Characterization of Epstein-Barr virus strains and LMP1-deletion variants in Portugal.

Variations in the genome sequence of Epstein-Barr Virus (EBV) are thought to lead to differential interaction with host cells, immune evasion, and transformation. The discussion regarding EBV strains as having a geographic or disease-association has been increasing and the majority of studies are performed in Asiatic populations. We developed a case-control study with 139 individuals, including 96 subjects with different malignancies and 43 healthy individuals, from the North region of Portugal. We have used PCR protocols for the characterization of EBV strains (type A or B) based on EBNA3C genome variation and for the LMP1 30bp-deletion variants (wt-LMP1 or del-LMP1). Our study showed that type A is the most prevalent in our population (100% of healthy controls, 96.9% of aHSCT patients, 90.8% of HNSCC patients, and 94.9% of NPC patients) and that type B was significantly associated with NPC (P = 0.019; RR = 8.90). Regarding the LMP1 30bp-deletion, we found a similar distribution of both wt- and del-LMP1 variants in controls and dispare results in cases: del-LMP1 was more frequent in aHSCT and HNSCC patients (64.7% and 63.2%, respectively) and wt-LMP1 in NPC patients (100%). In fact, the study reveals that wt-LPM1 was significantly associated with NPC (P < 0.001; RR = 18.4). Hence, our study showed that EBV type B and wt-LMP1 variant seem to be associated with NPC in our population, with a clear disease-association for wt-LMP1. These results contribute for the knowledge of EBV genetic diversity among Caucasian populations.