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Epstein-Barr virus (EBV)-associated post-transplant lymphoproliferative disease (PTLD) is a life-threatening complication of T-lymphocyte deplete allogeneic hematopoietic stem cell transplantation (allo-HSCT). For patients with PTLD refractory to Rituximab, donor lymphocyte infusion (DLI) is established as a successful option for salvage therapy. However, although in vivo lymphocyte expansion has been correlated with good clinical outcome following DLI, the specificity and functional characteristics of EBV-specific T-cell responses remain poorly characterized. Here we describe two patients with Rituximab-refractory PTLD complicating T-cell deplete allo-HSCT, both of whom were successfully rescued with 1 × 10 6 /Kg unselected stem cell donor-derived DLI. Prospective analyses revealed that complete clinical and radiological responses were associated with in vivo expansion of T and NK cells. Furthermore, EBV MHC tetramer, and interferon gamma analyses revealed a marked increase in EBV-specific T-cell frequency from 4 weeks after DLI. Reactivity was demonstrated against a range of EBV latent and lytic antigens, including those detected in tumor biopsy material. The immunodominant EBV-specific T cell response expanding in vivo following infusion matched the dominant response present in the DLI preparations prior to administration. Furthermore, differences in the repertoire of subdominant antigen-specific T-cells were also detected, suggesting that antigen-encounter in vivo can shape the immune response. These results demonstrate the value of prospectively studying in vivo T-cell responses, by facilitating the identification of important specificities required for clinical efficacy. Applying this approach on a larger scale promises to yield data which may be essential for the optimization of future adoptive immunotherapeutic strategies for PTLD., (Copyright © 2019 Burns, Ryan, Harvey, Nagy, Hughes, Murray, Russell, Fox and Long.)

Although a pathogenic role for the Epstein-Barr virus (EBV) is largely undisputed for tumors that are consistently EBV genome positive (eg, nasopharyngeal carcinoma, endemic Burkitt lymphoma), this is not the case for classical Hodgkin lymphoma (cHL), a tumor with only a variable EBV association. In light of recent developments in immunotherapeutics and small molecules targeting EBV, we believe it is now timely to reevaluate the role of EBV in cHL pathogenesis., (© 2019 by The American Society of Hematology.)

The Epstein-Barr virus (EBV) is found almost exclusively in the activated B-cell (ABC) subtype of diffuse large B-cell lymphoma (DLBCL), yet its contribution to this tumour remains poorly understood. We have focused on the EBV-encoded latent membrane protein-1 (LMP1), a constitutively activated CD40 homologue expressed in almost all EBV-positive DLBCLs and which can disrupt germinal centre (GC) formation and drive lymphomagenesis in mice. Comparison of the transcriptional changes that follow LMP1 expression with those that follow transient CD40 signalling in human GC B cells enabled us to define pathogenic targets of LMP1 aberrantly expressed in ABC-DLBCL. These included the down-regulation of S1PR2, a sphingosine-1-phosphate (S1P) receptor that is transcriptionally down-regulated in ABC-DLBCL, and when genetically ablated leads to DLBCL in mice. Consistent with this, we found that LMP1-expressing primary ABC-DLBCLs were significantly more likely to lack S1PR2 expression than were LMP1-negative tumours. Furthermore, we showed that the down-regulation of S1PR2 by LMP1 drives a signalling loop leading to constitutive activation of the phosphatidylinositol-3-kinase (PI3-K) pathway. Finally, core LMP1-PI3-K targets were enriched for lymphoma-related transcription factors and genes associated with shorter overall survival in patients with ABC-DLBCL. Our data identify a novel function for LMP1 in aggressive DLBCL. Copyright © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd., (Copyright © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.)

