Tissue specific distribution of Epstein-Barr virus (EBV) BZLF1 gene variants in nasopharyngeal carcinoma (NPC) bearing patients.

Using EBV BNLF1 gene polymorphism, we have recently shown that, in NPC bearing patients, lymphocytes and tumor cells of the same individual were infected by different viruses. It appeared as a rule that EBV infection was by multiple strains in these immunocompetent, HIV negative patients. Our data did not detect any evident association between tumor cells and a particular BNLF1 variant. In the present paper, we extend our analysis to the BZLF1 gene of the viruses present in different sites of the same patients. Only two main variants of the BZLF1 gene were identified. Despite this very weak polymorphism of this locus, our results entirely confirm the very frequent occurrence of multistrain infections in these patients, and the presence of different EBV strains in tumor cells and lymphocytes from the same individual. However, in contrast to our results concerning the BNLF1 gene, the BZLF1 variants appeared to be cell type specific, one being associated mainly with epithelial or tumor cells and the other with lymphocytes. The possible reasons for this distribution are discussed.