Expression of Epstein-Barr virus (EBV) transcripts encoding homologues to important human proteins in diverse EBV associated diseases

Functional Implications of Epstein-Barr Virus Lytic Genes in Carcinogenesis

Epstein-Barr virus (EBV) is associated with a diverse range of tumors of both lymphoid and epithelial origin. Similar to other herpesviruses, EBV displays a bipartite life cycle consisting of latent and lytic phases. Current dogma indicates that the latent genes are key drivers in the pathogenesis of EBV-associated cancers, while the lytic genes are primarily responsible for viral transmission. In recent years, evidence has emerged to show that the EBV lytic phase also plays an important role in EBV tumorigenesis, and the expression of EBV lytic genes is frequently detected in tumor tissues and cell lines. The advent of next generation sequencing has allowed the comprehensive profiling of EBV gene expression, and this has revealed the consistent expression of several lytic genes across various types of EBV-associated cancers. In this review, we provide an overview of the functional implications of EBV lytic gene expression to the oncogenic process and discuss possible avenues for future investigations.

Virus-Mediated Inhibition of Apoptosis in the Context of EBV-Associated Diseases: Molecular Mechanisms and Therapeutic Perspectives

Epstein-Barr virus (EBV), the representative of the Herpesviridae family, is a pathogen extensively distributed in the human population. One of its most characteristic features is the capability to establish latent infection in the host. The infected cells serve as a sanctuary for the dormant virus, and therefore their desensitization to apoptotic stimuli is part of the viral strategy for long-term survival. For this reason, EBV encodes a set of anti-apoptotic products. They may increase the viability of infected cells and enhance their resistance to chemotherapy, thereby contributing to the development of EBV-associated diseases, including Burkitt’s lymphoma (BL), Hodgkin’s lymphoma (HL), gastric cancer (GC), nasopharyngeal carcinoma (NPC) and several other malignancies. In this paper, we have described the molecular mechanism of anti-apoptotic actions of a set of EBV proteins. Moreover, we have reviewed the pro-survival role of non-coding viral transcripts: EBV-encoded small RNAs (EBERs) and microRNAs (miRNAs), in EBV-carrying malignant cells. The influence of EBV on the expression, activity and/or intracellular distribution of B-cell lymphoma 2 (Bcl-2) protein family members, has been presented. Finally, we have also discussed therapeutic perspectives of targeting viral anti-apoptotic products or their molecular partners.

Characterization of High-Risk HPV/EBV Co-Presence in Pre-Malignant Cervical Lesions and Squamous Cell Carcinomas

High-risk human papillomaviruses (HR-HPVs) are the etiological agents of cervical cancer. However, a low proportion of HR-HPV-infected women finally develop this cancer, which suggests the involvement of additional cofactors. Epstein−Barr virus (EBV) has been detected in cervical squamous cell carcinomas (SCCs) as well as in low- (LSIL) and high-grade (HSIL) squamous intraepithelial lesions, although its role is unknown. In this study, we characterized HR-HPV/EBV co-presence and viral gene expression in LSIL (n = 22), HSIL (n = 52), and SCC (n = 19) from Chilean women. Additionally, phenotypic changes were evaluated in cervical cancer cells ectopically expressing BamHI-A Rightward Frame 1 (BARF1). BARF1 is a lytic gene also expressed in EBV-positive epithelial tumors during the EBV latency program. HPV was detected in 6/22 (27.3%) LSIL, 38/52 (73.1%) HSIL, and 15/19 (78.9%) SCC cases (p < 0.001). On the other hand, EBV was detected in 16/22 (72.7%) LSIL, 27/52 (51.9%) HSIL, and 13/19 (68.4%) SCC cases (p = 0.177). HR-HPV/EBV co-presence was detected in 3/22 (13.6%) LSIL, 17/52 (32.7%) HSIL, and 11/19 (57.9%) SCC cases (p = 0.020). Additionally, BARF1 transcripts were detected in 37/55 (67.3%) of EBV positive cases and in 19/30 (63.3%) of HR-HPV/EBV positive cases. Increased proliferation, migration, and epithelial-mesenchymal transition (EMT) was observed in cervical cancer cells expressing BARF1. Thus, both EBV and BARF1 transcripts are detected in low- and high-grade cervical lesions as well as in cervical carcinomas. In addition, BARF1 can modulate the tumor behavior in cervical cancer cells, suggesting a role in increasing tumor aggressiveness.

Epstein-Barr Virus Infection in Lung Cancer: Insights and Perspectives

Lung cancer (LC) is the leading cause of cancer death worldwide. Tobacco smoke is the most frequent risk factor etiologically associated with LC, although exposures to other environmental factors such as arsenic, radon or asbestos are also involved. Additionally, the involvement of some viral infections such as high-risk human papillomaviruses (HR-HPVs), Merkel cell polyomavirus (MCPyV), Jaagsiekte Sheep Retrovirus (JSRV), John Cunningham Virus (JCV), and Epstein-Barr virus (EBV) has been suggested in LC, though an etiological relationship has not yet been established. EBV is a ubiquitous gamma herpesvirus causing persistent infections and some lymphoid and epithelial tumors. Since EBV is heterogeneously detected in LCs from different parts of the world, in this review we address the epidemiological and experimental evidence of a potential role of EBV. Considering this evidence, we propose mechanisms potentially involved in EBV-associated lung carcinogenesis. Additional studies are warranted to dissect the role of EBV in this very frequent malignancy.

The role of the Epstein-Barr virus-encoded BARF1 gene expressed in human gastric epithelial cells

BACKGROUND/AIMS

The study aimed to explore the effects of Epstein-Barr virus--encoded BARF1 in human gastric epithelial cells (GES-1).

MATERIALS AND METHODS

A eukaryotic expression vector carrying BARF1 gene (pcDNA3.1-BARF1) was constructed. The pcDNA3.1-BARF1 was transfected into GES-1 cells, and they were selected by G418. The GES-1 cells lines that expressed BARF1 (GES-1-BARF1) were obtained. The cycle of GES-1-pcDNA3.1 cells (GES-1 cells transfected with empty vector), GES-1-BARF1 cells (GES-1 cells transfected with BARF1), and TPA-GES-1-BARF1(GES-1-BARF1 cells stimulated by 12-O-tetradecanoylphorbol-13-acetate (TPA) were analyzed by flow cytometry. Colony formation in soft agar and tumorigenicity of the transfected cells in mice with severe combined immunodeficiency (SCID) were also observed.

RESULTS

The morphology of GES-1-BARF1 cells were changed from the original shuttle to round, the adhesion between the cells and bottle wall was weakened, and the cells showed overlapping growth. The proliferation rate of GES-1-BARF1 and TPA-GES-1-BARF1 cells were faster than GES-1 and GES-1-pcDNA3.1 cells; the S phase was significantly prolonged for GES-1-BARF1 and TPA-GES-1-BARF1. GES-1-BARF1 and TPA-GES-1-BARF1 cells formed colonies in soft agar, with a cloning rate of 24.2% (58/240) and 40.0% (96/240), respectively; GES-1 and GES-1-pcDNA3.1 cells did not form colonies in soft agar. Tumors were formed in mice with SCID after injecting TPA-GES-1-BARF1 cell groups. Tumor formation did not occur in mice with SCID after injecting GES-1 and GES-1-pcDNA3.1 cell groups, but nodules were formed in the mice with SCID after injecting GES-1-BARF1 cell groups.

CONCLUSION

GES-1-BARF1 cells malignant transformation was induced by transfected BARF1 gene and TPA stimulation. This result indicated that tumor formation not only require oncogenes, but also the stimulation of cancer-promoting substance.

