Interleukin-10 Abrogates the Inhibition of Epstein-Barr Virus–Induced B-Cell Transformation by Memory T-Cell Responses

Tumor Microenvironment Conditioning by Abortive Lytic Replication of Oncogenic γ-Herpesviruses

Epstein Barr virus (EBV) and Kaposi sarcoma-associated herpesvirus (KSHV) constitute the human γ-herpesviruses and two of the seven human tumor viruses. In addition to their viral oncogenes that primarily belong to the latent infection programs of these viruses, they encode proteins that condition the microenvironment. Many of these are early lytic gene products and are only expressed in a subset of infected cells of the tumor mass. In this chapter I will describe their function and the evidence that targeting them in addition to the latent oncogenes could be beneficial for the treatment of EBV- and KSHV-associated malignancies.

The EBV-DNA Can be Used as a Diagnostic and Follow-up Parameter of the Rhinopharyngeal Tumors in the Non-Endemic Population of the Western Sicily

To evaluate whether EBV-DNA can be used as a diagnostic and follow-up parameter for nasopharyngeal tumors in a non-endemic population. The study was carried out in a university hospital. A retrospective study was conducted on 40 paraffin samples of histological preparations. EB-DNA was detected by real-time PCR technique. A prospective study was also conducted on a group of 30 patients who underwent nasopharyngeal biopsy for suspected nasopharyngeal carcinoma (NPC) by comparing EBV-DNA concentrations between the histological specimen and the serum. Quantification of genomic copies of EBV-DNA in serum and detection of anti-EBV antibodies was performed. In both groups the presence of high viral load of EBV-DNA was found in nonkeratinizing squamous cell carcinomas, in three cases of lymphepitomyoma and in 4 out of 6 cases of non-differentiated non-carcinoma lymph node metastases. squamous keratinizing cells. In all cases of NPC, an antibody pattern typical of reactivations (IgGVCA+, IgG-EA+, IgG-EBNA+) and IgA-EA-D, frequently positive in cases of NPC, has been highlighted. A good correlation between the high EBV-DNA charges and the histological diagnosis was highlighted. Our study also found that the assessment of viral EBV load can also be considered in the prognostic evaluation and in the follow-up of patients with NPC.

The Epstein-Barr Virus Immunoevasins BCRF1 and BPLF1 Are Expressed by a Mechanism Independent of the Canonical Late Pre-initiation Complex

Subversion of host immune surveillance is a crucial step in viral pathogenesis. Epstein-Barr virus (EBV) encodes two immune evasion gene products, BCRF1 (viral IL-10) and BPLF1 (deubiquitinase/deneddylase); both proteins suppress antiviral immune responses during primary infection. The BCRF1 and BPLF1 genes are expressed during the late phase of the lytic cycle, an essential but poorly understood phase of viral gene expression. Several late gene regulators recently identified in beta and gamma herpesviruses form a viral pre-initiation complex for transcription. Whether each of these late gene regulators is necessary for transcription of all late genes is not known. Here, studying viral gene expression in the absence and presence of siRNAs to individual components of the viral pre-initiation complex, we identified two distinct groups of late genes. One group includes late genes encoding the two immunoevasins, BCRF1 and BPLF1, and is transcribed independently of the viral pre-initiation complex. The second group primarily encodes viral structural proteins and is dependent on the viral pre-initiation complex. The protein kinase BGLF4 is the only known late gene regulator necessary for expression of both groups of late genes. ChIP-seq analysis showed that the transcription activator Rta associates with the promoters of eight late genes including genes encoding the viral immunoevasins. Our results demonstrate that late genes encoding immunomodulatory proteins are transcribed by a mechanism distinct from late genes encoding viral structural proteins. Understanding the mechanisms that specifically regulate expression of the late immunomodulatory proteins could aid the development of antiviral drugs that impair immune evasion by the oncogenic EB virus.

