Prevalence of Epstein-Barr viral sequences and EBV LMP1 oncogene deletions in Burkitt's lymphoma from Pakistan: epidemiological correlations.

To investigate the potential relationship of socioeconomic status with the prevalence of Epstein-Barr virus (EBV) and to understand the significance of del-LMP-1 within EBV+ cases of Burkitt's lymphoma (BL), we studied 10 cases of BL, 30 cases of diffuse large cell lymphoma (DLCL) arising in nonimmunocompromised patients, and 30 reactive tonsillar biopsy specimens from Pakistan. Each lymphoma was analyzed for EBV by EBER1 RNA in situ hybridization (EBV-RISH). Cases showing hybridization signal within neoplastic cells and all reactive tonsillar tissues were analyzed for EBV strain type by EBNA-2 polymerase chain reaction (PCR) and for the presence of a del-LMP-1 by PCR. Eight of 10 (80%) of BL were EBV+, each containing EBV strain A and a wild-type LMP-1 gene. In contrast, only 4 of 30 DLCL (13%) cases were EBV positive (three strain A, one strain B), each containing a wild-type LMP-1 gene. Fifteen of 30 tonsillar biopsy specimens contained EBV, all of which were strain A and wild-type for LMP1. The prevalence of EBV in BL from Pakistan is slightly lower than in BL in endemic regions, but significantly higher than in BL in North America. EBV positivity probably reflects the socioeconomic status of the patient population and age at seroconversion. The absence of del-LMP-1 within all EBV+ BL cases is consistent with the view that del-LMP-1 is not involved in the pathogenesis of BL, and the presence of del-LMP-1 in EBV+ cases of BL reported in other studies may likely reflect the prevalence of a viral strain containing the 30-bp deletion within the respective population studied.