Detection and analysis of anti-latent membrane protein 2A antibodies in the sera of patients with Epstein-Barr virus associated malignancies

Background: Epstein-Barr virus (EBV) associated malignancies with a Type II latency gene expression pattern, such as Hodgkin' s disease, and nasopharyngeal carcinoma (NPC), frequently express the EBV antigen latent membrane protein 2A (LMP2A). We expected to establish a highly expressing LMP2A yeast cell strain and get the high quality LMP2A protein, which was used for detection, analysis and characterization of its antibodies in various patients' sera of EBV associated malignancies. Methods: The plasmid pPICZαA-LMP2A containing the full length of LMP2A cDNA was constructed and transformed to Pichia pastoris GS115 to express LMP2A protein. After fermentation and purification, the LMP2A protein was used as an antigen to detect anti-LMP2A antibodies (Abs) in the sera of patients with EBVassociated malignancies in enzyme linked immunosorbent assay (ELISA) or Western-blot. Results: LMP2A was expressed successfully with an expected molecular weight of approximately 54 kD and Abs to LMP2A were strikingly specific to NPC. Two-thirds or more sera from NPC patients were positive for antiLMP2A immunoglobulin G (IgG) Abs. The antibodies were absent from the sera of other EBV-associated diseases except a small fraction of the gastric carcinoma. Comparing anti-viral capsid Ags (VCA) IgA and LMP2A IgA titers in the sera from 76 NPC patients, only 55% were positive for anti-LMP2A IgA Abs while 70% were positive for anti-VCA IgA. However, we found that 3 sera negative for VCA IgA were positive for LMP2A IgA. Conclusion: The results suggested the potential significance of LMP2A specific Abs for the diagnosis of EBVassociated malignancies, especially NPC.