Late proteins are expressed during the productive cycle of Epstein-Barr virus (EBV) after the onset of viral DNA replication. Many late proteins serve structural functions; they form the capsid shell around the viral genome or mediate attachment and fusion of the virus to the host cell. EBV also encodes two late proteins that suppress the immune system during primary infection. The current model suggests that transcription of all late genes is regulated by a common mechanism involving seven late gene regulators. Here, we demonstrate that late genes encoding two viral immune suppressants are transcribed by a mechanism different from that regulating late genes encoding structural proteins. Abolishing expression of the late immunomodulators without disrupting expression of the antigenic viral structural proteins could serve as an approach to block EBV de novo infection and its associated malignancies.

Manipulation of the host cell membrane by human γ-herpesviruses EBV and KSHV for pathogenesis

The cell membrane regulates many physiological processes including cellular communication, homing and metabolism. It is therefore not surprising that the composition of the host cell membrane is manipulated by intracellular pathogens. Among these, the human oncogenic herpesviruses Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV) exploit the host cell membrane to avoid immune surveillance and promote viral replication. Accumulating evidence has shown that both EBV and KSHV directly encode several similar membrane-associated proteins, including receptors and receptor-specific ligands (cytokines and chemokines), to increase virus fitness in spite of host antiviral immune responses. These proteins are expressed individually at different phases of the EBV/KSHV life cycle and employ various mechanisms to manipulate the host cell membrane. In recent decades, much effort has been made to address how these membrane-based signals contribute to viral tumorigenesis. In this review, we summarize and highlight the recent understanding of how EBV and KSHV similarly manipulate host cell membrane signals, particularly how remodeling of the cell membrane allows EBV and KSHV to avoid host antiviral immune responses and favors their latent and lytic infection.

The Role of Gammaherpesviruses in Cancer Pathogenesis

Worldwide, one fifth of cancers in the population are associated with viral infections. Among them, gammaherpesvirus, specifically HHV4 (EBV) and HHV8 (KSHV), are two oncogenic viral agents associated with a large number of human malignancies. In this review, we summarize the current understanding of the molecular mechanisms related to EBV and KSHV infection and their ability to induce cellular transformation. We describe their strategies for manipulating major cellular systems through the utilization of cell cycle, apoptosis, immune modulation, epigenetic modification, and altered signal transduction pathways, including NF-kB, Notch, Wnt, MAPK, TLR, etc. We also discuss the important EBV latent antigens, namely EBNA1, EBNA2, EBNA3’s and LMP’s, which are important for targeting these major cellular pathways. KSHV infection progresses through the engagement of the activities of the major latent proteins LANA, v-FLIP and v-Cyclin, and the lytic replication and transcription activator (RTA). This review is a current, comprehensive approach that describes an in-depth understanding of gammaherpes viral encoded gene manipulation of the host system through targeting important biological processes in viral-associated cancers.

Latent Membrane Protein LMP2A Impairs Recognition of EBV-Infected Cells by CD8+ T Cells

The common pathogen Epstein-Barr virus (EBV) transforms normal human B cells and can cause cancer. Latent membrane protein 2A (LMP2A) of EBV supports activation and proliferation of infected B cells and is expressed in many types of EBV-associated cancer. It is not clear how latent EBV infection and cancer escape elimination by host immunity, and it is unknown whether LMP2A can influence the interaction of EBV-infected cells with the immune system. We infected primary B cells with EBV deleted for LMP2A, and established lymphoblastoid cell lines (LCLs). We found that CD8+ T cell clones showed higher reactivity against LMP2A-deficient LCLs compared to LCLs infected with complete EBV. We identified several potential mediators of this immunomodulatory effect. In the absence of LMP2A, expression of some EBV latent antigens was elevated, and cell surface expression of MHC class I was marginally increased. LMP2A-deficient LCLs produced lower amounts of IL-10, although this did not directly affect CD8+ T cell recognition. Deletion of LMP2A led to several changes in the cell surface immunophenotype of LCLs. Specifically, the agonistic NKG2D ligands MICA and ULBP4 were increased. Blocking experiments showed that NKG2D activation contributed to LCL recognition by CD8+ T cell clones. Our results demonstrate that LMP2A reduces the reactivity of CD8+ T cells against EBV-infected cells, and we identify several relevant mechanisms.

