Rescue of "crippled" germinal center B cells from apoptosis by Epstein-Barr virus

Epigenetic Mechanisms in Latent Epstein-Barr Virus Infection and Associated Cancers

The Epstein-Barr Virus (EBV) is a double-stranded DNA-based human tumor virus that was first isolated in 1964 from lymphoma biopsies. Since its initial discovery, EBV has been identified as a major contributor to numerous cancers and chronic autoimmune disorders. The virus is particularly efficient at infecting B-cells but can also infect epithelial cells, utilizing an array of epigenetic strategies to establish long-term latent infection. The association with histone modifications, alteration of DNA methylation patterns in host and viral genomes, and microRNA targeting of host cell factors are core epigenetic strategies that drive interactions between host and virus, which are necessary for viral persistence and progression of EBV-associated diseases. Therefore, understanding epigenetic regulation and its role in post-entry viral dynamics is an elusive area of EBV research. Here, we present current outlooks of EBV epigenetic regulation as it pertains to viral interactions with its host during latent infection and its propensity to induce tumorigenesis. We review the important epigenetic regulators of EBV latency and explore how the strategies involved during latent infection drive differential epigenetic profiles and host-virus interactions in EBV-associated cancers.

A Mouse Model to Study the Pathogenesis of γ-herpesviral Infections in Germinal Center B Cells

CD30-positive germinal center (GC)-derived B cell lymphomas are frequently linked to Epstein-Barr Virus (EBV) infection. However, a suitable animal model for the investigation of the interplay between γ-herpesvirus and host cells in B cell pathogenesis is currently lacking. Here, we present a novel in vivo model enabling the analysis of genetically modified viruses in combination with genetically modified GC B cells. As a murine γ-herpesvirus, we used MHV-68 closely mirroring the biology of EBV. Our key finding was that Cre-mediated recombination can be successfully induced by an MHV-68 infection in GC B cells from Cγ1-Cre mice allowing for deletion or activation of loxP-flanked cellular genes. The implementation of PrimeFlow RNA assay for MHV-68 demonstrated the enrichment of MHV-68 in GC and isotype-switched B cells. As illustrations of virus and cellular modifications, we inserted the EBV gene LMP2A into the MHV-68 genome and induced constitutively active CD30-signaling in GC B cells through MHV-68 infections, respectively. While the LMP2A-expressing MHV-68 behaved similarly to wildtype MHV-68, virally induced constitutively active CD30-signaling in GC B cells led to the expansion of a pre-plasmablastic population. The findings underscore the potential of our novel tools to address crucial questions about the interaction between herpesviral infections and deregulated cellular gene-expression in future studies.

CAR-T Cell Therapy for Classical Hodgkin Lymphoma

Classical Hodgkin lymphoma (cHL) is a malignancy characterized by the presence of Hodgkin and Reed-Sternberg (HRS) cells within a complex tumor microenvironment (TME). Despite advances in conventional therapies, a subset of cHL patients experience relapse or refractory disease, necessitating the exploration of novel treatment strategies. Chimeric antigen receptor T cell (CAR-T cell) therapy has emerged as a promising approach for the management of cHL, harnessing the power of genetically modified T cells to recognize and eliminate tumor cells. In this article, we provide an overview of the pathogenesis of cHL, highlighting the key molecular and cellular mechanisms involved. Additionally, we discuss the rationale for the development of CAR-T cell therapy in cHL, focusing on the identification of suitable targets on HRS cells (such as CD30, CD123, LMP1, and LMP2A), clonotypic lymphoma initiating B cells (CD19, CD20), and cells within the TME (CD123, CD19, CD20) for CAR-T cell design. Furthermore, we explore various strategies employed to enhance the efficacy and safety of CAR-T cell therapies in the treatment of cHL. Finally, we present an overview of the results obtained from clinical trials evaluating the efficacy of CAR-T cell therapies in cHL, highlighting their potential as a promising therapeutic option. Collectively, this article provides a comprehensive review of the current understanding of cHL pathogenesis and the rationale for CAR-T cell therapy development, offering insights into the future directions of this rapidly evolving field.

Expression of EBV-encoded genes in children with asymptomatic infection detected by sensitive methods

Epstein-Barr virus (EBV) is an usually harmless virus whose oncogenic properties in vitro are related to its ability to transform lymphoid cells, and, in consequence, it can be associated with lymphomas. Since a few studies detected EBV presence in supposedly EBV-negative lymphomas, our aim was to evaluate EBV presence by sensitive gene expression assays in the tonsils from healthy pediatric donors from a region with high incidence of EBV-associated lymphomas. EBERs transcripts were detected by View RNA ISH in all cases, even in cases assessed negative by widely used in situ hybridization. The presence of LMP1 transcripts was proved in 93% of cases, co-expressed with EBNA2 in 30%. In this study, evidence for the expression of different latent and lytic viral genes in a population of young age of primary infection, detected with more sensitive methods, in particular at the germinal center, where most EBV-associated lymphomas originate, was provided.

Open reading frames M12/M13 jointly contribute to MHV-68 latency

Murine gammaherpesvirus 68 (MHV-68), a widely used small-animal model for the analysis of gammaherpesvirus pathogenesis, encodes the MHV-68-specific ORFs M12 and M13. The function of M12 and M13 has not been investigated so far. Therefore, we constructed and analysed recombinant MHV-68 with mutations in either M12, M13 or M12/M13. Both the M12 and M13 mutants did not display any phenotype in vitro or in vivo. However, although the M12/13 double mutant showed similar lytic growth in fibroblasts in vitro and in the lungs of infected mice as wild-type MHV-68, it was significantly attenuated in vivo during latency. This phenotype was completely restored in a revertant of the M12/13 double mutant. Thus, it appears that M12 and M13 might have redundant functions that are only revealed if both genes are lacking. The observation that M12/13 have a function during latency not only contributes to the further understanding of the pathogenesis of MHV-68 infection but might also be of interest considering that M12/13 are located at a genomic position similar to that of LMP2A and K15. The latter are important proteins of their respective human gammaherpesviruses EBV and KSHV that contribute to cellular survival, cell activation and proliferation, which was deduced from in vitro studies.

Immunodeficiency-Associated Epstein-Barr Virus-Positive B-cell Lymphoproliferative Disorders

Sources of immune deficiency and dysregulation (IDD) are being increasingly recognized and defined, as are IDD-related B-cell lymphoproliferative lesions and lymphomas occurring in these patients. In this review, basic biology of Epstein-Barr virus (EBV) as it relates to classification of EBV-positive B-cell lymphoproliferative disorders (LPDs) is reviewed. Also discussed is the new paradigm of classification of IDD-related LPDs adopted by the fifth edition World Health Organization classification. IDD-related EBV-positive B-cell hyperplasias, LPDs, and lymphomas are discussed with particular attention to unifying and unique features that assist with recognition of these IDD-related lesions and their classification scheme.

An update on molecular features and therapeutic perspectives of pediatric classical Hodgkin Lymphoma. What the clinician needs to know?

