Regulation of Epstein-Barr virus reactivation from latency

Epstein-Barr virus replication within differentiated epithelia requires pRb sequestration of activator E2F transcription factors

Epstein-Barr virus (EBV) co-infections with human papillomavirus (HPV) have been observed in oropharyngeal squamous cell carcinoma. Modeling EBV/HPV co-infection in organotypic epithelial raft cultures revealed that HPV16 E7 inhibited EBV productive replication through the facilitated degradation of the retinoblastoma protein pRb/p105. To further understand how pRb is required for EBV productive replication, we generated CRISPR-Cas9 pRb knockout (KO) normal oral keratinocytes (NOKs) in the context of wild-type and mutant K120E p53. EBV replication was examined in organotypic rafts as a physiological correlate for epithelial differentiation. In pRb KO rafts, EBV DNA copy number was statistically decreased compared to vector controls, regardless of p53 context. Loss of pRb did not affect EBV binding or internalization of calcium-treated NOKs or early infection of rafts. Rather, the block in EBV replication correlated with impaired immediate early gene expression. An EBV infection time course in rafts with mutant p53 demonstrated that pRb-positive basal cells were initially infected with delayed replication occurring in differentiated layers. Loss of pRb showed increased S-phase progression makers and elevated activator E2F activity in raft tissues. Complementation with a panel of pRb/E2F binding mutants showed that wild type or pRb∆685 mutant capable of E2F binding reduced S-phase marker gene expression, rescued EBV DNA replication, and restored BZLF1 expression in pRb KO rafts. However, pRb KO complemented with pRb661W mutant, unable to bind E2Fs, failed to rescue EBV replication in raft culture. These findings suggest that EBV productive replication in differentiated epithelium requires pRb inhibition of activator E2Fs to restrict S-phase progression.IMPORTANCEA subset of human papillomavirus (HPV)-positive oropharyngeal squamous cell carcinoma is co-positive for Epstein-Barr virus (EBV). Potential oncogenic viral interactions revealed that HPV16 E7 inhibited productive EBV replication within the differentiated epithelium. As E7 mediates the degradation of pRb, we aimed to establish how pRb is involved in EBV replication. In the context of differentiated epithelium using organotypic raft culture, we evaluated how the loss of pRb affects EBV lytic replication to better comprehend EBV contributions to carcinogenesis. In this study, ablation of pRb interfered with EBV replication at the level of immediate early gene expression. Loss of pRb increased activator E2Fs and associated S-phase gene expression throughout the differentiated epithelium. Complementation studies showed that wild type and pRb mutant capable of binding to E2F rescued EBV replication, while pRb mutant lacking E2F binding did not. Altogether, these studies support that in differentiated tissues, HPV16 E7-mediated degradation of pRb inhibits EBV replication through unregulated E2F activity.

Characterization of latently infected EBV+ antibody-secreting B cells isolated from ovarian tumors and malignant ascites

Introduction

Intra-tumoral B cells mediate a plethora of immune effector mechanisms with key roles in anti-tumor immunity and serve as positive prognostic indicators in a variety of solid tumor types, including epithelial ovarian cancer (EOC). Several aspects of intra-tumoral B cells remain unclear, such as their state of activation, antigenic repertoires, and capacity to mature into plasma cells.

Methods

B lymphocytes were isolated from primary EOC tissue and malignant ascites and were maintained in cell culture medium. The stably maintained cell lines were profiled with flow cytometry and B cell receptor sequencing. Secreted antibodies were tested with a human proteome array comprising more than 21,000 proteins, followed by ELISA for validation. Originating tumor samples were used for spatial profiling with chip cytometry.

Results

Antibody-secreting B lymphocytes were isolated from the ovarian tumor microenvironment (TME) of four different EOC patients. The highly clonal cell populations underwent spontaneous immortalization in vitro, were stably maintained in an antibody-secreting state, and showed presence of Epstein-Barr viral (EBV) proteins. All originating tumors had high frequency of tumor-infiltrating B cells, present as lymphoid aggregates, or tertiary lymphoid structures. The antigens recognized by three of the four cell lines are coil-coil domain containing protein 155 (CCDC155), growth factor receptor-bound protein 2 (GRB2), and pyruvate dehydrogenase phosphatase2 (PDP2), respectively. Anti-CCDC155 circulating IgG antibodies were detected in 9 of 20 (45%) of EOC patients' sera. Tissue analyses with multiparameter chip cytometry shows that the antibodies secreted by these novel human B cell lines engage their cognate antigens on tumor cells.