Epstein-Barr virus (EBV) is carried by most humans. It can cause several types of cancer. In healthy infected people, EBV persists for life in a "latent" state in white blood cells called B cells. For infected persons to remain healthy, it is crucial that they harbor CD8-positive "killer" T cells that recognize and destroy precancerous EBV-infected cells. However, this protection is imperfect, because the virus is not eliminated from the body, and the danger of EBV-associated cancer remains. How does the virus counteract CD8+ T cell control? Here we study the effects of latent membrane protein 2A (LMP2A), which is an important viral molecule because it is present in several types of EBV-associated cancers, and in latently infected cells in healthy people. We show that LMP2A counteracts the recognition of EBV-infected B cells by antiviral killer cells. We found a number of mechanisms that are relevant to this effect. Notably, LMP2A disturbs expression of molecules on B cells that interact with NKG2D, a molecule on the surface of CD8+ T cells that aids their activation. In this way, LMP2A weakens important immune responses against EBV. Similar mechanisms may operate in different types of LMP2A-expressing cancers caused by EBV.

Regulation of Epstein-Barr virus reactivation from latency

The Epstein-Barr virus (EBV) is a human gamma-herpesvirus that is implicated in various types of proliferative diseases. Upon infection, it predominantly establishes latency in B cells and cannot ever be eradicated; it persists for the host's lifetime. Reactivation of the virus from latency depends on expression of the viral immediate-early gene, BamHI Z fragment leftward open reading frame 1 (BZLF1). The BZLF1 promoter normally exhibits only low basal activity but is activated in response to chemical or biological inducers, such as 12-O-tetradecanoylphorbol-13-acetate, calcium ionophore, histone deacetylase inhibitor, or anti-Ig. Transcription from the BZLF1 promoter is activated by myocyte enhancer factor 2, specificity protein 1, b-Zip type transcription factors and mediating epigenetic modifications of the promoter, such as histone acetylation and H3K4me3. In contrast, repression of the promoter is mediated by transcriptional suppressors, such as ZEB, ZIIR-BP, and jun dimerization protein 2, causing suppressive histone modifications like histone H3K27me3, H3K9me2/3 and H4K20me3. Interestingly, there is little CpG DNA methylation of the promoter, indicating that DNA methylation is not crucial for suppression of BZLF1. This review will focus on the molecular mechanisms by which the EBV lytic switch is controlled and discuss the physiological significance of this switching for its survival and oncogenesis.

Epstein-Barr Virus Lytic Cycle Reactivation

Epstein-Barr virus, which mainly infects B cells and epithelial cells, has two modes of infection: latent and lytic. Epstein-Barr virus infection is predominantly latent; however, lytic infection is detected in healthy seropositive individuals and becomes more prominent in certain pathological conditions. Lytic infection is divided into several stages: early gene expression, DNA replication, late gene expression, assembly, and egress. This chapter summarizes the most recent progress made toward understanding the molecular mechanisms that regulate the different lytic stages leading to production of viral progeny. In addition, the chapter highlights the potential role of lytic infection in disease development and current attempts to purposely induce lytic infection as a therapeutic approach.

Virus induced inflammation and cancer development

Chronic inflammation as a result of viral infection significantly increases the likelihood of cancer development. A handful of diverse viruses have confirmed roles in cancer development and progression, but the list of suspected oncogenic viruses is continually growing. Viruses induce cancer directly and indirectly, by activating inflammatory signalling pathways and cytokines, stimulating growth of infected cells and inhibiting apoptosis. Although oncogenic viruses induce inflammation by various mechanisms, it is generally mediated by the MAPK, NFκB and STAT3 signalling pathways. This review will explore the unique mechanisms by which different oncogenic viruses induce inflammation to promote cancer initiation and progression.

