Geographic sequence variation of latent membrane protein 1 gene of Epstein-Barr virus in Hodgkin's lymphomas.

To assess the role of the Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1) gene in the development of Hodgkin´s lymphoma (HL), the polymorphism of this gene in EBV isolates from different geographic locations was analyzed. A 497 bp fragment spanning LMP1 gene exons 1 and 2 was amplified by polymerase chain reaction (PCR), using a primer pair bracketing a Xhol restriction site. PCR products were subjected to Xhol digestion and to DNA sequencing analysis. Twenty-five HL biopsy specimens from the United States and five HL and four non-Hodgkin´s lymphoma (NHL) biopsy specimens from Italy were examined. Eighty percent of LMP1-positive samples (12 of 15) from the United States maintained the Xhol restriction site and the remaining 20% partially lost the Xhol site. One of four EBV-positive HL and one of the three EBV-positive NHL specimens from Italy lost the restriction site. The other three EBV-positive HL DNAs were partially cut by Xhol. Direct DNA sequencing analysis revealed that those Italian samples not digested by Xhol were due to a G to C transversion at the first base of codon 18, resulting in the change of glycine to arginine. Those DNA samples partially cut by Xhol were due to a mixture of G/C at the same location. In contrast, those partially digested American HL DNAs had a mixture of GTT at the second base of codon 17. The sequence variation found in the Italian samples differs from that of Asian EBV strains, in which G to T transversion was detected at codon 17, resulting in the substitution of arginine by leucine. Among the 72% (18 of 25) EBV-positive American HL samples, 67% (12 of 18) were associated with type A virus, 17% (3 of 18) with type B, and 17% (3 of 18) with dual viral sequences. EBV DNA was detected in 80% (four of five) of Italian HL biopsy specimens, in which 50% (two of four) were associated with type A and 50% (two of four) with type B. Despite these sequence variations at the Xhol recognition site between EBV isolates of different geographic locations, no direct correlation with a specific genotype was observed. These results, to our knowledge, represent the first observation of a specific point mutation at codon 18 of LMP1 gene associated with a particular geographic location. It appears that the Xhol polymorphism may be a useful molecular marker for epidemiologic study, and the alteration in the LMP1 gene may have functional significance in the development of HL in certain geographic areas.