Expression of Epstein-Barr Virus BamHI-A Rightward Transcripts in Latently Infected B Cells From Peripheral Blood

Epstein-Barr Virus BART Long Non-coding RNAs Function as Epigenetic Modulators in Nasopharyngeal Carcinoma

Epstein-Barr virus (EBV) establishes lifelong latent infection in humans and is associated with several lymphoid and epithelial cancers. In nasopharyngeal carcinoma (NPC), EBV expresses few viral proteins but elevated levels of Bam-HI A rightward transcripts (BARTs) RNA, which includes viral microRNAs and long non-coding RNAs (lncRNAs). BART lncRNAs localize within the nucleus of EBV-infected cells and knockdown of BART lncRNAs significantly affects the expression of genes associated with cell adhesion, oxidoreductase activity, inflammation, and immunity. Notably, downregulation of IKAROS family zinc finger 3 (IKZF3/Aiolos), which plays a role in lymphocyte development and cell attachment, occurred in NPC C666-1 cells following BART lncRNA-knockdown. Since Aiolos expression is normally restricted to lymphoid cells and rarely observed in epithelial cells, induction of Aiolos by BART lncRNA was confirmed by expressing the major BART lncRNA isoform, RPMS1, in EBV-positive and -negative cells. BART lncRNA associated with the CBP/p300 complex and RNA polymerase II (Pol II) in the nucleus, suggesting that BART lncRNAs may mediate epigenetic regulation of gene expression through interaction with the chromatin remodeling machinery. This contention is further supported by evidence that BART lncRNA appears to stall Pol II at the promoter region and may regulate IFNB1 and CXCL8 expression by inhibiting transcription by Pol II in NPC. We hypothesize that EBV BART lncRNA expression modulates host gene expression and maintains EBV latency by interfering with histone methylation and acetylation processes. Aberrant expression of affected host genes mediated by BART lncRNA may lead to immune evasion, progression, and metastasis of NPC.

Prophylactic and therapeutic strategies for Epstein-Barr virus-associated diseases: emerging strategies for clinical development

INTRODUCTION

Epstein-Barr virus (EBV) infects more than 95% of the world's population and is associated with infectious mononucleosis as well as a number of cancers in various geographical locations. Despite its significant health burden, no licenced prophylactic or therapeutic vaccines are available. Areas covered: Over the last two decades, our understanding of the role of EBV infection in the pathogenesis and immune regulation of EBV-associated diseases has provided new lines of research to conceptualize various novel prophylactic and therapeutic approaches to control EBV-associated disease. In this review, we evaluate the prophylactic and therapeutic vaccine approaches against EBV and various immunotherapeutic strategies against a number of EBV-associated malignancies. This review also describes the existing and future prospects of improved EBV-targeted therapeutic strategies. Expert opinion: It is anticipated that these emerging strategies will provide answers for the major challenges in EBV vaccine development and help improve the efficacy of novel therapeutic strategies.

Characterization of the subcellular localization of Epstein-Barr virus encoded proteins in live cells

Epstein-Barr virus (EBV) is the pathogenic factor of numerous human tumors, yet certain of its encoded proteins have not been studied. As a first step for functional identification, we presented the construction of a library of expression constructs for most of the EBV encoded proteins and an explicit subcellular localization map of 81 proteins encoded by EBV in mammalian cells. Viral open reading frames were fused with enhanced yellow fluorescent protein (EYFP) tag in eukaryotic expression plasmid then expressed in COS-7 live cells, and protein localizations were observed by fluorescence microscopy. As results, 34.57% (28 proteins) of all proteins showed pan-nuclear or subnuclear localization, 39.51% (32 proteins) exhibitted pan-cytoplasmic or subcytoplasmic localization, and 25.93% (21 proteins) were found in both the nucleus and cytoplasm. Interestingly, most envelope proteins presented pan-cytoplasmic or membranous localization, and most capsid proteins displayed enriched or complete localization in the nucleus, indicating that the subcellular localization of specific proteins are associated with their roles during viral replication. Taken together, the subcellular localization map of EBV proteins in live cells may lay the foundation for further illustrating the functions of EBV-encoded genes in human diseases especially in its relevant tumors.

Long-term Outcome of Extranodal NK/T Cell Lymphoma Patients Treated With Postremission Therapy Using EBV LMP1 and LMP2a-specific CTLs

Extranodal NK/T-cell lymphoma (ENKTCL) is associated with latent Epstein-Barr virus (EBV) infection and frequent relapse even after complete response (CR) to intensive chemotherapy and radiotherapy. The expression of EBV proteins in the tumor provides targets for adoptive immunotherapy with antigen-specific cytotoxic T cells (CTL). To evaluate the efficacy and safety of EBV latent membrane protein (LMP)-1 and LMP-2a-specific CTLs (LMP1/2a CTLs) stimulated with LMP1/2a RNA-transferred dendritic cells, we treated 10 ENKTCL patients who showed complete response to induction therapy. Patients who completed and responded to chemotherapy, radiotherapy, and/or high-dose therapy followed by stem cell transplantation (HDT/SCT) were eligible to receive eight doses of 2 × 10⁷ LMP1/2a CTLs/m². Following infusion, there were no immediate or delayed toxicities. The 4-year overall survival (OS) and progression-free survival (PFS) were 100%, and 90% (95% CI: 71.4 to 100%) respectively with a median follow-up of 55·5 months. Circulating IFN-γ secreting LMP1 and LMP2a-specific T cells within the peripheral blood corresponded with decline in plasma EBV DNA levels in patients. Adoptive transfer of LMP1/2a CTLs in ENKTCL patients is a safe and effective postremission therapeutic approach. Further randomized studies will be needed to define the role of EBV-CTLs in preventing relapse of ENKTCL.

