Use of recombinant Epstein-Barr virus early antigen for detection of antibody in patients with nasopharyngeal carcinoma.

BACKGROUND

Nasopharyngeal carcinoma (NPC) is one of the most common cancers in southern China and Taiwan. Serological studies revealed the close-relationship between NPC and Epstein-Barr virus (EBV). Elevated serum and saliva levels of anti-EBV antibodies are detected in patients with NPC. Therefore, Development Center for Biotechnology prepared the EBV-early antigen (EA-D) by recombinant DNA technique for screening the serum and throat washing samples from patients with head and neck cancers.

METHODS

The BMRF1 gene for EBV early antigen (EA-D) was placed into the plasmid pDB18, then transformed into an Escherichia coli strain containing the lambda cI857 temperature-sensitive repressor. Heat treatment of the transformant, at exponential growth phase, inactivated the cI protein and induced an over-expression of the EA-D protein. Next, the EA-D was purified by chromatography and characterized as a protein of molecular weight 47 kDa, by sodium dodecyl sulfate-polyacry lamide gel electrophoresis (SDS-PAGE) and Western blot analysis using monoclonal anti-EA antibody and sera from patients with nasopharyngeal carcinoma (NPC). Enzyme-linked immunosorbent assay (ELISA) with the purified EA-D antigen was used to screen 129 serum and throat washing (TW) samples from patients with head and neck tumors, 24 from patients with a nonmalignant disease and 44 from normal donors.

RESULTS

Experimental results indicated significantly higher positive rates of EA-D IgA (69%) and EA-D IgG (91%) in NPC sera than in the sera of patients with other head and neck tumors and normal controls. TW samples from patients with NPC also showed a higher positive rate (34%) than the other groups (7-20%).

CONCLUSIONS

Results in this study demonstrate that the bacterially expressed EA-D antigen could be recognized by sera from patients with NPC and monoclonal anti-EA antibody. Thus, it has potential use in ELISA for screening EBV-related diseases such as NPC.