral capsid antigen (VCA) and EA in the IgA and IgG classes were also studied for comparison. The DNA content analysis was also carried out to investigate the association with IgA antibody titres using ELISA. The sensitivity, specificity and accuracy of the ELISA test were 98.1%, 81.8% and 88.7% respectively. It was far better 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 of various factors was found 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 IgA antibody titres after initial treatment when the tumours disappeared (P = 0.0358). The ELISA kit to identify specific IgA antibodies with the combination of EBV EA and EBNA-1 recombinant antigens has high sensitivity and acceptable specificity and accuracy in the diagnosis of nasopharyngeal carcinoma. This assay should be useful for early diagnosis and mass screening of patients.