Our understanding of Hodgkin lymphoma (HL) molecular biology has been radically transformed over recent years due to the advent and the spreading of the new generation sequencing approaches. These advances offer new insights about genetic predisposition to HL in children and are currently being translated into promising and more selective drugs (brentuximab and checkpoint inhibitors) offering the perspective to reduce treatment-related toxicity. Thus, as more than 90% of pediatric patients are cured after the first line treatment, a major emphasis is placed on survivorship by reducing treatment intensity, in particular, the use of radiotherapy and chemotherapy associated with long-term toxicities. The purposes of this review are to summarize the recent advances performed in the field of molecular biology of HL, in particular the promising development of liquid biopsies. We also provide an update review of immunodeficiencies associated to HL in children recently identified. Finally, we report the recent studies supporting the efficacy of new targeted therapeutics in adult and pediatric cHL (anti-CD30 and anti-PD1).

Impact of Tumour Epstein–Barr Virus Status on Clinical Outcome in Patients with Classical Hodgkin Lymphoma (cHL): A Review of the Literature and Analysis of a Clinical Trial Cohort of Children with cHL

Simple Summary

The Epstein–Barr virus (EBV) contributes to different forms of human cancer, including a subset of classical Hodgkin lymphoma (cHL), a B-cell lymphoma with unusual histological features. Although the pathogenesis of EBV-associated cHL remains to be elucidated, biological investigations point to an important aetiological role for the virus in the development of this tumour. This is even more relevant now considering the potential opportunities that exist to treat EBV-associated disorders, for example, with immunotherapeutics or small molecule inhibitors targeting viral proteins. For this reason, we believe it is now timely to review the association between EBV and cHL and in particular to re-evaluate the impact of EBV status on clinical outcomes in cHL patients. Herein, we also report the impact of EBV on clinical outcomes in a cohort of children and adolescents with cHL.

Abstract

In this study, we have re-evaluated how EBV status influences clinical outcome. To accomplish this, we performed a literature review of all studies that have reported the effect of EBV status on patient outcome and also explored the effect of EBV positivity on outcome in a clinical trial of children with cHL from the UK. Our literature review revealed that almost all studies of older adults/elderly patients have reported an adverse effect of an EBV-positive status on outcome. In younger adults with cHL, EBV-positive status was either associated with a moderate beneficial effect or no effect, and the results in children and adolescents were conflicting. Our own analysis of a series of 166 children with cHL revealed no difference in overall survival between EBV-positive and EBV-negative groups (p = 0.942, log rank test). However, EBV-positive subjects had significantly longer event-free survival (p = 0.0026). Positive latent membrane protein 1 (LMP1) status was associated with a significantly lower risk of treatment failure in a Cox regression model (HR = 0.21, p = 0.005). In models that controlled for age, gender, and stage, EBV status had a similar effect size and statistical significance. This study highlights the age-related impact of EBV status on outcome in cHL patients and suggests different pathogenic effects of EBV at different stages of life.

Strategies of Epstein-Barr virus to evade innate antiviral immunity of its human host

Epstein-Barr virus (EBV) is a double-stranded DNA virus of the Herpesviridae family. This virus preferentially infects human primary B cells and persists in the human B cell compartment for a lifetime. Latent EBV infection can lead to the development of different types of lymphomas as well as carcinomas such as nasopharyngeal and gastric carcinoma in immunocompetent and immunocompromised patients. The early phase of viral infection is crucial for EBV to establish latency, but different viral components are sensed by cellular sensors called pattern recognition receptors (PRRs) as the first line of host defense. The efficacy of innate immunity, in particular the interferon-mediated response, is critical to control viral infection initially and to trigger a broad spectrum of specific adaptive immune responses against EBV later. Despite these restrictions, the virus has developed various strategies to evade the immune reaction of its host and to establish its lifelong latency. In its different phases of infection, EBV expresses up to 44 different viral miRNAs. Some act as viral immunoevasins because they have been shown to counteract innate as well as adaptive immune responses. Similarly, certain virally encoded proteins also control antiviral immunity. In this review, we discuss how the virus governs innate immune responses of its host and exploits them to its advantage.

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.

The Association of Epstein-Barr Virus With Cancer

Epstein-Barr virus (EBV) is classified as a herpesvirus and is known for being one of the few viruses that can lead to the development of cancer. This study has gathered several studies to provide evidence as to this association as well as some of the mechanisms specific to EBV that allow this to happen. The development of EBV into cancer as well as the proteins involved in this oncogenesis play a crucial role in understanding this problem as well as creating a solution for mitigating this disease process in the future. This study summarized three of the most common malignancies caused by EBV in order to consolidate information about each of them. Additional emphasis was placed on finding which EBV serum markers were seen to be most indicative of prognosis and likelihood of developing malignancy. Higher serum EBV viral DNA loads were seen to be a useful indicator in assessing the risk of various cancers and should be studied further in relation to cancers that were not mentioned in this review.

An Update on the Pathology and Molecular Features of Hodgkin Lymphoma

Simple Summary

Hodgkin lymphomas (HLs) include two main types, classic HL (CHL) and nodular lymphocyte predominant HL (NLPHL). Recent molecular findings in HLs have contributed to dramatic changes in the treatment and identification of tumor characteristics. For example, PD-1/PD-L1 blockade and brentuximab vedotin, an anti-CD30 antibody bearing a cytotoxic compound, are now widely used in patients with CHL. Biological continuity between NLPHL and T-cell/histiocyte-rich large B-cell lymphoma has been highlighted. An era of novel therapeutics for HL has begun. The aim of this paper is to review the morphologic, immunophenotypic, and molecular features of CHL and NLPHL, which must be understood for the development of novel therapeutics.

Abstract

Hodgkin lymphomas (HLs) are lymphoid neoplasms derived from B cells and consist histologically of large neoplastic cells known as Hodgkin and Reed–Sternberg cells and abundant reactive bystander cells. HLs include two main types, classic HL (CHL) and nodular lymphocyte predominant HL (NLPHL). Recent molecular analyses have revealed that an immune evasion mechanism, particularly the PD-1/PD-L1 pathway, plays a key role in the development of CHL. Other highlighted key pathways in CHL are NF-κB and JAK/STAT. These advances have dramatically changed the treatment for CHL, particularly relapsed/refractory CHL. For example, PD-1 inhibitors are now widely used in relapsed/refractory CHL. Compared with CHL, NLPHL is more characterized by preserved B cell features. Overlapping morphological and molecular features between NLPHL and T-cell/histiocyte-rich large B-cell lymphoma (THRLBCL) have been reported, and biological continuity between these two entities has been highlighted. Some THRLBCLs are considered to represent progression from NLPHLs. With considerable new understanding becoming available from molecular studies in HLs, therapies and classification of HLs are continually evolving. This paper offers a summary of and update on the pathological and molecular features of HLs for a better understanding of the diseases.