Evasion of adaptive and innate immune response mechanisms by γ-herpesviruses

γ-Herpesviral immune evasion mechanisms are optimized to support the acute, lytic and the longterm, latent phase of infection. During acute infection, specific immune modulatory proteins limit, but also exploit, the antiviral activities of cell intrinsic innate immune responses as well as those of innate and adaptive immune cells. During latent infection, a restricted gene expression program limits immune targeting and cis-acting mechanisms to reduce the antigen presentation as well as antigenicity of latency-associated proteins. Here, we will review recent progress in our understanding of γ-herpesviral immune evasion strategies.

The EBV immunoevasins vIL-10 and BNLF2a protect newly infected B cells from immune recognition and elimination

Lifelong persistence of Epstein-Barr virus (EBV) in infected hosts is mainly owed to the virus' pronounced abilities to evade immune responses of its human host. Active immune evasion mechanisms reduce the immunogenicity of infected cells and are known to be of major importance during lytic infection. The EBV genes BCRF1 and BNLF2a encode the viral homologue of IL-10 (vIL-10) and an inhibitor of the transporter associated with antigen processing (TAP), respectively. Both are known immunoevasins in EBV's lytic phase. Here we describe that BCRF1 and BNLF2a are functionally expressed instantly upon infection of primary B cells. Using EBV mutants deficient in BCRF1 and BNLF2a, we show that both factors contribute to evading EBV-specific immune responses during the earliest phase of infection. vIL-10 impairs NK cell mediated killing of infected B cells, interferes with CD4+ T-cell activity, and modulates cytokine responses, while BNLF2a reduces antigen presentation and recognition of newly infected cells by EBV-specific CD8+ T cells. Together, both factors significantly diminish the immunogenicity of EBV-infected cells during the initial, pre-latent phase of infection and may improve the establishment of a latent EBV infection in vivo.

Detection of EBV infection and gene expression in oral cancer from patients in Taiwan by microarray analysis

Epstein-Barr virus is known to cause nasopharyngeal carcinoma. Although oral cavity is located close to the nasal pharynx, the pathogenetic role of Epstein-Barr virus (EBV) in oral cancers is unclear. This molecular epidemiology study uses EBV genomic microarray (EBV-chip) to simultaneously detect the prevalent rate and viral gene expression patterns in 57 oral squamous cell carcinoma biopsies (OSCC) collected from patients in Taiwan. The majority of the specimens (82.5%) were EBV-positive that probably expressed coincidently the genes for EBNAs, LMP2A and 2B, and certain structural proteins. Importantly, the genes fabricated at the spots 61 (BBRF1, BBRF2, and BBRF3) and 68 (BDLF4 and BDRF1) on EBV-chip were actively expressed in a significantly greater number of OSCC exhibiting exophytic morphology or ulceration than those tissues with deep invasive lesions (P = .0265 and .0141, resp.). The results may thus provide the lead information for understanding the role of EBV in oral cancer pathogenesis.

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.

Dithiocarbamates and viral IL-10 collaborate in the immortalization and evasion of immune response in EBV-infected human B lymphocytes

Epstein-Barr virus (EBV) is implicated in the development of a number of human malignancies including several subtypes of non-Hodgkin lymphoma (NHL) [G. Pallesen, S.J. Hamilton-Dutoit, X. Zhou, The association of Epstein-Barr virus (EBV) with T cell lymphoproliferations and Hodgkin's disease: two new developments in the EBV Field, Adv. Cancer Res. 62 (1993) 179-239]. Lymphoproliferative disease and NHL occurring in severely immunosuppressed individuals almost always involve EBV and have been extensively studied and modeled in vitro. EBV has also been causally associated with some cases of NHL occurring in otherwise immunocompetent individuals. However, a direct role for EBV in the pathogenesis of neoplasms developing in the presence of an otherwise competent immune system has not been established. We investigated potential interactions between dithiocarbamates (DTC), an important class of thiono-sulfur compounds, and EBV leading to immortalization of human B lymphocytes and evasion of cell-mediated immune response in culture. Primary lymphocyte cultures employing wild-type and recombinant EBV mutants were used to assess the respective roles of DTC and viral genes in lymphocyte transformation and survival. Pretreatment of EBV-infected human B lymphocytes with DTC directly enhanced transformation in the absence of T cells (5 nM) and independently increased survival of transformed cells in the presence of competent autologous T cells (10 nM). Both DTC-induced transformation and immortalization of EBV-infected B lymphocytes were dependent on the expression of viral IL-10. These results provide a biological basis for studying collaborations between chemical and virus that alter lymphocyte biology, and provide a rationale for further molecular epidemiology studies to better understand the potential influence of these interactions on the development of NHL and perhaps other viral-associated malignancies.