Role of BamHI-A Rightward Frame 1 in Epstein-Barr Virus-Associated Epithelial Malignancies

Simple Summary

Epstein–Barr virus is a ubiquitous persistent virus, which is involved in the development of some human cancers. A licensed vaccine to prevent Epstein–Barr virus infection is lacking. BamHI-A rightward frame 1 is a viral protein specifically detected in both nasopharyngeal and Epstein–Barr virus-positive gastric cancers. It has been proposed that this viral protein confers cancer properties to infected epithelial cells and is involved in the escape of cancer cells from immune recognition. In this review, we summarize the properties of BamHI-A rightward frame 1 which confers cancer characteristics to infected epithelial cells. Thus, BamHI-A rightward frame 1 is a potential therapeutic target for the treatment of either Epstein–Barr virus (EBV)-positive nasopharyngeal or gastric cancers.

Abstract

Epstein–Barr virus (EBV) infection is associated with a subset of both lymphoid and epithelial malignancies. During the EBV latency program, some viral products involved in the malignant transformation of infected cells are expressed. Among them, the BamHI-A rightward frame 1 (BARF1) is consistently detected in nasopharyngeal carcinomas (NPC) and EBV-associated gastric carcinomas (EBVaGCs) but is practically undetectable in B-cells and lymphomas. Although BARF1 is an early lytic gene, it is expressed during epithelial EBV latency, mainly as a secreted protein (sBARF1). The capacity of sBARF1 to disrupt both innate and adaptive host antiviral immune responses contributes to the immune escape of infected cells. Additionally, BARF1 increases cell proliferation, shows anti-apoptotic effects, and promotes an increased hTERT activity and tumor formation in nude mice cooperating with other host proteins such as c-Myc and H-ras. These facts allow for the consideration of BARF1 as a key protein for promoting EBV-associated epithelial tumors. In this review, we focus on structural and functional aspects of BARF1, such as mechanisms involved in epithelial carcinogenesis and its capacity to modulate the host immune response.

Role of Epstein-Barr Virus and Human Papillomavirus Coinfection in Cervical Cancer: Epidemiology, Mechanisms and Perspectives

High-risk human papillomavirus (HR-HPV) is etiologically associated with the development and progression of cervical cancer, although other factors are involved. Epstein-Barr virus (EBV) detection in premalignant and malignant tissues from uterine cervix has been widely reported; however, its contribution to cervical cancer development is still unclear. Here, a comprehensive analysis regarding EBV presence and its potential role in cervical cancer, the frequency of EBV/HR-HPV coinfection in uterine cervix and EBV infection in tissue-infiltrating lymphocytes were revised. Overall, reports suggest a potential link of EBV to the development of cervical carcinomas in two possible pathways: (1) Infecting epithelial cells, thus synergizing with HR-HPV (direct pathway), and/or (2) infecting tissue-infiltrating lymphocytes that could generate local immunosuppression (indirect pathway). In situ hybridization (ISH) and/or immunohistochemical methods are mandatory for discriminating the cell type infected by EBV. However, further studies are needed for a better understanding of the EBV/HR-HPV coinfection role in cervical carcinogenesis.

The Phylogeographic Diversity of EBV and Admixed Ancestry in the Americas⁻Another Model of Disrupted Human-Pathogen Co-Evolution

Epstein-Barr virus (EBV) is an etiological agent for gastric cancer with significant worldwide variations. Molecular characterizations of EBV have shown phylogeographical variations among healthy populations and in EBV-associated diseases, particularly the cosegregated BamHI-I fragment and XhoI restriction site of exon 1 of the LMP-1 gene. In the Americas, both cosegregated variants are present in EBV carriers, which aligns with the history of Asian and European human migration to this continent. Furthermore, novel recombinant variants have been found, reflecting the genetic makeup of this continent. However, in the case of EBV-associated gastric cancer (EBV-associated GC), the cosegregated European BamHI-“i” fragment and XhoI restriction site strain prevails. Thus, we propose that a disrupted coevolution between viral phylogeographical strains and mixed human ancestry in the Americas might explain the high prevalence of this particular gastric cancer subtype. This cosegregated region contains two relevant transcripts for EBV-associated GC, the BARF-1 and miR-BARTs. Thus, genome-wide association studies (GWAS) or targeted sequencing of both transcripts may be required to clarify their role as a potential source of this disrupted coevolution.

The Methylation Status and Expression of Epstein-Barr Virus Early Genes BARF1 and BHRF1 in Epstein-Barr Virus-Associated Gastric Carcinomas

Epstein-Barr virus (EBV) is an important DNA virus which establishes latent infection in human malignancies. Expression of EBV-encoded genes in the associated tumors is strongly modulated by promoter CpG methylation of EBV genome. This study aimed to explore the methylation status of the promoters of EBV BamHI-A rightward frame 1 (BARF1) and BamHI-H rightward open reading frame 1 (BHRF1) and their influence on transcriptional expression, to further understand the roles of BARF1 and BHRF1 in the occurrence of EBV-associated cancer. We evaluated the methylation status of BARF1 and BHRF1 promoters in 43 EBV-associated gastric carcinoma (EBVaGC) tissues and EBV-positive cell lines. Their expressions were evaluated by real-time quantitative PCR. We found that the promoters of BARF1 and BHRF1 were methylated by varying degrees in different EBV-positive cell lines and were almost hypermethylated in all EBVaGC tissues. The methylation status of BARF1 and BHRF1 promoters were significantly reduced by 5-Aza-CdR along with the increasing gene expressions. Hypermethylation of Ap and Hp mediates the frequent silencing of BARF1 and BHRF1 in EBV-associated tumors, which could be reactivated by a demethylation agent, suggesting that promoter demethylation and activation is important for BARF1 and BHRF1 transcription and their further action.

Quantitative multi-target RNA profiling in Epstein-Barr virus infected tumor cells

Epstein-Barr virus (EBV) is etiologically linked to multiple acute, chronic and malignant diseases. Detection of EBV-RNA transcripts in tissues or biofluids besides EBV-DNA can help in diagnosing EBV related syndromes. Sensitive EBV transcription profiling yields new insights on its pathogenic role and may be useful for monitoring virus targeted therapy. Here we describe a multi-gene quantitative RT-PCR profiling method that simultaneously detects a broad spectrum (n=16) of crucial latent and lytic EBV transcripts. These transcripts include (but are not restricted to), EBNA1, EBNA2, LMP1, LMP2, BARTs, EBER1, BARF1 and ZEBRA, Rta, BGLF4 (PK), BXLF1 (TK) and BFRF3 (VCAp18) all of which have been implicated in EBV-driven oncogenesis and viral replication. With this method we determine the amount of RNA copies per infected (tumor) cell in bulk populations of various origin. While we confirm the expected RNA profiles within classic EBV latency programs, this sensitive quantitative approach revealed the presence of rare cells undergoing lytic replication. Inducing lytic replication in EBV tumor cells supports apoptosis and is considered as therapeutic approach to treat EBV-driven malignancies. This sensitive multi-primed quantitative RT-PCR approach can provide broader understanding of transcriptional activity in latent and lytic EBV infection and is suitable for monitoring virus-specific therapy responses in patients with EBV associated cancers.