It is more than 50 years since the Epstein-Barr virus (EBV), the first human tumour virus, was discovered. EBV has subsequently been found to be associated with a diverse range of tumours of both lymphoid and epithelial origin. Progress in the molecular analysis of EBV has revealed fundamental mechanisms of more general relevance to the oncogenic process. This Timeline article highlights key milestones in the 50-year history of EBV and discusses how this virus provides a paradigm for exploiting insights at the molecular level in the diagnosis, treatment and prevention of cancer.

Unlabelled: Epstein-Barr virus (EBV) infects most of the world's population and is causally associated with several human cancers, but little is known about how EBV genetic variation might influence infection or EBV-associated disease. There are currently no published wild-type EBV genome sequences from a healthy individual and very few genomes from EBV-associated diseases. We have sequenced 71 geographically distinct EBV strains from cell lines, multiple types of primary tumor, and blood samples and the first EBV genome from the saliva of a healthy carrier. We show that the established genome map of EBV accurately represents all strains sequenced, but novel deletions are present in a few isolates. We have increased the number of type 2 EBV genomes sequenced from one to 12 and establish that the type 1/type 2 classification is a major feature of EBV genome variation, defined almost exclusively by variation of EBNA2 and EBNA3 genes, but geographic variation is also present. Single nucleotide polymorphism (SNP) density varies substantially across all known open reading frames and is highest in latency-associated genes. Some T-cell epitope sequences in EBNA3 genes show extensive variation across strains, and we identify codons under positive selection, both important considerations for the development of vaccines and T-cell therapy. We also provide new evidence for recombination between strains, which provides a further mechanism for the generation of diversity. Our results provide the first global view of EBV sequence variation and demonstrate an effective method for sequencing large numbers of genomes to further understand the genetics of EBV infection., Importance: Most people in the world are infected by Epstein-Barr virus (EBV), and it causes several human diseases, which occur at very different rates in different parts of the world and are linked to host immune system variation. Natural variation in EBV DNA sequence may be important for normal infection and for causing disease. Here we used rapid, cost-effective sequencing to determine 71 new EBV sequences from different sample types and locations worldwide. We showed geographic variation in EBV genomes and identified the most variable parts of the genome. We identified protein sequences that seem to have been selected by the host immune system and detected variability in known immune epitopes. This gives the first overview of EBV genome variation, important for designing vaccines and immune therapy for EBV, and provides techniques to investigate relationships between viral sequence variation and EBV-associated diseases., (Copyright © 2015, Palser et al.)

Since the discovery in 1964 of the Epstein-Barr virus (EBV) in African Burkitt lymphoma, this virus has been associated with a remarkably diverse range of cancer types. Because EBV persists in the B cells of the asymptomatic host, it can easily be envisaged how it contributes to the development of B-cell lymphomas. However, EBV is also found in other cancers, including T-cell/natural killer cell lymphomas and several epithelial malignancies. Explaining the aetiological role of EBV is challenging, partly because the virus probably contributes differently to each tumour and partly because the available disease models cannot adequately recapitulate the subtle variations in the virus-host balance that exist between the different EBV-associated cancers. A further challenge is to identify the co-factors involved; because most persistently infected individuals will never develop an EBV-associated cancer, the virus cannot be working alone. This article will review what is known about the contribution of EBV to lymphoma development., (Copyright © 2014 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.)

The morphology of the pathognomonic Hodgkin and Reed-Sternberg cells (HRS) of Hodgkin lymphoma was described over a century ago, yet it was only relatively recently that the B-cell origin of these cells was identified. In a proportion of cases, HRS cells harbour monoclonal forms of the B lymphotropic Epstein-Barr virus (EBV). This review summarises current knowledge of the pathogenesis of Hodgkin lymphoma with a particular emphasis on the contribution of EBV.

Although Epstein-Barr virus (EBV) is present in the malignant Hodgkin/Reed-Sternberg (HRS) cells of a proportion of cases of classical Hodgkin lymphoma (cHL), how the virus contributes to the pathogenesis of this disease remains poorly defined. It is clear from the studies of other EBV-associated cancers that the virus is usually not sufficient for tumor development and that other oncogenic co-factors are required. This article reviews what is known about the contribution of EBV to the pathogenesis of cHL and focuses on emerging evidence implicating chronic inflammation as a potential oncogenic co-factor in this malignancy.