Review of Epstein–Barr virus and post-transplant lymphoproliferative disorder post-solid organ transplantation (Review Article)

Post-transplant lymphoproliferative disorder (PTLD) following solid organ transplantation is an important form of post-transplant malignancy. PTLD is typically associated with Epstein-Barr virus (EBV) and occurs in the setting of profound immunosuppression resulting in a deficiency of EBV-specific cytotoxic T lymphocytes (CTL). Predisposing factors include EBV mismatch between donor and recipient, use of immunosuppression especially T-cell depletive therapies and genetic predisposition of recipients. The standard approach has been to reduce immunosuppression but is often insufficient to induce tumour regression. Further understanding of the immunobiology of PTLD has resulted in improved monitoring techniques (including EBV viral load determined by polymerase chain reaction) and newer treatment options. Recent work has highlighted a potential role for dendritic cells in both the pathogenesis and treatment of PTLD. Current treatment modalities include adoptive immunotherapy using ex vivo generated autologous EBV-specific CTL or allogeneic CTL, cytokine therapies, antiviral agents, and more recently, rituximab and dendritic-cell based therapies. This review focuses on the developments and progress in the pathogenesis, diagnosis and treatment of PTLD.

Dominant expression of interleukin-10 and transforming growth factor-beta genes in activated T-cells of chronic active Epstein-Barr virus infection

Chronic active Epstein-Barr virus (EBV) infection is a chronic mononucleosis syndrome associated with clonal proliferation of EBV-carrying T-/natural killer (NK)-cells. High levels of circulating EBV and activated T-cells are sustained during the prolonged disease course, whereas it is not clear how ectopic EBV infection in T-/NK-cells has been established and maintained. To assess the biological role of activated T-cells in chronic active EBV infection (CAEBV), EBV DNA and cellular gene expressions in peripheral T-cells were quantified in CAEBV and infectious mononucleosis (IM) patients. In CAEBV, HLA-DR(+) T-cells had higher viral load and larger amounts of IFN gamma, IL-10, transforming growth factor-beta (TGF beta), and cytotoxic T lymphocyte antigen-4 (CTLA4) mRNA than HLA-DR(-)T-cells. HLA-DR(+) T cells of IM patients transcribed more IFN gamma and IL-10 than their HLA-DR(-)T cells. Expression levels of IFN gamma and forkhead box p3 (Foxp3) in CAEBV HLA-DR(+) T-cells were higher than in IM HLA-DR(+) T-cells. The effective variables to discriminate the positivity of HLA-DR were IL-10, IFN gamma, CTLA4, TGF beta, and IL-2 in the order of statistical weight. EBV load in CAEBV T-cells correlated with the expression levels of only IL-10 and TGF beta. These results suggest that CAEBV T-cells are activated to transcribe IFN gamma, IL-10, and TGF beta excessively, and the latter two genes are expressed preferentially in the EBV-infected subsets. The dominant expression of regulatory cytokines in T-cells may imply a viral evasion mechanism in the disease.

A novel function for the Epstein-Barr virus transcription factor EB1/Zta: induction of transcription of the hIL-10 gene

