Roles of lytic viral infection and IL-6 in early versus late passage lymphoblastoid cell lines and EBV-associated lymphoproliferative disease

[The incidence of infection in tumor and eye fluid system, and specific humoral immunity to herpes viruses in patients with uveal melanoma]

INTRODUCTION

Studies aimed at a direct research of human herpes viruses (HHVs) in the tumor material and eye media have not been carried out so far. Research goal to establish the frequency of detection HHVs DNA in the biomaterial of the eye and blood and to assess the specific humoral immunity to the causative agents of herpes virus infections in patients with uveal melanoma.

MATERIALS AND METHODS

38 patients with the uveal tract tumor were examined for the presence of DNA of HHV types 1 and 2 (HSV-1, 2), Cytomegalovirus (CMV), Varicella Zoster virus (VZV), EpsteinBarr virus (EBV) and herpes viruses 6 and 8 types (HHV-6, HHV-8) in tumor tissue, vitreous body, aqueous humour and blood plasma by real-time polymerase chain reaction; blood serum was studied by enzyme-linked immunosorbent assay (ELISA) for IgG and IgM antibodies to HHVs.

RESULTS

EBV DNA was present in tumor tissue in 20.6% of cases, in vitreous body in 4.2%, in blood plasma in 2.7%, and was not found in aqueous humor. Ig G antibodies to HSV-1, 2 and CMV were detected in 97.3% of cases, VZV 94.6%, HHV-6 32.4%, antibodies to HHV-8 were not detected. 20 patients (55.6%) had reactivation of chronic HSV-1, 2 infection, and 14 (38.9%) patients had reactivation of CMV infection. Markers of chronic EBV infection were found in all patients, its atypical reactivation was observed in 2 cases (5.4%).

CONCLUSION

Our findings suggest the possible participation of EBV in the oncogenesis of the uveal tract and emphasize the need for further in-depth study of this problem.

The lytic phase of Epstein-Barr virus plays an important role in tumorigenesis

Epstein-Barr virus (EBV) is a recognized oncogenic virus that is related to the occurrence of lymphoma, nasopharyngeal carcinoma (NPC), and approximately 10% of gastric cancer (GC). EBV is a herpesvirus, and like other herpesviruses, EBV has a biphasic infection mode made up of latent and lytic infections. It has been established that latent infection promotes tumorigenesis in previous research, but in recent years, there has been new evidence that suggests that the lytic infection mode could also promote tumorigenesis. In this review, we mainly discuss the contribution of the EBV lytic phase to tumorigenesis, and graphically illustrate their relationship in detail. In addition, we described the relationship between the lytic cycle of EBV and autophagy. Finally, we also preliminarily explored the influence of the tumorigenesis effect of the EBV lytic phase on the future treatment of EBV-associated tumors.

Co-Infection of the Epstein-Barr Virus and the Kaposi Sarcoma-Associated Herpesvirus

The two human tumor viruses, Epstein-Barr virus (EBV) and Kaposi sarcoma-associated herpesvirus (KSHV), have been mostly studied in isolation. Recent studies suggest that co-infection with both viruses as observed in one of their associated malignancies, namely primary effusion lymphoma (PEL), might also be required for KSHV persistence. In this review, we discuss how EBV and KSHV might support each other for persistence and lymphomagenesis. Moreover, we summarize what is known about their innate and adaptive immune control which both seem to be required to ensure asymptomatic persistent co-infection with these two human tumor viruses. A better understanding of this immune control might allow us to prepare for vaccination against EBV and KSHV in the future.

Epstein-Barr virus: Biology and clinical disease

Epstein-Barr virus (EBV) is a ubiquitous, oncogenic virus that is associated with a number of different human malignancies as well as autoimmune disorders. The expression of EBV viral proteins and non-coding RNAs contribute to EBV-mediated disease pathologies. The virus establishes life-long latency in the human host and is adept at evading host innate and adaptive immune responses. In this review, we discuss the life cycle of EBV, the various functions of EBV-encoded proteins and RNAs, the ability of the virus to activate and evade immune responses, as well as the neoplastic and autoimmune diseases that are associated with EBV infection in the human population.

EBV genome variations enhance clinicopathological features of nasopharyngeal carcinoma in a non-endemic region

Nasopharyngeal carcinoma (NPC) is caused by infection with Epstein–Barr virus (EBV) and endemic in certain geographic regions. EBV lytic gene, BALF2, closely associates with viral reactivation and BALF2 gene variation, the H‐H‐H strain, causes NPC in endemic region, southern China. Here, we investigate whether such EBV variations also affect NPC in a non‐endemic region, Japan. Viral genome sequencing with 47 EBV isolates of Japanese NPC were performed and compared with those of other EBV‐associated diseases from Japan or NPC in Southern China. EBV genomes of Japanese NPC are different from those of other diseases in Japan or endemic NPC; Japanese NPC was not affected by the endemic strain (the BALF2 H‐H‐H) but frequently carried the type 2 EBV or the strain with intermediate risk of endemic NPC (the BALF2 H‐H‐L). Seven single nucleotide variations were specifically associated with Japanese NPC, of which six were present in both type 1 and 2 EBV genomes, suggesting the contribution of the type 2 EBV‐derived haplotype. This observation was supported by a higher viral titer and stronger viral reactivation in NPC with either type 2 or H‐H‐L strains. Our results highlight the importance of viral strains and viral reactivation in the pathogenesis of non‐endemic NPC.

Hippo signaling effectors YAP and TAZ induce Epstein-Barr Virus (EBV) lytic reactivation through TEADs in epithelial cells

The Epstein-Barr virus (EBV) human herpesvirus is associated with B-cell and epithelial-cell malignancies, and both the latent and lytic forms of viral infection contribute to the development of EBV-associated tumors. Here we show that the Hippo signaling effectors, YAP and TAZ, promote lytic EBV reactivation in epithelial cells. The transcriptional co-activators YAP/TAZ (which are inhibited by Hippo signaling) interact with DNA-binding proteins, particularly TEADs, to induce transcription. We demonstrate that depletion of either YAP or TAZ inhibits the ability of phorbol ester (TPA) treatment, cellular differentiation or the EBV BRLF1 immediate-early (IE) protein to induce lytic EBV reactivation in oral keratinocytes, and show that over-expression of constitutively active forms of YAP and TAZ reactivate lytic EBV infection in conjunction with TEAD family members. Mechanistically, we find that YAP and TAZ interact with, and activate, the EBV BZLF1 immediate-early promoter. Furthermore, we demonstrate that YAP, TAZ, and TEAD family members are expressed at much higher levels in epithelial cell lines in comparison to B-cell lines, and find that EBV infection of oral keratinocytes increases the level of activated (dephosphorylated) YAP and TAZ. Finally, we have discovered that lysophosphatidic acid (LPA), a known YAP/TAZ activator that plays an important role in inflammation, induces EBV lytic reactivation in epithelial cells through a YAP/TAZ dependent mechanism. Together these results establish that YAP/TAZ are powerful inducers of the lytic form of EBV infection and suggest that the ability of EBV to enter latency in B cells at least partially reflects the extremely low levels of YAP/TAZ and TEADs in this cell type.