BamHI-A rightward frame 1, an Epstein-Barr virus-encoded oncogene and immune modulator

Epstein–Barr virus (EBV) causes several benign and malignant disorders of lymphoid and epithelial origin. EBV-related tumors display distinct patterns of viral latent gene expression, of which the BamHI-A rightward frame 1 (BARF1) is selectively expressed in carcinomas, regulated by cellular differentiation factors including ΔNp63α. BARF1 functions as a viral oncogene, immortalizing and transforming epithelial cells of different origin by acting as a mitogenic growth factor, inducing cyclin-D expression, and up-regulating antiapoptotic Bcl-2, stimulating host cell growth and survival. In addition, secreted hexameric BARF1 has immune evasive properties, functionally corrupting macrophage colony stimulating factor, as supported by recent functional and structural data. Therefore, BARF1, an intracellular and secreted protein, not only has multiple pathogenic functions but also can function as a target for immune responses. Deciphering the role of BARF1 in EBV biology will contribute to novel diagnostic and treatment options for EBV-driven carcinomas. Herein, we discuss recent insights on the regulation of BARF1 expression and aspects of structure-function relating to its oncogenic and immune suppressive properties. © 2013 The Authors. Reviews in Medical Virology published by John Wiley & Sons, Ltd.

Diversity of Epstein-Barr virus BamHI-A rightward transcripts and their expression patterns in lytic and latent infections

Epstein-Barr virus (EBV) BamHI-A rightward transcripts (BARTs; also designated complementary strand transcripts or CSTs) have been demonstrated to contain several splicing forms in EBV-infected cells. To date, however, little is known about the actual full-length splicing form and its functions. In the present study, we proved that six forms of BARTs were present in EBV-positive cell lines and various tissue specimens with different EBV infection patterns. Of the BART-encoded genes, mRNA of four major splicing forms, including BARF0, RPMS1, RPMS1A and A73, were expressed in all EBV-infected cells. On the other hand, mRNA of two minor splicing forms, RK-BARF0 and RB3, was rarely detected, or if at all, at very low expression levels. Both RPMS1A and RPMS1 mRNA was transcribed at higher levels in EBV-infected cells. In particular, RPMS1 mRNA was expressed abundantly in epithelial carcinoma cells, including gastric carcinoma and nasopharyngeal carcinoma, in association with a lytic infection signal, BZLF1 mRNA. The four major splicing forms were expressed much less in B-cell lines with an integrated EBV genome than in those with episomal EBV genomes. These data indicate that at least six splicing forms can be expressed by EBV-infected cells or tissues, although the expression patterns or levels differ for different infection states such as lytic and latent infections.

Biogenesis of Epstein-Barr virus microRNAs

Epstein-Barr virus (EBV) is a ubiquitous human herpesvirus implicated in lymphomas, such as Burkitt's lymphoma, Hodgkin's lymphoma, and NK/T cell lymphoma. MicroRNAs (miRNAs) are 19-25 nucleotide long single-stranded RNAs involved in post-transcriptional gene regulation. miRNAs are mainly transcribed by RNA polymerase II (pol II) to have stem-loop structures and subsequently processed by Drosha and Dicer. EBV miRNAs are expressed in B cells, nasopharyngeal carcinoma cells, and gastric carcinoma cells infected with EBV. EBV miRNAs can be divided into two groups: BHRF1 miRNAs and BART miRNAs. In this study, we investigated the biogenesis of EBV miRNAs. Treatment of the SNU-719 EBV-positive gastric cancer cell line with α-amanitin at a concentration that selectively inhibits RNA polymerase II activity decreased the expression levels of BART miRNAs. The expression levels of BART miRNAs were also reduced by RNA interference targeting Drosha and Dicer. Two of each C/EBPβ and c-Myc binding sites are located upstream of the proposed initiation sites for primary BART miRNA transcripts. Knockdown of C/EBPβ but not c-Myc using siRNAs reduced BART miRNA expression by 25-55% compared with the control. These results suggest that BART miRNAs are transcribed by pol II and undergo a similar biogenesis process with cellular miRNAs.

The role of miRNAs and EBV BARTs in NPC

The BamHI A rightward transcripts are a set of alternatively splicing transcripts produced by Epstein-Barr Virus that are highly expressed in nasopharyngeal carcinoma. These transcripts contain several open reading frames as well as precursors for twenty-two miRNAs. Although the putative proteins corresponding to these open reading frames have not been detected, several studies have identified properties that are interesting and potentially significant with respect to cellular transformation. The miRNAs, however, are very abundant in all nasopharyngeal carcinomas and several potentially significant functions have been identified for some of the miRNAs. This article will focus on the nature of this complicated set of transcripts and the evidence that they contribute to the development of nasopharyngeal carcinoma.