Prognostic Role of the Expression of Latent-Membrane Protein 1 of Epstein–Barr Virus in Classical Hodgkin Lymphoma

The prognostic impact of the presence of Epstein–Barr virus (EBV) in classical Hodgkin lymphoma (cHL) is controversial. Previous studies reported heterogeneous results, rendering difficult the clinical validation of EBV as a prognostic biomarker in this lymphoma. The objective of this study was to evaluate the survival impact of the expression of EBV Latent-Membrane Protein 1 (EBV-LMP1) in tumoral Hodgkin–Reed–Sternberg (HRS) cells of primary diagnostic samples of cHL. Formalin-Fixed Paraffin-Embedded (FFPE) lymph node samples from 88 patients with cHL were analyzed. Patients were treated with the standard first-line chemotherapy (CT) with Adriamycin, Bleomycin, Vinblastine and Dacarbazine (ABVD) followed by radiotherapy. The Kaplan–Meier method and the Cox proportional hazards model were used for carrying out the survival analysis. In order to investigate whether the influence of EBV was age-dependent, analyses were performed both for patients of all ages and for age-stratified subgroups. In bivariate analysis, the expression of EBV was associated with older age (p = 0.011), mixed cellularity subtype cHL (p < 0.001) and high risk International Prognostic Score (IPS) (p = 0.023). Overall survival (OS) and progression-free survival (PFS) were associated with the presence of bulky disease (p = 0.009) and advanced disease at diagnosis (p = 0.016). EBV-positive cases did not present a significantly lower OS and PFS in comparison with EBV-negative cases, for all ages and when stratifying for age. When adjusted for covariates, absence of bulky disease at diagnosis (HR: 0.102, 95% CI: 0.02–0.48, p = 0.004) and limited disease stages (I–II) (HR: 0.074, 95% CI: 0.01–0.47, p = 0.006) were associated with a significant better OS. For PFS, limited-disease stages also retained prognostic impact in the multivariate Cox regression (HR: 0.145, 95% CI: 0.04–0.57, p = 0.006). These results are of importance as the early identification of prognostic biomarkers in cHL is critical for guiding and personalizing therapeutic decisions. The prognostic role of EBV in cHL could be modulated by the type of CT protocol employed and interact with the rest of presenting features.

Epstein Barr Virus: Development of Vaccines and Immune Cell Therapy for EBV-Associated Diseases

Epstein-Barr virus (EBV) is the first human tumor virus discovered and is strongly implicated in the etiology of multiple lymphoid and epithelial cancers. Each year EBV associated cancers account for over 200,000 new cases of cancer and cause 150,000 deaths world-wide. EBV is also the primary cause of infectious mononucleosis, and up to 70% of adolescents and young adults in developed countries suffer from infectious mononucleosis. In addition, EBV has been shown to play a critical role in the pathogenesis of multiple sclerosis. An EBV prophylactic vaccine that induces neutralizing antibodies holds great promise for prevention of EBV associated diseases. EBV envelope proteins including gH/gL, gB and gp350 play key roles in EBV entry and infection of target cells, and neutralizing antibodies elicited by each of these proteins have shown to prevent EBV infection of target cells and markedly decrease EBV titers in the peripheral blood of humanized mice challenged with lethal dose EBV. Recent studies demonstrated that immunization with the combination of gH/gL, gB and/or gp350 induced markedly increased synergistic EBV neutralizing activity compared to immunization with individual proteins. As previous clinical trials focused on gp350 alone were partially successful, the inclusion of gH/gL and gB in a vaccine formulation with gp350 represents a promising approach of EBV prophylactic vaccine development. Therapeutic EBV vaccines have also been tested clinically with encouraging results. Immunization with various vaccine platforms expressing the EBV latent proteins EBNA1, LMP1, and/or LMP2 promoted specific CD4+ and CD8+ cytotoxic responses with anti-tumor activity. The addition of EBV envelope proteins gH/gL, gB and gp350 has the potential to increase the efficacy of a therapeutic EBV vaccine. The immune system plays a critical role in the control of tumors, and immune cell therapy has emerged as a promising treatment of cancers. Adoptive T-cell therapy has been successfully used in the prevention and treatment of post-transplant lymphoproliferative disorder. Chimeric antigen receptor T cell therapy and T cell receptor engineered T cell therapy targeting EBV latent proteins LMP1, LMP2 and/or EBNA1 have been in development, with the goal to increase the specificity and efficacy of treatment of EBV associated cancers.

The Role of Coinfections in the EBV-Host Broken Equilibrium

The Epstein–Barr virus (EBV) is a well-adapted human virus, and its infection is exclusive to our species, generally beginning in the childhood and then persisting throughout the life of most of the affected adults. Although this infection generally remains asymptomatic, EBV can trigger life-threatening conditions under unclear circumstances. The EBV lifecycle is characterized by interactions with other viruses or bacteria, which increases the probability of awakening its pathobiont capacity. For instance, EBV infects B cells with the potential to alter the germinal center reaction (GCR)—an adaptive immune structure wherein mutagenic-driven processes take place. HIV- and Plasmodium falciparum-induced B cell hyperactivation also feeds the GCR. These agents, along with the B cell tropic KSHV, converge in the ontogeny of germinal center (GC) or post-GC lymphomas. EBV oral transmission facilitates interactions with local bacteria and HPV, thereby increasing the risk of periodontal diseases and head and neck carcinomas. It is less clear as to how EBV is localized in the stomach, but together with Helicobacter pylori, they are known to be responsible for gastric cancer. Perhaps this mechanism is reminiscent of the local inflammation that attracts different herpesviruses and enhances graft damage and chances of rejection in transplanted patients. In this review, we discussed the existing evidence suggestive of EBV possessing the potential to synergize or cooperate with these agents to trigger or worsen the disease.

Germinal Centre Shutdown

Germinal Centres (GCs) are transient structures in secondary lymphoid organs, where affinity maturation of B cells takes place following an infection. While GCs are responsible for protective antibody responses, dysregulated GC reactions are associated with autoimmune disease and B cell lymphoma. Typically, ‘normal’ GCs persist for a limited period of time and eventually undergo shutdown. In this review, we focus on an important but unanswered question – what causes the natural termination of the GC reaction? In murine experiments, lack of antigen, absence or constitutive T cell help leads to premature termination of the GC reaction. Consequently, our present understanding is limited to the idea that GCs are terminated due to a decrease in antigen access or changes in the nature of T cell help. However, there is no direct evidence on which biological signals are primarily responsible for natural termination of GCs and a mechanistic understanding is clearly lacking. We discuss the present understanding of the GC shutdown, from factors impacting GC dynamics to changes in cellular interactions/dynamics during the GC lifetime. We also address potential missing links and remaining questions in GC biology, to facilitate further studies to promote a better understanding of GC shutdown in infection and immune dysregulation.

Association of Epstein-Barr virus latently expressed genes with multiple sclerosis

BACKGROUND

Despite mounting evidence supporting an etiologic role for Epstein-Barr virus (EBV) in multiple sclerosis (MS), the exact mechanisms through which the virus may contribute to disease development are still unknown. The aim of this study was to analyze seven highly polymorphic EBV latently expressed genes in individuals diagnosed with MS in comparison to healthy controls (HC), to investigate the possible association of EBV variants with an individual's risk towards MS.

METHODS

B-lymphocytes were isolated from MS patients (n = 30) and HC (n = 33) for the isolation of EBV genomic DNA. Sanger sequencing was employed to analyze EBV latent gene regions.