An MHV-68 Mutator Phenotype Mutant Virus, Confirmed by CRISPR/Cas9-Mediated Gene Editing of the Viral DNA Polymerase Gene, Shows Reduced Viral Fitness

Drug resistance studies on human γ-herpesviruses are hampered by the absence of an in vitro system that allows efficient lytic viral replication. Therefore, we employed murine γ-herpesvirus-68 (MHV-68) that efficiently replicates in vitro as a model to study the antiviral resistance of γ-herpesviruses. In this study, we investigated the mechanism of resistance to nucleoside (ganciclovir (GCV)), nucleotide (cidofovir (CDV), HPMP-5azaC, HPMPO-DAPy) and pyrophosphate (foscarnet (PFA)) analogues and the impact of these drug resistance mutations on viral fitness. Viral fitness was determined by dual infection competition assays, where MHV-68 drug-resistant viral clones competed with the wild-type virus in the absence and presence of antivirals. Using next-generation sequencing, the composition of the viral populations was determined at the time of infection and after 5 days of growth. Antiviral drug resistance selection resulted in clones harboring mutations in the viral DNA polymerase (DP), denoted Y383S^GCV, Q827R^HPMP-5azaC, G302W^PFA, K442T^PFA, G302W+K442T^PFA, C297W^HPMPO-DAPy and C981Y^CDV. Without antiviral pressure, viral clones Q827R^HPMP-5azaC, G302W^PFA, K442T^PFA and G302W+K442T^PFA grew equal to the wild-type virus. However, in the presence of antivirals, these mutants had a growth advantage over the wild-type virus that was moderately to very strongly correlated with antiviral resistance. The Y383S^GCV mutant was more fit than the wild-type virus with and without antivirals, except in the presence of brivudin. The C297W and C981Y changes were associated with a mutator phenotype and had a severely impaired viral fitness in the absence and presence of antivirals. The mutator phenotype caused by C297W in MHV-68 DP was validated by using a CRISPR/Cas9 genome editing approach.

Epstein-Barr virus inactivates the transcriptome and disrupts the chromatin architecture of its host cell in the first phase of lytic reactivation

Epstein-Barr virus (EBV), a herpes virus also termed HHV 4 and the first identified human tumor virus, establishes a stable, long-term latent infection in human B cells, its preferred host. Upon induction of EBV's lytic phase, the latently infected cells turn into a virus factory, a process that is governed by EBV. In the lytic, productive phase, all herpes viruses ensure the efficient induction of all lytic viral genes to produce progeny, but certain of these genes also repress the ensuing antiviral responses of the virally infected host cells, regulate their apoptotic death or control the cellular transcriptome. We now find that EBV causes previously unknown massive and global alterations in the chromatin of its host cell upon induction of the viral lytic phase and prior to the onset of viral DNA replication. The viral initiator protein of the lytic cycle, BZLF1, binds to >105 binding sites with different sequence motifs in cellular chromatin in a concentration dependent manner implementing a binary molar switch probably to prevent noise-induced erroneous induction of EBV's lytic phase. Concomitant with DNA binding of BZLF1, silent chromatin opens locally as shown by ATAC-seq experiments, while previously wide-open cellular chromatin becomes inaccessible on a global scale within hours. While viral transcripts increase drastically, the induction of the lytic phase results in a massive reduction of cellular transcripts and a loss of chromatin-chromatin interactions of cellular promoters with their distal regulatory elements as shown in Capture-C experiments. Our data document that EBV's lytic cycle induces discrete early processes that disrupt the architecture of host cellular chromatin and repress the cellular epigenome and transcriptome likely supporting the efficient de novo synthesis of this herpes virus.

Calcium-dependent signalling in B-cell lymphomas

Induced waves of calcium fluxes initiate multiple signalling pathways that play an important role in the differentiation and maturation of B-cells. Finely tuned transient Ca⁺² fluxes from the endoplasmic reticulum in response to B-cell receptor (BCR) or chemokine receptor activation are followed by more sustained calcium influxes from the extracellular environment and contribute to the mechanisms responsible for the proliferation of B-cells, their migration within lymphoid organs and their differentiation. Dysregulation of these well-balanced mechanisms in B-cell lymphomas results in uncontrolled cell proliferation and resistance to apoptosis. Consequently, several cytotoxic drugs (and anti-proliferative compounds) used in standard chemotherapy regimens for the treatment of people with lymphoma target calcium-dependent pathways. Furthermore, ~10% of lymphoma associated mutations are found in genes with functions in calcium-dependent signalling, including those affecting B-cell receptor signalling pathways. In this review, we provide an overview of the Ca²⁺-dependent signalling network and outline the contribution of its key components to B cell lymphomagenesis. We also consider how the oncogenic Epstein-Barr virus, which is causally linked to the pathogenesis of a number of B-cell lymphomas, can modify Ca²⁺-dependent signalling.

Epstein-Barr virus may contribute to the pathogenesis of adult-onset recurrent respiratory papillomatosis: A preliminary study

OBJECTIVE

Human papillomavirus (HPV) causes adult-onset recurrent respiratory papillomatosis (AORRP), but AORPP prevalence is much lower than HPV prevalence. Thus, HPV infection is necessary, but not sufficient, to cause AORRP and other factors likely contribute to its pathogenesis. The present study aimed to investigate whether co-infection with herpetic viruses may contribute to the pathogenesis of AORRP.

DESIGN

Prospective case-control study conducted from January 2018 to November 2019.

SETTINGS

Tertiary referral centre.

PARTICIPANTS

Eighteen consecutive patients with AORRP and 18 adults with healthy laryngeal mucosa (control group) undergoing surgery.

MAIN OUTCOME MEASURES

Cytomegalovirus, Epstein-Barr virus (EBV), herpes simplex viruses 1 and 2, human herpesvirus 6, varicella zoster virus and HPV (including genotyping) were detected in biopsies of papilloma or healthy mucosa using real-time polymerase chain reaction and reverse line blot. Dysplasia and Ki67 levels were determined in papilloma specimens.

RESULTS

EBV was present in 6 (33.3%) AORRP patients and no control patients (P = .019). Presence was not dependent on tobacco exposure (P = .413) or HPV genotype or concentration (P > .999). EBV presence was strongly related to increased cell proliferation (P = .005) and number of previous surgeries (P = .039), but not dysplasia (P > .999). Human herpesvirus 6 was found in 3 (16.7%) AORRP biopsies, with one false positive. No other herpetic virus was found.

CONCLUSIONS

Unlike other herpetic viruses, EBV seems to interact with HPV, enhancing cell proliferation and contributing to the pathogenesis and progression of AORRP. Further research is required to elucidate specific interactions and their role in the pathogenesis of AORRP.

Epstein-Barr Virus: How Its Lytic Phase Contributes to Oncogenesis

Epstein–Barr Virus (EBV) contributes to the development of lymphoid and epithelial malignancies. While EBV’s latent phase is more commonly associated with EBV-associated malignancies, there is increasing evidence that EBV’s lytic phase plays a role in EBV-mediated oncogenesis. The lytic phase contributes to oncogenesis primarily in two ways: (1) the production of infectious particles to infect more cells, and (2) the regulation of cellular oncogenic pathways, both cell autonomously and non-cell autonomously. The production of infectious particles requires the completion of the lytic phase. However, the regulation of cellular oncogenic pathways can be mediated by an incomplete (abortive) lytic phase, in which early lytic gene products contribute substantially, whereas late lytic products are largely dispensable. In this review, we discuss the evidence of EBV’s lytic phase contributing to oncogenesis and the role it plays in tumor formation and progression, as well as summarize known mechanisms by which EBV lytic products regulate oncogenic pathways. Understanding the contribution of EBV’s lytic phase to oncogenesis will help design ways to target it to treat EBV-associated malignancies.

