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Abstract
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Depending on geographic location and patient age Hodgkin's disease (HD) is associated with Epstein-Barr virus (EBV), mostly type A EBV, in 20% to 100%. The highest prevalence occurs in children of developing countries. Molecular analysis of the oncogene coding for the latent membrane protein 1 (LMP-1) revealed a 30-base pair (bp) deletion in up to 46% of EBV-positive HD. We investigated the presence of EBV in a series of Mexican classical HD (n = 57) and reactive lymphoid tissues (n = 20) from a private and a public hospital with special emphasis on the prevalence of the 30-bp deletion and the type of EBV. EBV infection was analyzed at the cellular level by Epstein-Barr encoded early RNA transcripts (EBER) in situ hybridization (ISH) and by LMP-1 protein immunohistochemistry (IHC). Molecular analysis of the LMP-1 gene configuration was performed by polymerase chain reaction (PCR) with primers spanning the site of the deletion and subsequent Southern and/or dot blot hybridization using wild-type and deletion-specific probes. The prevalence of type A and type B EBV was investigated by PCR-analysis for divergence in the coding region of Epstein-Barr nuclear antigen (EBNA)-2. EBV was detected in Hodgkin- and Reed-Sternberg cells (H-RS) by LMP-1 IHC and/or EBER ISH in 35/57 (61%) Mexican HD including 18/32 (56%) with nodular sclerosis, 15/20 (75%) with mixed cellularity and 2/4 (50%) with lymphocyte depletion. In addition, LMP-1 gene sequences were detected by PCR in 9 cases of HD without LMP/EBER expression by H-RS cells and in 17/20 (85%) reactive lymph nodes, supposedly originating from rare latently infected B cells. Surprisingly, the 30-bp LMP-1 deletion was found in 28/35 (80%) EBV-positive HD. This deletion, however, was also found in all 9 (100%) HD with H-RS cells negative for EBV and in 10/17 (59%) reactive lymph nodes. Thus, the overall LMP-1 del prevalence in reactive tissue is 73% (19/26). Typing of EBV was successful in 26 cases of EBV-positive HD, 10 of these were infected by type B EBV (38%). Of the reactive lymphoid tissue, 9 (47%) were infected by type A, and 10 (53%) by type B; All 20 cases (100%) associated with type B, whether neoplastic or reactive, displayed the LMP-1 del variant compared with 18/25 (72%) infected by type A EBV. To our knowledge, this is the highest incidence for both the LMP-1 deletion variant and the infection by type B EBV in HD reported so far worldwide. Our data suggest that EBV infection contributes to the pathogenesis of the majority of Hodgkin's disease cases in Mexico. The specific tumorigenic role of the LMP-1 deletion variant, however, is doubtful with regard to its high frequency in nonneoplastic lesions. Moreover, type B infection frequently occurs in Mexican HD and reactive lymphoid tissue and is consistently associated with the deletion variant pointing to a pathogenetic role of this combined genotype. |
