Immunohistochemical Detection of the Epstein-Barr Virus–Encoded Latent Membrane Protein 2A in Hodgkin's Disease and Infectious Mononucleosis

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.

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.

Hodgkin Lymphoma in People Living with HIV

Simple Summary

Hodgkin lymphoma (HL) is a non-AIDS defining neoplasm, but people living with HIV (PLWH) have between a 5- and 26-fold higher risk of developing it than the general population. Epstein-Barr virus is present in almost all HIV-related HL cases, and plays an important role in its etiopathogenesis. Despite the aggressive characteristics, the prognosis of HL affecting PLWH is similar to that of the general population if patients are treated following the same recommendations. Administration of cART concomitantly with chemotherapy is highly recommended. However, this combination may be challenging due to drug–drug interactions and overlapping toxicity. Thus, interdisciplinary collaboration between hemato-oncologists and HIV specialists is crucial for the optimal treatment of both lymphoma and HIV infection.

Abstract

Despite widespread use of combined antiretroviral therapy (cART) and increased life expectancy in people living with HIV (PLWH), HIV-related lymphomas (HRL) remain a leading cause of cancer morbidity and mortality for PLWH, even in patients optimally treated with cART. While the incidence of aggressive forms of non-Hodgkin lymphoma decreased after the advent of cART, incidence of Hodgkin lymphoma (HL) has increased among PLWH in recent decades. The coinfection of Epstein–Barr virus plays a crucial role in the pathogenesis of HL in the HIV setting. Currently, PLWH with HRL, including HL, are treated similarly to HIV-negative patients and, importantly, the prognosis of HL in PLWH is approaching that of the general population. In this regard, effective cART during chemotherapy is strongly recommended since it has been shown to improve survival rates in all lymphoma subtypes, including HL. As a consequence, interdisciplinary collaboration between HIV specialists and hemato-oncologists for the management of potential drug–drug interactions and overlapping toxicities between antiretroviral and antineoplastic drugs is crucial for the optimal treatment of PLWH with HL. In this article the authors review and update the epidemiological, clinical and biological aspects of HL presenting in PLWH with special emphasis on advances in prognosis and the factors that have contributed to it.

MicroRNA and Other Non-Coding RNAs in Epstein-Barr Virus-Associated Cancers

EBV is a direct causative agent in around 1.5% of all cancers. The oncogenic properties of EBV are related to its ability to activate processes needed for cellular proliferation, survival, migration, and immune evasion. The EBV latency program is required for the immortalization of infected B cells and involves the expression of non-coding RNAs (ncRNAs), including viral microRNAs. These ncRNAs have different functions that contribute to virus persistence in the asymptomatic host and to the development of EBV-associated cancers. In this review, we discuss the function and potential clinical utility of EBV microRNAs and other ncRNAs in EBV-associated malignancies. This review is not intended to be comprehensive, but rather to provide examples of the importance of ncRNAs.

[Epstein-Barr virus (Herpesviridae: Gammaherpesvirinae: Lymphocryptovirus: Human gammaherpesvirus 4): replication strategies]

The Epstein-Barr virus (EBV), one of the most common in the human population, is capable of lifelong persistence in resting memory B-cells, in T-cells in case of type 2 EBV, and in some undifferentiated epithelial cells. In most people, EBV persistence is not accompanied by significant symptoms, but frequent virus activations are associated with the increased risks of severe diseases, such as chronic active Epstein-Barr virus infection, hemophagocytic lymphohistiocytosis, multiple sclerosis, systemic lupus erythematosus, gastric and nasopharyngeal carcinomas, and a variety of T- and B-cell lymphomas. Therefore, the molecular viral and host cell processes during asymptomatic or low-symptom EBV persistence are of great interest. This review describes the behavior of the viral DNA in an infected cell and the forms of its existence (linear, circular episome, chromosomally integrated forms), as well as methods of EBV genome copying. Two closely related cycles of viral reproduction are considered. Lytic activation is unfavorable for the survival of a particular viral genome in the cell, and may be a result of differentiation of a latently infected cell, or the arrival of stress signals due to adverse extracellular conditions. The EBV has a large number of adaptive mechanisms for limiting lytic reactivation and reducing hostility of host immune cells. Understanding the molecular aspects of EBV persistence will help in the future develop more effective targeted drugs for the treatment of both viral infection and associated diseases.

EBV-Positive Lymphoproliferations of B- T- and NK-Cell Derivation in Non-Immunocompromised Hosts

The contribution of Epstein-Barr virus (EBV) to the development of specific types of benign lymphoproliferations and malignant lymphomas has been extensively studied since the discovery of the virus over the last 50 years. The importance and better understanding of the EBV-associated lymphoproliferative disorders (LPD) of B, T or natural killer (NK) cell type has resulted in the recognition of new entities like EBV+ mucocutaneous ulcer or the addition of chronic active EBV (CAEBV) infection in the revised 2016 World Health Organization (WHO) lymphoma classification. In this article, we review the definitions, morphology, pathogenesis, and evolving concepts of the various EBV-associated disorders including EBV+ diffuse large B-cell lymphoma, not otherwise specified (DLBCL, NOS), EBV+ mucocutaneous ulcer, DLBCL associated with chronic inflammation, fibrin-associated DLBCL, lymphomatoid granulomatosis, the EBV+ T and NK-cell LPD of childhood, aggressive NK leukaemia, extranodal NK/T-cell lymphoma, nasal type, and the new provisional entity of primary EBV+ nodal T- or NK-cell lymphoma. The current knowledge regarding the pathogenesis of B-cell lymphomas that can be EBV-associated including Burkitt lymphoma, plasmablastic lymphoma and classic Hodgkin lymphoma will be also explored.

Latent membrane protein 1 (LMP1) expression in Hodgkin lymphoma and its correlation with clinical and histologic parameters

Background

Hodgkin lymphoma is one of the most prevalent lymphoproliferative disorders in Pakistan; however, no risk factors for this disease have yet to be established in our population. Epstein–Barr virus (EBV) is a well-known risk factor for Hodgkin lymphoma in endemic regions of the world; however, frequency of its association in our population has not been widely studied. Latent membrane protein 1 (LMP1) expression by immunohistochemistry (IHC) is a surrogate marker of EBV in Hodgkin lymphoma. Therefore, we aimed to evaluate the frequency of expression of LMP1 in cases of Hodgkin lymphoma at our institute and its correlation with other clinical and histologic parameters.

Methods

The study included 66 cases of Hodgkin lymphoma diagnosed at Liaquat National Hospital over a duration of 2 years from January 2014 to December 2015. The slides and blocks of all cases were retrieved, and representative blocks were selected for LMP1 by IHC. LMP1 expression of >10% of cells was considered as positive expression and correlated with histologic subtypes and clinical parameters like age, gender, and site of involvement.