Widespread sequence variation in the Epstein-Barr virus latent membrane protein 2A gene among northern Chinese isolates

Latent membrane protein 2A (LMP2A) is expressed in most Epstein-Barr virus (EBV)-associated malignancies. Besides its roles in the maintenance of latent infection and epithelial-cell transformation, LMP2A could also act as the target for a CTL-based therapy for EBV-associated malignancies. In the present study, sequence polymorphisms in LMP2A from northern Chinese EBV-associated gastric carcinoma patients, nasopharyngeal carcinoma patients and healthy donors were identified and compared with the prototype B95-8 strain. Four consistent mutations were detected in all isolates. Frequent mutations in the analysed sequences distinguished two and seven types of sequence variation in exon 1 and exons 2-8, respectively, with no consistent association shown between the genotyping of the two gene fragments. The immunoreceptor tyrosine-based activation motif and PY motif in the amino terminus were strictly conserved. Nine of the 16 identified CTL epitopes were affected by at least one point mutation, which may confer complexity to proposed immunotherapeutic approaches for EBV-associated malignancies. Most changed epitopes showed higher mutation rates in tumour isolates than in throat-washing samples from healthy donors, in accordance with the idea that virus strains can evade immune surveillance by altering amino acids within LMP epitopes. This first detailed investigation of sequence variations in the LMP2A gene reveals classifiable sequence polymorphisms in exon 1 and exons 2-8, and encourages further work on the impact of viral gene variations on tumour persistence and CTL-based immunotherapy.

Epstein-Barr virus BART gene expression

Introns from the Epstein-Barr virus (EBV) BART RNAs produce up to 20 micro RNAs (miRNAs) but the spliced exons of the BART RNAs have also been investigated as possible mRNAs, with the potential to express the RPMS1 and A73 proteins. Recombinant RPMS1 and A73 proteins were expressed in Escherichia coli and used to make new monoclonal antibodies that reacted specifically with artificially expressed RPMS1 and A73. These antibodies did not detect endogenous expression of A73 and RPMS1 proteins in a panel of EBV-infected cell lines representing the different known types of EBV infection. BART RNA could not be detected on Northern blots of cytoplasmic poly(A)(+) RNA from the C666.1 NPC cell line and BART RNA was found to be mainly in the nucleus of C666.1 cells, arguing against an mRNA role for BART RNAs. In contrast, some early lytic cycle EBV mRNAs were found to be expressed in C666.1 cells. Artificially expressed A73 protein was known to be able to bind to the cellular RACK1 protein and has now also been shown to be able to regulate calcium flux, presumably via RACK1. Overall, the results support the conclusion that the miRNAs are functionally important products of BART transcription in the cell lines studied because the A73 and RPMS1 proteins could not be detected in natural EBV infections. However, the possibility remains that A73 and RPMS1 might be expressed in some situations because of the clear potential relevance of their biochemical functions.

EBV-associated diseases in the AIDS patient

EBV-associated malignancies remain a considerable problem in HIV-infected individuals, even in the era of HAART. Although EBV is a common factor, each disease has a unique pathogenesis. Study of these diseases reveals the viral proteins expressed in the malignancies that might contribute to the development of the disease as well as the molecular basis for pathogenesis. It is likely that this knowledge will contribute to the development of novel therapeutics that will result in more favorable outcomes in the future.

Epstein-Barr virus microRNAs are evolutionarily conserved and differentially expressed

The pathogenic lymphocryptovirus Epstein–Barr virus (EBV) is shown to express at least 17 distinct microRNAs (miRNAs) in latently infected cells. These are arranged in two clusters: 14 miRNAs are located in the introns of the viral BART gene while three are located adjacent to BHRF1. The BART miRNAs are expressed at high levels in latently infected epithelial cells and at lower, albeit detectable, levels in B cells. In contrast to the tissue-specific expression pattern of the BART miRNAs, the BHRF1 miRNAs are found at high levels in B cells undergoing stage III latency but are essentially undetectable in B cells or epithelial cells undergoing stage I or II latency. Induction of lytic EBV replication was found to enhance the expression of many, but not all, of these viral miRNAs. Rhesus lymphocryptovirus, which is separated from EBV by ≥13 million years of evolution, expresses at least 16 distinct miRNAs, seven of which are closely related to EBV miRNAs. Thus, lymphocryptovirus miRNAs are under positive selection and are likely to play important roles in the viral life cycle. Moreover, the differential regulation of EBV miRNA expression implies distinct roles during infection of different human tissues.