RESULTS

A total of 26 variants were detected in our cohort, 17 of which were significantly associated with the MS group while nine were significantly associated with HC. Following the designation of EBV alleles based on these variants, MS risk was found to be significantly associated with the presence of the EBNA3B2.1 allele (p = 0.0008) and LMP1.1 allele (p = 0.01), whereas the EBNA1.3 allele (p = 0.005), EBNA2.1 allele (p = 0.001) as well as the EBNA3B2.2 allele (p = 0.0003) appeared to provide a protective role.

CONCLUSIONS

This study indicates a marked association between EBV genetic variants and MS, lending further support towards possible molecular mechanisms through which EBV may contribute to disease development.

Critical review of Epstein-Barr virus microRNAs relation with EBV-associated gastric cancer

Epstein-Barr virus (EBV)-associated gastric cancer (EBVaGC) is regarded as the most prevalent malignant tumor triggered by EBV infection. In recent years, increasing attention has been considered to recognize more about the disease process's exact mechanisms. There is accumulating evidence that showing epigenetic modifications play critical roles in the EBVaGC pathogenesis. MicroRNAs (miRNAs), as critical epigenetic modulators, are single-strand short noncoding RNA (length ~ <200 bp), which regulate gene expression through binding to the 3'-untranslated region (3'-UTR) of target RNA transcripts and either degrade or repress their activities. In the latest research on EBV, it was found that this virus could encode miRNAs. Mechanistically, EBV-encoded miRNAs are involved in carcinogenesis and the progression of EBV-associated malignancies. Moreover, these miRNAs implicated in immune evasion, identification of pattern recognition receptors, regulation of lymphocyte activation and lethality, modulation of infected host cell antigen, maintain of EBV infection status, promotion of cell proliferation, invasion and migration, and reduction of apoptosis. As good news, not only has recent data demonstrated the crucial function of EBV-encoded miRNAs in the pathogenesis of EBVaGC, but it has also been revealed that aberrant expression of exosomal miRNAs in EBVaGC has made them biomarkers for detection of EBVaGC. Regarding these substantial characterizes, the critical role of EBV-encoded miRNAs has been a hot topic in research. In this review, we will focus on the multiple mechanisms involved in EBVaGC caused by EBV-encoded miRNAs and briefly discuss their potential application in the clinic as a diagnostic biomarker.

Proteomic approaches to investigate gammaherpesvirus biology and associated tumorigenesis

The DNA viruses, Kaposi's sarcoma-associated herpesvirus (KSHV) and Epstein-Barr virus (EBV), are members of the gammaherpesvirus subfamily, a group of viruses whose infection is associated with multiple malignancies, including cancer. The primary host for these viruses is humans and, like all herpesviruses, infection with these pathogens is lifelong. Due to the persistence of gammaherpesvirus infection and the potential for cancer formation in infected individuals, there is a driving need to understand not only the biology of these viruses and how they remain undetected in host cells but also the mechanism(s) by which tumorigenesis occurs. One of the methods that has provided much insight into these processes is proteomics. Proteomics is the study of all the proteins that are encoded by a genome and allows for (i) identification of existing and novel proteins derived from a given genome, (ii) interrogation of protein-protein interactions within a system, and (iii) discovery of druggable targets for the treatment of malignancies. In this chapter, we explore how proteomics has contributed to our current understanding of gammaherpesvirus biology and their oncogenic processes, as well as the clinical applications of proteomics for the detection and treatment of gammaherpesvirus-associated cancers.

Rewiring of B cell receptor signaling by Epstein-Barr virus LMP2A

Epstein-Barr virus (EBV) infects human B cells and reprograms them to allow virus replication and persistence. One key viral factor in this process is latent membrane protein 2A (LMP2A), which has been described as a B cell receptor (BCR) mimic promoting malignant transformation. However, how LMP2A signaling contributes to tumorigenesis remains elusive. By comparing LMP2A and BCR signaling in primary human B cells using phosphoproteomics and transcriptome profiling, we identified molecular mechanisms through which LMP2A affects B cell biology. Consistent with the literature, we found that LMP2A mimics a subset of BCR signaling events, including tyrosine phosphorylation of the kinase SYK, the calcium initiation complex consisting of BLNK, BTK, and PLCγ2, and its downstream transcription factor NFAT. However, the majority of LMP2A-induced signaling events markedly differed from those induced by BCR stimulation. These included differential phosphorylation of kinases, phosphatases, adaptor proteins, transcription factors such as nuclear factor κB (NF-κB) and TCF3, as well as widespread changes in the transcriptional output of LMP2A-expressing B cells. LMP2A affected apoptosis and cell-cycle checkpoints by dysregulating the expression of apoptosis regulators such as BCl-xL and the tumor suppressor retinoblastoma-associated protein 1 (RB1). LMP2A cooperated with MYC and mutant cyclin D3, two oncogenic drivers of Burkitt lymphoma, to promote proliferation and survival of primary human B cells by counteracting MYC-induced apoptosis and by inhibiting RB1 function, thereby promoting cell-cycle progression. Our results indicate that LMP2A is not a pure BCR mimic but rather rewires intracellular signaling in EBV-infected B cells that optimizes cell survival and proliferation, setting the stage for oncogenic transformation.

Modeling oncogenic herpesvirus infections in humanized mice

The creation of humanized mice generally involves the reconstitution of immunodeficient mice with human immune constituents. Different methodologies have been employed, and significant progress has been made towards the development of robustly humanized mouse models. Some of the techniques used include the injection of mature human immune cells, the injection of human hematopoietic stem cells (HSCs) capable of reconstituting radiation-depleted murine bone marrow, and the implantation of human fetal liver and thymus fragments under the kidney capsule to create a thymic organoid that can support thympoiesis. This review will serve as a brief introduction to the three most commonly utilized humanized mouse models for the study of gammaherpesvirus-driven pathogenesis, and highlight some of the critical discoveries these models have enabled.

Molecular Pathogenesis of Hodgkin Lymphoma: Past, Present, Future

Our understanding of the tumorigenesis of classical Hodgkin lymphoma (cHL) and the formation of Reed–Sternberg cells (RS-cells) has evolved drastically in the last decades. More recently, a better characterization of the signaling pathways and the cellular interactions at play have paved the way for new targeted therapy in the hopes of improving outcomes. However, important gaps in knowledge remain that may hold the key for significant changes of paradigm in this lymphoma. Here, we discuss the past, present, and future of cHL, and review in detail the more recent discoveries pertaining to genetic instability, anti-apoptotic signaling pathways, the tumoral microenvironment, and host-immune system evasion in cHL.