Ubiquitin Modification of the Epstein-Barr Virus Immediate Early Transactivator Zta

The Epstein-Barr virus (EBV) immediate early transactivator Zta plays a key role in regulating the transition from latency to the lytic replication stages of EBV infection. Regulation of Zta is known to be controlled through a number of transcriptional and posttranscriptional events. Here, we show that Zta is targeted for ubiquitin modification and that this can occur in EBV-negative and in EBV-infected cells. Genetic studies show critical roles for both an amino-terminal region of Zta and the basic DNA binding domain of Zta in regulating Zta ubiquitination. Pulse-chase experiments demonstrate that the bulk population of Zta is relatively stable but that at least a subset of ubiquitinated Zta molecules are targeted for degradation in the cell. Mutation of four out of a total of nine lysine residues in Zta largely abrogates its ubiquitination, indicating that these are primary ubiquitination target sites. A Zta mutant carrying mutations at these four lysine residues (lysine 12, lysine 188, lysine 207, and lysine 219) cannot induce latently infected cells to produce and/or release infectious virions. Nevertheless, this mutant can induce early gene expression, suggesting a possible defect at the level of viral replication or later in the lytic cascade. As far as we know, this is the first study that has investigated the targeting of Zta by ubiquitination or its role in Zta function.IMPORTANCE Epstein-Barr virus (EBV) is a ubiquitous human pathogen and associated with various human diseases. EBV undergoes latency and lytic replication stages in its life cycle. The transition into the lytic replication stage, at which virus is produced, is mainly regulated by the viral gene product, Zta. Therefore, the regulation of Zta function becomes a central issue regarding viral biology and pathogenesis. Known modifications of Zta include phosphorylation and sumoylation. Here, we report the role of ubiquitination in regulating Zta function. We found that Zta is subjected to ubiquitination in both EBV-infected and EBV-negative cells. The ubiquitin modification targets 4 lysine residues on Zta, leading to both mono- and polyubiquitination of Zta. Ubiquitination of Zta affects the protein's stability and likely contributes to the progression of viral lytic replication. The function and fate of Zta may be determined by the specific lysine residue being modified.

Oncogenic Properties of the EBV ZEBRA Protein

Epstein Barr Virus (EBV) is one of the most common human herpesviruses. After primary infection, it can persist in the host throughout their lifetime in a latent form, from which it can reactivate following specific stimuli. EBV reactivation is triggered by transcriptional transactivator proteins ZEBRA (also known as Z, EB-1, Zta or BZLF1) and RTA (also known as BRLF1). Here we discuss the structural and functional features of ZEBRA, its role in oncogenesis and its possible implication as a prognostic or diagnostic marker. Modulation of host gene expression by ZEBRA can deregulate the immune surveillance, allow the immune escape, and favor tumor progression. It also interacts with host proteins, thereby modifying their functions. ZEBRA is released into the bloodstream by infected cells and can potentially penetrate any cell through its cell-penetrating domain; therefore, it can also change the fate of non-infected cells. The features of ZEBRA described in this review outline its importance in EBV-related malignancies.

B cells infected with Type 2 Epstein-Barr virus (EBV) have increased NFATc1/NFATc2 activity and enhanced lytic gene expression in comparison to Type 1 EBV infection

Humans are infected with two distinct strains (Type 1 (T1) and Type 2 (T2)) of Epstein-Barr virus (EBV) that differ substantially in their EBNA2 and EBNA 3A/B/C latency genes and the ability to transform B cells in vitro. While most T1 EBV strains contain the "prototype" form of the BZLF1 immediate-early promoter ("Zp-P"), all T2 strains contain the "Zp-V3" variant, which contains an NFAT binding motif and is activated much more strongly by B-cell receptor signalling. Whether B cells infected with T2 EBV are more lytic than cells infected with T1 EBV is unknown. Here we show that B cells infected with T2 EBV strains (AG876 and BL5) have much more lytic protein expression compared to B cells infected with T1 EBV strains (M81, Akata, and Mutu) in both a cord blood-humanized (CBH) mouse model and EBV-transformed lymphoblastoid cell lines (LCLs). Although T2 LCLs grow more slowly than T1 LCLs, both EBV types induce B-cell lymphomas in CBH mice. T1 EBV strains (M81 and Akata) containing Zp-V3 are less lytic than T2 EBV strains, suggesting that Zp-V3 is not sufficient to confer a lytic phenotype. Instead, we find that T2 LCLs express much higher levels of activated NFATc1 and NFATc2, and that cyclosporine (an NFAT inhibitor) and knockdown of NFATc2 attenuate constitutive lytic infection in T2 LCLs. Both NFATc1 and NFATc2 induce lytic EBV gene expression when combined with activated CAMKIV (which is activated by calcium signaling and activates MEF2D) in Burkitt Akata cells. Together, these results suggest that B cells infected with T2 EBV are more lytic due to increased activity of the cellular NFATc1/c2 transcription factors in addition to the universal presence of the Zp-V3 form of BZLF1 promoter.

Dipyridamole as a new drug to prevent Epstein-Barr virus reactivation

Epstein-Barr virus (EBV) is a widely distributed gamma-herpesvirus that has been associated with various cancers mainly from lymphocytic and epithelial origin. Although EBV-mediated oncogenesis has been associated with viral oncogenes expressed during latency, a growing set of evidence suggested that antiviral treatments directed against EBV lytic phase may contribute to prevent some forms of cancers, including EBV-positive Post-Transplant Lymphoproliferative Diseases. It is shown here that dipyridamole (DIP), a safe drug with favorable and broad pharmacological properties, inhibits EBV reactivation from B-cell lines. DIP repressed immediate early and early genes expression mostly through its ability to inhibit nucleoside uptake. Considering its wide clinical use, DIP repurposing could shortly be evaluated, alone or in combination with other antivirals, to treat EBV-related diseases where lytic replication plays a deleterious role.

Novel Therapeutics for Epstein⁻Barr Virus

Epstein–Barr virus (EBV) is a human γ-herpesvirus that infects up to 95% of the adult population. Primary EBV infection usually occurs during childhood and is generally asymptomatic, though the virus can cause infectious mononucleosis in 35–50% of the cases when infection occurs later in life. EBV infects mainly B-cells and epithelial cells, establishing latency in resting memory B-cells and possibly also in epithelial cells. EBV is recognized as an oncogenic virus but in immunocompetent hosts, EBV reactivation is controlled by the immune response preventing transformation in vivo. Under immunosuppression, regardless of the cause, the immune system can lose control of EBV replication, which may result in the appearance of neoplasms. The primary malignancies related to EBV are B-cell lymphomas and nasopharyngeal carcinoma, which reflects the primary cell targets of viral infection in vivo. Although a number of antivirals were proven to inhibit EBV replication in vitro, they had limited success in the clinic and to date no antiviral drug has been approved for the treatment of EBV infections. We review here the antiviral drugs that have been evaluated in the clinic to treat EBV infections and discuss novel molecules with anti-EBV activity under investigation as well as new strategies to treat EBV-related diseases.

A cancer-associated Epstein-Barr virus BZLF1 promoter variant enhances lytic infection

Latent Epstein-Barr virus (EBV) infection contributes to both B-cell and epithelial-cell malignancies. However, whether lytic EBV infection also contributes to tumors is unclear, although the association between malaria infection and Burkitt lymphomas (BLs) may involve excessive lytic EBV replication. A particular variant of the viral promoter (Zp) that controls lytic EBV reactivation is over-represented, relative to its frequency in non-malignant tissue, in EBV-positive nasopharyngeal carcinomas and AIDS-related lymphomas. To date, no functional differences between the prototype Zp (Zp-P) and the cancer-associated variant (Zp-V3) have been identified. Here we show that a single nucleotide difference between the Zp-V3 and Zp-P promoters creates a binding site for the cellular transcription factor, NFATc1, in the Zp-V3 (but not Zp-P) variant, and greatly enhances Zp activity and lytic viral reactivation in response to NFATc1-inducing stimuli such as B-cell receptor activation and ionomycin. Furthermore, we demonstrate that restoring this NFATc1-motif to the Zp-P variant in the context of the intact EBV B95.8 strain genome greatly enhances lytic viral reactivation in response to the NFATc1-activating agent, ionomycin, and this effect is blocked by the NFAT inhibitory agent, cyclosporine, as well as NFATc1 siRNA. We also show that the Zp-V3 variant is over-represented in EBV-positive BLs and gastric cancers, and in EBV-transformed B-cell lines derived from EBV-infected breast milk of Kenyan mothers that had malaria during pregnancy. These results demonstrate that the Zp-V3 enhances EBV lytic reactivation to physiologically-relevant stimuli, and suggest that increased lytic infection may contribute to the increased prevalence of this variant in EBV-associated malignancies.