Vertebrate cells express a large family of diverse small RNAs, called microRNAs, that can inhibit the expression of specific target genes. Recently, it has become apparent that several pathogenic human viruses, and in particular herpes viruses, also encode microRNAs that these viruses likely use to prevent infected cells and individuals from mounting effective antiviral responses. Here, we demonstrate that Epstein–Barr virus (EBV), which causes infectious mononucleosis and also some cancers in humans, makes 17 different microRNAs in infected human cells. These microRNAs are found in two clusters in the viral genome, one of three microRNAs, the second of 14 microRNAs, that are differentially expressed in different kinds of EBV-induced human tumors. Analysis of the closely related rhesus lymphocryptovirus shows that seven of these EBV microRNAs have been conserved in this simian virus across >13 million years of divergent evolution. This argues that these microRNAs likely play an important role in EBV replication and represents the first demonstration of the evolutionary conservation of viral microRNAs.

Establishment of a novel human B-CLL-like xenograft model in nude mouse

We have developed a novel murine model for B-CLL by engrafting human prolymphocytic leukemia (PLL) or B-CLL cell line cells (JVM-3 and MEC-2 cell lines, respectively) into nude mice. Not only treatment of the mice was a prerequisite for the success of the graft, but also for the first time, females appeared to accept the cells more easily than males. Surprisingly, tumoral murine models for B-CLL could be established with PLL cells but not with B-CLL cells. JVM-3 cells were efficiently transplanted into nude mice through subcutaneous or intravenous routes. Irradiated female mice appeared to be the optimal recipients for tumor growth. Such murine models for human B-CLL may help the development of therapeutic agents.

Epstein-Barr virus-encoded LMP2A regulates viral and cellular gene expression by modulation of the NF-kappaB transcription factor pathway

Epstein-Barr virus (EBV)-associated malignancies display distinct patterns of virus latent gene expression that reflect the complex interplay between the virus and its host cell. In the EBV-associated epithelial tumor nasopharyngeal carcinoma (NPC), the virus-encoded latent membrane protein LMP2A is consistently expressed whereas the oncogenic LMP1 protein appears to be restricted to only a proportion of tumors. In an attempt to understand the contribution of LMP2A to the pathogenesis of NPC, we established carcinoma cell lines stably infected in vitro with either a wild-type recombinant EBV (rEBV) or a mutant rEBV in which LMP2A is deleted (rEBV-2A). An NPC-like pattern of EBV gene expression including LMP2A but not LMP1 was consistently observed in carcinoma cells infected with rEBV. However, carcinoma cells infected with rEBV-2A expressed high levels of LMP1 from the signal transducer and activator of transcription (STAT)-regulated L1-TR promoter. Consistent with this effect, basal STAT activity was reduced in rEBV-infected carcinoma cells, and this repression was relieved in the absence of LMP2A. This modulation of STAT activity correlated with the ability of LMP2A to inhibit the autocrine secretion of IL-6 from carcinoma cell lines. Exogenous IL-6 was able to induce expression of LMP1 by means of STAT3 activation both in rEBV-infected carcinoma cell lines and in the EBV-positive C666-1 NPC cell line. The LMP2A-mediated suppression of IL-6 was a consequence of NF-kappaB inhibition. These data reveal that LMP2A modulates two key transcription factor pathways in carcinoma cells and suggest that this finding may be important in the pathogenesis of EBV-associated tumors.

Epstein-Barr virus: 40 years on

Epstein-Barr virus (EBV) was discovered 40 years ago from examining electron micrographs of cells cultured from Burkitt's lymphoma, a childhood tumour that is common in sub-Saharan Africa, where its unusual geographical distribution - which matches that of holoendemic malaria -indicated a viral aetiology. However, far from showing a restricted distribution, EBV - a gamma-herpesvirus - was found to be widespread in all human populations and to persist in the vast majority of individuals as a lifelong, asymptomatic infection of the B-lymphocyte pool. Despite such ubiquity, the link between EBV and 'endemic' Burkitt's lymphoma proved consistent and became the first of an unexpectedly wide range of associations discovered between this virus and tumours.

Viral interactions with the Notch pathway

The Notch signaling pathway influences cell fate decisions, proliferation versus differentiation and cell survival. Viruses both utilize and manipulate the differentiation state of infected cells, promote or block cell cycling and employ a variety of mechanisms to evade innate cellular anti-viral responses and promote cell survival. In light of these commonalities, it is perhaps not surprising that several viruses have tapped into the Notch pathway to advance their own life cycles. This first became apparent from studies showing targeting of Epstein-Barr virus proteins to the nuclear effector of Notch signaling CSL (CBF1/RBPJk). More recently the Kaposi's sarcoma-associated herpesvirus RTA protein has been found to bind CSL. Notch pathway interactions have also been described for adenovirus SV40 and human papilloma virus. This review focuses on the herpesvirus protein interactions with the Notch pathway and the insights that these interactions have provided.