Broadening Specificity and Enhancing Cytotoxicity of Adoptive T Cells for Nasopharyngeal Carcinoma Immunotherapy

Although promising, clinical responses to adoptive immunotherapy for nasopharyngeal carcinoma (NPC) are still limited by the restricted number of Epstein-Barr virus (EBV) antigens that can be targeted and their poor immunogenicity. Our previous work indicated that the immunogenic features of the NPC-associated viral antigen BARF1 may be exploited for immunotherapeutic purposes. Nevertheless, T-cell lines obtained with current protocols include only negligible numbers of BARF1-specific cytotoxic T lymphocytes, pointing to the need to enrich these effectors in BARF1 specificities. Considering that in B lymphocytes BARF1 is mainly a lytic EBV antigen, we tested different EBV lytic-cycle inducers (TPA/butyric acid, doxorubicin, and cisplatin) used at suboptimal concentrations for their ability to upregulate BARF1 expression in lymphoblastoid B-cell lines (LCL), the commonly used antigen-presenting cells, without compromising their survival. The LCLs treated with doxorubicin (DX-LCL) can reproducibly and efficiently generate EBV-specific effectors enriched in BARF1 specificities from both healthy donors and NPC patients. These DX-LCLs also had more pronounced immunogenic properties, including HLA class I upregulation and expression of immunogenic cell death markers, such as enhanced calreticulin exposure and HMGB1 release. In particular, doxorubicin triggers an HMGB1 autocrine/paracrine loop with its receptor, TLR4, which is also upregulated in DX-LCLs and is responsible for NF-κB activation and a delayed apoptosis that allows a prolonged stimulation of EBV-specific T-cell precursors. This protocol may thus constitute a valid alternative to the use of engineered LCLs to generate EBV-specific T-cell lines for adoptive immunotherapy, being relatively simple, easily upgradable to Good Manufacturing Practice standards, and therefore more broadly applicable. Cancer Immunol Res; 4(5); 431-40. ©2016 AACR.

Sequence analysis of Epstein-Barr virus (EBV) early genes BARF1 and BHRF1 in NK/T cell lymphoma from Northern China

Background

NK/T cell lymphoma is an aggressive lymphoma almost always associated with EBV. BamHI-A rightward open reading frame 1 (BARF1) and BamHI-H rightward open reading frame 1 (BHRF1) are two EBV early genes, which may be involved in the oncogenicity of EBV. It has been found that V29A strains, a BARF1 mutant subtype, showed higher prevalence in NPC, which may suggest the association between this variation and nasopharyngeal carcinoma (NPC). To characterize the sequence variation patterns of the Epstein-Barr virus (EBV) early genes and to elucidate their association with NK/T cell lymphoma, we analyzed the sequences of BARF1 and BHRF1 in EBV-positive NK/T cell lymphoma samples from Northern China.

Methods

In situ hybridization (ISH) performed for EBV-encoded small RNA1 (EBER1) with specific digoxigenin-labeled probes was used to select the EBV positive lymphoma samples. Nested-polymerase chain reaction (nested-PCR) and DNA sequence analysis technique were used to obtain the sequences of BARF1 and BHRF1. The polymorphisms of these two genes were classified according to the signature changes and compared with the known corresponding EBV gene variation data.

Results

Two major subtypes of BARF1 gene, designated as B95-8 and V29A subtype, were identified. B95-8 subtype was the dominant subtype. The V29A subtype had one consistent amino acid change at amino acid residue 29 (V → A). Compared with B95-8, AA change at 88 (L → V) of BHRF1 was found in the majority of the isolates, and AA79 (V → L) mutation in a few isolates. Functional domains of BARF1 and BHRF1 were highly conserved. The distributions of BARF1 and BHRF1 subtypes had no significant differences among different EBV-associated malignancies and healthy donors.

Conclusion

The sequences of BARF1 and BHRF1 are highly conserved which may contribute to maintain the biological function of these two genes. There is no evidence that particular EBV substrains of BARF1 or BHRF1 is region-restricted or disease-specific.

Characteristics of viral IL-10 gene in Epstein–Barr virus infection in children in China

ABSTRACT 

The viral IL-10 (vIL-10) gene of Epstein–Barr virus (EBV) exhibits high homology with human IL-10 gene. In order to characterize vIL-10 gene in EBV-infected children in China, DNA sequencing of this gene was performed in 249 cases of EBV-associated infectious mononucleosis, 46 EBV-associated hemophagocytic lymphohistiocytosis and six chronic active EBV infection. Eight silent and seven nonsilent mutations were identified, of which silent mutation c9980a was prominently presented (75.7%, 228/301) in the studied cases. Two subtypes of the vIL-10 gene, including pattern B95–8 and pattern SPM (mutation in the signal peptide), were identified. Pattern B95-8 was the dominant subtype in infectious mononucleosis, EBV-hemophagocytic lymphohistiocytosis and chronic active EBV infection. These results indicated that the vIL-10 gene exists as a highly conservative form in EBV-associated infection in Chinese children.

Epstein-Barr virus interactions with the Bcl-2 protein family and apoptosis in human tumor cells

Epstein-Barr virus (EBV), a human gammaherpesvirus carried by more than 90% of the world's population, is associated with malignant tumors such as Burkitt's lymphoma (BL), Hodgkin lymphoma, post-transplant lymphoma, extra-nodal natural killer/T cell lymphoma, and nasopharyngeal and gastric carcinomas in immune-compromised patients. In the process of infection, EBV faces challenges: the host cell environment is harsh, and the survival and apoptosis of host cells are precisely regulated. Only when host cells receive sufficient survival signals may they immortalize. To establish efficiently a lytic or long-term latent infection, EBV must escape the host cell immunologic mechanism and resist host cell apoptosis by interfering with multiple signaling pathways. This review details the apoptotic pathway disrupted by EBV in EBV-infected cells and describes the interactions of EBV gene products with host cellular factors as well as the function of these factors, which decide the fate of the host cell. The relationships between other EBV-encoded genes and proteins of the B-cell leukemia/lymphoma (Bcl) family are unknown. Still, EBV seems to contribute to establishing its own latency and the formation of tumors by modifying events that impact cell survival and proliferation as well as the immune response of the infected host. We discuss potential therapeutic drugs to provide a foundation for further studies of tumor pathogenesis aimed at exploiting novel therapeutic strategies for EBV-associated diseases.

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.

Cellular localization of BARF1 oncoprotein and its cell stimulating activity in human epithelial cell

BARF1 gene encoded by Epstein-Barr virus is capable of immortalizing the primary monkey epithelial cells and of inducing malignant transformation in human EBV-negative B cell lines as well as rodent fibroblast. This oncoprotein is a secreted protein capable of acting as a powerful mitogen. We have studied the effect of BARF1 protein in transfected or BARF1 protein treated human HaCaT epithelial cells. In BARF1-transfected cells, cell growth was activated and its protein was found both in culture medium and cellular compartment (membrane, cytoplasm and nuclei). When purified BARF1 protein was exogenously added in the cell culture medium of HaCaT cells in absence of fetal calf serum led to its entrance into cells and its intracellular localization in cytoplasm, nuclear periphery and nuclei at 14h treatment, determined by confocal and immunoelectron microscopy. Cell fractionation confirmed its nuclear localization. Nuclear localization was observed in both systems. More interestingly, purified BARF1 protein p29 exogenously added in the cell culture medium activated cell passage of G1 to S phase. S phase activation by its autocrine activity and its tumorigenic activity would be associated with the development of EBV-associated carcinomas.

Unique variations of Epstein-Barr virus-encoded BARF1 gene in nasopharyngeal carcinoma biopsies

The Epstein-Barr virus (EBV) BamHI-A rightward frame 1 (BARF1) gene is frequently expressed in EBV-associated epithelial malignancies and involves in oncogenicity and immunomodulation. To characterize the variations of BARF1 gene in different populations, the sequences of BARF1 gene in Northern Chinese nasopharyngeal carcinoma (NPC), EBV-associated gastric carcinoma (EBVaGC) and healthy donors were analyzed. The correlation of BARF1 variation with polymorphisms of BamHI F fragment (type F and f variants) and EBV-coded viral interleukin-10 (vIL-10) gene (B95-8 and SPM patterns) was also explored. Two major subtypes of BARF1 gene, designated as B95-8 and V29A, were identified. B95-8 subtype had identical amino acid sequence to B95-8 and was the dominant subtype among the EBV isolates from Northern China. V29A subtype, with one consistent amino acid change at residue 29 (V→A) and several nucleotide changes, showed higher frequency in NPC cases (25.3%, 20/79) than in EBVaGC cases (0/45) or healthy donors (4.3%, 2/46) (NPC vs. EBVaGC: P=0.0001; NPC vs. healthy donor: P=0.004). A preferential linkage between BamHI F and BARF1/vIL-10 polymorphisms was found. Type f isolates was specially correlated with the V29A/SPM genotype in NPC isolates and type f/V29A/SPM was preferentially found in NPC. BARF1/c-fms homology domain, transforming domain and cytotoxic T lymphocyte (CTL) epitopes of BARF1 were highly conserved in most isolates, suggesting the important role of BARF1 in virus infection and the potential usefulness in EBV-targeting immunotherapy of EBV-associated tumors. The relatively higher prevalence of type f/V29A/SPM strains in NPC may also suggest the association between these variations in multiple viral genes and NPC.