The relationship between Epstein-Barr virus (EBV) and the germinal centre (GC) of the asymptomatic host remains an enigma. The occasional appearance of EBV-positive germinal centres in some patients, particularly those with a history of immunosuppression, suggests that EBV numbers in the GC are subject to immune control. The relationship, if any, between lymphoid hyperplasia with EBV-positive germinal centres and subsequent or concurrent lymphomagenesis remains to be clarified. As far as the development of EBV-associated Hodgkin's lymphoma is concerned, the suppression of virus replication, mediated by LMP1 on the one hand, and the loss of B-cell receptor signalling on the other, appears to be an important pathogenic mechanism. A further important emerging concept is that alterations in the microenvironment of the EBV-infected B-cell may be important for lymphomagenesis., (© 2014 The Authors.)

The malignant Hodgkin and Reed-Sternberg (HRS) cells of Hodgkin lymphoma are surrounded by a tumor microenvironment that is composed of a variety of cell types, as well as noncellular components such as collagen. Although HRS cells harbor oncogenic Epstein-Barr virus (EBV) in approximately 50% of cases, it is not known if the tumor microenvironment contributes to EBV-driven lymphomagenesis. We show that expression of the EBV-encoded latent membrane protein-1 (LMP1) in primary human germinal center B cells, the presumed progenitors of HRS cells, upregulates discoidin domain receptor 1 (DDR1), a receptor tyrosine kinase activated by collagen. We also show that HRS cells intimately associated with collagen frequently overexpress DDR1 and that short-term exposure to collagen is sufficient to activate DDR1 in Hodgkin lymphoma-derived cell lines. The ectopic expression of DDR1 significantly increased the survival of collagen-treated DG75 Burkitt lymphoma cells, following etoposide treatment. Conversely, knockdown of DDR1 significantly decreased the survival of collagen-treated L428 Hodgkin lymphoma cells in the absence of specific apoptotic stimulus, suggesting that DDR1 also influences baseline survival. Our results identify a hitherto unknown function for collagen in protecting Hodgkin lymphoma cells from apoptosis and suggest an important contribution of the tumor microenvironment in promoting the oncogenic effects of EBV.

Hodgkin's lymphoma is unusual among B cell lymphomas, in so far as the malignant Hodgkin/Reed-Sternberg (HRS) cells lack a functional B cell receptor (BCR), as well as many of the required downstream signalling components. In Epstein-Barr virus (EBV)-positive cases of Hodgkin's lymphoma, HRS cells express the viral latent membrane proteins (LMP)-1 and -2A. LMP2A is thought to contribute to the pathogenesis of Hodgkin's lymphoma by providing a surrogate BCR-like survival signal. However, LMP2A has also been shown to induce the virus-replicative cycle in B cells, an event presumably incompatible with lymphomagenesis. In an attempt to resolve this apparent paradox, we compared the transcriptional changes observed in primary HRS cells with those induced by LMP2A and by BCR activation in primary human germinal centre (GC) B cells, the presumed progenitors of HRS cells. We found a subset of genes that were up-regulated by both LMP2A expression and BCR activation but which were down-regulated in primary HRS cells. These genes included EGR1, an immediate-early gene that is required for BCR-induced entry to the virus-replicative cycle. We present data supporting a model for the pathogenesis of EBV-positive Hodgkin's lymphoma in which LMP2A-expressing HRS cells lacking BCR signalling functions cannot induce EGR1 and are consequently protected from entry to the virus lytic cycle. The primary microarray data are available from GEO (http://www.ncbi.nlm.nih.gov/geo/) under series Accession No 46143., (Copyright © 2013 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.)

