In nasopharyngeal carcinoma-bearing patients, tumors and lymphocytes are infected by different Epstein-Barr virus strains

Despite the fact that most adult humans worldwide are latently infected by the Epstein-Barr virus (EBV), only a very small percentage of them will dev elop an EBV-associated malignancy. We do not know whether this situation re flects the existence of more sensitive individuals or of particularly tumor igenic EBV strains, We postulated that if highly tumorigenic EBV strains di d exist, they would be preferentially found in consistently EBV-associated tumors, such as nasopharyngeal carcinoma (NPC), and differ significantly fr om the strains present in other, non-pathological sites of the same patient s. To test this hypothesis, we compared the BNLF1 gene of the EBV strains p resent in tumors and in "reservoir lymphocytes" of 6 NPC-bearing patients f rom Tunisia, Our results show that all of these patients were infected by m ore than 1 (and up to 7) EBV strains. Moreover, lymphocytes and tumor cells from the same individual were systematically infected by different viral s trains, The origin and biological significance of these multistrain infecti ons are discussed. (C) 2001 Wiley-Liss, Inc.