Antiviral Drugs for EBV

Epstein–Barr virus (EBV) infects up to 95% of the adult human population, with primary infection typically occurring during childhood and usually asymptomatic. However, EBV can cause infectious mononucleosis in approximately 35–50% cases when infection occurs during adolescence and early adulthood. Epstein–Barr virus is also associated with several B-cell malignancies including Burkitt lymphoma, Hodgkin lymphoma, and post-transplant lymphoproliferative disease. A number of antiviral drugs have proven to be effective inhibitors of EBV replication, yet have resulted in limited success clinically, and none of them has been approved for treatment of EBV infections.

EBV Positive Diffuse Large B Cell Lymphoma and Chronic Lymphocytic Leukemia Patients Exhibit Increased Anti-dUTPase Antibodies

The Epstein-Barr virus (EBV), which is a ubiquitous γ-herpesvirus, establishes a latent infection in more than 90% of the global adult population. EBV-associated malignancies have increased by 14.6% over the last 20 years, and account for approximately 1.5% of all cancers worldwide and 1.8% of all cancer deaths. However, the potential involvement/contribution of lytic proteins to the pathophysiology of EBV-associated cancers is not well understood. We have previously demonstrated that the EBV-deoxyuridine triphosphate nucleotidohydrolase (dUTPase) modulates innate and adaptive immune responses by engaging the Toll-Like Receptor 2 (TLR2), which leads to the modulation of downstream genes involved in oncogenesis, chronic inflammation, and in effector T-cell function. Furthermore, examination of serum samples from diffuse large B-cell lymphoma (DLBCL) and chronic lymphocytic leukemia patients revealed the presence of increased levels of anti-dUTPase antibodies in both cohorts compared to controls with the highest levels (3.67-fold increase) observed in DLBCL female cases and the lowest (2.12-fold increase) in DLBCL males. Using computer-generated algorithms, dUTPase amino acid sequence alignments, and functional studies of BLLF3 mutants, we identified a putative amino acid motif involved with TLR2 interaction. These findings suggest that the EBV-dUTPase: TLR2 interaction is a potential molecular target that could be used for developing novel therapeutics (small molecules/vaccines).

The Immunomodulatory Capacity of an Epstein-Barr Virus Abortive Lytic Cycle: Potential Contribution to Viral Tumorigenesis

Epstein-Barr virus (EBV) is characterized by a bipartite life cycle in which latent and lytic stages are alternated. Latency is compatible with long-lasting persistency within the infected host, while lytic expression, preferentially found in oropharyngeal epithelial tissue, is thought to favor host-to-host viral dissemination. The clinical importance of EBV relates to its association with cancer, which we think is mainly a consequence of the latency/persistency mechanisms. However, studies in murine models of tumorigenesis/lymphomagenesis indicate that the lytic cycle also contributes to cancer formation. Indeed, EBV lytic expression is often observed in established cell lines and tumor biopsies. Within the lytic cycle EBV expresses a handful of immunomodulatory (BCRF1, BARF1, BNLF2A, BGLF5 & BILF1) and anti-apoptotic (BHRF1 & BALF1) proteins. In this review, we discuss the evidence supporting an abortive lytic cycle in which these lytic genes are expressed, and how the immunomodulatory mechanisms of EBV and related herpesviruses Kaposi Sarcoma herpesvirus (KSHV) and human cytomegalovirus (HCMV) result in paracrine signals that feed tumor cells. An abortive lytic cycle would reconcile the need of lytic expression for viral tumorigenesis without relaying in a complete cycle that would induce cell lysis to release the newly formed infective viral particles.

Herpesviruses dUTPases: A New Family of Pathogen-Associated Molecular Pattern (PAMP) Proteins with Implications for Human Disease

The human herpesviruses are ubiquitous viruses and have a prevalence of over 90% in the adult population. Following a primary infection they establish latency and can be reactivated over a person's lifetime. While it is well accepted that human herpesviruses are implicated in numerous diseases ranging from dermatological and autoimmune disease to cancer, the role of lytic proteins in the pathophysiology of herpesvirus-associated diseases remains largely understudies. Only recently have we begun to appreciate the importance of lytic proteins produced during reactivation of the virus, in particular the deoxyuridine triphosphate nucleotidohydrolases (dUTPase), as key modulators of the host innate and adaptive immune responses. In this review, we provide evidence from animal and human studies of the Epstein-Barr virus as a prototype, supporting the notion that herpesviruses dUTPases are a family of proteins with unique immunoregulatory functions that can alter the inflammatory microenvironment and thus exacerbate the immune pathology of herpesvirus-related diseases including myalgic encephalomyelitis/chronic fatigue syndrome, autoimmune diseases, and cancer.

Monitoring of Epstein-Barr virus load and killer T cells in patients with juvenile idiopathic arthritis treated with methotrexate or tocilizumab

OBJECTIVES

Methotrexate (MTX) is used for the treatment of polyarticular juvenile idiopathic arthritis (JIA), and an anti-interleukin-6 receptor monoclonal antibody (tocilizumab: TCZ) is also used and added for the treatment of intractable JIA. It has been reported that MTX might induce Epstein-Barr virus (EBV)-associated lymphoma, but the discussion about the effect of MTX and/or TCZ against reactivation of EBV in pediatric patients has been incomplete.

METHODS

The EBV loads in four polyarticular JIA and three systemic arthritis JIA patients treated with MTX and/or TCZ, and the percentage of EBV-specific killer T cells (EBV-CTLs) in some patients were prospectively monitored.

RESULTS

No patients had EBV-associated symptoms during the observation period. EBV loads in all patients were not significantly increased, and the levels of EBV loads were the same as EBV-seropositive healthy children following the administration of MTX and/or TCZ. EBV-CTLs were detectable during the observation period, but some patients had slightly low levels of EBV-CTLs.

CONCLUSION

Treatment with MTX and/or TCZ did not severely affect EBV load and prevent induction of EBV-CTLs in JIA patients.

Age and cellular composition influence overall survival in a collective of non-immunocompromised patients with EBV-positive diffuse large B-cell lymphoma from a German lymphoma center

We investigated 41 diffuse large B-cell lymphomas (DLBCL) diagnosed at one center harboring ≥50% of latently Epstein-Barr virus (EBV)-infected neoplastic cells occurring in 34 patients aged ≥50 years and in 7 patients younger than 50 years in the absence of any known immunodeficiency for the expression patterns of EBV latent and immediate-early proteins, for the differentiation stage of the neoplastic cells, the presence of cytogenetic alterations and a possible co-infection with the human herpes virus (HHV)-8. Here, we show that EBV-positive DLBCLs rarely arise from naïve and more frequently from post-germinal center B-cells that often contain crippling immunoglobulin gene mutations. Most of the lymphomas did not exhibit breaks in the BCL2, BCL6, and MYC genes and none of the cases investigated contained HHV-8 sequences. Patients aged <50 years performed better than older ones while in patients aged ≥50 years only the cellular composition had an impact on overall survival.

The Epstein-Barr Virus BART miRNA Cluster of the M81 Strain Modulates Multiple Functions in Primary B Cells

The Epstein-Barr virus (EBV) is a B lymphotropic virus that infects the majority of the human population. All EBV strains transform B lymphocytes, but some strains, such as M81, also induce spontaneous virus replication. EBV encodes 22 microRNAs (miRNAs) that form a cluster within the BART region of the virus and have been previously been found to stimulate tumor cell growth. Here we describe their functions in B cells infected by M81. We found that the BART miRNAs are downregulated in replicating cells, and that exposure of B cells in vitro or in vivo in humanized mice to a BART miRNA knockout virus resulted in an increased proportion of spontaneously replicating cells, relative to wild type virus. The BART miRNAs subcluster 1, and to a lesser extent subcluster 2, prevented expression of BZLF1, the key protein for initiation of lytic replication. Thus, multiple BART miRNAs cooperate to repress lytic replication. The BART miRNAs also downregulated pro- and anti-apoptotic mediators such as caspase 3 and LMP1, and their deletion did not sensitize B-cells to apoptosis. To the contrary, the majority of humanized mice infected with the BART miRNA knockout mutant developed tumors more rapidly, probably due to enhanced LMP1 expression, although deletion of the BART miRNAs did not modify the virus transforming abilities in vitro. This ability to slow cell growth could be confirmed in non-humanized immunocompromized mice. Injection of resting B cells exposed to a virus that lacks the BART miRNAs resulted in accelerated tumor growth, relative to wild type controls. Therefore, we found that the M81 BART miRNAs do not enhance B-cell tumorigenesis but rather repress it. The repressive effects of the BART miRNAs on potentially pathogenic viral functions in infected B cells are likely to facilitate long-term persistence of the virus in the infected host.