Epstein-Barr virus (EBV) is an oncogenic virus that is associated with the pathogenesis of several human lymphoid malignancies, including Hodgkin's lymphoma. Infection of normal resting B cells with EBV results in activation to lymphoblasts that are phenotypically similar to those generated by physiological stimulation with CD40L plus IL-4. One important difference is that infection leads to the establishment of permanently growing lymphoblastoid cell lines, whereas CD40L/IL-4 blasts have finite proliferation lifespans. To identify early events which might later determine why EBV infected blasts go on to establish transformed cell lines, we performed global transcriptome analyses on resting B cells and on EBV and CD40L/IL-4 blasts after 7 days culture. As anticipated there was considerable overlap in the transcriptomes of the two types of lymphoblasts when compared to the original resting B cells, reflecting common changes associated with lymphocyte activation and proliferation. Of interest to us was a subset of 255 genes that were differentially expressed between EBV and CD40L/IL-4 blasts. Genes which were more highly expressed in EBV blasts were substantially and significantly enriched for a set of interferon-stimulated genes which on further in silico analyses were found to be repressed by IL-4 in other cell contexts and to be up-regulated in micro-dissected malignant cells from Hodgkin's lymphoma biopsies when compared to their normal germinal center cell counterparts. We hypothesized that EBV and IL-4 were targeting and discordantly regulating a common set of genes. This was supported experimentally in our B cell model where IL-4 stimulation partially reversed transcriptional changes which follow EBV infection and it impaired the efficiency of EBV-induced B cell transformation. Taken together, these data suggest that the discordant regulation of interferon and IL-4 pathway genes by EBV that occurs early following infection of B cells has relevance to the development or maintenance of an EBV-associated malignancy.

Epstein-Barr virus (EBV) persistently infects more than 90% of the human population and is etiologically linked to several B cell malignancies, including Burkitt lymphoma (BL), Hodgkin lymphoma (HL), and diffuse large B cell lymphoma (DLBCL). Despite its growth transforming properties, most immune-competent individuals control EBV infection throughout their lives. EBV encodes various oncogenes, and of the 6 latency-associated EBV-encoded nuclear antigens, only EBNA3B is completely dispensable for B cell transformation in vitro. Here, we report that infection with EBV lacking EBNA3B leads to aggressive, immune-evading monomorphic DLBCL-like tumors in NOD/SCID/γc-/- mice with reconstituted human immune system components. Infection with EBNA3B-knockout EBV (EBNA3BKO) induced expansion of EBV-specific T cells that failed to infiltrate the tumors. EBNA3BKO-infected B cells expanded more rapidly and secreted less T cell-chemoattractant CXCL10, reducing T cell recruitment in vitro and T cell-mediated killing in vivo. B cell lines from 2 EBV-positive human lymphomas encoding truncated EBNA3B exhibited gene expression profiles and phenotypic characteristics similar to those of tumor-derived lines from the humanized mice, including reduced CXCL10 secretion. Screening EBV-positive DLBCL, HL, and BL human samples identified additional EBNA3B mutations. Thus, EBNA3B is a virus-encoded tumor suppressor whose inactivation promotes immune evasion and virus-driven lymphomagenesis.