Interleukin-10 (IL-10) plays a critical role in Epstein-Barr virus (EBV) biology. Indeed, the EBV genome contains a gene (BCRF1) with homology to the human IL-10 (hIL-10) gene. In addition to viral IL-10, which is secreted late in the productive cycle, hIL-10 production is also induced in B cells infected by EBV. The EBV protein LMP-1 and the viral small non-polyadenylated RNAs (EBERs) expressed during latency are involved in hIL-10 induction. In this study, we show that in B cells the viral transcription factor EB1, which is the main inducer of the EBV productive cycle, also activates transcription of the hIL-10 gene and secretion of the hIL-10 protein. Accordingly, EB1 bound directly to specific DNA sequences in the hIL-10 minimal promoter. Moreover, specific disruption of EB1 binding to some of these sites impaired EB1-mediated activation of transcription at the hIL-10 promoter in a transient expression assay. Therefore, an increase in IL-10 production occurs during latency and early and late during the productive cycle. This production of IL-10 might favour the survival of EBV-infected cells in vivo and/or create a microenvironment required for efficient de novo infection of B lymphocytes by EBV virions.

Manipulation of immune responses by Epstein–Barr virus

Epstein-Barr virus (EBV) infects and persists for life in the majority of the human population. Persistence is achieved through a combination of strictly regulated programs of latent infection in B-cells and chronic reactivation of virus replication in lymphoid tissue and mucosal surfaces. The resulting multiple patterns of virus-host interaction have selected unique strategies of immune escape. T-cell mediated immunity plays a central role in the control of EBV latency and several immune escape mechanism that protect the virus at this stage of its life circle have been characterized in details. In contrast, the contribution of innate immunity and the immune regulation of productive infection are largely unexplored areas that may yield important clues on the establishment and maintenance of EBV persistence. This review summarizes well known and emerging mechanisms of EBV immune escape that may reveal new strategies of immunoregulation and promote new approaches to the prophylaxis and treatment of EBV associated diseases.

Interferon--gamma control of EBV-transformed B cells: a role for CD8+ T cells that poorly kill EBV-infected cells

Control of Epstein-Barr virus (EBV) infection requires CD8+ T cells. Surprisingly, many EBV-specific CD8+ T cells kill autologous EBV-transformed B lymphoblasts poorly. We investigated the effector functions used by poorly cytotoxic EBV-specific CD8+ D7 cloned T cells and by EBV-stimulated peripheral blood lymphocytes. D7 T cells did not inhibit B lymphoblast growth in long-term coculture, but prevented the outgrowth of newly infected autologous B cells. Optimally stimulated D7 T cells and EBV-stimulated peripheral blood lymphocytes produced interferon (IFN)-y at levels that inhibited EBV-transformed B cell outgrowth. Inhibitory factor activity was neutralized by anti-IFN-gamma monoclonal antibodies (mAb), but not by antibodies to several other cytokines. These data suggest an in vivo role for IFN-y secreting EBV-specific CD8+ T cells.

Epstein-Barr virus infection and human malignancies

The Epstein-Barr virus (EBV) is a herpes virus which establishes a life-long persistent infection in over 90% of the human adult population world-wide. Based on its association with a variety of lymphoid and epithelial malignancies, EBV has been classified as a group 1 carcinogen by the International Agency for Research on Cancer. In this article we discuss the evidence supporting an aetiological role for EBV in the pathogenesis of human tumours. The biology of EBV infection will be described with special emphasis on viral transforming gene products. A brief survey of EBV-associated tumours is followed by a discussion of specific problems. Evidence is presented which suggests that failures of the EBV-specific immunity may play a role in the pathogenesis of EBV-associated tumours also in patients without clinically manifest immunodeficiencies. Finally, the timing of EBV infection in the pathogenesis of virus-associated malignancies is discussed. There is good evidence that EBV infection precedes expansion of the malignant cell populations in some virus-associated tumours. However, this is clearly not always the case and for some of these tumours there are indications that clonal genetic alterations may occur prior to EBV infection. Thus, whilst there is good evidence to suggest that EBV is a human carcinogen, its precise role(s) in the development of virus-associated human tumours requires clarification.