Discussion

These studies demonstrate that within the tumor-infiltrating lymphocyte population in EOC resides a low frequency population of antibody-secreting B cells that have been naturally exposed to EBV. Once stably maintained, these novel cell lines offer unique opportunities for future studies on intratumor B cell biology and new target antigen recognition, and for studies on EBV latency and/or viral reactivation in the TME of non-EBV related solid tumors such as the EOC.

The Gut Connection: Exploring the Possibility of Implementing Gut Microbial Metabolites in Lymphoma Treatment

Recent research has implicated the gut microbiota in the development of lymphoma. Dysbiosis of the gut microbial community can disrupt the production of gut microbial metabolites, thereby impacting host physiology and potentially contributing to lymphoma. Dysbiosis-driven release of gut microbial metabolites such as lipopolysaccharides can promote chronic inflammation, potentially elevating the risk of lymphoma. In contrast, gut microbial metabolites, such as short-chain fatty acids, have shown promise in preclinical studies by promoting regulatory T-cell function, suppressing inflammation, and potentially preventing lymphoma. Another metabolite, urolithin A, exhibited immunomodulatory and antiproliferative properties against lymphoma cell lines in vitro. While research on the role of gut microbial metabolites in lymphoma is limited, this article emphasizes the need to comprehend their significance, including therapeutic applications, molecular mechanisms of action, and interactions with standard chemotherapies. The article also suggests promising directions for future research in this emerging field of connection between lymphoma and gut microbiome.

Targeting the crosstalk of epigenetic modifications and immune evasion in nasopharyngeal cancer

Nasopharyngeal carcinoma (NPC) is a distinct type of head and neck cancer that is highly associated with Epstein-Barr virus (EBV) infection. EBV acts as an epigenetic driver in NPC tumorigenesis, reprogramming the viral and host epigenomes to regulate viral latent gene expression, and creating an environment conducive to the malignant transformation of nasopharyngeal epithelial cells. Targeting epigenetic mechanisms in pre-clinical studies has been shown promise in eradicating tumours and overcoming immune resistance in some solid tumours. However, its efficacy in NPC remains inclusive due to the complex nature of this cancer. In this review, we provide an updated understanding of the roles of epigenetic factors in regulating EBV latent gene expression and promoting NPC progression. We also explore the crosstalk between epigenetic mechanisms and immune evasion in NPC. Particularly, we discuss the potential roles of DNA methyltransferase (DNMT) and histone deacetylase (HDAC) inhibitors in reversing immune suppression and augmenting antitumour immunity. Furthermore, we highlight the advantages of combining epigenetic therapy and immune checkpoint inhibitor to reverse immune resistance and improve clinical outcomes. Epigenetic drugs have the potential to modulate both epigenetic mediators and immune factors involved in NPC. However, further research is needed to fully comprehend the diverse range of epigenetic modifications in NPC. A deeper understanding of the crosstalk between epigenetic mechanisms and immune evasion during NPC progression is crucial for the development of more effective treatments for this challenging disease.

Alzheimer's disease as a viral disease: Revisiting the infectious hypothesis

Alzheimer's disease (AD) represents the most frequent type of dementia in elderly people. Two major forms of the disease exist: sporadic - the causes of which have not yet been fully understood - and familial - inherited within families from generation to generation, with a clear autosomal dominant transmission of mutations in Presenilin 1 (PSEN1), 2 (PSEN2) or Amyloid Precursors Protein (APP) genes. The main hallmark of AD consists of extracellular deposits of amyloid-beta (Aβ) peptide and intracellular deposits of the hyperphosphorylated form of the tau protein. An ever-growing body of research supports the viral infectious hypothesis of sporadic forms of AD. In particular, it has been shown that several herpes viruses (i.e., HHV-1, HHV-2, HHV-3 or varicella zoster virus, HHV-4 or Epstein Barr virus, HHV-5 or cytomegalovirus, HHV-6A and B, HHV-7), flaviviruses (i.e., Zika virus, Dengue fever virus, Japanese encephalitis virus) as well as Human Immunodeficiency Virus (HIV), hepatitis viruses (HAV, HBV, HCV, HDV, HEV), SARS-CoV2, Ljungan virus (LV), Influenza A virus and Borna disease virus, could increase the risk of AD. Here, we summarized and discussed these results. Based on these findings, significant issues for future studies are also put forward.