Although Epstein-Barr virus (EBV) usually establishes an asymptomatic lifelong infection, it is also implicated in the development of germinal center (GC) B-cell-derived malignancies, including Hodgkin's lymphoma (HL). Following primary infection, EBV remains latent in the memory B-cell population, where host-driven methylation of viral DNA contributes to the repression of viral gene expression. However, it is still unclear how EBV harnesses the cell's methylation machinery in B cells, how this contributes to viral persistence, and what impact this has on the methylation of cellular genes. We show that EBV infection of GC B cells is followed by upregulation of the DNA methyltransferase DNMT3A and downregulation of DNMT3B and DNMT1. We show that the EBV latent membrane protein 1 (LMP1) oncogene downregulates DNMT1 and that DNMT3A binds to the viral promoter Wp. Genome-wide promoter arrays performed with these cells showed that EBV-associated methylation changes in cellular genes were not randomly distributed across the genome but clustered at chromosomal locations, consistent with an instructive pattern of methylation, and were in part determined by promoter CpG content. Both DNMT3B and DNMT1 were downregulated and DNMT3A was upregulated in HL cell lines, recapitulating the pattern of expression observed following EBV infection of GC B cells. We also found, by using gene expression profiling, that genes differentially expressed following EBV infection of GC B cells were significantly enriched for those reported to be differentially expressed in HL. These observations suggest that EBV-infected GC B cells are a useful model for studying virus-associated changes contributing to the pathogenesis of HL.

We have performed the first extensive profiling of Epstein-Barr virus (EBV) miRNAs on in vivo derived normal and neoplastic infected tissues. We describe a unique pattern of viral miRNA expression by normal infected cells in vivo expressing restricted viral latency programs (germinal center: Latency II and memory B: Latency I/0). This includes the complete absence of 15 of the 34 miRNAs profiled. These consist of 12 BART miRNAs (including approximately half of Cluster 2) and 3 of the 4 BHRF1 miRNAs. All but 2 of these absent miRNAs become expressed during EBV driven growth (Latency III). Furthermore, EBV driven growth is accompanied by a 5-10 fold down regulation in the level of the BART miRNAs expressed in germinal center and memory B cells. Therefore, Latency III also expresses a unique pattern of viral miRNAs. We refer to the miRNAs that are specifically expressed in EBV driven growth as the Latency III associated miRNAs. In EBV associated tumors that employ Latency I or II (Burkitt's lymphoma, Hodgkin's disease, nasopharyngeal carcinoma and gastric carcinoma), the Latency III associated BART but not BHRF1 miRNAs are up regulated. Thus BART miRNA expression is deregulated in the EBV associated tumors. This is the first demonstration that Latency III specific genes (the Latency III associated BARTs) can be expressed in these tumors. The EBV associated tumors demonstrate very similar patterns of miRNA expression yet were readily distinguished when the expression data were analyzed either by heat-map/clustering or principal component analysis. Systematic analysis revealed that the information distinguishing the tumor types was redundant and distributed across all the miRNAs. This resembles "secret sharing" algorithms where information can be distributed among a large number of recipients in such a way that any combination of a small number of recipients is able to understand the message. Biologically, this may be a consequence of functional redundancy between the miRNAs.

An important pathogenic event in Epstein-Barr virus (EBV)-associated lymphomas is the suppression of virus replication, which would otherwise lead to cell death. Because virus replication in B cells is intimately linked to their differentiation toward plasma cells, we asked whether the physiologic signals that drive normal B-cell differentiation are absent in EBV-transformed cells. We focused on BLIMP1α, a transcription factor that is required for plasma cell differentiation and that is inactivated in diffuse large B-cell lymphomas. We show that BLIMP1α expression is down-regulated after EBV infection of primary germinal center B cells and that the EBV oncogene, latent membrane protein-1 (LMP-1), is alone capable of inducing this down-regulation in these cells. Furthermore, the down-regulation of BLIMP1α by LMP-1 was accompanied by a partial disruption of the BLIMP1α transcriptional program, including the aberrant induction of MYC, the repression of which is required for terminal differentiation. Finally, we show that the ectopic expression of BLIMP1α in EBV-transformed cells can induce the viral lytic cycle. Our results suggest that LMP-1 expression in progenitor germinal center B cells could contribute to the pathogenesis of EBV-associated lymphomas by down-regulating BLIMP1α, in turn preventing plasma cell differentiation and induction of the viral lytic cycle.