The Epstein-Barr virus (EBV) infects more than 90% of the human adult population. Although EBV usually causes an asymptomatic infection, it is oncogenic in a small proportion of infected individuals. EBV produces a large number of microRNAs, a type of RNA that controls the production of their proteins though multiple mechanisms. We addressed the role played by the BART microRNAs, a subgroup of the EBV microRNAs, by generating a virus that lacks them and by comparing the characteristics of this modified virus with those of the unmodified virus. We found that the BART microRNAs cooperate to curb EBV multiplication, both in infected cells and in humanized mice. Furthermore, the BART miRNAs did not potentiate EBV’s ability to form tumors in different types of mice, some of which are unable to mount an immune reaction against the virus, as could have been expected from the literature. This can be explained at the molecular level by the ability of the BART microRNAs to downregulate the synthesis of multiple cellular and viral proteins, among which caspase 3 and LMP1, two essential modulator of cell death and cell proliferation, are likely to play an important role in the outcome of the virus infection. Thus, the BART microRNAs negatively impact on two essential viral functions, probably to maintain a balance between the virus and its host.

Knockout of Epstein-Barr virus BPLF1 retards B-cell transformation and lymphoma formation in humanized mice

BPLF1 of Epstein-Barr virus (EBV) is classified as a late lytic cycle protein but is also found in the viral tegument, suggesting its potential involvement at both initial and late stages of viral infection. BPLF1 possesses both deubiquitinating and deneddylating activity located in its N-terminal domain and is involved in processes that affect viral infectivity, viral DNA replication, DNA repair, and immune evasion. A recently constructed EBV BPLF1-knockout (KO) virus was used in conjunction with a humanized mouse model that can be infected with EBV, enabling the first characterization of BPLF1 function in vivo. Results demonstrate that the BPLF1-knockout virus is approximately 90% less infectious than wild-type (WT) virus. Transformation of human B cells, a hallmark of EBV infection, was delayed and reduced with BPLF1-knockout virus. Humanized mice infected with EBV BPLF1-knockout virus showed less weight loss and survived longer than mice infected with equivalent infectious units of WT virus. Additionally, splenic tumors formed in 100% of mice infected with WT EBV but in only 25% of mice infected with BPLF1-KO virus. Morphological features of spleens containing tumors were similar to those in EBV-induced posttransplant lymphoproliferative disease (PTLD) and were almost identical to cases seen in human diffuse large B-cell lymphoma. The presence of EBV genomes was detected in all mice that developed tumors. The results implicate BPLF1 in human B-cell transformation and tumor formation in humanized mice.

Epstein-Barr virus infects approximately 90% of the world’s population and is the causative agent of infectious mononucleosis. EBV also causes aggressive lymphomas in individuals with acquired and innate immune disorders and is strongly associated with diffuse large B-cell lymphomas, classical Hodgkin lymphoma, Burkitt lymphoma, and nasopharyngeal carcinoma (NPC). Typically, EBV initially infects epithelial cells in the oropharynx, followed by a lifelong persistent latent infection in B-cells, which may develop into lymphomas in immunocompromised individuals. This work is the first of its kind in evaluating the effects of EBV’s BPLF1 in terms of pathogenesis and lymphomagenesis in humanized mice and implicates BPLF1 in B-cell transformation and tumor development. Currently, there is no efficacious treatment for EBV, and therapeutic targeting of BPLF1 may lead to a new path to treatment for immunocompromised individuals or transplant recipients infected with EBV.

Delivery of miR-155 to retinal pigment epithelial cells mediated by Burkitt's lymphoma exosomes

Exosomes are extracellularly secreted vesicles ranging from 40 to 100 nm in diameter that are thought to play important roles in intercellular communication. Exosomes contain numerous proteins, RNA, and lipids that can affect the status of recipient cells under various pathological conditions. MicroRNAs (miRNAs) are small non-coding RNAs that play a major role in post-transcriptional gene silencing by interacting with the 3'-untranslated regions of target genes. Epstein-Barr virus (EBV) has been reported to induce sustained elevation of cellular miRNAs such as miR-155. We hypothesized that miRNAs delivered by exosomes might affect the angiogenesis of retinal pigment epithelial (RPE) cells. Here, we demonstrated that co-culture of EBV-positive Burkitt's lymphoma (BL) cells (Raji) with retinal pigment epithelial (ARPE-19) cells increased the level of miR-155 in recipient cells whereas no major difference was detected for co-culture with EBV-negative BL cells (Ramos). Isolated Raji exosomes increased transcriptional and translational levels of VEGF-A in ARPE-19 cells, which was reversely correlated with von Hippel-Lindau expression. A human umbilical vein endothelial cell tube formation assay showed that delivery of ectopic miR-155 rendered ARPE-19 cells proangiogenic. Our results demonstrate that sustained accumulation of miR-155 mediated by exosomes might affect remote recipient cells such as retinal pigment epithelial cells.

A natural HIV p17 protein variant up-regulates the LMP-1 EBV oncoprotein and promotes the growth of EBV-infected B-lymphocytes: implications for EBV-driven lymphomagenesis in the HIV setting

Human immunodeficiency virus p17 matrix protein is released by infected cells and may accumulate within lymphoid tissues where it may deregulate the biological activities of different cell populations by binding to CXCR1 and CXCR2 cellular receptors. S75X, a natural p17 variant, was recently shown to enhance the malignant properties of lymphoma cells. We investigated a reference p17 protein and the S75X variant for their ability to bind to Epstein-Barr virus (EBV)-infected primary and fully transformed B-lymphocytes and trigger downstream effects of potential pathogenic relevance. We demonstrate that EBV infection of primary B-lymphocytes or the ectopic expression of the latent membrane protein-1 viral oncoprotein in EBV-negative B-cells up-regulates CXCR2, but not CXCR1. Multispectral imaging flow cytometry showed that EBV-infected primary B-cells more efficiently bind and internalize p17 proteins as compared with activated B-lymphocytes. The S75X variant bound more efficiently to EBV-infected primary and fully transformed B-lymphocytes compared with reference p17, because of a higher affinity to CXCR2, and enhanced the proliferation of these cells, an effect associated with cyclin D2 and D3 up-regulation and increased interleukin-6 production. Notably, the S75X variant markedly up-regulated latent membrane protein-1 expression at both mRNA and protein levels and enhanced the activation of Akt, ERK1/2 and STAT3 signaling, thereby contributing to EBV(+) B-cell growth promotion. These results indicate that EBV infection sensitizes B-lymphocytes to CXCR2-mediated effects of p17 proteins and provide evidence supporting a possible contribution of natural p17 variants to EBV-driven lymphomagenesis in the human immunodeficiency virus setting.