Purified hexameric Epstein-Barr virus-encoded BARF1 protein for measuring anti-BARF1 antibody responses in nasopharyngeal carcinoma patients

WHO type III nasopharyngeal carcinoma (NPC) is highly prevalent in Indonesia and 100% associated with Epstein-Barr virus (EBV). NPC tumor cells express viral proteins, including BARF1, which is secreted and is considered to have oncogenic and immune-modulating properties. Recently, we found conserved mutations in the BARF1 gene in NPC isolates. This study describes the expression and purification of NPC-derived BARF1 and analyzes humoral immune responses against prototype BARF1 (B95-8) and purified native hexameric BARF1 in sera of Indonesian NPC patients (n = 155) compared to healthy EBV-positive (n = 56) and EBV-negative (n = 16) individuals. BARF1 (B95-8) expressed in Escherichia coli and baculovirus, as well as BARF1-derived peptides, did not react with IgG or IgA antibodies in NPC. Purified native hexameric BARF1 protein isolated from culture medium was used in enzyme-linked immunosorbent assay (ELISA) and revealed relatively weak IgG and IgA responses in human sera, although it had strong antibody responses to other EBV proteins. Higher IgG reactivity was found in NPC patients (P = 0.015) than in regional Indonesian controls or EBV-negative individuals (P < 0.001). IgA responses to native BARF1 were marginal. NPC sera with the highest IgG responses to hexameric BARF1 in ELISA showed detectable reactivity with denatured BARF1 by immunoblotting. In conclusion, BARF1 has low immunogenicity for humoral responses and requires native conformation for antibody binding. The presence of antibodies against native BARF1 in the blood of NPC patients provides evidence that the protein is expressed and secreted as a hexameric protein in NPC patients.

Conserved mutation of Epstein-Barr virus-encoded BamHI-A Rightward Frame-1 (BARF1) gene in Indonesian nasopharyngeal carcinoma

BACKGROUND

BamHI-A rightward frame-1 (BARF1) is a carcinoma-specific Epstein-Barr virus (EBV) encoded oncogene. Here we describe the BARF1 sequence diversity in nasopharyngeal carcinoma (NPC), other EBV-related diseases and Indonesian healthy EBV carriers in relation to EBV genotype, viral load and serology markers. Nasopharyngeal brushings from 56 NPC cases, blood or tissue from 15 other EBV-related disorders, spontaneous B cell lines (LCL) from 5 Indonesian healthy individuals and several prototype EBV isolates were analysed by PCR-direct sequencing.

RESULTS

Most NPC isolates revealed specific BARF1 nucleotide changes compared to prototype B95-8 virus. At the protein level these mutations resulted in 3 main substitutions (V29A, W72G, H130R), which are not considered to cause gross tertiary structure alterations in the hexameric BARF1 protein. At least one amino acid conversion was detected in 80.3% of NPC samples compared to 33.3% of non-NPC samples (p < 0.001) and 40.0% of healthy LCLs (p = 0.074). NPC isolates also showed more frequent codon mutation than non-NPC samples. EBV strain typing revealed most isolates as EBV type 1. The viral load of either NPC or non-NPC samples was high, but only in non- NPC group it related to a particular BARF1 variant. Serology on NPC sera using IgA/EBNA-1 ELISA, IgA/VCA-p18 ELISA and immunoblot score showed no relation with BARF1 sequence diversity (p = 0.802, 0.382 and 0.058, respectively). NPC patients had variable antibody reactivity against purified hexameric NPC-derived BARF1 irrespective of the endogenous BARF1 sequence.

CONCLUSION

The sequence variation of BARF1 observed in Indonesian NPC patients and controls may reflect a natural selection of EBV strains unlikely to be predisposing to carcinogenesis. The conserved nature of BARF1 may reflect an important role in EBV (epithelial) persistence.

Using Epstein-Barr viral load assays to diagnose, monitor, and prevent posttransplant lymphoproliferative disorder

Epstein-Barr virus (EBV) DNA measurement is being incorporated into routine medical practice to help diagnose, monitor, and predict posttransplant lymphoproliferative disorder (PTLD) in immunocompromised graft recipients. PTLD is an aggressive neoplasm that almost always harbors EBV DNA within the neoplastic lymphocytes, and it is often fatal if not recognized and treated promptly. Validated protocols, commercial reagents, and automated instruments facilitate implementation of EBV load assays by real-time PCR. When applied to either whole blood or plasma, EBV DNA levels reflect clinical status with respect to EBV-related neoplasia. While many healthy transplant recipients have low viral loads, high EBV loads are strongly associated with current or impending PTLD. Complementary laboratory assays as well as histopathologic examination of lesional tissue help in interpreting modest elevations in viral load. Circulating EBV levels in serial samples reflect changes in tumor burden and represent an effective, noninvasive tool for monitoring the efficacy of therapy. In high-risk patients, serial testing permits early clinical intervention to prevent progression toward frank PTLD. Restoring T cell immunity against EBV is a major strategy for overcoming PTLD, and novel EBV-directed therapies are being explored to thwart virus-driven neoplasia.

EBV-positive human sera contain antibodies against the EBV BMRF-2 protein

We previously showed that the EBV glycoprotein BMRF-2 contains a functional integrin-binding Arg-Gly-Asp (RGD) domain that plays an important role in viral infection and cell-to-cell spread of progeny virions in oral epithelial cells. In this study, we found that EBV-seropositive human sera contain antibodies against BMRF-2. The inhibitory effect of EBV-positive sera on EBV infection of oral epithelial cells was substantially reduced by pre-incubation of serum samples with the BMRF-2 RGD peptide, suggesting that anti-BMRF-2 human antibodies possess neutralizing activity. EBV-specific sera reacted strongly with the BMRF-2 extracellular domain (170-213 aa) containing the RGD motif, whereas they reacted only weakly or not at all with a mutated form of the BMRF-2 extracellular domain containing AAA instead of RGD. These data indicate that RGD motif of BMRF-2 is part of an immunodominant antigenic determinant within the extracellular domain of BMRF-2 that may contribute to EBV neutralization during EBV reactivation.

NucliSENS EasyQ HPV v1 test - Testing for oncogenic activity of human papillomaviruses

BACKGROUND

Analytical sensitivity of DNA-based assays to detect infection with human papillomaviruses is very high, but clinical specificity for cervical cancer strongly depends on the age of the patient and case classification. To solve the dilemma between sensitivity and specificity, a new generation of assays focuses on the pathogenic factors that underlie the development of HPV-associated tumors: the expression of the viral oncogenes E6 and E7. Demonstration of persistent expression of these mRNAs or expression in the context of relevant clinical symptoms has a strong positive predictive value for the development of HPV-associated carcinomas and strongly warrants further diagnostic action.

OBJECTIVES

The NucliSENS EasyQ HPV v1 test was designed to test cervical scrapes for the expression of the oncogenic E6/E7 mRNA from the five most common carcinogenic HPV types (16, 18, 31, 33 and 45). The test can be used for confirmation and risk stratification of individuals with proven infection with high risk papillomaviruses.