Results

The mean age of patients was 35.11 (+20.22). LMP1 expression was found in 68.1% (45/66) of cases of Hodgkin lymphoma. Mean age of the patients with LMP1 expression was 32.04 (+21.02). LMP1 expression was found in 40% cases of lymphocyte-rich, 66.7% of lymphocyte-depleted, 73.9% of mixed cellularity, 66.7% of nodular sclerosis, and 73.7% of classic Hodgkin lymphoma, NOS. No significant correlation of LMP1 expression with any clinical or histological parameter could be established in our studied patient population.

Conclusions

A high frequency of expression of LMP1 is seen in cases of Hodgkin lymphoma at our setup comparable to endemic regions of the world; therefore, preventive and treatment protocols should be designed accordingly.

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.

Human serum antibodies against EBV latent membrane protein 1 cross-react with α-synuclein

Objectives:

To identify the epitope on α-synuclein (α-syn) to which antibodies against the Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1) bind and to determine whether antibodies targeting this mimicry domain are present in human sera.

Methods:

Reactivity of the α-syn-cross-reacting anti-LMP1 monoclonal antibody CS1-4 to a synthetic peptide containing the putative mimicry domain was compared to those in which this domain was mutated and to murine and rat α-syn (which differ from human α-syn at this site) in Western blots. Using ELISA, sera from EBV+ (n = 4) and EBV− (n = 12) donors as well as those with infectious mononucleosis (IM; n = 120), and Hodgkin disease (HD; n = 33) were interrogated for antibody reactivity to synthetic peptides corresponding to regions of α-syn and LMP1 containing the mimicry domain.

Results:

CS1-4 showed strong reactivity to wild-type human α-syn, but not to the mutant peptides or rodent α-syn. Control EBV− and EBV+ sera showed no reactivity to α-syn or LMP1 peptides. However, a significant proportion of IM and HD sera contained immunoglobulin M (IgM) (59% and 70%, in IM and HD, respectively), immunoglobulin G (IgG) (40% and 48%), and immunoglobulin A (IgA) (28% and 36%) antibodies to both peptides, as well as a significant correlation in the titers of IgM (ρ = 0.606 and 0.664, for IM and HD, respectively), IgG (0.526 and 0.836), and IgA (0.569 and 0.728) antibodies targeting LMP1 and α-syn peptides.

Conclusions:

Anti-EBV-LMP1 antibodies cross-reacting with a defined epitope in α-syn are present in human patients. These findings may have implications for the pathogenesis of synucleinopathies.

Epstein-Barr virus latent genes

Latent Epstein–Barr virus (EBV) infection has a substantial role in causing many human disorders. The persistence of these viral genomes in all malignant cells, yet with the expression of limited latent genes, is consistent with the notion that EBV latent genes are important for malignant cell growth. While the EBV-encoded nuclear antigen-1 (EBNA-1) and latent membrane protein-2A (LMP-2A) are critical, the EBNA-leader proteins, EBNA-2, EBNA-3A, EBNA-3C and LMP-1, are individually essential for in vitro transformation of primary B cells to lymphoblastoid cell lines. EBV-encoded RNAs and EBNA-3Bs are dispensable. In this review, the roles of EBV latent genes are summarized.

Contribution of the Epstein-Barr Virus to the Pathogenesis of Hodgkin Lymphoma

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

EBV Persistence--Introducing the Virus

Persistent infection by EBV is explained by the germinal center model (GCM) which provides a satisfying and currently the only explanation for EBVs disparate biology. Since the GCM touches on every aspect of the virus, this chapter will serve as an introduction to the subsequent chapters. EBV is B lymphotropic, and its biology closely follows that of normal mature B lymphocytes. The virus persists quiescently in resting memory B cells for the lifetime of the host in a non-pathogenic state that is also invisible to the immune response. To access this compartment, the virus infects naïve B cells in the lymphoepithelium of the tonsils and activates these cells using the growth transcription program. These cells migrate to the GC where they switch to a more limited transcription program, the default program, which helps rescue them into the memory compartment where the virus persists. For egress, the infected memory cells return to the lymphoepithelium where they occasionally differentiate into plasma cells activating viral replication. The released virus can either infect more naïve B cells or be amplified in the epithelium for shedding. This cycle of infection and the quiescent state in memory B cells allow for lifetime persistence at a very low level that is remarkably stable over time. Mathematically, this is a stable fixed point where the mechanisms regulating persistence drive the state back to equilibrium when perturbed. This is the GCM of EBV persistence. Other possible sites and mechanisms of persistence will also be discussed.

Immunohistochemical approach to study cylindrospermopsin distribution in tilapia (Oreochromis niloticus) under different exposure conditions

Cylindrospermopsin (CYN) is a cytotoxic cyanotoxin produced by several species of freshwater cyanobacteria (i.e., Aphanizomenon ovalisporum). CYN is a tricyclic alkaloid combined with a guanidine moiety. It is well known that CYN inhibits both protein and glutathione synthesis, and also induces genotoxicity and the alteration of different oxidative stress biomarkers. Although the liver and kidney appear to be the main target organs for this toxin based on previous studies, CYN also affects other organs. In the present study, we studied the distribution of CYN in fish (Oreochromis niloticus) under two different exposure scenarios using immunohistochemical (IHC) techniques. In the first method, fish were exposed acutely by intraperitoneal injection or by gavage to 200 µg pure CYN/Kg body weight (bw), and euthanized after 24 h or five days of exposure. In the second method, fish were exposed by immersion to lyophilized A. ovalisporum CYN-producing cells using two concentration levels (10 or 100 µg/L) for two different exposure times (7 or 14 days). The IHC was carried out in liver, kidney, intestine, and gills of fish. Results demonstrated a similar pattern of CYN distribution in both experimental methods. The organ that presented the most immunopositive results was the liver, followed by the kidney, intestine, and gills. Moreover, the immunolabeling signal intensified with increasing time in both assays, confirming the delayed toxicity of CYN, and also with the increment of the dose, as it is shown in the sub-chronic assay. Thus, IHC is shown to be a valuable technique to study CYN distribution in these organisms.

Histopathological and immunohistochemical analysis of Tilapia (Oreochromis niloticus) exposed to cylindrospermopsin and the effectiveness of N-Acetylcysteine to prevent its toxic effects

Cylindrospermopsin (CYN) is a cytotoxic cyanotoxin produced by several cyanobacteria species. It has been demonstrated that CYN is a potent protein and glutathione synthesis inhibitor, and induces genotoxicity and oxidative stress. The present study investigated the protective role of two different doses of N-Acetylcysteine (NAC) (22 and 45 mg/fish/day) against the pathological changes induced in tilapia (Oreochromis niloticus) orally exposed to a single dose of pure CYN or CYN from an Aphanizomenon ovalisporum CYN-producer strain (200 μg/kg of CYN in both cases). Moreover, an immunohistochemical (IHC) analysis was carried out in order to elucidate the CYN distribution in exposed fish. The histological findings were more pronounced when fish were intoxicated with CYN from the cyanobacterial strain, being liver and kidney the main targets for CYN toxicity. NAC pre-treatment was effective reducing the damage induced by CYN, especially at the highest dose employed (45 mg/fish/day), with a total prevention in all organs. The IHC analysis showed that CYN-antigen appeared mainly in the liver and gastrointestinal tract, although it was also present in kidney and gills. In this case, the immunopositive results were more abundant in those fish exposed to pure CYN. NAC reduced the number of immunopositive cases in a dose-dependent way. Therefore, NAC can be considered a useful chemoprotectant in the prophylaxis and treatment of CYN-related intoxications in fish.