The Epstein-Barr virus (EBV) is a lymphotropic herpes virus with oncogenetic properties which can lead to the development of lymphomas such as Burkitt's lymphoma (BL), Hodgkin's lymphoma (HL), or post-transplant lymphoma. This review discusses our current understanding of lymphomagenesis in relation to EBV and the potential for targeted therapies., (2010 Elsevier Ltd. All rights reserved.)

The Epstein-Barr virus (EBV) contributes to the growth and survival of Hodgkin lymphoma (HL) cells. Here we report that down-regulation of the transforming growth factor-beta (TGF-beta) target gene, protein tyrosine phosphatase receptor kappa (PTPRK), followed EBV infection of HL cells and was also more frequently observed in the Hodgkin and Reed-Sternberg (HRS) cells of EBV-positive compared with EBV-negative primary HL. The viability and proliferation of EBV-positive HL cells was decreased by overexpression of PTPRK, but increased following the knockdown of PTPRK expression in EBV-negative HL cells, demonstrating that PTPRK is a functional tumor suppressor in HL. EBV suppressed the TGF-beta-mediated activation of PTPRK expression, suggesting disruption of TGF-beta signaling upstream of PTPRK. This was confirmed when we showed that the Epstein-Barr nuclear antigen-1 (EBNA1) decreased Smad2 protein levels and that this was responsible for PTPRK down-regulation. EBNA1 decreased the half-life of Smad2 but did not interact with Smad2. By down-regulating Smad2 protein expression, EBNA1 apparently disables TGF-beta signaling, which subsequently decreases transcription of the PTPRK tumor suppressor. We speculate that loss of the phosphatase function of PTPRK may activate as-yet-unidentified growth-promoting protein tyrosine kinases, which in turn contribute to the pathogenesis of EBV-positive HL.

Polycomb group (PcG) proteins are chromatin modifiers that are necessary for the maintenance and renewal of embryonic and adult stem cells. However, overexpression of the PcG protein, Bmi-1, causes lymphoma in transgenic mice. We show that Bmi-1 is up-regulated in Hodgkin lymphoma (HL) cells by the Epstein-Barr virus (EBV) oncogene latent membrane protein-1 (LMP1) and that this up-regulation is mediated by NF-kappaB signaling. We also show that Bmi-1 is up-regulated by NF-kappaB in EBV-negative HL cells. Down-regulation of LMP1 and Bmi-1 decreased the survival of HL cells, suggesting that Bmi-1 may mediate the prosurvival effects of LMP1-induced NF-kappaB signaling in HL cells. Transcriptional targets of Bmi-1 were identified after its knockdown in an HL cell line. We show here that Bmi-1 and LMP1 down-regulate the ataxia telangiectasia-mutated (ATM) tumor suppressor and conclude that Bmi-1 contributes to LMP1-induced oncogenesis in HL.

Epstein-Barr virus (EBV) is a B-lymphotropic virus that is associated with a range of human malignancies. Although for many of these tumors the association has long been established, unraveling the precise role of EBV in disease pathogenesis has been more difficult. This review summarizes current knowledge concerning the association between EBV and human cancers, and illustrates how a deeper insight into viral latent gene expression, regulation and functions in different cell environments is already helping towards a better understanding of both the natural history of infection in normal individuals and how EBV contributes to malignant transformation. Finally, therapeutic strategies targeting EBV in tumors are discussed.

A proportion of patients with Hodgkin lymphoma carry Epstein-Barr virus (EBV), an oncogenic herpesvirus, in their tumor cells. Although it is generally assumed that EBV contributes to the malignant phenotype of Hodgkin lymphoma cells, direct evidence in support of this is lacking. Here we show that EBV infection of Hodgkin lymphoma cells results in the induction of autotaxin, a secreted tumor-associated factor with lysophospholipase-D activity. Up-regulation of autotaxin increased the generation of lysophosphatidic acid (LPA) and led to the enhanced growth and survival of Hodgkin lymphoma cells, whereas specific down-regulation of autotaxin decreased LPA levels and reduced cell growth and viability. In lymphoma tissues, autotaxin expression was mainly restricted to CD30+ anaplastic large-cell lymphomas and Hodgkin lymphoma; in the latter, high levels of autotaxin were strongly associated with EBV positivity (P = .006). Our results identify the induction of autotaxin and the subsequent generation of LPA as key molecular events that mediate the EBV-induced growth and survival of Hodgkin lymphoma cells and suggest that this pathway may provide opportunities for novel therapeutic intervention.