STUDY DESIGN

In order to establish performance of the assay, sensitivity, specificity, repeatability, and reproducibility were determined with artificial and clinical specimens. Further, a total of 420 cervical scrapes were tested and the results directly compared to the CE-market device PreTect HPV-Proofer assay (NorChip, Klokkarstua, Norway). For arbitration of discordant clinical results, the specimens were rated according to Pap-classification and the presence of HPV DNA was determined.

RESULTS

The limit of detection for the five HPV types 16, 18, 31, 33, and 45 ranged from 2.3x10(2) to 3.0x10(4) copies/mL on a background of 5x10(3) HPV-negative HS67 cells. No cross-reactivity for other viral, bacterial, or fungal agents known to be potentially present in cervical fluids was detected. Repeatability and reproducibility were shown by testing panels of HPV-spiked artificial and clinical samples. A comparative analysis of 420 cervical scrapes demonstrated an overall concordance of >90% between the NucliSENS EasyQ HPV test and the technologically related PreTect HPV-Proofer assay.

Significance of Epstein-Barr virus (EBV) load and Interleukin-10 in post-transplant lymphoproliferative disorders

The complex relationship between EBV, IL-10 and lymphomagenesis has been widely investigated and several studies have highlighted the diagnostic value of EBV DNA copies and serum IL-10, that may be considered as tumor markers. Notwithstanding the great number of data published in the last few years on the behavior of EBV DNA copies in the peripheral blood of transplanted patients, a threshold value significant for impending or overt post-transplant lymphoproliferative disorder (PTLD) has not yet been defined. Too many factors, both technical and clinicopathological, may affect the results of clinical studies, making their comparison difficult. On the contrary, although the role of IL-10 in PTLDs has been well documented, a sufficient number of studies exploring sensitivity and specificity of serum IL-10 measurement is lacking. The aim of this review is to summarise data on EBV load quantification and serum IL-10 detection in transplanted patients, providing clinicians with wide and useful information in order to improve bedside management of transplanted patients with regard to PTLDs occurrence and treatment.

Epstein-Barr virus BDLF2-BMRF2 complex affects cellular morphology

Herpesvirus glycoproteins often form specific heterodimers that can fulfil functions that cannot be carried out by either of the partners acting alone. This study showed that interactions between the Epstein-Barr virus (EBV) multi-spanning transmembrane envelope protein BMRF2 and type II membrane protein BDLF2 influence the way in which these proteins are trafficked in the cell, and hence the subcellular compartment in which they accumulate. When expressed transiently in mammalian cells, BDLF2 accumulated in the endoplasmic reticulum (ER), whereas BMRF2 accumulated in the ER and Golgi apparatus. However, when the two proteins were co-expressed, BDLF2 was transported with BMRF2 to the Golgi apparatus and from there to the plasma membrane, where the proteins co-localized extensively. The distribution of the two proteins at the plasma membrane was reproducibly associated with dramatic changes in cellular morphology, including the formation of enlarged membrane protrusions and cellular processes whose adhesion extremities were organized by the actin cytoskeleton. A dominant-active form of the small GTPase RhoA was epistatic to this morphological phenotype, suggesting that RhoA is a central component of the signalling pathway that reorganizes the cytoskeleton in response to BDLF2-BMRF2. It was concluded that EBV produces a glycoprotein heterodimer that induces changes in cellular morphology through reorganization of the actin cytoskeleton and may facilitate virion spread between cells.

EBV-associated lymphoproliferative disorders: classification and treatment

Since its discovery as the first human tumor virus, Epstein-Barr virus (EBV) has been implicated in the development of a wide range of B-cell lymphoproliferative disorders, including Burkitt's lymphoma, classic Hodgkin's lymphoma, and lymphomas arising in immunocompromised individuals (post-transplant and HIV-associated lymphoproliferative disorders). T-cell lymphoproliferative disorders that have been reported to be EBV associated include a subset of peripheral T-cell lymphomas, angioimmunoblastic T-cell lymphoma, extranodal nasal type natural killer/T-cell lymphoma, and other rare histotypes. EBV encodes a series of products interacting with or exhibiting homology to a wide variety of antiapoptotic molecules, cytokines, and signal transducers, hence promoting EBV infection, immortalization, and transformation. However, the exact mechanism by which EBV promotes oncogenesis is an area of active debate. The focus of this review is on the pathology, diagnosis, classification, and pathogenesis of EBV-associated lymphomas. Recent advances in EBV cell-based immunotherapy, which is beginning to show promise in the treatment of EBV-related disorders, are discussed.

Laboratory assays for Epstein-Barr virus-related disease

Epstein-Barr virus (EBV) infects various cell types in a wide spectrum of benign and malignant diseases. Laboratory tests for EBV have improved and are increasingly used in diagnosis, prognosis, prediction, and prevention of diseases ranging from infectious mononucleosis to selected subtypes of lymphoma, sarcoma, and carcinoma. Indeed, the presence of EBV is among the most effective tumor markers supporting clinical management of cancer patients. In biopsies, localization of EBER transcripts by in situ hybridization remains the gold standard for identifying latent infection. Other RNA- and protein-based assays detect lytic viral replication and can distinguish carcinoma-derived from lymphocyte-derived EBV in saliva or nasopharyngeal brushings. Analysis of blood using EBV viral load and serology reflects disease status and risk of progression. This review summarizes prior research in the context of basic virologic principles to provide a rational strategy for applying and interpreting EBV tests in various clinical settings. Such assays have been incorporated into standard clinical practice in selected settings such as diagnosis of primary infection and management of patients with immune dysfunction or nasopharyngeal carcinoma. As novel therapies are developed that target virus-infected cells or overcome the adverse effects of infection, laboratory testing becomes even more critical for determining when intervention is appropriate and the extent to which it has succeeded.

Secretion of Epstein-Barr virus-encoded BARF1 oncoprotein from latently infected B cells

Epstein-Barr virus (EBV) encodes two oncogenes, LMP1(Latent Membrane Protein-1) and BARF1 (BamH1-A Reading Frame-1). LMP1 belongs to latent gene family and BARF1 is considered so far as one of early gene family. However BARF1 oncogene was expressed highly in Nasopharyngeal (NPC) and gastric (GC) carcinoma as a type II latency, and in EBV-positive Akata cell and primary epithelial cell infected in vitro by EBV as type I latency. Its expression was also reported in Burkitt's lymphoma's biopsy frequent in Malawi in Africa as well as in nasal NK/T-cell lymphoma. We recently observed a massive secretion of BARF1 protein in serum and saliva of NPC patients. NPC-derived c666-1 epithelial cells also expressed and secreted BARF1 protein without other lytic genes expression. We asked whether this oncogene belongs to latent gene family. To investigate, we examined its transcriptional and translational expression in IB4 and Akata B cells where both cell lines belong to latent cell family. Transcriptional expression was analyzed by RT-PCR. As BARF1 protein is one of secreted proteins, its translational expression was analyzed by immunoblot after concentration of culture medium. Secreted BARF1 protein was futher purified by concanavalin A affinity column. BARF1 was transcribed in both EBV-positive AKATA and IB4 cells, and BARF1 protein was secreted from these latently infected human B cells. Its secretion does not depend EBV genome form in infected cells. Both episomal and integrated form of EBV genome were capable of expressing BARF1 gene. These results suggests that BARF1 is expressed in latent stage and increases its expression during lytic stage.