Epstein-Barr virus latent membrane protein 2 effects on epithelial acinus development reveal distinct requirements for the PY and YEEA motifs

Epstein-Barr virus (EBV) is a gammaherpesvirus associated with numerous cancers, including the epithelial cancers nasopharyngeal carcinoma (NPC) and gastric carcinoma. The latent membrane protein 2 (LMP2) encoded by EBV is consistently detected in NPC tumors and promotes a malignant phenotype when expressed in epithelial cells by inducing transformation and migration and inhibiting differentiation. Grown in three dimensions (3D) on Matrigel, the nontumorigenic mammary epithelial cell line MCF10A forms hollow, spherical acinar structures that maintain normal glandular features. Expression of oncogenes in these cells allows for the study of multiple aspects of tumor development in a 3D culture system. This study sought to examine the effects of LMP2 on the generation of MCF10A acini. LMP2 expression induced abnormal acini that were large, misshapen, and filled, indicating that LMP2 induced proliferation, impaired cellular polarization, and induced resistance to cell death, leading to luminal filling. Induction of cell death resistance required the PY, immunoreceptor tyrosine activation motif (ITAM), and YEEA signaling domains of LMP2 and activation of the Src and Akt signaling pathways. The PY domain was required for the inhibition of anoikis and also the delayed proliferative arrest of the LMP2-expressing cells. In addition to directly altering acinus formation, expression of LMP2 also induced morphological and protein expression changes consistent with epithelial-mesenchymal transition (EMT) in a manner that required only the YEEA signaling motif of LMP2. These findings indicate that LMP2 has considerable transforming properties that are not evident in standard tissue culture and requires the ability of LMP2A to bind ubiquitin ligases and Src family kinases.

The labyrinth of interactions of Epstein-Barr virus-encoded small RNAs

Epstein-Barr Virus (EBV) is an oncogenic herpesvirus implicated in the pathogenesis of a number of human malignancies. However, the mechanism by which EBV leads to malignant transformation is not clear. A number of viral latent gene products, including non-protein coding small RNAs, are believed to be involved. Epstein-Barr virus-encoded RNA 1 (EBER1) and EBER2 are two such RNA molecules that are abundantly expressed (up to 10(7) copies) in all EBV-infected cells, but their function remains poorly understood. These polymerase III transcripts have extensive secondary structure and exist as ribonucleoproteins. An accumulating body of evidence suggests that EBERs play an important role, directly or indirectly, in EBV-induced oncogenesis. Here, we summarize the current understanding of the complex interactions of EBERs with various cellular factors and the potential pathways by which these small RNAs are able to influence EBV-infected cells to proliferate and to induce tumorigenesis. The exosome pathway is probably involved in the cellular excretion of EBERs and facilitating some of their biological effects.

Epstein-Barr virus-encoded latent membrane protein-1 upregulates 14-3-3σ and Reprimo to confer G(2)/M phase cell cycle arrest

Epstein-Barr virus (EBV) is a ubiquitous tumor-causing virus which infects more than 90% of the world population asymptomatically. Recent studies suggest that LMP-1, -2A and -2B cooperate in the tumorigenesis of EBV-associated epithelial cancers such as nasopharygeal carcinoma, oral and gastric cancer. In this study, LMPs were expressed in the HEK293T cell line to reveal their oncogenic mechanism via investigation on their involvement in the regulation of the cell cycle and genes that are involved. LMPs were expressed in HEK293T in single and co-expression manner. The transcription of cell cycle arrest genes were examined via real-time PCR. Cell cycle progression was examined via flow cytometry. 14-3-3σ and Reprimo were upregulated in all LMP-1 expressing cells. Moreover, cell cycle arrest at G(2)/M progression was detected in all LMP-1 expressing cells. Therefore, we conclude that LMP-1 may induce cell cycle arrest at G(2)/M progression via upregulation of 14-3-3σ and Reprimo.

Atypical prediagnosis Epstein-Barr virus serology restricted to EBV-positive Hodgkin lymphoma

An altered anti-Epstein-Barr virus (EBV) serologic profile preceding diagnosis is associated with an increased risk of Hodgkin lymphoma. It is unknown whether this atypical pattern predicts Hodgkin lymphoma risk further subdivided by determination of EBV in tumor cells. A nested case-control study of 128 incident Hodgkin lymphoma cases and 368 matched controls from active-duty military personnel with archived serum in the US Department of Defense Serum Repository was conducted to determine whether a panel of anti-EBV antibody titers differed in EBV(+) and EBV(-) Hodgkin lymphoma. Among 40 EBV(+) Hodgkin lymphoma cases and matched controls, statistically significant increased risks were associated with elevated anti-EBV VCA IgG antibody titers (relative risk = 3.1; 95% confidence interval [CI], 1.1-8.7), and an anti-EBNA-1/anti-EBNA-2 antibody ratio ≤ 1.0 versus > 1.0 (relative risk = 4.7; 95% CI, 1.6-13.8). In contrast, no significant associations were found among 88 EBV(-) Hodgkin lymphoma cases relative to their matched controls. In case-case analysis, EBV(+) disease was significantly associated with a low anti-EBNA-1/anti-EBNA-2 antibody ratio. This distinctive serologic response to EBV latent antigens, indicative of immune dysfunction in other clinical settings, is associated with an increased risk of developing EBV(+) but not EBV(-) Hodgkin lymphoma.

Immune evasion strategies of the human gamma-herpesviruses: implications for viral tumorigenesis

Two human gamma-herpesviruses, Epstein-Barr virus and Kaposi's sarcoma associated herpesvirus/human herpesvirus 8 display oncogenic potential, causing benign and malignant lymphoproliferative disorders in genetically susceptible or immunosuppressed individuals. As a family of viruses that establish persistent life-long infections, herpesviruses have evolved strategies to limit innate antiviral responses and evade host immune surveillance. Herpesviruses have developed mechanisms to disrupt antigen presentation, pirate the production of immune regulating cytokines, and inhibit pro-apoptotic signaling pathways. Although these strategies are designed to facilitate the long-term persistence of herpesviruses, in certain circumstances they can contribute to viral-driven carcinogenesis.