EBNA2-deleted Epstein-Barr virus (EBV) isolate, P3HR1, causes Hodgkin-like lymphomas and diffuse large B cell lymphomas with type II and Wp-restricted latency types in humanized mice

EBV transforms B cells in vitro and causes human B-cell lymphomas including classical Hodgkin lymphoma (CHL), Burkitt lymphoma (BL) and diffuse large B-cell lymphoma (DLBCL). The EBV latency protein, EBNA2, transcriptionally activates the promoters of all latent viral protein-coding genes expressed in type III EBV latency and is essential for EBV's ability to transform B cells in vitro. However, EBNA2 is not expressed in EBV-infected CHLs and BLs in humans. EBV-positive CHLs have type II latency and are largely driven by the EBV LMP1/LMP2A proteins, while EBV-positive BLs, which usually have type I latency are largely driven by c-Myc translocations, and only express the EBNA1 protein and viral non-coding RNAs. Approximately 15% of human BLs contain naturally occurring EBNA2-deleted viruses that support a form of viral latency known as Wp-restricted (expressing the EBNA-LP, EBNA3A/3B/3C, EBNA1 and BHRF1 proteins), but whether Wp-restricted latency and/or EBNA2-deleted EBV can induce lymphomas in humanized mice, or in the absence of c-Myc translocations, is unknown. Here we show that a naturally occurring EBNA2-deleted EBV strain (P3HR1) isolated from a human BL induces EBV-positive B-cell lymphomas in a subset of infected cord blood-humanized (CBH) mice. Furthermore, we find that P3HR1-infected lymphoma cells support two different viral latency types and phenotypes that are mutually exclusive: 1) Large (often multinucleated), CD30-positive, CD45-negative cells reminiscent of the Reed-Sternberg (RS) cells in CHL that express high levels of LMP1 but not EBNA-LP (consistent with type II viral latency); and 2) smaller monomorphic CD30-negative DLBCL-like cells that express EBNA-LP and EBNA3A but not LMP1 (consistent with Wp-restricted latency). These results reveal that EBNA2 is not absolutely required for EBV to form tumors in CBH mice and suggest that P3HR1 virus can be used to model EBV positive lymphomas with both Wp-restricted and type II latency in vivo.

Gammaherpesviruses and B Cells: A Relationship That Lasts a Lifetime

Gammaherpesviruses are highly prevalent pathogens that establish life-long infection and are associated with diverse malignancies, including lymphoproliferative diseases and B cell lymphomas. Unlike other viruses that either do not infect B cells or infect B cells transiently, gammaherpesviruses manipulate physiological B cell differentiation to establish life-long infection in memory B cells. Disruption of such viral manipulation by genetic or environmental causes is likely to seed viral lymphomagenesis. In this review, we discuss physiological and unique host and viral mechanisms usurped by gammaherpesviruses to fine tune host B cell biology for optimal infection establishment and maintenance.

The interplay between Epstein-Bar virus (EBV) with the p53 and its homologs during EBV associated malignancies

p53, p63, and p73, the members of the p53 family of proteins, are structurally similar proteins that play central roles regulating cell cycle and apoptotic cell death. Alternative splicing at the carboxyl terminus and the utilization of different promoters further categorizes these proteins as having different isoforms for each. Among such isoforms, TA and ΔN versions of each protein serve as the pro and the anti-apoptotic proteins, respectively. Changes in the expression patterns of these isoforms are noted in many human cancers. Proteins of certain human herpesviruses, like Kaposi's sarcoma-associated herpesvirus (KSHV) and Epstein-Barr virus (EBV), interact with p53 family members and alter their expressions in many malignancies. Upon infections in the B cells and epithelial cells, EBV expresses different lytic or latent proteins during viral replication and latency respectively to preserve viral copy number, chromosomal integrity and viral persistence inside the host. In this review, we have surveyed and summarised the interactions of EBV gene products, known so far, with the p53 family proteins. The interactions between P53 and EBV oncoproteins are observed in stomach cancer, non-Hodgkin's lymphoma (NHL) of the head and neck, Nasopharyngeal Cancer (NPC), Gastric carcinoma (GC) and Burkitt's lymphoma (BL). EBV latent protein EBNA1, EBNA3C, LMP-1, and lytic proteins BZLF-1 can alter p53 expressions in many cancer cell lines. Interactions of p63 with EBNA-1, 2, 5, LMP-2A and BARF-1 have also been investigated in several cancers. Similarly, associations of p73 isoform with EBV latent proteins EBNA3C and LMP-1 have been reported. Methylation and single nucleotide polymorphisms in p53 have also been found to be correlated with EBV infection. Therefore, interactions and altered expression strategies of the isoforms of p53 family proteins in EBV associated cancers propose an important field for further molecular research.

An intronic deletion in megakaryoblastic leukemia 1 is associated with hyperproliferation of B cells in triplets with Hodgkin lymphoma

Megakaryoblastic leukemia 1 (MKL1) is a coactivator of serum response factor and together they regulate transcription of actin cytoskeleton genes. MKL1 is associated with hematologic malignancies and immunodeficiency, but its role in B cells is unexplored. Here we examined B cells from monozygotic triplets with an intronic deletion in MKL1, two of whom had been previously treated for Hodgkin lymphoma (HL). To investigate MKL1 and B-cell responses in the pathogenesis of HL, we generated Epstein-Barr virus-transformed lymphoblastoid cell lines from the triplets and two controls. While cells from the patients with treated HL had a phenotype close to that of the healthy controls, cells from the undiagnosed triplet had increased MKL1 mRNA, increased MKL1 protein, and elevated expression of MKL1-dependent genes. This profile was associated with elevated actin content, increased cell spreading, decreased expression of CD11a integrin molecules, and delayed aggregation. Moreover, cells from the undiagnosed triplet proliferated faster, displayed a higher proportion of cells with hyperploidy, and formed large tumors in vivo This phenotype was reversible by inhibiting MKL1 activity. Interestingly, cells from the triplet treated for HL in 1985 contained two subpopulations: one with high expression of CD11a that behaved like control cells and the other with low expression of CD11a that formed large tumors in vivo similar to cells from the undiagnosed triplet. This implies that pre-malignant cells had re-emerged a long time after treatment. Together, these data suggest that dysregulated MKL1 activity participates in B-cell transformation and the pathogenesis of HL.

First Days in the Life of Naive Human B Lymphocytes Infected with Epstein-Barr Virus

Epstein-Barr virus (EBV) infects and activates resting human B lymphocytes, reprograms them, induces their proliferation, and establishes a latent infection in them. In established EBV-infected cell lines, many viral latent genes are expressed. Their roles in supporting the continuous proliferation of EBV-infected B cells in vitro are known, but their functions in the early, prelatent phase of infection have not been investigated systematically. In studies during the first 8 days of infection using derivatives of EBV with mutations in single genes of EBVs, we found only Epstein-Barr nuclear antigen 2 (EBNA2) to be essential for activating naive human B lymphocytes, inducing their growth in cell volume, driving them into rapid cell divisions, and preventing cell death in a subset of infected cells. EBNA-LP, latent membrane protein 2A (LMP2A), and the viral microRNAs have supportive, auxiliary functions, but mutants of LMP1, EBNA3A, EBNA3C, and the noncoding Epstein-Barr virus with small RNA (EBERs) had no discernible phenotype compared with wild-type EBV. B cells infected with a double mutant of EBNA3A and 3C had an unexpected proliferative advantage and did not regulate the DNA damage response (DDR) of the infected host cell in the prelatent phase. Even EBNA1, which has very critical long-term functions in maintaining and replicating the viral genomic DNA in established cell lines, was dispensable for the early activation of infected cells. Our findings document that the virus dose is a decisive parameter and indicate that EBNA2 governs the infected cells initially and implements a strictly controlled temporal program independent of other viral latent genes. It thus appears that EBNA2 is sufficient to control all requirements for clonal cellular expansion and to reprogram human B lymphocytes from energetically quiescent to activated cells.IMPORTANCE The preferred target of Epstein-Barr virus (EBV) is human resting B lymphocytes. We found that their infection induces a well-coordinated, time-driven program that starts with a substantial increase in cell volume, followed by cellular DNA synthesis after 3 days and subsequent rapid rounds of cell divisions on the next day accompanied by some DNA replication stress (DRS). Two to 3 days later, the cells decelerate and turn into stably proliferating lymphoblast cell lines. With the aid of 16 different recombinant EBV strains, we investigated the individual contributions of EBV's multiple latent genes during early B-cell infection and found that many do not exert a detectable phenotype or contribute little to EBV's prelatent phase. The exception is EBNA2 that is essential in governing all aspects of B-cell reprogramming. EBV relies on EBNA2 to turn the infected B lymphocytes into proliferating lymphoblasts preparing the infected host cell for the ensuing stable, latent phase of viral infection. In the early steps of B-cell reprogramming, viral latent genes other than EBNA2 are dispensable, but some, EBNA-LP, for example, support the viral program and presumably stabilize the infected cells once viral latency is established.