Cyclin D1 expression is induced by viral BARF1 and is overexpressed in EBV-associated gastric cancer

Approximately 10% of gastric carcinomas (GC) worldwide are associated with Epstein-Barr virus (EBV). GC is one of the most frequent human malignancies associated with EBV. The latent expression of the EBV-oncogene BARF1 is restricted to epithelial malignancies. To investigate the underlying BARF1-related mechanisms of oncogenic epithelial transformation, we analyzed gene expression profiles of a BARF1-transfected epithelial (HaCaT+) and the corresponding BARF1-negative (HaCaT-) cell line by cDNA microarray analysis. Real-time PCR was performed to confirm the cDNA microarray results. In addition, immunohistochemistry and fluorescence in situ hybridization were performed on a tissue microarray of 181 GC including 11 EBV-associated GC. Among other genes cyclin D1 expression was significantly upregulated in HaCaT+ on the transcriptional and protein level. Cyclin D1 protein expression in GC revealed a significant overexpression of cyclin D1 in EBV-associated GC (p<0.012) but not in EBV-negative GC. Cyclin D1 FISH showed that cyclin D1 overexpression was not due to gene amplification in EBV-associated GC. Cyclin D1 is induced in HaCaT+ by BARF1 and is overexpressed in EBV-associated GC indicating an interaction of viral BARF1 and cyclin D1.

Reconstitution of nasopharyngeal carcinoma-type EBV infection induces tumorigenicity

Several reports have shown that the EBV-encoded BARF1 gene has oncogenic activity. We have recently reported that BARF1 is expressed as a latent gene in most nasopharyngeal carcinomas (NPC), suggesting that BARF1 may have an important role in NPC oncogenesis. However, we found that when the NPC-derived EBV-negative cell lines, HONE-1 and CNE-1, were infected with EBV in vitro, BARF1 was not expressed, although the expression of other latent genes was identical to that of NPC tumors. Therefore, we generated a recombinant EBV (rEBV) carrying the BARF1 gene (BARF1-rEBV) under the SV40 promoter to reconstitute the NPC-type EBV infection. NPC-derived EBV-negative cell lines were stably infected with either a wild-type rEBV (wild-rEBV) or BARF1-rEBV. The resultant BARF1-rEBV-infected NPC cell clones represented NPC-type EBV expression, and BARF1 expression was similar to that observed in NPC tissues. BARF1-rEBV-infected cell clones grew to a higher cell density and were more resistant to apoptosis than wild-rEBV-infected counterparts. BARF1 protein was quickly secreted into the culture medium, and secreted BARF1 contributed to the increase of cell densities in NPC cells, but it had no effect on resistance to apoptosis. Furthermore, BARF1-rEBV-infected cell clones became tumorigenic in nude mice. These results suggest that BARF1 plays an important role in NPC development.

A new diagnostic marker for secreted Epstein-Barr virus encoded LMP1 and BARF1 oncoproteins in the serum and saliva of patients with nasopharyngeal carcinoma

PURPOSE

EBV has been associated with nasopharyngeal carcinomas (NPC). In North Africa, the incidence is bimodal-the first peak occurring at approximately 20 years of age and the second peak occurring at approximately 50 years. Standard diagnostic tests based on immunofluorescence using anti-IgA EBV have shown that young North African patients have a negative serology compared with older patients. We are interested in two EBV-encoded oncoproteins, LMP1 and BARF1, which have thus far not been studied in terms of their potential as diagnostic markers for NPC. These two viral oncoproteins have been detected in cell culture media, so we tested whether they could be detected in the serum and saliva of patients with NPC.

EXPERIMENTAL DESIGN

LMP1 and BARF1 proteins were analyzed in the sera and saliva of young patients and adult patients with NPC from North Africa and China. We then examined whether the secreted proteins had biological activity by analyzing their mitogenic activity.

RESULTS

Both LMP1 and BARF1 were present in the serum and saliva from North African and Chinese patients with NPC. All young North African patients secreted both proteins, whereas 62% and 100% of adult patients secreted LMP1 and BARF1, respectively. From animal studies, the secreted LMP1 was associated with exosome-like vesicles. These secreted EBV oncoproteins showed a powerful mitogenic activity in B cells.

CONCLUSION

Both proteins will be a good diagnostic marker for NPC whereas BARF1 is a particularly promising marker for all ages of patients with NPC. Their mitogenic activity suggests their implication in the oncogenic development of NPC.

IFN-alpha-stimulated genes and Epstein-Barr virus gene expression distinguish WHO type II and III nasopharyngeal carcinomas

Nonkeratinizing nasopharyngeal carcinoma (NPC) is 100% associated with Epstein-Barr Virus (EBV) and divided into two subtypes (WHO types II and III) based on histology. We tested whether these subtypes can be distinguished at the molecular genetic level using an algorithm that analyzes sets of related genes (gene set enrichment analysis). We found that a class of IFN-stimulated genes (ISG), frequently associated with the antiviral response, was significantly activated in type III versus type II NPC. Consistent with this, replication of the endogenous EBV was suppressed in type III. A strong association was also seen with a subset of ISGs previously identified in systemic lupus erythematosus, another disease in which 'normal' EBV biology is deregulated, suggesting that this pattern of ISG expression may be linked to the increased EBV activity in both diseases. In contrast, unsupervised hierarchical clustering of the complete expression profiles failed to distinguish the two subsets. These results suggest that type II and III NPC have not originated from obviously distinct epithelial precursors; rather, the histologic differences may be a consequence of a differential antiviral response, involving IFNs, to chronic EBV infection.

Epstein-Barr virus in oral diseases

Epstein-Barr virus (EBV), a B-lymphotropic gamma-herpesvirus, causes infectious mononucleosis and oral hairy leukoplakia, and is associated with various types of lymphoid and epithelial malignancies. Saliva is the main vehicle for EBV transmission from individual to individual. Recent studies have also implicated EBV in the pathogenesis of advanced types of periodontal disease. EBV DNA is detected in 60-80% of aggressive periodontitis lesions and in 15-20% of gingivitis lesions or normal periodontal sites. The periodontal presence of EBV is associated with an elevated occurrence of periodontopathic anaerobic bacteria. Moreover, EBV active infection occurs in approximately 70% of symptomatic and large-size periapical lesions. EBV and cytomegalovirus often co-exist in marginal and apical periodontitis. Periodontal therapy can markedly suppress the EBV load in periodontal pockets as well as in saliva, which has the potential to reduce the risk of viral transmission between close individuals. EBV proteins up-regulate cytokines and growth factors, which seem to play a central role in the proliferative response of tongue epithelial cells in oral hairy leukoplakia and in the cell-transformation process of EBV-associated malignancies. Further research is needed to identify the full range of EBV-related diseases in the human oral cavity.

Noninvasive diagnosis of nasopharyngeal carcinoma: nasopharyngeal brushings reveal high Epstein-Barr virus DNA load and carcinoma-specific viral BARF1 mRNA

Nasopharyngeal carcinoma (NPC) is the most prevalent ENT-tumour in Indonesia. We investigated the primary diagnostic value of Epstein-Barr virus (EBV) DNA load and mRNA detection in noninvasive nasopharyngeal (NP) brushings, obtained prospectively from consecutive Indonesian ENT-patients with suspected NPC (N=106) and controls. A subsequent routine NP biopsy was taken for pathological examination and EBER-RISH, yielding 85 confirmed NPC and 21 non-NPC tumour patients. EBV DNA and human DNA load were quantified by real-time PCR. NP brushings from NPC patients contained extremely high EBV DNA loads compared to the 88 non-NPC controls (p<0.0001). Using mean EBV DNA load in controls plus 3 SD as cut-off value, specificity, sensitivity, positive and negative predictive values were 98, 90, 97 and 91%, respectively. Epstein-Barr nuclear antigen 1 (EBNA1) and the carcinoma-specific BARF1 mRNA were detected by nucleic acid sequence based amplification and found in 86 and 74% of NP brushings, confirming NPC tumour cell presence. EBV RNA positivity was even higher in fresh samples stored at -80 degrees C until RNA expression analyses (88% for both EBNA1 and BARF1). EBV RNA-negative NP brushings from proven NPC cases had the lowest EBV DNA loads, indicating erroneous sampling. No EBV mRNA was detected in NP brushings from healthy donors and non-NPC patients. In conclusion, EBV DNA load measurement combined with detection of BARF1 mRNA in simple NP brushings allows noninvasive NPC diagnosis. It reflects carcinoma-specific EBV involvement at the anatomical site of tumour development and reduces the need for invasive biopsies. This procedure may be useful for confirmatory diagnosis in large serological NPC screening programs and has potential as prognostic tool.