Epstein-Barr virus in the multiple sclerosis brain: a controversial issue--report on a focused workshop held in the Centre for Brain Research of the Medical University of Vienna, Austria

Recent epidemiological and immunological studies provide evidence for an association between Epstein-Barr virus infection and multiple sclerosis, suggesting a role of Epstein-Barr virus infection in disease induction and pathogenesis. A key question in this context is whether Epstein-Barr virus-infected B lymphocytes are present within the central nervous system and the lesions of patients with multiple sclerosis. Previous studies on this topic provided highly controversial results, showing Epstein-Barr virus reactivity in B cells in the vast majority of multiple sclerosis cases and lesions, or only exceptional Epstein-Barr virus-positive B cells in rare cases. In an attempt to explain the reasons for these divergent results, a workshop was organized under the umbrella of the European Union FP6 NeuroproMiSe project, the outcome of which is presented here. This report summarizes the current knowledge of Epstein-Barr virus biology and shows that Epstein-Barr virus infection is highly complex. There are still major controversies, how to unequivocally identify Epstein-Barr virus infection in pathological tissues, particularly in situations other than Epstein-Barr virus-driven lymphomas or acute Epstein-Barr virus infections. It further highlights that unequivocal proof of Epstein-Barr virus infection in multiple sclerosis lesions is still lacking, due to issues related to the sensitivity and specificity of the detection methods.

A novel latent membrane 2 transcript expressed in Epstein-Barr virus-positive NK- and T-cell lymphoproliferative disease encodes a target for cellular immunotherapy

Therapeutic targeting of virus-encoded proteins using cellular immunotherapy has proved successful for Epstein-Barr virus (EBV)-associated posttransplant lymphoproliferative disease. However, the more limited repertoire and immunogenicity of EBV-encoded proteins in other malignancies such as Hodgkin lymphoma and extranodal natural killer (NK)/T lymphoma has been more challenging to target. The immunosubdominant latent membrane protein 2 (LMP2) is considered the optimal target in such Latency II tumors, although data relating to its expression in T/NK malignancies are limited. In addressing the validity of LMP2 as an immunotherapeutic target we found that LMP2-specific effector CD8(+) T cells recognized and killed EBV-positive NK- and T-cell tumor lines, despite an apparent absence of LMP2A protein and barely detectable levels of LMP2 transcripts from the conventional LMP2A and LMP2B promoters. We resolved this paradox by identifying in these lines a novel LMP2 mRNA, initiated from within the EBV terminal repeats and containing downstream, epitope-encoding exons. This same mRNA was also highly expressed in primary (extra-nodal) NK/T lymphoma tissue, with virtually undetectable levels of conventional LMP2A/B transcripts. Expression of this novel transcript in T/NK-cell lymphoproliferative diseases validates LMP2 as an attractive target for cellular immunotherapy and implicates this truncated LMP2 protein in NK- and T-cell lymphomagenesis. This study is registered at clinicaltrials.gov as NCT00062868.

NCI First International Workshop on the Biology, Prevention, and Treatment of Relapse after Allogeneic Hematopoietic Stem Cell Transplantation: Report from the Committee on Treatment of Relapse after Allogeneic Hematopoietic Stem Cell Transplantation

Relapse is a major cause of treatment failure after allogeneic hematopoietic stem cell transplantation (alloHSCT). Treatment options for relapse have been inadequate, and the majority of patients ultimately die of their disease. There is no standard approach to treating relapse after alloHSCT. Withdrawal of immune suppression and donor lymphocyte infusions are commonly used for all diseases; although these interventions are remarkably effective for relapsed chronic myelogenous leukemia, they have limited efficacy in other hematologic malignancies. Conventional and novel chemotherapy, monoclonal antibody therapy, targeted therapies, and second transplants have been utilized in a variety of relapsed diseases, but reports on these therapies are generally anecdotal and retrospective. As such, there is an immediate need for well-designed, disease-specific trials for treatment of relapse after alloHSCT. This report summarizes current treatment options under investigation for relapse after alloHSCT in a disease-specific manner. In addition, recommendations are provided for specific areas of research necessary in the treatment of relapse after alloHSCT.

Epstein-Barr virus latent infection and BAFF expression in B cells in the multiple sclerosis brain: implications for viral persistence and intrathecal B-cell activation

A cardinal feature of multiple sclerosis (MS) is the persistent intrathecal synthesis of antibodies. Our previous finding that a large fraction of B cells infiltrating the MS brain are infected with Epstein-Barr virus (EBV) raises the possibility that this virus, because of its ability to establish a latent infection in B cells and interfere with their differentiation, contributes to B-cell dysregulation in MS. The aim of this study was to gain further insight into EBV latency programs and their relationship to B-cell activation in the MS brain. Immunohistochemical analysis of postmortem MS brain samples harboring large EBV deposits revealed that most B cells in white matter lesions, meninges, and ectopic B-cell follicles are CD27+ antigen-experienced cells and coexpress latent membrane protein 1 and latent membrane protein 2A, 2 EBV-encoded proteins that provide survival and maturation signals to B cells. By combining laser-capture microdissection with preamplification reverse transcription-polymerase chain reaction techniques, EBV latency transcripts (latent membrane protein 2A, EBV nuclear antigen 1) were detected in all MS brain samples analyzed. We also found that B cell-activating factor of the tumor necrosis factor family is expressed in EBV-infected B cells in acute MS lesions and ectopic B-cell follicles. These findings support a role for EBV infection in B-cell activation in the MS brain and suggest that B cell-activating factor of the tumor necrosis factor family produced by EBV-infected B cells may contribute to this process resulting in viral persistence and, possibly, disruption of B-cell tolerance.

Lymphoma in adolescents and young adults

Non-Hodgkin (NHL) and Hodgkin (HL) lymphomas are represented prominently in the adolescent and young adult (AYA) population. These diseases represent 11% of total cancer diagnoses in children, 4% in those 40 years of age and older, and 13% in AYA (aged 15-39 years). Although age-adjusted incidence rates of NHL increase with age, the more aggressive lymphomas are seen more commonly in the younger population with a transition to low-grade, indolent subtypes as the population ages. Burkitt lymphoma, diffuse large B-cell lymphoma, lymphoblastic lymphoma, and anaplastic large cell lymphoma make up the most common subtypes in the AYA population, although within the subgroup age 30-39 years, follicular lymphoma becomes more prominent. As a result, much of the armamentarium in the treatment of aggressive NHL and HL in adults is based on data from pediatric clinical trials. There are obvious limitations to this approach. It is vital that we gain a more thorough understanding of the biology and therapeutic responsiveness of NHL and HL in the AYA population. Thus, we must leverage the large prospective and retrospective trials that have been completed to date and redirect our approaches to cancer care in this unique population. We review the epidemiological data on NHL and HL from the Surveillance, Epidemiology and End Results registries as a cornerstone for a comparative analysis of therapeutic outcomes available in this population.