Epstein-Barr virus (EBV) LMP2A alters normal transcriptional regulation following B-cell receptor activation

The latent membrane protein 2A (LMP2A) of Epstein-Barr virus (EBV) is an important mediator of viral latency in infected B-lymphocytes. LMP2A inhibits B-cell receptor (BCR) signaling in vitro and allows for the survival of BCR-negative B cells in vivo. In this study, we compared gene transcription in BCR-activated B cells from non-transgenic and LMP2A Tg6 transgenic mice. We found that the transcriptional induction and down-regulation of many genes that normally occurs in B cells following BCR activation did not occur in B cells from LMP2A Tg6 transgenic mice. Furthermore, LMP2A induced the expression of various transcription factors and genes associated with DNA/RNA metabolism, which may allow for the altered transcriptional regulation observed in BCR-activated B cells from LMP2A Tg6 mice. These results suggest that LMP2A may inhibit the downstream effects of BCR signaling by directly or indirectly altering gene transcription to ensure EBV persistence in infected B cells.

Epstein-Barr virus latent membrane 2A (LMP2A) down-regulates telomerase reverse transcriptase (hTERT) in epithelial cell lines

The latent membrane protein (LMP) 2A, one of the membrane-spanning polypeptides encoded by the Epstein-Barr virus (EBV), has been implicated in the maintenance of viral latency and appears to function in part by inhibiting B-cell receptor (BCR) signaling through its ITAM motifs. It has also been suggested that LMP2A is involved in tumorigenesis mediated by EBV. In our study, we determined regulatory effects of LMP2A on the telomerase reverse transcriptase (hTERT) expression. We observed a significant and constant reduction of hTERT mRNA accompanied by decreased telomerase activity in epithelial cells expressing LMP2A. It was further shown that LMP2A inhibited the hTERT promoter activity in transient transfections of both B cells and epithelial cells, and that the ITAM motif was required for this inhibition. Thus LMP2A expression leads to the transcriptional repression of the hTERT gene through specific pathways, which may thereby contribute to the control of EBV-latency.

Epstein-Barr Virus (EBV) LMP2A induces alterations in gene transcription similar to those observed in Reed-Sternberg cells of Hodgkin lymphoma

Epstein-Barr virus (EBV) is associated with the development of a variety of malignancies, including Hodgkin lymphoma. One of the few viral transcripts expressed in EBV-positive Hodgkin/Reed-Sternberg (HRS) cells of Hodgkin lymphoma is latent membrane protein 2A (LMP2A). This viral protein blocks B-cell receptor (BCR)-signaling in vitro. Furthermore, expression of LMP2A in developing B cells in vivo induces a global down-regulation of genes necessary for proper B-cell development. In this study we have analyzed gene transcription in primary B cells from LMP2A transgenic mice, LMP2A-expressing human B-cell lines, and LMP2A-positive and -negative EBV-infected lymphoblastoid cell lines (LCLs). We demonstrate that LMP2A increases the expression of genes associated with cell cycle induction and inhibition of apoptosis, alters the expression of genes involved in DNA and RNA metabolism, and decreases the expression of B-cell-specific factors and genes associated with immunity. Furthermore, many alterations in gene expression induced by LMP2A are similar to those recently described in HRS cells of Hodgkin lymphoma and activated, proliferating germinal center centroblasts/centrocytes. These correlations suggest that LMP2A expression in EBV-infected B cells may lead to the induction and maintenance of an activated, proliferative state that could ultimately result in the development of Hodgkin lymphoma.

In vivo transcription of the Epstein–Barr virus (EBV) BamHI-A region without associated in vivo BARF0 protein expression in multiple EBV-associated disorders

The in vivo expression of the Epstein–Barr virus (EBV) BamHI-A rightward transcripts (BARTs) as well as the putative BART-encoded BARF0 and RK-BARF0 proteins in various EBV-associated malignancies was investigated. RT-PCRs specific for the different splice variants of the BARTs and both a nucleic acid sequence-based amplification assay and an RT-PCR specific for the BARF0 ORF were used. Abundant transcription of BARTs was found in EBV-associated Hodgkin's lymphomas, Burkitt's lymphomas (BL), T-cell non-Hodgkin's lymphomas, post-transplant lymphoproliferative disorders, AIDS-related lymphomas and gastric carcinomas. Using RNA in situ hybridization (RISH), BARTs were detected within the neoplastic cells of these malignancies. BARTs encoding RK-BARF0 were not detected. The BARTs detected were shown possibly to encode the RPMS1 and BARF0 proteins, based on their splicing. However, BARTs actually harbouring the BARF0 ORF were detected only in specimens containing a relatively large number of EBV-positive cells. New monoclonal antibodies against the BARF0 protein were generated that efficiently recognized prokaryotic and eukaryotic recombinant BARF0. However, the BARF0 protein was not detected in clinical samples, nor in EBV-positive cell lines, even though these were positive for BARTs by RISH and/or BARF0 RNA in vitro analysis. Using immunoblot analysis, no antibodies against baculovirus-expressed BARF0 protein were detected in the sera of nasopharyngeal carcinoma patients, BL patients and Hodgkin's disease patients, patients with chronic EBV infection, infectious mononucleosis patients or EBV-positive healthy donors. Thus, BARTs containing the BARF0 ORF are expressed in vivo but the BARF0 protein cannot be detected and may be expressed only marginally. It is concluded that the BARF0 protein is unlikely to play a role in vivo in EBV-positive malignancies.