Shikonin, an inhibitor of inflammasomes, inhibits Epstein-Barr virus reactivation

Epstein-Barr virus (EBV) is a highly prevalent human herpesvirus that persists for life in more than 95% of the adult population. EBV usually establishes an asymptomatic life-long infection, but it is also associated with malignancies affecting B lymphocytes and epithelial cells mainly. The virus alternates between a latent phase and a lytic phase, both of which contribute to the initiation of the tumor process. So far, there is only a limited number of antiviral molecules against the lytic phase, most of them targeting viral replication. Recent studies provided evidence that EBV uses components of the NLRP3 inflammasome to enter the productive phase of its cycle following activation in response to various stimuli. In the present work, we demonstrate that shikonin, a natural molecule with low toxicity which is known to inhibit inflammasome, can efficiently repress EBV reactivation. Similar results were obtained with apigenin and OLT 1177, two other NLRP3 inflammasome inhibitors. It is shown herein that shikonin repressed the transcription of reactivation-induced NLRP3 thereby inhibiting inflammasome activation and EBV lytic phase induction.

Follicular Helper and Regulatory T Cells Drive the Development of Spontaneous Epstein-Barr Virus Lymphoproliferative Disorder

Epstein-Barr virus (EBV) is a ubiquitous herpes virus associated with various cancers. EBV establishes latency with life-long persistence in memory B-cells and can reactivate lytic infection placing immunocompromised individuals at risk for EBV-driven lymphoproliferative disorders (EBV-LPD). Despite the ubiquity of EBV, only a small percentage of immunocompromised patients (~20%) develop EBV-LPD. Engraftment of immunodeficient mice with peripheral blood mononuclear cells (PBMCs) from healthy EBV-seropositive donors leads to spontaneous, malignant, human B-cell EBV-LPD. Only about 20% of EBV+ donors induce EBV-LPD in 100% of engrafted mice (High-Incidence, HI), while another 20% of donors never generate EBV-LPD (No-Incidence, NI). Here, we report HI donors to have significantly higher basal T follicular helper (Tfh) and regulatory T-cells (Treg), and depletion of these subsets prevents/delays EBV-LPD. Transcriptomic analysis of CD4+ T cells from ex vivo HI donor PBMC revealed amplified cytokine and inflammatory gene signatures. HI vs. NI donors showed a marked reduction in IFNγ production to EBV latent and lytic antigen stimulation. In addition, we observed abundant myeloid-derived suppressor cells in HI donor PBMC that decreased CTL proliferation in co-cultures with autologous EBV+ lymphoblasts. Our findings identify potential biomarkers that may identify individuals at risk for EBV-LPD and suggest possible strategies for prevention.

Advancing therapeutic strategies for Epstein-Barr virus-associated malignancies through lytic reactivation

Epstein-Barr virus (EBV) is a widespread human herpes virus associated with lymphomas and epithelial cell cancers. It establishes two separate infection phases, latent and lytic, in the host. Upon infection of a new host cell, the virus activates several pathways, to induce the expression of lytic EBV antigens and the production of infectious virus particles. Although the carcinogenic role of latent EBV infection has been established, recent research suggests that lytic reactivation also plays a significant role in carcinogenesis. In this review, we summarize the mechanism of EBV reactivation and recent findings about the role of viral lytic antigens in tumor formation. In addition, we discuss the treatment of EBV-associated tumors with lytic activators and the targets that may be therapeutically effective in the future.

T cell-mediated immunity during Epstein-Barr virus infections in children

Epstein-Barr virus (EBV) infection is extremely common worldwide, with approximately 90% of adults testing positive for EBV antibodies. Human are susceptible to EBV infection, and primary EBV infection typically occurs early in life. EBV infection can cause infectious mononucleosis (IM) as well as some severe non-neoplastic diseases, such as chronic active EBV infection (CAEBV) and EBV-associated hemophagocytic lymphohistiocytosis (EBV-HLH), which can have a heavy disease burden. After primary EBV infection, individuals develop robust EBV-specific T cell immune responses, with EBV-specific CD8⁺ and part of CD4⁺ T cells functioning as cytotoxic T cells, defending against virus. Different proteins expressed during EBV's lytic replication and latent proliferation can cause varying degrees of cellular immune responses. Strong T cell immunity plays a key role in controlling infection by decreasing viral load and eliminating infected cells. However, the virus persists as latent infection in EBV healthy carriers even with robust T cell immune response. When reactivated, it undergoes lytic replication and then transmits virions to a new host. Currently, the relationship between the pathogenesis of lymphoproliferative diseases and the adaptive immune system is still not fully clarified and needs to be explored in the future. Investigating the T cell immune responses evoked by EBV and utilizing this knowledge to design promising prophylactic vaccines are urgent issues for future research due to the importance of T cell immunity.