B-cell differentiation immunophenotypes in classical Hodgkin lymphomas

The bcl6/CD10/MUM1/CD138 B-cell differentiation immunophenotypes were analysed in 101 cases of classical Hodgkin lymphomas (cHL) aiming to elucidate their histogenesis. Three major bcl6/CD10/MUM1/CD138 immunophenotypes were distinguished on the basis of the immunohistochemical positivity of Hodgkin and Reed-Sternberg (H/RS) cells: (a) the late germinal center (GC)/early post-GC B-cell-like immunophenotype (bcl6-/CD10-/MUM1+/CD138-); 59/101 cases (59%), (b) the post-GC B-cell-like immunophenotype (bcl6-/CD10-/MUM1+/CD138+); 24/101 cases (24%) and (c) the indeterminate immunophenotype (bcl6+/CD10-/MUM1+/CD138-: 14 cases and bcl6+/CD10-/MUM1+/CD138+: four cases); 18/101 cases (18%). The above findings indicate that H/RS cells in most cHL display bcl6/CD10/MUM1/CD138 immunophenotypes consistent with late GC/early post-GC or post-GC B-cell differentiation. In addition, H/RS cells in a small fraction of cHL display indeterminate bcl6/CD10/MUM1/CD138 immunophenotypic profiles which are characterized by simultaneous expression of GC, late GC/early post-GC and post-GC B-cell differentiation proteins. These immunophenotypic profiles do not correspond to the differentiation immunophenotypes of normal B-cells and their identification in a part of cHL suggests that the differentiation process of H/RS cells is not complete in a fraction of these cells and/or is still ongoing at the time of observation.

Activated human gammadelta T cells as stimulators of specific CD8+ T-cell responses to subdominant Epstein Barr virus epitopes: potential for immunotherapy of cancer

The efficacy of current cancer vaccines is limited by the functional heterogeneity and poor availability and expansion of professional antigen-presenting cells (APCs). Besides their potent innate effector properties, gammadelta T cells have been suggested to be involved in the initiation and maintenance of adaptive immune responses. Here, we investigated the capacity of human gammadelta T cells to induce expansion of virus-specific T cells to Epstein Barr virus (EBV) antigens. Aminobisphosphonate-stimulated human peripheral blood-derived gammadelta T cells (Vgamma2+Vdelta2+) acquired a dual phenotype characteristic for both APCs and effector memory T cells. Coincubation of activated gammadelta T cells pulsed with human leukocyte antigen-restricted epitopes of either the highly stimulatory EBV lytic cycle antigen Bam H1 Z fragment leftward open reading frame or the tumor-associated latent EBV antigen latent membrane protein 2a (LMP2a) with autologous peripheral blood lymphocytes induced selective expansion of peptide-specific, fully functional CD3CD8 cytolytic effector memory T cells. Furthermore, gammadelta T APCs efficiently processed and presented endogenous antigen, as demonstrated by the capacity of LMP2a gene-transduced gammadelta T cells to induce expansion of T cells with broad specificity for various LMP2a peptides. The capacity of autologous gammadelta T cells to induce LMP2a-specific autologous cytotoxic T lymphocytes was confirmed in 2 patients with Hodgkin lymphoma. In summary, bisphosphonate-activated human gammadelta T cells stimulate expansion of cytotoxic effector T cells specific for both subdominant and dominant viral epitopes and thus show promise as a novel source of efficient APCs for immunotherapy of viral and malignant disease.

Allogeneic transplantation for Hodgkin lymphoma

The majority of patients with Hodgkin lymphoma (HL) can now expect to be cured with conventional chemo- and/or radio-therapy. However, a subgroup still exists that have poor outcomes, even following dose escalation and autologous stem cell transplantation. Furthermore, patients relapsing after autografting have limited therapeutic options available. Whilst the application of allogeneic transplantation strategies has historically been limited by prohibitive transplant-related mortality, the exploration of reduced intensity approaches has demonstrated the feasibility of delivering allogeneic immunotherapies with more acceptable mortality rates. Although its role remains controversial, we are beginning to re-evaluate the use of allogeneic transplantation in the management of patients with HL and to address a number of critical questions. These include whether a clinically relevant graft-versus-tumour response occurs in HL, and whether subgroups of patients who might benefit from allogeneic approaches can be identified in order to inform development of rational clinical studies. This review focuses on evaluating recent experience with reduced intensity allogeneic approaches in HL in order to inform opinion on its current role and to highlight areas for future investigation.

In vitro methods for generating highly purified EBV associated tumor antigen-specific T cells by using solid phase T cell selection system for immunotherapy

Adoptive cell transfer immunotherapy has been utilized to treat EBV related human malignancies including post-transplant lymphoproliferative diseases, Hodgkin's lymphoma and nasopharyngeal carcinoma. However, there are limited options available for tumor antigen-specific T cell purification. Here we describe a novel solid phase T cell selection system, in which monocytes or EBV transformed B-lymphocytes are immobilized on solid support for antigen-specific T cell purification. We hypothesize and prove that antigen-specific T cells recognize their cognate antigens and bind to them faster than non-antigen specific T cells. Therefore antigen-specific T cells can be concentrated on the surface after removing the non-adherent cells by washing. The optimal selection time for both EBV-specific T cells and LMP2-specific T cells is studied. Our data demonstrate that the frequency of antigen-specific T cells can be increased by >20-fold after selection. Moreover, activated antigen-specific T cells proliferate more rapidly than non-specific T cells, further increasing the frequency and purity of antigen-specific T cells. This new T cell selection system is superior to traditional repeated stimulation methods in generating tumor antigen-specific T cells. We are able to generate large quantities of highly purified T cells of subdominant antigens LMP2 within 2 weeks after T cell activation for adoptive cell transfer immunotherapy with this simple, rapid and inexpensive T cell selection system.

Epstein-Barr virus latent membrane protein 2A is a B-cell receptor mimic and essential for B-cell survival

Many cells latently infected with Epstein-Barr virus (EBV), including certain virus-associated tumors, express latent membrane protein 2A (LMP2A), suggesting an important role for this protein in viral latency and oncogenesis. LMP2A mimics B-cell receptor signaling but can also act as a decoy receptor blocking B-cell receptor (BCR) activation. Studies of peripheral B cells have not resolved this apparent contradiction because LMP2A seems to be dispensable for EBV-induced transformation of these B cells in vitro. We show here that LMP2A is essential for growth transformation of germinal center B cells, which do not express the genuine BCR because of deleterious somatic hypermutations in their immunoglobulin genes. BCR-positive (BCR(+)) and BCR-negative (BCR(-)) B cells are readily transformed with a recombinant EBV encoding a conditional, floxed LMP2A allele, but the survival and continued proliferation of both BCR(+) and BCR(-) B cells is strictly dependent on LMP2A. These findings indicate that LMP2A has potent, distinct antiapoptotic and/or transforming characteristics and point to its role as an indispensable BCR mimic in certain B cells from which human B-cell tumors such as Hodgkin lymphoma originate.