Epstein-Barr virus lytic infection contributes to lymphoproliferative disease in a SCID mouse model

Most Epstein-Barr virus (EBV)-positive tumor cells contain one of the latent forms of viral infection. The role of lytic viral gene expression in EBV-associated malignancies is unknown. Here we show that EBV mutants that cannot undergo lytic viral replication are defective in promoting EBV-mediated lymphoproliferative disease (LPD). Early-passage lymphoblastoid cell lines (LCLs) derived from EBV mutants with a deletion of either viral immediate-early gene grew similarly to wild-type (WT) virus LCLs in vitro but were deficient in producing LPD when inoculated into SCID mice. Restoration of lytic EBV gene expression enhanced growth in SCID mice. Acyclovir, which prevents lytic viral replication but not expression of early lytic viral genes, did not inhibit the growth of WT LCLs in SCID mice. Early-passage LCLs derived from the lytic-defective viruses had substantially decreased expression of the cytokine interleukin-6 (IL-6), and restoration of lytic gene expression reversed this defect. Expression of cellular IL-10 and viral IL-10 was also diminished in lytic-defective LCLs. These results suggest that lytic EBV gene expression contributes to EBV-associated lymphoproliferative disease, potentially through induction of paracrine B-cell growth factors.

Epstein-Barr virus encoded BALF1 gene is transcribed in Burkitt's lymphoma cell lines and in nasopharyngeal carcinoma's biopsies

BACKGROUND

The Epstein-Barr virus (EBV) encodes two anti-apoptotic cellular Bcl2 homologs, BALF1 and BHRF1. BHRF1 has an anti-apoptotic activity but is rarely expressed in nasopharyngeal carcinoma (NPC). However, BALF1 is not yet well characterized.

OBJECTIVES

The objective of the study was to characterize BALF1 gene. First, the search of its transcriptional expression in EBV-positive B cell lines, EBV-positive Burkitt's lymphoma's cell lines and nasopharyngeal carcinoma's biopsies. Second, the examination of its anti-apoptotic activity in serum dependent assays.

STUDY DESIGN

We first analysed the transcriptional expression of BALF1 by reverse transcriptase DNA polymerase chain reaction (RT-PCR) method. For the analysis of its anti-apoptotic activity, we transfected NIH3T3 cells with pBABE-BALF1 expression plasmid and studied serum dependence of these transfectants.

RESULTS

BALF1 expression was detected in the latent stage and increased more significantly during the lytic phase in IgG-treated AKATA and TPA-SB-treated P3HR1-TK negative cell lines. As its expression was not affected by the inhibitor of viral DNA synthesis, this gene does not belong to late gene family. When analysed its transcription in Burkitt's lymphoma (BL)-derived cell lines and NPC biopsies, all BL-derived cell lines and more than 80% of NPC biopsies transcribed this gene. The study of serum dependence of BALF1-transfected NIH3T3 cells showed: with 10% of serum, BALF1 transfectants grew significantly more higher cell density than vector alone transfected NIH3T3 cell lines and with 1% of serum, BALF1 transfectants were capable of growing, but with about 40% reduced rate in comparison with those with 10% serum, while vector alone transfected NIH3T3 cells could not almost grow.

CONCLUSION

BALF1 gene was transcribed in EBV-associated tumor cells. BALF1 could render cells to serum independent. These results suggest that BALF1 gene could play its role in EBV oncogenesis.

Absence of caspase 3 activation in neoplastic cells of nasopharyngeal carcinoma biopsies predicts rapid fatal outcome

Poor prognosis in nasopharyngeal carcinoma patients may result from resistance to the apoptosis-inducing effect of radio- and/or chemotherapy. Apoptosis depends on proper activation of caspase 3, resulting in cleavage of key proteins like PARP-1. To investigate whether disruption of the apoptosis pathway results in therapy-resistant tumour cells, we investigated whether absence of caspase 3 activation in tumour biopsies of nasopharyngeal carcinoma patients is related to poor clinical outcome. Moreover, we investigated whether absence of caspase 3 activation is related to loss of procaspase 3 expression or expression of the apoptosis regulators p53, bcl-2 and XIAP. We studied 36 Indonesian nasopharyngeal carcinoma patients without evidence of distant metastases who were treated with curative intent by radiotherapy only. Activation of caspase 3 and expression of the different markers were determined using specific antibodies. Levels of caspase 3 activation were determined by quantifying positively staining tumour cells. Nasopharyngeal carcinoma-derived C15 and C17 tumour cells were used as control. Absence of caspase 3 activation was strongly related to a poor clinical response to radiotherapy and to a higher T and N stage, resulting in a particularly poor clinical outcome with regard to progression-free (P<0.0001) and overall survival time (P<0.0001). Absence of caspase 3 activation was significantly correlated to loss of expression of procaspase 3 (P=0.04). In nasopharyngeal carcinoma patients treated with curative intent, absence of active caspase 3-positive neoplastic cells predicts rapid fatal outcome, and is associated with poor response to radiotherapy and high T and N stage at time of presentation.

Diagnostic value of measuring Epstein-Barr virus (EBV) DNA load and carcinoma-specific viral mRNA in relation to anti-EBV immunoglobulin A (IgA) and IgG antibody levels in blood of nasopharyngeal carcinoma patients from Indonesia

Nasopharyngeal carcinoma (NPC) is a prevalent malignancy in Southeast Asia and is strongly associated with Epstein-Barr virus (EBV). We investigated the primary diagnostic value of circulating EBV DNA and anti-EBV immunoglobulin G (IgG) and IgA levels in Indonesian NPC patients (n = 149). By a 213-bp Epstein-Barr virus nuclear antigen 1 (EBNA1)-based real-time LightCycler PCR, 72.5% of patients were positive for EBV DNA in whole blood, with 29.5% having levels above a previously determined clinical cutoff value (COV) of 2,000 EBV DNA copies/ml, the upper level in healthy carriers. In a 99-bp LightCycler PCR, 85.9% of patients were positive and 60.4% had levels above the COV. This assay quantified a significantly higher EBV load than the 213-bp PCR assay (P < 0.0001), suggesting that circulating EBV DNA is fragmented. Using data from 11 different studies, we showed a significant inverse correlation between PCR amplicon size and the percentage of patients positive for circulating EBV DNA (Spearman's rho = -0.91; P < 0.0001). EBV DNA loads were unrelated to anti-EBV IgG or IgA levels, as measured by VCA-p18 and EBNA1-specific synthetic peptide-based enzyme-linked immunosorbent assays. The presence of circulating tumor cells was assessed by amplification of BamHI-A rightward frame 1 (BARF1) mRNA, a viral oncogene abundantly expressed in EBV-carrying carcinomas but virtually absent from EBV-associated lymphomas. Despite high EBV DNA loads and the presence of EBNA1 and human U1A small nuclear ribonucleoprotein mRNA, BARF1 mRNA was never detected in blood. We conclude that amplicon size significantly influences EBV DNA load measurement in NPC patients. The circulating EBV DNA load is independent of serological parameters and does not reflect intact tumor cells. The primary diagnostic value of the EBV DNA load for the detection of NPC is limited.