Nasopharyngeal Carcinoma: An Evolving Role for the Epstein-Barr Virus

The Epstein-Barr herpesvirus (EBV) is an important human pathogen that is closely linked to several major malignancies including the major epithelial tumor, undifferentiated nasopharyngeal carcinoma (NPC). This important tumor occurs with elevated incidence in specific areas, particularly in southern China but also in Mediterranean Africa and some regions of the Middle East. Regardless of tumor prevalence, undifferentiated NPC is consistently associated with EBV. The consistent detection of EBV in all cases of NPC, the maintenance of the viral genome in every cell, and the continued expression of viral gene products suggest that EBV is a necessary factor for the malignant growth in vivo. However, the molecular characterization of the infection and identification of critical events have been hampered by the difficulty in developing in vitro models of NPC. Epithelial cell infection is difficult in vitro and in contrast to B-cell infection does not result in immortalization and transformation. Cell lines established from NPC usually do not retain the genome, and the successful establishment of tumor xenografts is difficult. However, critical genetic changes that contribute to the onset and progression of NPC and key molecular properties of the viral genes expressed in NPC have been identified. In some cases, viral expression becomes increasingly restricted during tumor progression and tumor cells may express only the viral nuclear antigen EBNA1 and viral noncoding RNAs. As NPC develops in the immunocompetent, the continued progression of deregulated growth likely reflects the combination of expression of viral oncogenes in some cells and viral noncoding RNAs that likely function synergistically with changes in cellular RNA and miRNA expression.

A comprehensive analysis of the cellular and EBV-specific microRNAome in primary CNS PTLD identifies different patterns among EBV-associated tumors

Primary central nervous system (pCNS) posttransplant lymphoproliferative disorder (PTLD) is a complication of solid organ transplantation characterized by poor outcome. In contrast to systemic PTLD, Epstein-Barr virus (EBV)-association of pCNS PTLD is almost universal, yet viral and cellular data are limited. To identify differences in the pattern of EBV-association of pCNS and systemic PTLD, we analyzed the expression of latent and lytic EBV transcripts and the viral and cellular microRNAome in nine pCNS (eight EBV-associated) and in 16 systemic PTLD samples (eight EBV-associated). Notably although 15/16 EBV-associated samples exhibited a viral type III latency pattern, lytic transcripts were also strongly expressed. Members of the ebv-miR-BHRF1 and ebv-miR-BART clusters were expressed in virtually all EBV-associated PTLD samples. There were 28 cellular microRNAs differentially expressed between systemic and pCNS PTLD. pCNS PTLD expressed lower hsa-miR-199a-5p/3p and hsa-miR-143/145 (implicated in nuclear factor kappa beta and c-myc signaling) as compared to systemic PTLD. Unsupervised nonhierarchical clustering of the viral and cellular microRNAome distinguished non-EBV-associated from EBV-associated samples and identified a separate group of EBV-associated pCNS PTLD that displayed reduced levels of B cell lymphoma associated oncomiRs such as hsa-miR-155, -21, -221 and the hsa-miR-17-92 cluster. EBV has a major impact on viral and cellular microRNA expression in EBV-associated pCNS PTLD.

Inhibition of Epstein-Barr virus lytic cycle by an ethyl acetate subfraction separated from Polygonum cuspidatum root and its major component, emodin

Polygonum cuspidatum is widely used as a medicinal herb in Asia. In this study, we examined the ethyl acetate subfraction F3 obtained from P. cuspidatum root and its major component, emodin, for their capacity to inhibit the Epstein-Barr virus (EBV) lytic cycle. The cell viability was determined by the MTT [3-(4,5-dimethyldiazol-2-yl)-2,5-diphenyltetrazolium bromide] method. The expression of EBV lytic proteins was analyzed by immunoblot, indirect immunofluorescence and flow cytometric assays. Real-time quantitative PCR was used to assess the EBV DNA replication and the transcription of lytic genes, including BRLF1 and BZLF1. Results showed that the F3 and its major component emodin inhibit the transcription of EBV immediate early genes, the expression of EBV lytic proteins, including Rta, Zta, and EA-D and reduces EBV DNA replication, showing that F3 and emodin are potentially useful as an anti-EBV drug.

Differences in gastric carcinoma microenvironment stratify according to EBV infection intensity: implications for possible immune adjuvant therapy

Epstein-Barr virus (EBV) is associated with roughly 10% of gastric carcinomas worldwide (EBVaGC). Although previous investigations provide a strong link between EBV and gastric carcinomas, these studies were performed using selected EBV gene probes. Using a cohort of gastric carcinoma RNA-seq data sets from The Cancer Genome Atlas (TCGA), we performed a quantitative and global assessment of EBV gene expression in gastric carcinomas and assessed EBV associated cellular pathway alterations. EBV transcripts were detected in 17% of samples but these samples varied significantly in EBV coverage depth. In four samples with the highest EBV coverage (hiEBVaGC – high EBV associated gastric carcinoma), transcripts from the BamHI A region comprised the majority of EBV reads. Expression of LMP2, and to a lesser extent, LMP1 were also observed as was evidence of abortive lytic replication. Analysis of cellular gene expression indicated significant immune cell infiltration and a predominant IFNG response in samples expressing high levels of EBV transcripts relative to samples expressing low or no EBV transcripts. Despite the apparent immune cell infiltration, high levels of the cytotoxic T-cell (CTL) and natural killer (NK) cell inhibitor, IDO1, was observed in the hiEBVaGCs samples suggesting an active tolerance inducing pathway in this subgroup. These results were confirmed in a separate cohort of 21 Vietnamese gastric carcinoma samples using qRT-PCR and on tissue samples using in situ hybridization and immunohistochemistry. Lastly, a panel of tumor suppressors and candidate oncogenes were expressed at lower levels in hiEBVaGC versus EBV-low and EBV-negative gastric cancers suggesting the direct regulation of tumor pathways by EBV.

Epstein-Barr virus (EBV) is detected in roughly 10% of gastric carcinoma (GC) cases worldwide. Despite a strong link between EBV and gastric carcinoma, the contribution of EBV to the tumor environment in EBV associated gastric carcinoma is unclear. We performed a global assessment of EBV and host cell gene expression in gastric carcinoma tumors from 71 patients to link EBV genes (and expression intensities) to cell and microenvironmental changes. In addition to the finding that EBV is associated with down-regulated tumor regulatory genes, this study revealed that samples with high levels of EBV gene expression (hiEBVaGCs) displayed elevated immune cell infiltration with high interferon-gamma (IFNG) expression compared to samples with low or no EBV gene expression. Despite this evidence of increased immune posturing, hiEBVaGC samples also showed elevated expression of the potent immune cell inhibitor, IDO1. This finding may partly explain the persistence of these virus associated tumors in the face of local immune cell concentration. Importantly, the small molecule IDO inhibitor, 1MT (1-methyl Tryptophan), has been shown to reverse the tolerance inducing effects of IDO1 in other tumors. We propose that stratification of gastric carcinomas into EBV-negative, EBV-low and EBV-high may provide indicator value for the use of IDO1 inhibitors as adjuvant therapies against hiEBVaGCs.

Variable EBV DNA load distributions and heterogeneous EBV mRNA expression patterns in the circulation of solid organ versus stem cell transplant recipients

Epstein-Barr virus (EBV) driven post-transplant lymphoproliferative disease (PTLD) is a heterogeneous and potentially life-threatening condition. Early identification of aberrant EBV activity may prevent progression to B-cell lymphoma. We measured EBV DNA load and RNA profiles in plasma and cellular blood compartments of stem cell transplant (SCT; n = 5), solid organ transplant recipients (SOT; n = 15), and SOT having chronic elevated EBV-DNA load (n = 12). In SCT, EBV DNA was heterogeneously distributed, either in plasma or leukocytes or both. In SOT, EBV DNA load was always cell associated, predominantly in B cells, but occasionally in T cells (CD4 and CD8) or monocytes. All SCT with cell-associated EBV DNA showed BARTs and EBNA1 expression, while LMP1 and LMP2 mRNA was found in 1 and 3 cases, respectively. In SOT, expression of BARTs was detected in all leukocyte samples. LMP2 and EBNA1 mRNA was found in 5/15 and 2/15, respectively, but LMP1 mRNA in only 1, coinciding with severe PTLD and high EBV DNA.

CONCLUSION

EBV DNA is differently distributed between white cells and plasma in SOT versus SCT. EBV RNA profiling in blood is feasible and may have added value for understanding pathogenic virus activity in patients with elevated EBV-DNA.