Complete responses of relapsed lymphoma following genetic modification of tumor-antigen presenting cells and T-lymphocyte transfer

Epstein-Barr virus (EBV)-associated tumors developing in immunocompetent individuals present a challenge to immunotherapy, since they lack expression of immunodominant viral antigens. However, the tumors consistently express viral proteins including LMP2, which are immunologically "weak" but may nonetheless be targets for immune T cells. We previously showed that a majority of cytotoxic T lymphocytes (CTLs) reactivated using EBV-transformed B-lymphoblastoid cells lines (LCLs) contained minor populations of LMP2-specific T cells and homed to tumor sites. However, they did not produce remissions in patients with bulky disease. We have now used gene transfer into antigen-presenting cells (APCs) to augment the expression and immunogenicity of LMP2. These modified APCs increased the frequency of LMP2-specific CTLs by up to 100-fold compared with unmodified LCL-APCs. The LMP2-specific population expanded and persisted in vivo without adverse effects. Nine of 10 patients treated in remission of high-risk disease remain in remission, and 5 of 6 patients with active relapsed disease had a tumor response, which was complete in 4 and sustained for more than 9 months. It is therefore possible to generate immune responses to weak tumor antigens by ex vivo genetic modification of APCs and the CTLs so produced can have substantial antitumor activity. This study is registered at http://www.cancer.gov/clinicaltrials (protocol IDs: BCM-H-9936, NCT00062868, NCT00070226).

Comprehensive epitope mapping of the Epstein-Barr virus latent membrane protein-2 in normal, non tumor-bearing individuals

Latent membrane protein (LMP)-2 is one of the Epstein-Barr virus (EBV)-encoded proteins consistently expressed by nasopharyngeal carcinoma (NPC). EBV-transformed lymphoblastoid cell lines (LCL) have been used in patients with NPC to induce LMP-2-recognizing T cell lines which have been in turn utilized for protein-wide mapping of T cell epitopes. However, comprehensive mapping of naturally recognized LMP-2 epitopes in non tumor-bearing individuals has not been reported. Here, we applied a low sensitivity epitope-defining technique for the identification of LMP-2 CTL responses detectable ex vivo in EBV-experienced individuals. This screening tool has been previously validated by analyzing memory CTL responses to Flu, cytomegalovirus (CMV), and the melanoma associated antigen gp100/Mel17. Peripheral blood monocytes (PBMC) from ten Caucasian and ten Chinese individuals were stimulated ex vivo with pools of nonamer (9-mer) peptides overlapping in a stepwise fashion each single amino acid of the LMP-2 sequence. No obvious differences were observed between the immune response of the two ethnic groups save for those related to the divergence in the ethnic prevalence of HLA haplotypes. Several novel and known LMP-2 epitopes were identified. Reactivity toward at least one LMP-2 epitope was detected in 18 of the 20 donors but no prevalent human leukocyte antigen (HLA)/epitope combination was observed confirming that LMP-2 reactivity in the context of common HLA alleles is more pleiotropic than that of FLU and CMV. We believe that the usefulness of these epitopes occurring naturally in non-cancer bearing patients as reagents for the immunization of patients with early or advanced stage NPC deserves further evaluation.

The relationships between Epstein-Barr virus latent membrane protein 1 and regulatory T cells in Hodgkin's lymphoma

OBJECTIVE

Epstein-Barr virus (EBV) encoded latent membrane protein 1 (LMP1) is expressed by the malignant cells of about 30% of cases of Hodgkin's lymphoma (HL) and is therefore a potential target for immune attack. Given the predominantly immunosuppressive nature of HL infiltrating lymphocytes (HLILs) and the ability of LMP1 to stimulate regulatory T (Treg) responses in healthy donors, we hypothesized that LMP1 was important in the generation of Treg responses in HL.

METHODS

We compared T helper (Th) 1, Th2, and Treg responses to LMP1 by peripheral blood mononuclear cells (PBMCs) and HLILs from EBV-positive and -negative HL patients. The number of Treg cells in patients' PBMCs and HLILs was determined by flow cytometry ex vivo. Proliferation ((3)H-thymidine incorporation) and cytokine (interleukin [IL]-10, IL-4 and gamma-interferon) secretion by LMP1-stimulated PBMCs and HLILs was also measured.

RESULTS

Ex vivo EBV-positive HL patients had increased numbers of IL-10-secreting/cytotoxic T-lymphocyte-associated antigen-4-expressing cells compared with EBV-negative HL patients. PBMC/HLIL responses to LMP1 from most patients were characterized by IL-10 secretion, although isolated HL patients mounted Th1-like responses. Several responses to LMP1 peptides were made by HLILs, which were otherwise unresponsive to control stimuli.

CONCLUSIONS

These results suggest that LMP1 epitopes can induce HLIL Treg cells. However, there was no clear evidence of a greater bias toward regulation in EBV-positive HL cases over EBV-negative cases, and thus there are likely to be other mechanisms of Treg cell induction in EBV-negative HL patients. Manipulating the balance of T-helper response to LMP1 might be exploited in immunotherapy of these lymphomas.

Infectious Agents

There is substantial evidence that infectious agents play a causal role in a variety of human malignancies. These cancers include the liver, cervix, stomach, nasopharynx, bladder, and bile duct as well as Kaposi sarcoma (KS) and several lymphomas. This chapter summarizes the biological and epidemiologic features of each of the major oncogenic infections, beginning with the viruses, followed by H. pylori, and with a brief summary of the relevant parasites.

Expression of Epstein-Barr virus (EBV)-encoded latent membrane proteins and STAT3 activation in nasopharyngeal carcinoma

The Epstein-Barr virus (EBV) is associated with virtually all cases of undifferentiated nasopharyngeal carcinoma (NPC), and it was proposed that the EBV-encoded transforming protein, latent membrane protein (LMP) 1, may play a role in the neoplastic process. It was proposed recently that LMP1 expression in epithelial cells may be regulated through a loop involving activated signal transducer and activator of transcription 3 (STAT3), LMP1, LMP1-mediated induction of interleukin (IL)-6 expression and STAT3 activation through the IL-6 receptor. This autoregulatory loop may be suppressed by another viral protein, LMP2A, an effect which in turn can be overcome by exogenous IL-6. Here we show that, as expected, expression of LMP1 and LMP2A tend to be exclusive in NPC tumours. Rare cases showing a co-expression of both proteins can be explained by STAT3 activation via the receptors for IL-6 or epidermal growth factor. STAT3 activation was a consistent feature of NPC tumour cells. However, in most cases, this was not accompanied by detectable expression of LMP1, suggesting either that LMP2A expression may suffice to suppress LMP1 expression or that additional factors may be operational. This study emphasises the need to correlate in vitro results with observational studies of ex vivo tumour tissues.

Expression of the human germinal center-associated lymphoma (HGAL) protein identifies a subset of classic Hodgkin lymphoma of germinal center derivation and improved survival

The human germinal-center-associated lymphoma (HGAL) gene and its cognate protein are expressed in a germinal center (GC)-specific manner. Its expression in classic Hodgkin lymphoma (cHL) prompted us to address whether HGAL expression could distinguish biologically distinct subgroups of cHL. Tissue microarrays from 145 patients treated with curative intent showed HGAL staining in 75% and was closely correlated with MUM1/IRF4 (92%) expression. BCL6 (26%), CD10 (0%), BCL2 (31%), Blimp1 (0.02%), and Epstein-Barr virus (EBV) (20%) showed no specific correlation; neither did phospho-STAT6, a key mediator of IL-4 and IL-13 signaling that induces HGAL and is implicated in cHL pathogenesis. In our study cohort, the 5-year overall survival (OS) correlated with young age (less than 45 years, P < .001), low stage (stage I and II, P = .04), and low International Prognostic Score (P = .002). In univariate analysis, HGAL expression was associated with improved OS (P = .01) and failure-free survival (FFS) (P = .05) but was not independent of other factors in multivariate analysis of OS or FFS. The expression of the GC-specific marker HGAL in a subset of cHL suggests that these cHLs retain characteristics of GC-derived lymphomas. The association with improved OS in univariate but not multivariate analysis suggests that HGAL expression is related to known clinical parameters of improved survival.