An etiological role for the Epstein-Barr virus in the pathogenesis of classical Hodgkin lymphoma

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

Mechanisms of B-Cell Oncogenesis Induced by Epstein-Barr Virus

Epstein-Barr virus (EBV) is a ubiquitous gammaherpesvirus which asymptomatically infects the majority of the world population. Under immunocompromised conditions, EBV can trigger human cancers of epithelial and lymphoid origin. The oncogenic potential of EBV is demonstrated by in vitro infection and transformation of quiescent B cells into lymphoblastoid cell lines (LCLs). These cell lines, along with primary infection using genetically engineered viral particles coupled with recent technological advancements, have elucidated the underlying mechanisms of EBV-induced B-cell lymphomagenesis.

Epstein-Barr virus LMP2A utilizes Syk and PI3K to activate NF-κB in B-cell lymphomas to increase MIP-1α production

The incidence of Hodgkin's lymphoma (HL) is growing due to an increase in Epstein-Barr virus (EBV)-associated HL in AIDS patients. The HL tumor microenvironment is vital for the survival of the malignant Hodgkin-Reed Sternberg (HRS) cells of HL, which express the EBV protein latent membrane protein 2A (LMP2A). While previous work shows that LMP2A mimics B-cell receptor (BCR) signaling to promote the survival of HRS cells, the ability of LMP2A to establish and maintain the tumor microenvironment through the production of chemokines remains unknown. Since BCR signaling induces the production of the chemokine macrophage inflammatory protein-1α (MIP-1α), and since LMP2A is a BCR mimic, we hypothesized that LMP2A increases MIP-1α levels. A comparison of multiple LMP2A-negative and -positive cell lines demonstrates that LMP2A increases MIP-1α. Additionally, LMP2A-mutant cell lines and pharmacologic inhibitors indicate that LMP2A activates a Syk/PI3K/NF-κB pathway to enhance MIP-1α. Finally, based on the finding that an NF-κB inhibitor decreased MIP-1α RNA/protein in LMP2A-positive cells, we are the first to demonstrate that LMP2A increases the nuclear localization of the NF-κB p65 subunit using DNA-binding assays and confocal microscopy in human B cells. These findings not only have implications for the treatment of HL, but also other LMP2A-expressing B-cell tumors that overexpress NF-κB.

Molecular mechanisms of EBV-driven cell cycle progression and oncogenesis

The early stage of oncogenesis is linked to the disorder of the cell cycle. Abnormal gene expression often leads to cell cycle disorders, resulting in malignant transformation of human cells. Epstein–Barr virus (EBV) is associated with a diverse range of human neoplasms, such as malignant lymphoma, nasopharyngeal carcinoma and gastric cancer. EBV mainly infects human lymphocytes and oropharyngeal epithelial cells. EBV is latent in lymphocytes for a long period of time, is detached from the cytoplasm by circular DNA, and can integrate into the chromosome of cells. EBV expresses a variety of latent genes during latent infection. The interaction between EBV latent genes and oncogenes leads to host cell cycle disturbances, including the promotion of G₁/S phase transition and inhibition of cell apoptosis, thereby promoting the development of EBV-associated neoplasms. Molecular mechanisms of EBV-driven cell cycle progression and oncogenesis involve diverse genes and signal pathways. Here, we review the molecular mechanisms of EBV-driven cell cycle progression and promoting oncogenesis.

Co-Expression of the Epstein-Barr Virus-Encoded Latent Membrane Proteins and the Pathogenesis of Classic Hodgkin Lymphoma

The Epstein-Barr virus (EBV) is present in the tumour cells of a subset of patients with classic Hodgkin lymphoma (cHL), yet the contribution of the virus to the pathogenesis of these tumours remains only poorly understood. The EBV genome in virus-associated cHL expresses a limited subset of genes, restricted to the non-coding Epstein-Barr virus-encoded RNAs (EBERs) and viral miRNA, as well as only three virus proteins; the Epstein-Barr virus nuclear antigen-1 (EBNA1), and the two latent membrane proteins, known as LMP1 and LMP2, the latter of which has two isoforms, LMP2A and LMP2B. LMP1 and LMP2A are of particular interest because they are co-expressed in tumour cells and can activate cellular signalling pathways, driving aberrant cellular transcription in infected B cells to promote lymphomagenesis. This article seeks to bring together the results of recent studies of the latent membrane proteins in different B cell systems, including experiments in animal models as well as a re-analysis of our own transcriptional data. In doing so, we summarise the potentially co-operative and antagonistic effects of the LMPs that are relevant to B cell lymphomagenesis.

Contribution of Epstein⁻Barr Virus Latent Proteins to the Pathogenesis of Classical Hodgkin Lymphoma

Pathogenic viruses have evolved to manipulate the host cell utilising a variety of strategies including expression of viral proteins to hijack or mimic the activity of cellular functions. DNA tumour viruses often establish latent infection in which no new virions are produced, characterized by the expression of a restricted repertoire of so-called latent viral genes. These latent genes serve to remodel cellular functions to ensure survival of the virus within host cells, often for the lifetime of the infected individual. However, under certain circumstances, virus infection may contribute to transformation of the host cell; this event is not a usual outcome of infection. Here, we review how the Epstein–Barr virus (EBV), the prototypic oncogenic human virus, modulates host cell functions, with a focus on the role of the EBV latent genes in classical Hodgkin lymphoma.

Anti-citrullinated protein antibody response after primary EBV infection in kidney transplant patients

Rheumatoid arthritis (RA) is a chronic inflammatory disease of synovial joints, characterized by the presence of the highly disease-specific anti-citrullinated protein antibodies (ACPA) in approximately 70% of patients. Epstein-Barr virus (EBV) has previously been suggested to be involved in the pathophysiology of RA. However, given the high incidence of EBV in the general population and the difficulty of detecting initial infection, providing a direct link between EBV infection and RA development has remained elusive. We hypothesized that primary EBV infection may be a trigger for the development of the ACPA response in vivo. Using a unique cohort of 26 kidney transplant patients with a primary EBV infection, the presence of ACPA before and following infection was determined. No increase in IgG anti-CCP2 titers was detected following EBV infection. IgG anti-CCP2 antibodies were present in two patients and borderline positive in another. These three patients were HLA-DR4 negative. To test whether EBV infection may trigger a non-class switched anti-CCP2 response, IgM anti-CCP2 antibodies were analyzed. No general trend in the IgM anti-CCP2 response was observed following EBV infection. Since two out of the three IgG anti-CCP2 (borderline) positive patients were diagnosed with IgA nephropathy, 23 additional IgA nephropathy patients were tested for IgG anti-CCP2, regardless of their EBV status. All of these patients were IgG anti-CCP2 negative, indicating that IgG anti-CCP2 is not commonly present in IgA nephropathy patients. Collectively, these data do not support the hypothesis that EBV does trigger the highly RA specific ACPA response.

