Molecular analysis of the Epstein-Barr virus LMP1 in Hodgkin lymphoma from Argentina and Brazil: Identification of a distinct LMP1 deleted variant

Abstract

21099 Background: Epstein Barr virus (EBV), a human oncogenic virus, has two types, EBV1 and 2, and several polymorphic markers allow individual variants to be distinguished. Variations in EBV latent membrane protein 1 (LMP1) gene could define a more oncogenic strain or reflect geographic EBV origin. By sequence analysis of C-ter, N-ter and promoter (prom) regions, 4 distinct EBV groups (A to D) have been defined. Aim: To analyze LMP1 molecular variability of two different groups of Hodgkin`s lymphoma (HL) from the same geographic area. Methods: EBV association by EBERs in situ hibridization and LMP1 immunohistochemistry was analyzed in 27 HL from Argentina (Arg) and 36 HL from Brazil (Br). EBV type was assessed by EBNA PCR. C-ter LMP1 PCR was done in all cases. Sequencing of C-ter, N-ter and prom regions was done in 16 patients. Results: 21/27 (78%) Arg HL and 31/36 (86%) Br HL were EBV1, while 6/27 (22%) and 4/36 (11%) were EBV2, respectively (p= 0.29). Coinfection was observed in 1 (3%) Br HL. LMP1 deleted (del) variant was observed in 20/27 (74%) Arg HL and 20/36 (55%) Br HL (p= 0.18), as well as in non-neoplastic controls, 4/11 and 3/10 (36 and 30%) from Arg and Br respectively. Most LMP1 del displayed high number (5–7) of 33bp repeats (86% LMP1 del Br HL and 77% LMP1 del Arg HL) compared with LMP1 wt that exhibited low number (3–4) 33bp repeats (68% LMP1 wt Br HL and 100% LMP1 wt Arg HL). Analysis of LMP1 sequences showed that: LMP1 wt C-ter regions had unmutated N-ter and prom as B95.8, A and B groups (31%), except for a case showing new mutations. LMP1 del C-ter regions showed molecular identity with C group, but they showed new, undescribed mutations in prom and N-ter (63%). Conclusions: We found high frequency of LMP1 del variants in HL from Argentina and Brazil, which was associated with high number of 33bp repeats in C-ter region. This suggests a role for this variant in lymphomagenesis. A new molecular variant with characteristic promoter and N-ter mutations was identified in LMP1 del cases, which could be proposed as a regional South American variant. No significant financial relationships to disclose.