Molecular biology of Hodgkin's and Reed/Sternberg cells in Hodgkin's lymphoma

Hodgkin's and Reed/Sternberg (HRS) cells, the tumour cells in classical Hodgkin's lymphoma (HL), represent transformed B cells in nearly all cases. The detection of destructive somatic mutations in the rearranged immunoglobulin (Ig) genes of HRS cells in classical HL indicated that they originate from preapoptotic germinal centre (GC) B cells that lost the capacity to express a high-affinity B-cell receptor (BCR). Several aberrantly activated signalling pathways and transcription factors have been identified that contribute to the rescue of HRS cells from apoptosis. Among the deregulated signalling pathways, activation of multiple receptor tyrosine kinases in HRS cells appears to be a specific feature of HL. In about 40% of cases of classical HL the HRS cells are infected by Epstein-Barr virus (EBV), indicating an important role of EBV in HL pathogenesis. Interestingly, nearly all cases of HL with destructive Ig gene mutations eliminating BCR expression (e.g. nonsense mutations) are EBV-positive, suggesting that EBV-encoded genes have a particular function to prevent apoptosis of HRS-cell precursors that acquired such crippling mutations. This idea is further supported by the recent demonstration that isolated human GC B cells harbouring crippled Ig genes can be rescued by EBV from cell death, giving rise to lymphoblastoid cell lines. The molecular analysis of composite Hodgkin's and non-Hodgkin's lymphomas indicated that many cases develop from a common GC B-cell precursor in a multistep transformation process with both shared and distinct oncogenic events.

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

Epstein-Barr virus (EBV) is associated with B-cell lymphomas such as Hodgkin lymphoma, Burkitt lymphoma, and post-transplantation lymphoma, which originate from clonal germinal center (GC) B cells. During the process of somatic hypermutation, GC B cells can acquire deleterious or nonsense mutations in the heavy and light immunoglobulin genes. Such mutations abrogate the cell surface expression of the B-cell receptor (BCR), which results in the elimination of these nonfunctional B cells by immediate apoptosis. EBV encodes several latent genes, among them latent membrane protein 1 (LMP1) and LMP2A, which are regularly expressed in EBV-positive Hodgkin lymphoma and posttransplantation lymphomas. Since LMP1 and LMP2A mimic the function of 2 key receptors on B cells, CD40 and BCR, respectively, we wanted to learn whether EBV infection can rescue proapoptotic GC B cells with crippling mutations in the heavy chain immunoglobulin locus from apoptosis. We show here that BCR-negative GC B cells readily enter the cell cycle upon infection with EBV in vitro and yield clonal lymphoblastoid cell lines that are incapable of expressing a functional BCR because the rearranged and formerly functional heavy chain immunoglobulin alleles carry deleterious mutations. Our findings imply an important role for EBV in the process of lymphomagenesis in certain cases of Hodgkin lymphoma and posttransplantation lymphomas.

Characterization of latent membrane protein 2 specificity in CTL lines from patients with EBV-positive nasopharyngeal carcinoma and lymphoma

Viral proteins expressed by EBV-associated tumors provide target Ags for immunotherapy. Adoptive T cell therapy has proven effective for posttransplant EBV-associated lymphoma in which all EBV latent Ags are expressed (type III latency). Application of immunotherapeutic strategies to tumors such as nasopharyngeal carcinoma and Hodgkin's lymphoma that have a restricted pattern of EBV Ag expression (type II latency) is under investigation. Potential EBV Ag targets for T cell therapy expressed by these tumors include latent membrane proteins (LMP) 1 and 2. A broad panel of epitopes must be identified from these target Ags to optimize vaccination strategies and facilitate monitoring of tumor-specific T cell populations after immunotherapeutic interventions. To date, LMP2 epitopes have been identified for only a limited number of HLA alleles. Using a peptide library spanning the entire LMP2 sequence, 25 CTL lines from patients with EBV-positive malignancies expressing type II latency were screened for the presence of LMP2-specific T cell populations. In 21 of 25 lines, T cell responses against one to five LMP2 epitopes were identified. These included responses to previously described epitopes as well as to newly identified HLA-A*0206-, A*0204/17-, A29-, A68-, B*1402-, B27-, B*3501-, B53-, and HLA-DR-restricted epitopes. Seven of the nine newly identified epitopes were antigenically conserved among virus isolates from nasopharyngeal carcinoma tumors. These new LMP2 epitopes broaden the diversity of HLA alleles with available epitopes, and, in particular, those epitopes conserved between EBV strains provide valuable tools for immunotherapy and immune monitoring.

Evidence of abortive plasma cell differentiation in Hodgkin and Reed-Sternberg cells of classical Hodgkin lymphoma

Hodgkin and Reed-Sternberg (HRS) cells of classical Hodgkin lymphoma (cHL) show genotypic features of germinal centre-derived B-cells in most cases. Nevertheless, these cells typically lack expression of B-cell antigens. Previous studies have suggested that plasma cell differentiation may occur in HRS cells and that this may account for the down-regulation of B-cell antigens. However, these results are controversial. We have addressed this question using immunohistochemistry and a panel of antibodies directed against antigens which are differentially expressed during terminal B-cell differentiation. Pax-5, a transcription factor required for B-lineage commitment, and IRF4/Mum1, which is physiologically expressed in germinal centre cells and plasma cells, were consistently detectable in HRS cells. Bcl-6, a transcription factor expressed in germinal centre B-cells, was present in HRS cells of approximately 25% of cHL cases. Expression of the B-lymphocyte-induced maturation protein-1 (Blimp-1), a key regulator of plasma cell differentiation, was observed in HRS cells of 23% of cHL cases. In these cases, Blimp-1 expression was restricted to a small proportion of HRS cells. HRS cells were consistently negative for the plasma cell marker CD138. These results suggest that plasma cell differentiation may be initiated in a small subset of HRS cells but remains abortive. Thus, terminal differentiation is unlikely to explain the lack of B-cell antigen expression in HRS cells.