Role of cytotoxic T lymphocytes in Epstein-Barr virus-associated diseases

Adaptation of persistent infection within the cells of the immune system is a unique characteristic of gamma herpes viruses. A classic example of this is Epstein-Barr virus (EBV), which may have co-evolved with Homo sapiens over millions of years, thus achieving a balance between viral persistence and immune control. In this review, we present an overview of virus and the host immune system interactions that regulate the life-long host-virus relationship in healthy virus carriers and EBV-associated diseases. Extensive analysis of cytotoxic T lymphocyte-mediated immune responses in healthy virus carriers has revealed unique mechanisms used by EBV to maintain a benign persistent state in vivo. On the other hand, this relationship in EBV-associated diseases favors the escape of the virus from the hostile effects of the immune response. This escape is achieved by either down-regulating the expression of highly immunogenic antigens of the virus or by direct modulation of the host cytotoxic T lymphocyte response by virus-encoded proteins.

Abolished angiogenicity and tumorigenicity of Burkitt lymphoma by interleukin-10

Because of its immunosuppressive properties, interleukin-10 (IL-10) is thought to play an important role in a number of human disease states, including inflammation, autoimmunity, and transplant rejection. In this study, we demonstrate that introduction of human or viral IL-10 genes into Burkitt's lymphoma cells markedly reduced their ability to grow as subcutaneous (sc) tumors in SCID mice. In vivo assays for angiogenesis revealed an inhibition of the angiogenic capacity of the IL-10–transfected lines. Recombinant human IL-10 abolished and viral IL-10 reduced vascular endothelial growth factor (VEGF)-165–induced neovascularization. Furthermore, IL-10 blocked the VEGF- and fibroblast growth factor (FGF)-2–induced proliferation of microvascular endothelial cells in vitro. The current observations suggest a direct role for IL-10 in the prevention of angiogenesis in human lymphoid malignancies.

Chronic, active Epstein-Barr virus infection

Chronic active Epstein-Barr virus (EBV) infection is an uncommon outcome of EBV infection and may present as a waxing and waning or fulminant syndrome. Unlike acute infectious mononucleosis, wherein EBV establishes lifelong infection and survives by maintaining a delicate balance with the host as a latent infection, in chronic active EBV infection the host-virus balance is disturbed. The mechanisms by which this balance becomes perturbed are likely to be heterogenous and may involve host immune factors, viral factors, or both. A number of subtle immunologic defects have been reported in patients with chronic active EBV infection. Enhanced expression of viral genes has also been noted in some cases. Treatment of chronic active EBV infection has proven difficult, but new modalities including etoposide-based regimens and adoptive transfer of EBV-specific cytotoxic T lymphocytes have shown promise.

Cytokines in the evolution and treatment of AIDS-lymphoma

AIDS-lymphoma is a heterogeneous disease that most likely results from the complex interaction of several contributing factors, including chronic antigenic activation of B lymphocytes, dysregulated cytokine and co-stimulatory networks, infection with potentially oncogenic viruses (human herpesvirus-8 [HHV-8], Epstein-Barr virus), and accumulation of secondary genetic mutations. Cytokines are believed to play an important role in the immunologic decline that favors opportunistic infection and malignancy in advanced HIV infection. Recent work has provided some evidence that cytokine therapy can partially reverse the immune dysregulation seen in AIDS. This suggests that cytokines are likely to have an important role in both the pathogenesis and treatment or prevention of AIDS-lymphoma.

Epstein-Barr virus in Hodgkin's disease

Epstein-Barr virus (EBV), a B-lymphotropic herpesvirus widespread in human populations, is carried by most individuals as an asymptomatic lifelong infection. Much progress has been made in our understanding of virus infection/persistence, and in the role of the cytotoxic T lymphocyte response in control of that infection. This same virus is linked to several malignancies, including endemic Burkitt's lymphoma, post-transplant lymphoproliferative disease and to many cases of Hodgkin's disease (HD). Recent evidence showing that HD, like the other EBV-associated lymphomas, is of B-cell origin suggests that the pathogenesis of these malignancies may share more common ground than previously thought. The biology and cytotoxic T-cell control of primary and persistent EBV infection, and the links between EBV and all three lymphomas are reviewed. The expression of viral antigens in EBV-positive HD raises the possibility of developing tumour immunotherapy, using relevant components of the EBV-specific T-cell response; progress to date, and future prospects for immune control of EBV-positive HD are discussed.