The Fight against the Carcinogenic Epstein-Barr Virus: Gut Microbiota, Natural Medicines, and Beyond

Despite recent advances in oncology, cancer has remained an enormous global health burden, accounting for about 10 million deaths in 2020. A third of the cancer cases in developing counties are caused by microbial infections such as human papillomavirus (HPV), Epstein-Barr Virus (EBV), and hepatitis B and C viruses. EBV, a member of the human gamma herpesvirus family, is a double-stranded DNA virus and the primary cause of infectious mononucleosis. Most EBV infections cause no long-term complications. However, it was reported that EBV infection is responsible for around 200,000 malignancies worldwide every year. Currently, there are no vaccines or antiviral drugs for the prophylaxis or treatment of EBV infection. Recently, the gut microbiota has been investigated for its pivotal roles in pathogen protection and regulating metabolic, endocrine, and immune functions. Several studies have investigated the efficacy of antiviral agents, gut microbial metabolites, and natural products against EBV infection. In this review, we aim to summarise and analyse the reported molecular mechanistic and clinical studies on the activities of gut microbial metabolites and natural medicines against carcinogenic viruses, with a particular emphasis on EBV. Gut microbial metabolites such as short-chain fatty acids were reported to activate the EBV lytic cycle, while bacteriocins, produced by Enterococcus durans strains, have shown antiviral properties. Furthermore, several natural products and dietary bioactive compounds, such as curcumin, epigallocatechin gallate, resveratrol, moronic acid, and andrographolide, have shown antiviral activity against EBV. In this review, we proposed several exciting future directions for research on carcinogenic viruses.

Cancers associated with human gammaherpesviruses

Epstein-Barr virus (EBV; human herpesvirus 4; HHV-4) and Kaposi sarcoma-associated herpesvirus (KSHV; human herpesvirus 8; HHV-8) are human gammaherpesviruses that have oncogenic properties. EBV is a lymphocryptovirus, whereas HHV-8/KSHV is a rhadinovirus. As lymphotropic viruses, EBV and KSHV are associated with several lymphoproliferative diseases or plasmacytic/plasmablastic neoplasms. Interestingly, these viruses can also infect epithelial cells causing carcinomas and, in the case of KSHV, endothelial cells, causing sarcoma. EBV is associated with Burkitt lymphoma, classic Hodgkin lymphoma, nasopharyngeal carcinoma, plasmablastic lymphoma, lymphomatoid granulomatosis, leiomyosarcoma, and subsets of diffuse large B-cell lymphoma, post-transplant lymphoproliferative disorder, and gastric carcinoma. KSHV is implicated in Kaposi sarcoma, primary effusion lymphoma, multicentric Castleman disease, and KSHV-positive diffuse large B-cell lymphoma. Pathogenesis by these two herpesviruses is intrinsically linked to viral proteins expressed during the lytic and latent lifecycles. This comprehensive review intends to provide an overview of the EBV and KSHV viral cycles, viral proteins that contribute to oncogenesis, and the current understanding of the pathogenesis and clinicopathology of their related neoplastic entities.

Progress in Prophylactic and Therapeutic EBV Vaccine Development Based on Molecular Characteristics of EBV Target Antigens

Epstein–Barr virus (EBV) was discovered in 1964 in the cell line of Burkitt lymphoma and became first known human oncogenic virus. EBV belongs to the Herpesviridae family, and is present worldwide as it infects 95% of people. Infection with EBV usually happens during childhood when it remains asymptomatic; however, in adults, it can cause an acute infection known as infectious mononucleosis. In addition, EBV can cause wide range of tumors with origins in B lymphocytes, T lymphocytes, and NK cells. Its oncogenicity and wide distribution indicated the need for vaccine development. Research on mice and cultured cells as well as human clinical trials have been in progress for a few decades for both prophylactic and therapeutic EBV vaccines. The main targets of the vaccines are EBV envelope glycoproteins such as gp350 and EBV latent genes. The long wait for the EBV vaccine is due to the complexity of the EBV replication cycle and the wide range of its host cells. Although some strategies such as the use of dendritic cells and recombinant Vaccinia viral vectors have shown success, ongoing clinical trials using mRNA-based vaccines as well as new delivery systems as nanoparticles are yet to show the best choice of vaccine target and its production strategy.

