Antibodies against the large subunit of the EBV-encoded ribonucleotide reductase in patients with nasopharyngeal carcinoma.

The open reading frame corresponding to BORF2 and encoding the large subunit of the Epstein-Barr virus (EBV) ribonucleotide reductase has been inserted into the prokaryotic expression vector pUC19. A 90-kDa protein was produced when the intact plasmid was used as a template for in vitro DNA-directed protein synthesis. Using templates generated by restriction digests within the BORF2 open reading frame, in the same system, truncated polypeptides resulted confirming the identity of the 90-kDa protein. The protein was then produced in a heterologous expression system and used in protein immunoblotting to screen for antibodies in sera from nasopharyngeal carcinoma (NPC), Burkitt's lymphoma (BL) or control subjects. Twenty out of 33 NPC sera were positive for antibodies against the large subunit, 13 of these were positive for both IgG and IgA, whilst 7 were positive for IgG only. Out of 15 BL sera and 10 control sera, none were positive. These results are similar to those observed for other EBV-encoded enzymes, including the DNase which had been used as an early marker for the development of NPC. The results presented here indicate that antibodies against the large subunit of ribonucleotide reductase could serve as an additional marker for NPC.