Latency pattern of Epstein-Barr virus and methylation status in Epstein-Barr virus-associated hemophagocytic syndrome

Expression of different panels of latent gene transcripts is controlled by usage of three distinct Epstein-Barr virus (EBV) nuclear antigen (EBNA) promoters (Wp, Cp, and Qp). EBV-associated hemophagocytic syndrome, which is often a fatal disease and generally occurs after primary EBV infection, is characterized by monoclonal or oligoclonal proliferation of EBV-infected T cells. The latency pattern and EBNA promoter (Wp, Cp, and Qp) usage in EBV-infected cells from three patients with EBV-associated hemophagocytic syndrome were examined by reverse transcription-polymerase chain reaction (PCR). Three samples from the patients expressed EBER, EBNA1, EBNA2, latent membrane protein (LMP)1, and LMP2A transcripts. The transcripts of EBNA1 were initiated from not only Wp/Cp but also Qp. Lytic cycle Fp-initiated EBNA1 and EBV lytic gene BZLF1 transcripts were not detected. The methylation statuses of three EBNA promoters in three patients with EBV-associated hemophagocytic syndrome and in two patients with infectious mononucleosis were also analyzed using bisulfite PCR analysis. Wp was hypermethylated, and Qp was unmethylated in both diseases. Cp was highly methylated in EBV-associated hemophagocytic syndrome, however, whereas Cp was almost unmethylated in infectious mononucleosis. These results suggest that there may be distinct EBV-infected cell populations in EBV-associated hemophagocytic syndrome, which exhibit different patterns of EBV latent gene expression. The methylation status in Cp and phenotype of EBV-infected cells may be critical differences in EBV-associated hemophagocytic syndrome and infectious mononucleosis.

No role for Epstein-Barr virus in Dutch hepatocellular carcinoma: a study at the DNA, RNA and protein levels

Epstein-Barr virus (EBV) has been suggested to play a role in hepatocellular carcinoma (HCC). However, reports on detailed EBV transcript analyses in HCCs are limited. It was shown recently that expression of the transforming BARF1 (BamHI A rightward open reading frame 1) gene of EBV is restricted to latently EBV-infected epithelial malignancies, i.e. nasopharyngeal carcinoma and gastric carcinoma. The aim of this study was to test the presence of EBV in Dutch HCCs. A semiquantitative DNA PCR-enzyme immunoassay (PCR-EIA) for the BamHI W fragment of EBV was used to assess the presence of EBV in frozen and paraffin-embedded tissues of 16 HCCs. In addition, several RNA detection techniques, i.e. nucleic acid sequence-based amplification (NASBA), RT-PCR, RNA in situ hybridization (RISH) and immunohistochemistry (IHC), were applied. Five of 16 HCCs and two of four hepatitis C virus hepatitis samples were weakly positive for EBV DNA by PCR-EIA. Using sensitive RNA transcription techniques, no transcripts were found for BARF1, EBNA-1 and BARTs (BamHI A rightward transcripts) in any of the liver tissues tested. In addition, RISH for EBER1/2 and BARTs and IHC for EBNA-1, LMP-1 and ZEBRA, performed on the paraffin-embedded tissue of the PCR-EIA-positive cases and on adjacent non-neoplastic liver tissues, were negative. The absence of epithelial-specific BARF1 transcripts and other EBV transcripts and proteins in the EBV DNA PCR-positive cases argues strongly against a role for EBV in HCC.

Updated Epstein-Barr virus (EBV) DNA sequence and analysis of a promoter for the BART (CST, BARF0) RNAs of EBV

Two sequences required for activity of the Epstein-Barr virus BART RNA promoter in transfection assays have been identified by site-directed mutagenesis. One contains a consensus AP-1 site; the other has some similarity to Ets and Stat consensus binding sites. Candidate sequences were suggested by mapping a region of unmethylated DNA in EBV around the BART promoter followed by in vivo footprinting the promoter in the C666-1 nasopharyngeal carcinoma cell line, which expresses BART RNAs. The data are presented in the context of a revised EBV DNA sequence, known as EBV wt, that is proposed as a future standard sequence for EBV.

Pathogenic roles for Epstein-Barr virus (EBV) gene products in EBV-associated proliferative disorders

Epstein-Barr virus (EBV) is associated with a still growing spectrum of clinical disorders, ranging from acute and chronic inflammatory diseases to lymphoid and epithelial malignancies. Based on a combination of in vitro and in vivo findings, EBV is thought to contribute in the pathogenesis of these diseases. The different EBV gene expression patterns in the various disorders, suggest different EBV-mediated pathogenic mechanisms. In the following pages, an overview of the biology of EBV-infection is given and functional aspects of EBV-proteins are discussed and their putative role in the various EBV-associated disorders is described. EBV gene expression patterns and possible pathogenic mechanisms are discussed. In addition, expression of the cellular genes upregulated by EBV in vitro is discussed, and a comparison with the in vivo situation is made.