Mechanisms of Immune Evasion and Immune Modulation by Lymphoma Cells

Purpose

Targeting cancer cells by modulating the immune system has become an important new therapeutic option in many different malignancies. Inhibition of CTLA4/B7 and PD1/PDL1 signaling is now also being investigated and already successfully applied to various hematologic malignancies.

Methods

A literature review of PubMed and results of our own studies were compiled in order to give a comprehensive overview on this topic.

Results

We elucidate the pathophysiological role of immunosuppressive networks in lymphomas, ranging from changes in the cellular microenvironment composition to distinct signaling pathways such as PD1/PDL1 or CTLA4/B7/CD28. The prototypical example of a lymphoma manipulating and thereby silencing the immune system is Hodgkin lymphoma. Also other lymphomas, e.g., primary mediastinal B-cell lymphoma and some Epstein–Barr virus (EBV)-driven malignancies, use analogous survival strategies, while diffuse large B-cell lymphoma of the activated B-cell type, follicular lymphoma and angioimmunoblastic T-cell lymphoma to name a few, exert further immune escape strategies each. These insights have already led to new treatment opportunities and results of the most important clinical trials based on this concept are briefly summarized. Immune checkpoint inhibition might also have severe side effects; the mechanisms of the rather un(der)recognized hematological side effects of this treatment approach are discussed.

Conclusion

Silencing the host’s immune system is an important feature of various lymphomas. Achieving a better understanding of distinct pathways of interactions between lymphomas and different immunological microenvironment compounds yields substantial potential for new treatment concepts.

Autoimmunity checkpoints as therapeutic targets in B cell malignancies

Targeted therapy of cancer typically focuses on inhibitors (for example, tyrosine kinase inhibitors) that suppress oncogenic signalling below a minimum threshold required for survival and proliferation of cancer cells. B cell acute lymphoblastic leukaemia and B cell lymphomas originate from various stages of development of B cells, which, unlike other cell types, are under intense selective pressure. The vast majority of newly generated B cells are autoreactive and die by negative selection at autoimmunity checkpoints (AICs). Owing to ubiquitous encounters with self-antigen, autoreactive B cells are eliminated by the overwhelming signalling strength of their autoreactive B cell receptor (BCR). A series of recent findings suggests that, despite malignant transformation, AICs are fully functional in B cell malignancies. This Opinion article proposes targeted engagement of AICs as a previously unrecognized therapeutic opportunity to overcome drug resistance in B cell malignancies.

Hodgkin's lymphoma and its association with EBV and HIV infection

Hodgkin's lymphoma (HL) constitutes a clonal expansion of what appears to be malignant B cells. Viruses are involved in its pathogenesis, such as the Epstein-Barr virus (EBV) and human immunodeficiency virus (HIV). Since these viral infections have been shown to play key roles in the pathogenesis of HL, countries with a prevalence of HIV and EBV represent interesting population targets to study the pathogenesis of HL, linking the evolution of the disease with viral infections. Usually, patients present with late stage disease often involving the bone marrow at the time of diagnosis. The present paper discusses the role of viral infection in African countries, as HL is considered to be a malignant disease characterized by an inflammatory reaction to an aberrant B cell clone that is well known as the Reed-Sternberg cell (HRS).

EBV and Apoptosis: The Viral Master Regulator of Cell Fate?

Epstein-Barr virus (EBV) was first discovered in cells from a patient with Burkitt lymphoma (BL), and is now known to be a contributory factor in 1-2% of all cancers, for which there are as yet, no EBV-targeted therapies available. Like other herpesviruses, EBV adopts a persistent latent infection in vivo and only rarely reactivates into replicative lytic cycle. Although latency is associated with restricted patterns of gene expression, genes are never expressed in isolation; always in groups. Here, we discuss (1) the ways in which the latent genes of EBV are known to modulate cell death, (2) how these mechanisms relate to growth transformation and lymphomagenesis, and (3) how EBV genes cooperate to coordinately regulate key cell death pathways in BL and lymphoblastoid cell lines (LCLs). Since manipulation of the cell death machinery is critical in EBV pathogenesis, understanding the mechanisms that underpin EBV regulation of apoptosis therefore provides opportunities for novel therapeutic interventions.

Advantages of targeting B cell receptor complex to treat B-cell derived autoimmune diseases and lymphomas

Antibodies produced by B-cells provide protection from infectious agents. However, impaired cell death signaling pathways in B-cells can lead to cancer, immunodeficiency or autoimmune diseases. B-cell signaling molecules such as CD20, CD19, Btk, and BAFF-R are targeted by therapeutic drugs and used to treat B-cell derived lymphomas or autoimmune diseases. Nevertheless, B-cells could develop resistance to these therapeutic drugs or the therapeutic drugs may have off-target effects. For instance, repeated rituximab (anti-CD20 antibody) treatment may lead to the loss of its target cell surface molecule, CD20. In addition, in B-cell malignancies, loss of CD19 expression has been observed. Another target molecule, Btk is expressed not only in B-cells but also in mast cells, macrophages, and dendritic cells. Thus, targeting Btk could negatively regulate the functions of innate immunity. The expression of BAFF-R is thought to be restricted to B-cells but it is also expressed on T-cells. Targeting BAFF-R, therefore, may lead to depletion of T-cells in addition to B-cells. B cell receptor (BCR) expression and signaling, however, are critically important for development, differentiation and survival of B-cells. Moreover, BCR is exclusively expressed on B-cells, which makes it an excellent target to avoid off-target effects.