Genome-wide analyses of Zta binding to the Epstein-Barr virus genome reveals interactions in both early and late lytic cycles and an epigenetic switch leading to an altered binding profile

The Epstein-Barr virus (EBV) genome sustains substantial epigenetic modification involving chromatin remodelling and DNA methylation during lytic replication. Zta (ZEBRA, BZLF1), a key regulator of the EBV lytic cycle, is a transcription and replication factor, binding to Zta response elements (ZREs) in target promoters and EBV lytic origins of replication. In vitro, Zta binding is modulated by DNA methylation; a subset of CpG-containing Zta binding sites (CpG ZREs) is bound only in a DNA methylation-dependent manner. The question of how the dynamic epigenetic environment impacts Zta interaction during the EBV lytic cycle is unknown. To address this, we used chromatin immunoprecipitation coupled with next-generation sequencing (ChIP-Seq) to identify Zta binding sites across the EBV genome before and after viral DNA replication. Replication did not alter the association of Zta across many regions of the EBV genome, but a striking reduction in Zta binding occurred at some loci that contain CpG ZREs. Separating Zta-bound DNA into methylated and nonmethylated fractions, we found that promoters that contain CpG ZREs were enriched in the methylated fraction but that Zta binding to promoters lacking CpG ZREs was not reduced. We hypothesize that the loss of DNA methylation on the EBV genome during the lytic cycle causes the reduced binding to CpG ZREs; this may act as a lytic cycle epigenetic switch. However, the epigenetic changes associated with the replicated EBV genome do not affect the interaction of Zta with many loci that are rich in non-CpG ZREs; this leads to sustained binding at these regions.

Resveratrol inhibits Epstein Barr Virus lytic cycle in Burkitt's lymphoma cells by affecting multiple molecular targets

Resveratrol (RV), a polyphenolic natural product present in many plants and fruits, exhibits anti-inflammatory, cardio-protective and anti-proliferative properties. Moreover, RV affects a wide variety of viruses including members of the Herpesviridae family, retroviruses, influenza A virus and polyomavirus by altering cellular pathways that affect viral replication itself. Epstein Barr Virus (EBV), the causative agent of infectious mononucleosis, is associated with different proliferative diseases in which it establishes a latent and/or a lytic infection. In this study, we examined the antiviral activity of RV against the EBV replicative cycle and investigated the molecular targets possibly involved. In a cellular context that allows in vitro EBV activation and lytic cycle progression through mechanisms closely resembling those that in vivo initiate and enable productive infection, we found that RV inhibited EBV lytic genes expression and the production of viral particles in a dose-dependent manner. We demonstrated that RV inhibited protein synthesis, decreased reactive oxygen species (ROS) levels, and suppressed the EBV-induced activation of the redox-sensitive transcription factors NF-kB and AP-1. Further insights into the signaling pathways and molecular targets modulated by RV may provide the basis for exploiting the antiviral activity of this natural product on EBV replication.

An Epstein-Barr Virus (EBV) mutant with enhanced BZLF1 expression causes lymphomas with abortive lytic EBV infection in a humanized mouse model

Immunosuppressed patients are at risk for developing Epstein-Barr Virus (EBV)-positive lymphomas that express the major EBV oncoprotein, LMP1. Although increasing evidence suggests that a small number of lytically infected cells may promote EBV-positive lymphomas, the impact of enhanced lytic gene expression on the ability of EBV to induce lymphomas is unclear. Here we have used immune-deficient mice, engrafted with human fetal hematopoietic stem cells and thymus and liver tissue, to compare lymphoma formation following infection with wild-type (WT) EBV versus infection with a "superlytic" (SL) mutant with enhanced BZLF1 (Z) expression. The same proportions (2/6) of the WT and SL virus-infected animals developed B-cell lymphomas by day 60 postinfection; the remainder of the animals had persistent tumor-free viral latency. In contrast, all WT and SL virus-infected animals treated with the OKT3 anti-CD3 antibody (which inhibits T-cell function) developed lymphomas by day 29. Lymphomas in OKT3-treated animals (in contrast to lymphomas in the untreated animals) contained many LMP1-expressing cells. The SL virus-infected lymphomas in both OKT3-treated and untreated animals contained many more Z-expressing cells (up to 30%) than the WT virus-infected lymphomas, but did not express late viral proteins and thus had an abortive lytic form of EBV infection. LMP1 and BMRF1 (an early lytic viral protein) were never coexpressed in the same cell, suggesting that LMP1 expression is incompatible with lytic viral reactivation. These results show that the SL mutant induces an "abortive" lytic infection in humanized mice that is compatible with continued cell growth and at least partially resistant to T-cell killing.

Prospective monitoring of Epstein-Barr virus and other herpesviruses in patients with juvenile idiopathic arthritis treated with methotrexate and tocilizumab

Methotrexate (MTX) is widely used for the treatment of articular-type juvenile idiopathic arthritis (JIA), but patients receiving MTX for rheumatoid arthritis have been reported to be at increased risk of reactivation of Epstein-Barr virus (EBV) and the development of lymphoproliferative disorder. The association between MTX and reactivation of herpesviruses in pediatric patients is not yet understood. We prospectively monitored the viral load of EBV, cytomegalovirus (CMV), and herpesvirus 6 (HHV-6) in four JIA patients treated with MTX for 12-24 months. Tocilizumab, an anti-interleukin 6 receptor monoclonal antibody, was added to the therapeutic regimen in three patients during the observation period. Prior to the administration of MTX, EBV and HHV-6 were detected by PCR in two patients. Significant increases in EBV and HHV-6 load were not observed following the administration of MTX or tocilizumab. In one patient, a relatively high EBV load remained detectable during 21 months of observation in the absence of clinical symptoms. CMV was not detected throughout the observation period in any patient. This is the first report monitoring the longitudinal DNA loads of EBV and other herpesviruses in JIA patients. EBV and HHV-6 were often detectable, but treatment with MTX and tocilizumab did not appear to influence the viral load.

Epstein-Barr virus Zta-induced immunomodulators from nasopharyngeal carcinoma cells upregulate interleukin-10 production from monocytes

During lytic infection with Epstein-Barr virus (EBV), several viral lytic proteins function to evade immune recognition or to actively suppress immune cells. An EBV lytic transactivator, Zta, induces an immunosuppressive cytokine interleukin 10 (IL-10) in B cells, but whether it regulates IL-10 in the context of epithelial cells is unclear. In this study, we tested nasopharyngeal carcinoma (NPC) cell lines and found that Zta did not induce IL-10 in these epithelial cells. Interestingly, the conditioned medium of Zta-expressing NPC cells enhanced IL-10 production from monocytes. We further revealed that the IL-10-inducing effect involved at least two immunomodulators that were upregulated by Zta and secreted from NPC cells: granulocyte-macrophage colony-stimulating factor (GM-CSF) and prostaglandin E(2) (PGE(2)). Zta was recruited to and activated the GM-CSF promoter, thus upregulating GM-CSF expression. Zta also activated the promoter of cyclooxygenase-2 (COX-2), and Zta-induced COX-2 increased downstream PGE(2) production. Cotreatment with GM-CSF and PGE(2) synergistically induced IL-10 production from monocytes. The IL-10-inducing effect of the Zta-conditioned medium was reduced when GM-CSF or the COX-2/PGE(2) pathway was blocked. The conditioned medium of NPC cells with EBV lytic infection showed a similar increase of GM-CSF and PGE(2) levels as well as the IL-10-inducing effect on monocytes, and knockdown of Zta abolished all the effects. Therefore, through Zta-induced immunomodulators, EBV lytic infection in NPC cells can direct bystander monocytes to produce IL-10, which may be a novel way of EBV to promote local immunosuppression.