Epstein-Barr virus EBNA2 blocks Nur77- mediated apoptosis

Epstein-Barr virus infection in vitro immortalizes primary B cells. EBNA2 is an Epstein-Barr virus-encoded transcriptional transactivator that mimics the effects of activated Notch signaling and is essential for this proliferative response. An assay using Sindbis virus (SV) as a cell death inducer revealed that, like Notch, EBNA2 also has antiapoptotic activity. We show that Nur77 is a mediator of SV-induced cell death and that EBNA2 antiapoptotic activity results from interaction with Nur77. EBNA2 colocalized with Nur77 in transfected cells and coprecipitated with Nur77 in IB4 B cells. EBNA2 binds to Nur77 through sequences in the EBNA2 amino acid 123-147 conserved domain and an EBNA2 mutant unable to bind Nur77 also lost the ability to protect cells from SV-induced apoptosis. EBNA2 exerted its antideath function by retaining Nur77 in the nucleus and preventing Nur77 from targeting mitochondria in response to apoptotic stimuli. Thus, targeting of Nur77 can be added to the list of strategies used by viruses to counter apoptosis.

Lysine-independent ubiquitination of Epstein-Barr virus LMP2A

Latent membrane protein 2A (LMP2A) of latent Epstein-Barr virus (EBV) specifically associates with HECT domain-containing Nedd4-family ubiquitin-protein ligases (E3s). Here we demonstrate that LMP2A is specifically ubiquitinated by the HECT domains of AIP4 and WWP2. Deletion and site-specific mutation of LMP2A indicates that LMP2A is ubiquitinated at its amino-terminus and is not ubiquitinated on lysine residues. LMP2A and LMP1, also encoded by EBV, are two of only four proteins that have been identified that are ubiquitinated at the amino-terminus, indicating that EBV may specifically target and utilize this host cell protein modification.

Role of Epstein-Barr virus DNA load monitoring in prevention and early detection of post-transplant lymphoproliferative disease

Posttransplant lymphoproliferative disease (PTLD) is a severe and life-threatening complication after stem cell or solid-organ transplantation, virtually always associated with presence of Epstein-Barr virus (EBV) in the proliferating cells. PTLD is probably caused by the iatrogenically impaired T-cell response allowing outgrowth of EBV-positive B-cells. Quantitative EBV DNA load monitoring is a minimally invasive technique increasingly recognized as a valuable tool in posttransplant patient management. In this review, we focus on the clinical utility of EBV DNA load monitoring in the peripheral blood of transplant recipients using PCR and we discuss the currently most-widely used techniques and their value and limitations in predicting and diagnosing PTLD. Options for EBV DNA load-guided pre-emptive therapy and application of monitoring EBV DNA load dynamics in the prediction of clinical response after therapy are described. Origins of elevated EBV DNA loads in immunosuppressed patients and recent insights in the EBV life cycle in the immuncompromised host are discussed. Finally, a standardization of methodology, clinical specimen type, and cut-off values is proposed. This is essential for comparisons between different institutes and more adequate patient management.

Epstein-Barr virus nuclear antigen 1 activates transcription from episomal but not integrated DNA and does not alter lymphocyte growth

By binding to a cis-acting element (oriP) in the Epstein-Barr virus (EBV) genome, EBV nuclear antigen 1 (EBNA1) enables persistence and enhances transcription from EBV episomes. To investigate whether EBNA1 also directly affects cell gene transcription, we conditionally expressed a Flag-tagged dominant negative EBNA1 (FDNE) in an EBV immortalized lymphoblastoid cell line, in which the EBV genome is integrated into cell DNA. FDNE induction inhibited expression from an EBNA1-dependent oriP reporter plasmid by more than 90% in these cells but did not affect expression from integrated EBV or oriP reporter DNA. FDNE induction also did not alter expression of more than 1,800 cellular mRNAs. Lymphoblastoid cell line growth under a variety of conditions was unaffected by FDNE induction. Although Gal4-VP16 and EBNA1 strongly activated and coactivated a Gal4-VP16- and oriP-dependent promoter that was on an episome, only Gal4-VP16 activated the promoter when it was integrated into chromosomal DNA. These data indicate that EBNA1 is specifically deficient in activation of an integrated oriP enhancer and does not affect cell growth or gene expression through an interaction with cognate chromosomal DNA.

From Burkitt's lymphoma to chronic active Epstein-Barr virus (EBV) infection: an expanding spectrum of EBV-associated diseases

Epstein-Barr virus (FBV) is one of 8 known human herpesviruses. EBV infection usually occurs in early childhood and is subclinical. However, primary infection in adolescence or adulthood causes infectious mononucleosis in approximately half of infected individuals. Recently, the spectrum of human diseases associated with EBV injection has increased, primarily due to methodological advances in EBV detection. Initially, EBV was isolated from a cultured Burkitt lymphoma cell line, and has been felt to be etiologically linked to the development of Burkitt lymphoma, as well as other human malignancies. This review mainly focuses on pathogenetic mechanisms, many of which remain enigmatic, for the various human diseases, which are considered to be associated with EBV injection.