Background: The natural history of Epstein-Barr virus (EBV) infection is poorly defined. We report the prevalence and subsequent incidence of EBV infection in a cohort of sexually active young women and explore the social and sexual determinants of incident infections., Methods: The study population was drawn from a cohort of young women, who were recruited for a longitudinal study of risk factors for early cervical neoplasia. A case-control analysis, nested within the cohort of 45 women for whom the first EBV sample tested was EBV-negative and who had further follow-up, was undertaken. EBV serostatus was determined in serum with a synthetic peptide-based enzyme-linked immunosorbent assay; EBV DNA was measured in cervical smears with the use of quantitative polymerase chain reaction., Results: Of 1023 women 15-19 years of age included in this analysis, 978 (95.6%) tested positive for antibodies to EBV in their first serum sample. Of 45 women who tested negative, 22 subsequently acquired an asymptomatic EBV infection; the median time to seroconversion was 25 months (range, 1-60 months), and the median age at seroconversion was 18 years (range, 16-21 years). The risk of seroconversion increased with increasing number of sexual partners [compared with 1 partner, odds ratio (OR) was 1.28 for 2 partners and 2.23 for 3 or more; chiTREND 5.02; df 1; P < 0.05] and was greatest when a new sexual partner had been acquired in the 2 years before seroconversion (OR 4.78; chi 4.62; df 1; P < 0.05). EBV DNA was detected in 9 of 14 women who seroconverted and who also provided cervical samples., Conclusions: In susceptible young women, the acquisition of EBV infection is associated with their sexual behavior.

Evidence implicates Epstein-Barr virus (EBV) in the pathogenesis of tumours arising in lymphoid or epithelial tissue. EBV may adopt different forms of latent infection in different tumour types, reflecting the complex interplay between virus and host-cell environment. Immune response is another important factor influencing EBV gene expression, and viral latent proteins to which immunodominant CTL responses are directed (namely the EBNA3 family), are downregulated in virus-associated tumours arising in overtly immunocompetent individuals. Understanding the functions of EBV latent proteins will improve our knowledge of the role of the virus in transformation, and may help to identify novel therapies.

Epstein-Barr virus (EBV) is a ubiquitous human herpesvirus associated with the development of both lymphoid and epithelial tumours. As a common virus infection, EBV appears to have evolved to exploit the process of B cell development to persist as a life-long asymptomatic infection. However, the virus can contribute to oncogenesis as evidenced by its frequent detection in certain tumours, namely Burkitt's lymphoma (BL), post-transplant B cell lymphomas, Hodgkin's disease (HD) and nasopharyngeal carcinoma (NPC), and by its unique ability to efficiently transform resting B cells in vitro into permanently growing lymphoblastoid cell lines (LCLs). These transforming effects are associated with the restricted expression of EBV genes such that only a subset of so-called latent virus proteins are expressed in virus infected tumours and in LCLs. Distinct forms of EBV latency are manifest in the different tumours and these appear to be a vestige of the pattern of latent gene expression used by the virus during the establishment of persistent infection within the B cell pool. This review summarises our current knowledge of EBV latent gene function and how this relates to the role of the virus in the aetiology of different tumours.

