[A basic study on the association of Epstein-Barr virus with nasopharyngeal carcinoma--detection and genotypic analysis of Epstein-Barr virus associated with nasopharyngeal carcinoma in Japanese patients].

Epstein-Barr virus (EBV) is known to be associated with two human malignant diseases, nasopharyngeal carcinoma (NPC) and endemic Burkitt's lymphoma. In this study, the genotypes of EBV in tissues from 13 NPC patients in Japan were analyzed by Southern blot hybridization using EBV genome fragment probes. Ten of the cases contained reiterated sequences (EBV BamHI-H, -B1*, -K fragments), showing that only one genotype was detected in each specimen. One of these had a BamHI fragment containing a fused sequence of BamHI-Y and -H. In all except one case, a single-sized EBV-joined terminus was observed in each NPC specimen, implying evolution of the carcinoma from a single EBV-infected cell. One metastatic lymph node (which was not a primary epipharyngeal tumor) contained EBV with heterogeneous termini suggesting production of linear virion DNA. The type C variant resulting from loss of a BamHI site between the BamHI-W1* and -I1* regions was observed in 7 of the 10 cases, and the other 3 cases had a separated BamHI-I1* fragment. As reported by Lung et al. (Virology, 177: 44-53, 1990), the type C variant appears to be dominant among Japanese strains, as it is in Southern China. In contrast to their findings, however, the "f" variant with an extra BamHI site in the BamHI-F region which they found to be strongly associated with NPC specimens from Southern China, was detected in only one case. The present study, therefore, did not support the specific association of the "f" variant with NPC in Japanese patients. We conclude that the EBV in NPC tissues exists in variants. Further studies along these lines, could help to explain the epidemiology of EBV.