Latent Membrane Protein 1 (LMP1) and LMP2A Collaborate To Promote Epstein-Barr Virus-Induced B Cell Lymphomas in a Cord Blood-Humanized Mouse Model but Are Not Essential

Epstein-Barr virus (EBV) infection is associated with B cell lymphomas in humans. The ability of EBV to convert human B cells into long-lived lymphoblastoid cell lines (LCLs) in vitro requires the collaborative effects of EBNA2 (which hijacks Notch signaling), latent membrane protein 1 (LMP1) (which mimics CD40 signaling), and EBV-encoded nuclear antigen 3A (EBNA3A) and EBNA3C (which inhibit oncogene-induced senescence and apoptosis). However, we recently showed that an LMP1-deleted EBV mutant induces B cell lymphomas in a newly developed cord blood-humanized mouse model that allows EBV-infected B cells to interact with CD4 T cells (the major source of CD40 ligand). Here we examined whether the EBV LMP2A protein, which mimics constitutively active B cell receptor signaling, is required for EBV-induced lymphomas in this model. We find that the deletion of LMP2A delays the onset of EBV-induced lymphomas but does not affect the tumor phenotype or the number of tumors. The simultaneous deletion of both LMP1 and LMP2A results in fewer tumors and a further delay in tumor onset. Nevertheless, the LMP1/LMP2A double mutant induces lymphomas in approximately half of the infected animals. These results indicate that neither LMP1 nor LMP2A is absolutely essential for the ability of EBV to induce B cell lymphomas in the cord blood-humanized mouse model, although the simultaneous loss of both LMP1 and LMP2A decreases the proportion of animals developing tumors and increases the time to tumor onset. Thus, the expression of either LMP1 or LMP2A may be sufficient to promote early-onset EBV-induced tumors in this model.IMPORTANCE EBV causes human lymphomas, but few models are available for dissecting how EBV causes lymphomas in vivo in the context of a host immune response. We recently used a newly developed cord blood-humanized mouse model to show that EBV can cooperate with human CD4 T cells to cause B cell lymphomas even when a major viral transforming protein, LMP1, is deleted. Here we examined whether the EBV protein LMP2A, which mimics B cell receptor signaling, is required for EBV-induced lymphomas in this model. We find that the deletion of LMP2A alone has little effect on the ability of EBV to cause lymphomas but delays tumor onset. The deletion of both LMP1 and LMP2A results in a smaller number of lymphomas in infected animals, with an even more delayed time to tumor onset. These results suggest that LMP1 and LMP2A collaborate to promote early-onset lymphomas in this model, but neither protein is absolutely essential.

Frequency of Epstein Barr Virus Type 1 Among Nasopharyngeal Carcinomas in Iranian Patients

Background: Around 95% of the world’s population are infected with the Epstein-Barr virus (EBV), which can persist latent in B lymphocytes and epithelial cells life-long. EBV has been linked with lymphoid and epithelial cancers and persistence of EBV infection in lymphoid or epithelial cells may result in virus-associated B-cell tumors or nasopharyngeal carcinomas (NPC). This study was conducted to determine the frequency of EBV DNA in nasopharyngeal carcinoma tissue of Iranian patients. Materials and methods: A total of 50 blocks of formalin-fixed paraffin-embedded tissue of NPCs from 38 (76 %) male and 12 (24%) female patients were collected from archives of Ahvaz hospitals. Sections were cut at 5 μm and DNA was extracted for detection of EBV DNA and EBV typing by mested PCR. DNA sequencing was performed to confirm PCR results. The distribution of EBV DNA was compared among WHO histological subtypes of NPC. Results: Some 3 female and 11 (22%) male NPC samples showed positive for EBV DNA type 1, 2/14(22.2%)WHO histological type II and 12/41(29.3%) WHO histological type III. Conclusions: The frequency of EBV DNA among NPCs in Iranian patients was found to be 28%, EBV type I predominating. Both WHO histological type II and III NPC subtypes demonstrated approximately the same detection prevalence.

Epstein-Barr virus: more than 50 years old and still providing surprises

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

Mouse model for acute Epstein-Barr virus infection

Epstein-Barr Virus (EBV) infects human B cells and drives them into continuous proliferation. Two key viral factors in this process are the latent membrane proteins LMP1 and LMP2A, which mimic constitutively activated CD40 receptor and B-cell receptor signaling, respectively. EBV-infected B cells elicit a powerful T-cell response that clears the infected B cells and leads to life-long immunity. Insufficient immune surveillance of EBV-infected B cells causes life-threatening lymphoproliferative disorders, including mostly germinal center (GC)-derived B-cell lymphomas. We have modeled acute EBV infection of naive and GC B cells in mice through timed expression of LMP1 and LMP2A. Although lethal when induced in all B cells, induction of LMP1 and LMP2A in just a small fraction of naive B cells initiated a phase of rapid B-cell expansion followed by a proliferative T-cell response, clearing the LMP-expressing B cells. Interfering with T-cell activity prevented clearance of LMP-expressing B cells. This was also true for perforin deficiency, which in the human causes a life-threatening EBV-related immunoproliferative syndrome. LMP expression in GC B cells impeded the GC reaction but, upon loss of T-cell surveillance, led to fatal B-cell expansion. Thus, timed expression of LMP1 together with LMP2A in subsets of mouse B cells allows one to study major clinically relevant features of human EBV infection in vivo, opening the way to new therapeutic approaches.

Epstein-Barr virus latent membrane protein-1 up-regulates cytokines and correlates with older age and poorer prognosis in Hodgkin lymphoma

AIMS

Previously, we reported an association between Epstein-Barr virus (EBV)-positive Hodgkin lymphoma (HL), older age, and poorer prognosis. The aim of this study was to investigate the mechanisms underlying this association.

METHODS AND RESULTS

Transfection of HL cell lines with EBV latent membrane protein-1 (LMP1) resulted in up-regulation of many cytokine genes as assessed by the use of oligonucleotide microarrays. The up-regulation of cytokines was validated by using an inflammatory cytokine protein array: macrophage inflammatory protein (MIP)-1α, MIP-1β, and interleukin (IL)-13. Immunostaining of HL samples (n = 104) showed that expression of MIP-1α, MIP-1β and IL-13 correlated with EBV infection and LMP1 expression. Combined expression of these cytokines was more common in patients aged >60 years (P < 0.001), and was associated with a poorer prognosis (P = 0.042). In another cohort, serum levels of MIP-1α, MIP-1β and IL-13 were increased in HL patients (n = 53) and highest in EBV-positive HL patients as compared with healthy controls (n = 40). Xenograft mice injected with EBV-positive HL cells had higher serum levels of MIP-1α, MIP-1β and IL-13 than mice injected with EBV-negative HL cells, although there was no difference in growth.

CONCLUSIONS

EBV infection appears to promote the release of cytokines in HL patients, and negatively impacts on patient survival. Physiological immunosenescence probably explains the association between EBV infection and older age. Cytokine modulation is a potential therapeutic target for EBV-positive HL patients.

Epstein-Barr Virus Latent Membrane Protein 2A (LMP2A) enhances IL-10 production through the activation of Bruton's tyrosine kinase and STAT3

Previous data demonstrate that Epstein-Barr Virus Latent Membrane Protein 2A (LMP2A) enhances IL-10 to promote the survival of LMP2A-expressing B cell lymphomas. Since STAT3 is an important regulator of IL-10 production, we hypothesized that LMP2A activates a signal transduction cascade that increases STAT3 phosphorylation to enhance IL-10. Using LMP2A-negative and -positive B cell lines, the data indicate that LMP2A requires the early signaling molecules of the Syk/RAS/PI3K pathway to increase IL-10. Additional studies indicate that the PI3K-regulated kinase, BTK, is responsible for phosphorylating STAT3, which ultimately mediates the LMP2A-dependent increase in IL-10. These data are the first to show that LMP2A signaling results in STAT3 phosphorylation in B cells through a PI3K/BTK-dependent pathway. With the use of BTK and STAT3 inhibitors to treat B cell lymphomas in clinical trials, these findings highlight the possibility of using new pharmaceutical approaches to treat EBV-associated lymphomas that express LMP2A.