The Epstein-Barr virus (EBV) has recently been associated with hepatocellular carcinoma (HCC) arising in Japanese patients. We analyzed 82 cases of HCC from Germany and the U.K. for the presence of EBV DNA and viral gene products within tumor cells. Initial screening of whole sections using quantitative (Q)-PCR detected EBV DNA in 9/58 U.K. cases and in 9/24 German cases; in positive cases viral load was very low, ranging between 1.4 and 49.1 copies of the EBV genome/1000 cell equivalents, compared to much higher values for EBV-positive Hodgkin's disease and nasopharyngeal carcinoma controls (range, 714-3259/1000 cells). EBV DNA was not detected in the tumor cells of any of the Q-PCR-positive cases either by Q-PCR of pure tumor cell populations isolated by laser capture microdissection or by isotopic in situ hybridization. Furthermore, none of the German or U.K. HCC tumors tested positive for EBER or EBNAI expression in tumor cells. Our results provide strong evidence that HCCs from the U.K. or Germany are not associated with EBV.

Background: Epstein-Barr virus (EBV)-associated post-transplant lymphoproliferative disease (PTLD) encompasses a histologically broad range of lesions, arising from the expanded pool of EBV-infected B cells in the immunocompromised host. Identification of the precise cellular origin of these tumours could clarify their pathogenesis., Methods: Of 13 cases of EBV-positive cases of PTLD characterised by histological analysis, pattern of EBV gene expression, and clinical course, 11 had monoclonal or biclonal lesions in which we determined the progenitor B cell by immunoglobulin heavy chain (IgH) genotyping., Results: Two tumours had a naive B cell genotype and two showed patterns of IgH somatic mutation typical of antigen-selected (post-germinal-centre) memory cells. All four arose early post-transplant and expressed the markers of EBV transformation--Epstein-Barr nuclear antigen (EBNA) 2 and latent membrane protein (LMP) 1. However, seven tumours, either of early or late onset and including some with downregulated EBNA 2 and LMP 1, arose from post-germinal cells with randomly mutated or sterile IgH genotypes usually incompatible with B-cell survival in vivo., Interpretation: PTLD can arise from a broad range of target B cells and not only from the pool of antigen-selected memory cells that EBV generally colonises in immunocompetent individuals. Tumour development seems frequently associated with the EBV-induced rescue and expansion of B cells that have failed the physiological process of germinal centre selection into memory. This finding shows an unexpected connection between pathogenesis of PTLD and that of EBV-positive Hodgkin's lymphoma, another B-cell malignancy of atypical post-germinal-centre cell origin.

The oncogenic Epstein-Barr virus (EBV)-encoded latent infection membrane protein 1 (LMP1) mimics a constitutive active tumor necrosis factor (TNF) family receptor in its ability to recruit TNF receptor-associated factors (TRAFs) and TNF receptor-associated death domain protein (TRADD) in a ligand-independent manner. As a result, LMP1 constitutively engages signaling pathways, such as the JNK and p38 mitogen-activated protein kinases (MAPK), the transcription factor NF-kappaB, and the JAK/STAT cascade, and these activities may explain many of its pleiotropic effects on cell phenotype, growth, and transformation. In this study we demonstrate the ability of the TRAF-binding domain of LMP1 to signal on the JNK/AP-1 axis in a cell type- dependent manner that critically involves TRAF1 and TRAF2. Thus, expression of this LMP1 domain in TRAF1-positive lymphoma cells promotes significant JNK activation, which is blocked by dominant-negative TRAF2 but not TRAF5. However, TRAF1 is absent in many established epithelial cell lines and primary nasopharyngeal carcinoma (NPC) biopsy specimens. In these cells, JNK activation by the TRAF-binding domain of LMP1 depends on the reconstitution of TRAF1 expression. The critical role of TRAF1 in the regulation of TRAF2-dependent JNK signaling is particular to the TRAF-binding domain of LMP1, since a homologous region in the cytoplasmic tail of CD40 or the TRADD-interacting domain of LMP1 signal on the JNK axis independently of TRAF1 status. These data further dissect the signaling components used by LMP1 and identify a novel role for TRAF1 as a modulator of oncogenic signals.