Terminal differentiation into plasma cells initiates the replicative cycle of Epstein-Barr virus in vivo

In this paper we demonstrate that the cells which initiate replication of Epstein-Barr virus (EBV) in the tonsils of healthy carriers are plasma cells (CD38hi, CD10-, CD19+, CD20lo, surface immunoglobulin negative, and cytoplasmic immunoglobulin positive). We further conclude that differentiation into plasma cells, and not the signals that induce differentiation, initiates viral replication. This was confirmed by in vitro studies showing that the promoter for BZLF1, the gene that begins viral replication, becomes active only after memory cells differentiate into plasma cells and is also active in plasma cell lines. This differs from the reactivation of BZLF1 in vitro, which occurs acutely and is associated with apoptosis and not with differentiation. We suggest that differentiation and acute stress represent two distinct pathways of EBV reactivation in vivo. The fraction of cells replicating the virus decreases as the cells progress through the lytic cycle such that only a tiny fraction actually release infectious virus. This may reflect abortive replication or elimination of cells by the cellular immune response. Consistent with the later conclusion, the cells did not down regulate major histocompatibility complex class I molecules, suggesting that this is not an immune evasion tactic used by EBV and that the cells remain vulnerable to cytotoxic-T-lymphocyte attack.

Expression and analysis of the Epstein-Barr virus BARF1-encoded protein from a tetracycline-regulatable adenovirus system

Epstein-Barr virus (EBV) has been associated with human cancers of lymphocytic or epithelial origin. Potential functions of the BARF1 early gene in EBV oncogenesis emerged from our observations showing expression of BARF1-encoded protein in nasopharyngeal carcinoma biopsies, and induction of either malignant transformation (in rodent fibroblast and human B cell lines) or immortalization (in monkey primary epithelial cells) following BARF1 transfection. We previously reported expression of the BARF1 product as a cytoplasm/membrane-associated protein from 293-tTA cells infected with a BARF1-recombinant adenovirus. Since constitutive expression of BARF1 from this heterologous system became inefficient, we developed a tetracycline-regulatable recombinant vector expressing BARF1 and green fluorescent protein from a dicistronic message. As here reported, stable and efficient expression of BARF1 from this vector in either permissive or non-permissive cell lines, allowed the first sequencing identification and further molecular characterization of BARF1-encoded protein.

Epstein-Barr virus and cancer

EBV was the first human virus to be directly implicated in carcinogenesis. It infects >90% of the world's population. Although most humans coexist with the virus without serious sequelae, a small proportion will develop tumors. Normal host populations can have vastly different susceptibility to EBV-related tumors as demonstrated by geographical and immunological variations in the prevalence of these cancers. EBV has been implicated in the pathogenesis of Burkitt's lymphoma, Hodgkin's disease, non-Hodgkin's lymphoma, nasopharyngeal carcinoma, and lymphomas, as well as leiomyosarcomas arising in immunocompromised individuals. The presence of this virus has also been associated with epithelial malignancies arising in the gastric region and the breast, although some of this work remains in dispute. EBV uses its viral proteins, the actions of which mimic several growth factors, transcription factors, and antiapoptotic factors, to usurp control of the cellular pathways that regulate diverse homeostatic cellular functions. Recent advances in antiviral therapeutics, application of monoclonal antibodies, and generation of EBV-specific CTLs are beginning to show promise in the treatment of EBV-related disorders.

Mitogenic activity of Epstein-Barr virus-encoded BARF1 protein

We previously reported that BARF1 gene has either an immortalizing effect, when expressed in primary primate epithelial cells, or a malignant transforming activity, when expressed in established and nontumoral rodent fibroblast or human B-cell lines. As predicted from sequence analysis, we found that BARF1 coded protein can be secreted from different cell lines, among them BARF1-transfected Balb/c3T3 rodent fibroblasts. Thus, as an initial step to clarify BARF1 oncogenic functions, we investigated whether the secreted form of BARF1 protein can activate the cell cycle as a growth factor. Since efficient BARF1 expression could be obtained from 293-tTA cells infected with a tetracycline-regulatable recombinant adenovirus, secreted BARF1 product could be purified from the culture medium of such cells by ammonium sulfate precipitation, ion exchange chromotography and sucrose gradient sedimentation. We describe in this paper that addition of a purified product of secreted BARF1 protein to serum-free culture medium of Balb/c3T3 rodent fibroblasts, human Louckes B-cell line and primary monkey kidney epithelial cells resulted in a cell cycle activation that was inhibited by affinity-purified anti-BARF1 antibody. Our demonstration of a specific stimulation of cell cycle in vitro by BARF1 secreted product suggests that this EBV-encoded BARF1 protein could act as a growth factor in vivo.

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.

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.

Regulatory T cells secreting IL-10 dominate the immune response to EBV latent membrane protein 1

Viruses exploit a number of strategies to evade immune recognition. In this study, we describe a novel mechanism by which EBV, rather than avoiding detection, subverts the immune response by stimulating regulatory T cells that secrete IL-10. Human PBMC from all EBV-seropositive, but not -seronegative, donors responded to both purified latent membrane protein 1 and the corresponding immunodominant peptides with high levels of IL-10 secretion by CD4(+) T cells. These IL-10 responses, characteristic of T regulatory 1 cells, inhibited T cell proliferation and IFN-gamma secretion induced by both mitogen and recall Ag. It was confirmed that the inhibition was IL-10 dependent by the use of neutralizing Ab. The deviation of the immune response toward suppression is likely to be important in maintaining latency and EBV-associated tumors.

Carcinogenicity testing of IL-10: principles and practicalities

IL-10 is a cytokine with actions at many levels of the immune system. In the course of development of recombinant human IL-10 (rhuIL-10) as a potential treatment for a number of chronic diseases of man, the question 'What about its carcinogenicity testing?' was repeatedly asked, based on scientific evaluation by toxicologists, beliefs about regulatory requirements, and questions considered likely to be raised by physicians, patients, and lawyers. The feasibility of various approaches to the carcinogenicity testing of rhuIL-10 is critically discussed here as a contribution to rational consideration of the general need for and value of such testing, and its particular feasibility for a recombinant human protein with profound effects on the immune system. The physiological functions of IL-10 in man and rodents are reviewed in detail, as there are notable differences between species in its normal activities, followed by detailed evaluation of the potential procedures and practical problems of its carcinogenicity testing as a heterologous, immunogenic protein in rodents. The value of information that might be obtained from transgenic mice is also evaluated, and so are the results of studies exploring its actions on human tumour cell biopsies and rodent and human cell lines. It is concluded that despite the probable popular and regulatory expectations that carcinogenicity test results would be provided, all the physiological and pathological information reveals no indication that rhuIL-10 would pose a carcinogenic risk to humans on prolonged administration, and that it would not be feasible to undertake such experimentation. It is argued that in this, as in other instances, professional and popular expectations have run beyond practical feasibility or theoretical justification. Cautious and critical evaluation should be made every time shorter or longer term toxicity studies of any candidate drug are planned or even considered, especially if it is a recombinant protein, to decide on objective grounds whether the studies are really necessary and whether they can be done in a way that will give meaningful results that will help in risk assessment.

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.

A method to detect major serotypes of foot-and-mouth disease virus

Nucleic acid sequence-based amplification (NASBA) is an isothermal technique that allows the rapid amplification of specific regions of nucleic acid obtained from a diverse range of sources. It is especially suitable for amplifying RNA sequences. A rapid and specific NASBA technique was developed, allowing the detection of foot-and-mouth disease virus genetic material in a range of sample material, including preserved skin biopsy material from infected animals, vaccines prepared from denatured cell-free material, and cell-free antigen-based detection kits. A single pair of DNA oligonucleotide primers was able to amplify examples of all major FMD virus subtypes. The amplified viral RNA was detected by electrochemiluminescence. The method was at least as sensitive as existing cell-free antigen detection methods.