Getting the message direct manipulation of host mRNA accumulation during gammaherpesvirus lytic infection

The Gammaherpesvirinae subfamily of herpesviruses comprises lymphotropic viruses, including the oncogenic human pathogens Epstein-Barr virus and Kaposi's sarcoma-associated herpesvirus. During lytic infection, gammaherpesviruses manipulate host gene expression to optimize the cellular environment for viral replication and to evade the immune response. Additionally, although a lytically infected cell will itself be killed in the process of viral replication, lytic infection can contribute to pathogenesis by inducing the secretion of paracrine factors with functions in cell survival and proliferation, and angiogenesis. The mechanisms by which these viruses manipulate host gene expression are varied and target the accumulation of cellular mRNAs and their translation, signaling pathways, and protein stability. Here, we discuss how gammaherpesviral proteins directly influence host mRNA biogenesis and stability, either selectively or globally, in order to fine-tune the cellular environment to the advantage of the virus. Appreciation of the mechanisms by which these viruses interface with and adapt normal cellular processes continues to inform our understanding of gammaherpesviral biology and the regulation of mRNA accumulation and turnover in our own cells.

Epstein-Barr virus genetics: talking about the BAC generation

Genetic mutant organisms pervade all areas of Biology. Early on, herpesviruses (HV) were found to be amenable to genetic analysis using homologous recombination techniques in eukaryotic cells. More recently, HV genomes cloned onto a bacterial artificial chromosome (BAC) have become available. HV BACs can be easily modified in E.coli and reintroduced in eukaryotic cells to produce infectious viruses. Mutants derived from HV BACs have been used both to understand the functions of all types of genetic elements present on the virus genome, but also to generate mutants with potentially medically relevant properties such as preventative vaccines. Here we retrace the development of the BAC technology applied to the Epstein-Barr virus (EBV) and review the strategies available for the construction of mutants. We expand on the appropriate controls required for proper use of the EBV BACs, and on the technical hurdles researchers face in working with these recombinants. We then discuss how further technological developments might successfully overcome these difficulties. Finally, we catalog the EBV BAC mutants that are currently available and illustrate their contributions to the field using a few representative examples.

A new model of Epstein-Barr virus infection reveals an important role for early lytic viral protein expression in the development of lymphomas

Epstein-Barr virus (EBV) infects cells in latent or lytic forms, but the role of lytic infection in EBV-induced lymphomas is unclear. Here, we have used a new humanized mouse model, in which both human fetal CD34(+) hematopoietic stem cells and thymus/liver tissue are transplanted, to compare EBV pathogenesis and lymphoma formation following infection with a lytic replication-defective BZLF1-deleted (Z-KO) virus or a lytically active BZLF1(+) control. Both the control and Z-KO viruses established long-term viral latency in all infected animals. The infection appeared well controlled in some animals, but others eventually developed CD20(+) diffuse large B cell lymphomas (DLBCL). Animals infected with the control virus developed tumors more frequently than Z-KO virus-infected animals. Specific immune responses against EBV-infected B cells were generated in mice infected with either the control virus or the Z-KO virus. In both cases, forms of viral latency (type I and type IIB) were observed that are less immunogenic than the highly transforming form (type III) commonly found in tumors of immunocompromised hosts, suggesting that immune pressure contributed to the outcome of the infection. These results point to an important role for lytic EBV infection in the development of B cell lymphomas in the context of an active host immune response.

Inhibitory effects of resveratrol on the Epstein-Barr virus lytic cycle

Reactivation of Epstein-Barr virus (EBV) from latency to the lytic cycle is required for the production of viral particles. Here, we examine the capacity of resveratrol to inhibit the EBV lytic cycle. Our results show that resveratrol inhibits the transcription of EBV immediate early genes, the expression of EBV lytic proteins, including Rta, Zta, and EA-D and reduces viron production, suggesting that this compound may be useful for preventing the proliferation of the virus.

AP-1 homolog BZLF1 of Epstein-Barr virus has two essential functions dependent on the epigenetic state of the viral genome

EBV, a member of the herpes virus family, is a paradigm for human tumor viruses and a model of viral latency amenable for study in vitro. It induces resting human B lymphocytes to proliferate indefinitely in vitro and initially establishes a strictly latent infection in these cells. BZLF1, related to the cellular activating protein 1 (AP-1) family of transcription factors, is the viral master gene essential and sufficient to mediate the switch to induce the EBV lytic phase in latently infected B cells. Enigmatically, after infection BZLF1 is expressed very early in the majority of primary B cells, but its early expression fails to induce the EBV lytic phase. We show that the early expression of BZLF1 has a critical role in driving the proliferation of quiescent naïve and memory B cells but not of activated germinal center B cells. BZLF1's initial failure to induce the EBV lytic phase relies on the viral DNA at first being unmethylated. We have found that the eventual and inevitable methylation of viral DNA is a prerequisite for productive infection in stably, latently infected B cells which then yield progeny virus lacking cytosine-phosphatidyl-guanosine (CpG) methylation. This progeny virus then can repeat EBV's epigenetically regulated, biphasic life cycle. Our data indicate that the viral BZLF1 protein is crucial both to establish latency and to escape from it. Our data also indicate that EBV has evolved to appropriate its host's mode of methylating DNA for its own epigenetic regulation.

Quantitative evaluation of the role of Epstein-Barr virus immediate-early protein BZLF1 in B-cell transformation

The Epstein-Barr virus (EBV) immediate-early transactivator BZLF1 plays a key role in switching EBV infection from the latent to the lytic form by stimulating the expression cascade of lytic genes; it also regulates the expression of several cellular genes. Recently, we reported that BZLF1 is expressed in primary human B cells early after EBV infection. To investigate whether this BZLF1 expression early after infection plays a role in the EBV-induced growth transformation of primary B cells, we generated BZLF1-knockout EBV and quantitatively evaluated its transforming ability compared with that of wild-type EBV. We found that the 50% transforming dose of BZLF1-knockout EBV was quite similar to that of wild-type EBV. Established lymphoblastoid cell lines (LCLs) harbouring BZLF1-knockout EBV were indistinguishable from LCLs harbouring wild-type EBV in their pattern of latent gene expression and in their growth in vitro. Furthermore, the copy numbers of EBV episomes were very similar in the LCLs harbouring BZLF1-knockout EBV and in those harbouring wild-type EBV. These data indicate that disrupting BZLF1 expression in the context of the EBV genome, and the resultant inability to enter lytic replication, have little impact on the growth of LCLs and the steady-state copy number of EBV episomes in established LCLs.

Epstein-Barr virus lytic transactivator Zta enhances chemotactic activity through induction of interleukin-8 in nasopharyngeal carcinoma cells

Epstein-Barr virus (EBV)-associated, undifferentiated type of nasopharyngeal carcinoma (NPC) is characterized by intensive leukocyte infiltration. Interaction between the infiltrating cells and the tumor cells has been considered crucial for NPC development. Recruitment of the infiltrates can be directed by certain chemokines present in the NPC tissues. It is unknown whether and how EBV lytic infection regulates expression of the chemokines. Using an antibody array, we first found that several chemokines secreted from EBV-infected NPC cells are increased upon EBV reactivation into the lytic cycle, and interleukin-8 (IL-8) is the chemokine upregulated most significantly and consistently. Further studies showed that the EBV lytic transactivator Zta is a potent inducer of IL-8 in NPC cells, augmenting secreted and intracellular IL-8 proteins, as well as IL-8 RNA. Zta upregulates Egr-1, a cellular transcription factor that has been involved in upregulation of IL-8, but the Zta-induced IL-8 expression is independent of Egr-1. The ability of Zta to transactivate the IL-8 promoter is important for the induction of IL-8, and we have identified two Zta-responsive elements in the promoter. Zta can bind to these two elements in vitro and can also be recruited to the IL-8 promoter in vivo. DNA-binding-defective Zta mutants can neither activate the IL-8 promoter nor induce IL-8 production. In addition, Zta-expressing NPC cells exert enhanced chemotactic activity that is mainly mediated by IL-8. Since IL-8 may contribute to not only leukocyte infiltration but also multiple oncogenic processes, the present study provides a potential link between EBV lytic infection and pathogenesis of NPC.