Heterogeneous, restricted patterns of Epstein-Barr virus (EBV) latent gene expression in patients with chronic active EBV infection

Epstein-Barr virus (EBV) has been shown to infect T lymphocytes and to be associated with a chronic active infection (CAEBV), which has been recognized as a mainly non-neoplastic T-cell lymphoproliferative disorder (T-cell LPD). The systemic distribution of EBV genomes was studied, by real-time PCR, in multiple tissues from six patients with CAEBV, including three patients with T-cell LPD, one patient with B-cell LPD and two patients with undetermined cell-type LPD. There were extremely high loads of EBV genomes in all tissues from the patients. This reflects an abundance of circulating and infiltrating EBV-infected cells and a wide variety of clinical symptoms in the affected tissues. We chose one sample from each patient that was shown by real-time PCR to contain a high load of EBV genomes and examined the expression of EBV latent genes by RT-PCR. EBER1 and EBNA1 transcripts were detected in all samples. Only one sample also expressed EBNA2, LMP1 and LMP2A transcripts in addition to EBER1 and EBNA1 transcripts. Two of the remaining five samples expressed LMP1 and LMP2A transcripts. One sample expressed LMP2A but not LMP1 and EBNA2 transcripts. Another sample expressed EBNA2 but not LMP1 and LMP2A transcripts. The other sample did not express transcripts of any of the other EBNAs or LMPs. None of the samples expressed the viral immediate-early gene BZLF1. These results showed that EBV latent gene expression in CAEBV is heterogeneous and that restricted forms of EBV latency might play a pathogenic role in the development of CAEBV.

Haematological associations of Epstein-Barr virus infection

Epstein-Barr virus (EBV) is one of eight human herpesviruses and is ubiquitous. Primary infection with EBV in childhood is generally silent, but often causes overt diseases such as infectious mononucleosis (IM) and lymphoproliferative disorders (LPD). The latter occurs in immunologically compromised individuals. Historically, EBV has been thought to be aetiologically linked to human malignancies such as EBV genome-positive Burkitt's lymphoma (BL) and nasopharyngeal carcinoma (NPC). Furthermore, studies using recent developments in molecular and immunological diagnostic approaches have suggested that this virus has a causative role in a spectrum of human diseases of previously unknown pathogenesis, including chronic active EBV infection syndrome (CAEBV), EBV-related haemophagocytic lymphohistiocytosis (HLH), and certain disorders such as EBV genome-positive T-cell lymphoma, natural killer (NK) cell leukaemia/lymphoma, Hodgkin's disease (HD) and gastric carcinoma. This chapter reviews recent progress regarding EBV-associated diseases.

Regulation of cell growth and death by Epstein-Barr virus

Epstein-Barr virus (EBV) efficiently induces growth of human B cells and prevents cell death. Considerable progress has been made in understanding these processes, the role of EBV in human cancer cells and the relationship of viral gene expression to virus persistence and cancer.

The biology of Epstein-Barr virus in post-transplant lymphoproliferative disease

Post-transplant lymphoproliferative disease (PTLD) is a B cell proliferative disorder that is associated with Epstein-Barr virus (EBV), an ubiquitous herpesvirus. EBV-seronegative organ transplant recipients are at highest risk. EBV infection in PTLD lesions exists in a latent rather than lytic state, making tumor regression in response to antiviral agents unlikely. Viral latency proteins drive proliferation of T cells but also allow T cells to target PTLD lesions for destruction. Augmentation of the cellular immune response via the infusion of EBV-specific cytotoxic T cells has yielded promising results in the prevention and treatment of PTLD in bone marrow transplant recipients. Efforts to extend this strategy to solid organ transplant recipients are ongoing.

The Epstein-Barr virus latency BamHI-Q promoter is positively regulated by STATs and Zta interference with JAK/STAT activation leads to loss of BamHI-Q promoter activity

In Epstein-Barr virus (EBV)-associated tumors in nonimmunocompromised patients, EBV gene expression is highly restricted. EBV-encoded nuclear antigen (EBNA)-1 is expressed, whereas the immunogenic and proliferative EBNAs are not. This pattern of EBNA expression is generated by usage of the BamHI-Q promoter (Qp). We have determined that the JAK/STAT pathway positively regulates Qp activity. In transient-transfection assays, a Qp-CAT reporter was activated by cotransfected JAK-1 and by treatment of cells with the cytokine IL-6. The ability of Qp to bind signal transducer and activator of transcription (STAT) proteins was directly demonstrated by electrophoretic mobility-shift assay, and mutation of potential STAT-binding sites reduced Qp responsiveness to Janus kinase (JAK)-1. Consistent with a role for STATs in Qp function, Qp using Burkitt's lymphoma Rael cells and cultured nasopharyngeal carcinoma (NPC) cells contained nuclear STAT protein. We investigated whether the inability to maintain EBV-positive NPC cell lines in culture was related to Qp activity. Passaging of the NPC cell line HK666 led to activation of expression of BZLF1, which encodes Zta and loss of Qp function. Transient expression assays linked Zta expression to the down-regulation of Qp. Cotransfection of Zta reduced Qp activity in reporter assays. This negative regulation required Zta DNA-binding activity. We provide evidence that Zta up-regulation of p53 leads to p53-mediated interference with JAK/STAT activation of Qp. The data imply that JAK/STAT signaling has a role in EBV-associated malignancies.