Roles of the ITAM and PY motifs of Epstein-Barr virus latent membrane protein 2A in the inhibition of epithelial cell differentiation and activation of {beta}-catenin signaling

Epstein-Barr virus (EBV) latent membrane protein 2A (LMP2A) is important for maintenance of latency in infected B lymphocytes. Through its immunoreceptor tyrosine-based activation motif (ITAM) and PY motifs, LMP2A is able to block B-cell receptor (BCR) signaling, bind BCR-associated kinases, and manipulate the turnover of itself and these kinases via a PY-mediated interaction with the Nedd4 family of ubiquitin ligases. In epithelial cells, LMP2A has been shown to activate the phosphatidylinositol 3'-OH kinase/Akt and beta-catenin signaling pathways. In the present study, the biological consequences of LMP2A expression in the normal human foreskin keratinocyte (HFK) cell line were investigated and the importance of the ITAM and PY motifs for LMP2A signaling effects in HFK cells was ascertained. The ITAM was essential for the activation of Akt by LMP2A in HFK cells, while both the ITAM and PY motifs contributed to LMP2A-mediated accumulation and nuclear translocation of the oncoprotein beta-catenin. LMP2A inhibited induction of differentiation in an assay conducted with semisolid methylcellulose medium, and the PY motifs were critical for this inhibition. LMP2A is expressed in the EBV-associated epithelial malignancies nasopharyngeal carcinoma and gastric carcinoma, and these data indicate that LMP2A affects cellular processes that likely contribute to carcinogenesis.

Reactivation of Epstein-Barr virus from latency

The general problem in cancer treatment centres on finding agents that specifically affect cancer cells without damaging normal cells. The differences between cancer cells and normal cells are usually very subtle but about 15% of all human cancers involve a virus infection, for example the Epstein-Barr virus associated cancers. In these cancers, every tumour cell carries the virus in a latent infection but the number of normal cells infected is very low. So a treatment that could somehow cause the elimination of EBV infected cells would be very specific for the cancer in such cases. One potential approach could involve finding ways to reactivate the latent virus in cancer cells into the early part of the lytic cycle, impeding cell proliferation, targeting chemotherapeutic agents to the cancer and causing the cancer cells to become targets for immune surveillance. This review considers the mechanisms by which EBV reactivation is controlled and discusses possible therapeutic approaches.

Phenotype and frequency of Epstein-Barr virus-infected cells in pretreatment blood samples from patients with Hodgkin lymphoma

An accumulating body of data suggests that the Epstein-Barr virus (EBV), a lymphotropic herpesvirus, is involved in the pathogenesis of a proportion of cases of Hodgkin lymphoma (HL). In this study, we showed that the frequency of circulating EBV-infected cells was significantly higher (P < 0.001) in pretreatment blood samples from EBV-associated cases when compared with non-EBV-associated cases. We further showed that in patients with EBV-associated disease, the virus persisted in the peripheral blood in memory B cells. This phenotype is consistent with that seen in healthy seropositive controls, post-transplant patients and patients with acute infectious mononucleosis. The data suggest that an increased frequency of EBV carrying B cells in peripheral blood is associated with EBV-associated HL.

Epstein-Barr virus quantitation by real-time PCR targeting multiple gene segments: a novel approach to screen for the virus in paraffin-embedded tissue and plasma

Epstein-Barr Virus (EBV) infects nearly all humans and then persists for the life of the host. In some people who later develop cancer, EBV DNA is present within malignant cells and circulates at elevated levels in the plasma. In the current study, we validated five novel quantitative polymerase chain reaction (Q-PCR) assays targeting disparate but highly conserved segments of the EBV genome (BamH1W, EBNA1, LMP1, LMP2, and BZLF1). Each assay was sensitive to as few as 50 copies of EBV DNA per reaction and was linear across at least four orders of magnitude. When applied to paraffin-embedded tissues in concert with EBV-encoded RNA (EBER) in situ hybridization, the BamH1W and EBNA1 assays were the most informative, while use of the entire battery of EBV PCR assays may help identify genomic polymorphisms or deletions. Higher viral loads were found in the 17 EBER-positive compared with the 13 EBER-negative tumors (means 84,978 versus 22 copies of EBV per 100,000 cells, respectively). The five Q-PCR assays were also informative in plasma samples where EBV was measurable in all nine patients with lymphoma or infectious mononucleosis, whereas EBV was undetectable in all nine healthy controls. The findings suggest that Q-PCR is an effective method of distinguishing disease-associated virus from incidental virus in paraffin-embedded tissue and in plasma samples.

Constitutive activation of phosphatidyl-inositide 3 kinase contributes to the survival of Hodgkin's lymphoma cells through a mechanism involving Akt kinase and mTOR

The molecular mechanisms underlying the pathogenesis of the malignant Hodgkin's/Reed-Sternberg (HRS) cells of Hodgkin's lymphoma (HL) are largely unknown. This study investigates the contribution of phosphatidyl-inositide 3 kinase (PI3-kinase) and demonstrates that Akt, a substrate of PI3-kinase, is constitutively activated in HL-derived cell lines. Several downstream effectors of Akt signalling, including glycogen synthase kinase 3 (GSK-3) alpha and beta and mTOR substrates 4E-BP1 and p70 S6 kinase, were also phosphorylated in HL cells. The mTOR inhibitor, rapamycin, inhibited phosphorylation of these proteins. Furthermore, LY294002 inhibited phosphorylation of p70 S6 kinase and 4E-BP1, suggesting that the phosphorylation of p70 S6 kinase and 4E-BP1 in HL cells is PI3-kinase dependent. Importantly, HRS cells of primary tumour samples not only expressed high levels of activated Akt but also displayed phosphorylation of downstream targets of Akt activation including GSK-3, 4E-BP1, and p70 S6 Kinase. Inhibition of PI3-kinase and mTOR showed only modest effects on cell survival at the lower serum concentrations. However, rapamycin and doxorubicin acted synergistically to reduce HL cell survival. A combination of rapamycin and chemotherapy should be investigated in the treatment of HL.

Epstein-Barr virus (EBV) LMP2A mediates B-lymphocyte survival through constitutive activation of the Ras/PI3K/Akt pathway

Epstein-Barr virus (EBV) establishes a lifelong latent infection in host B cells and is associated with the development of a variety of malignancies. The viral LMP2A protein mediates viral latency by mimicking a constitutively activated B-cell receptor (BCR). In vivo LMP2A provides developmental and survival signals to BCR-negative B cells, allowing them to survive in peripheral lymphoid organs. In this study, we have demonstrated that Ras is constitutively active in peripheral, BCR-negative B cells from LMP2A transgenic mice. Furthermore, increased expression of activated Ras correlated with elevated levels of Bcl-xL expression and a slower migrating, band-shifted form of Bcl-2. B cells from LMP2A transgenic mice were sensitive to apoptosis induction in the presence of specific inhibitors of Ras, phosphatidylinositol 3-kinase (PI3K), and Akt, indicating that LMP2A activates the Ras/PI3K/Akt pathway to mediate B-cell survival. Increased B-cell apoptosis correlated with reduced expression of Bcl-xL, suggesting that this Bcl-2 family member may be involved in apoptosis inhibition mediated by LMP2A. The ability of LMP2A to activate constitutively the Ras pathway, a common event during tumorigenesis, suggests that this viral protein plays an active role in the development of EBV-associated malignancies.