Andrographolide Inhibits Epstein–Barr Virus Lytic Reactivation in EBV-Positive Cancer Cell Lines through the Modulation of Epigenetic-Related Proteins

Reactivation of Epstein–Barr virus (EBV) is associated with EBV-associated malignancies and is considered to be a benefit target for treatment. Andrographolide is claimed to have antiviral and anti-tumor activities. Therefore, this study aimed to investigate the effect of andrographolide on the inhibition of EBV lytic reactivation in EBV-positive cancer cells. The cytotoxicity of andrographolide was firstly evaluated in EBV-positive cancer cells; P3HR1, AGS-EBV and HONE1-EBV cells, using an MTT assay. Herein, the spontaneous expression of EBV lytic genes; BALF5, BRLF1 and BZLF1, was significantly inhibited in andrographolide-treated cells. Accordingly, andrographolide inhibited the expression of Zta and viral production in sodium butyrate (NaB)-induced EBV lytic reactivation. Additionally, proteomics and bioinformatics analysis revealed the differentially expressed proteins that inhibit EBV lytic reactivation in all treated cell lines were functionally related with the histone modifications and chromatin organization, such as histone H3-K9 modification and histone H3-K27 methylation. Taken together, andrographolide inhibits EBV reactivation in EBV-positive cancer cells by inhibiting EBV lytic genes, probably, through the histone modifications.

Epstein-Barr virus tegument protein BGLF2 in exosomes released from virus-producing cells facilitates de novo infection

Background

Viruses must adapt to the environment of their host cells to establish infection and persist. Diverse mammalian cells, including virus-infected cells, release extracellular vesicles such as exosomes containing proteins and miRNAs, and use these vesicles to mediate intercellular communication. However, the roles of exosomes in viral infection remain unclear.

Results

We screened viral proteins to identify those responsible for the exosome-mediated enhancement of Epstein–Barr virus (EBV) infection. We identified BGLF2 protein encapsulated in exosomes, which were released by EBV-infected cells. BGLF2 protein is a tegument protein that exists in the space between the envelope and nucleocapsid, and it is released into the cytoplasm shortly after infection. BGLF2 protein-containing exosomes enhanced viral gene expression and repressed innate immunity, thereby supporting the EBV infection.

Conclusions

The EBV tegument protein BGLF2 is encapsulated in exosomes and released by infected cells to facilitate the establishment of EBV infection. These findings suggest that tegument proteins support viral infection not only between the envelope and nucleocapsid, as well as in extraviral particles such as exosomes.

Graphical abstract

Estrogen induces the expression of EBV lytic protein ZEBRA, a marker of poor prognosis in nasopharyngeal carcinoma

Several epidemiological studies have suggested that Epstein-Barr virus (EBV) lytic infection is essential for the development of nasopharyngeal carcinoma (NPC), as elevation of antibody titers against EBV lytic proteins is a common feature of NPC. Although ZEBRA protein is a key trigger for the initiation of lytic infection, whether its expression affects the prognosis and pathogenesis of NPC remains unclear. In this study, 64 NPC biopsy specimens were analyzed using immunohistochemistry. We found that ZEBRA was significantly associated with a worsening of progression-free survival in NPC (adjusted hazard ratio, 3.58; 95% confidence interval, 1.08-11.87; P = 0.037). Moreover, ZEBRA expression positively correlated with key endocrinological proteins, estrogen receptor α, and aromatase. The transcriptional level of ZEBRA is activated by estrogen in an estrogen receptor α-dependent manner, resulting in an increase in structural gene expression levels and extracellular virus DNA copy number in NPC cell lines, reminiscent of lytic infection. Interestingly, it did not suppress cellular proliferation or increase apoptosis, in contrast to cells treated with 12-O-tetradecanoylphorbol-13-acetate and sodium butyrate, indicating that viral production induced by estrogen is not a cell lytic phenomenon. Our results suggest that intratumoral estrogen overproduced by aromatase could induce ZEBRA expression and EBV reactivation, contributing to the progression of NPC.

Mono a Mano: ZBP1’s Love–Hate Relationship with the Kissing Virus

Z-DNA binding protein (ZBP1) very much represents the nuclear option. By initiating inflammatory cell death (ICD), ZBP1 activates host defenses to destroy infectious threats. ZBP1 is also able to induce noninflammatory regulated cell death via apoptosis (RCD). ZBP1 senses the presence of left-handed Z-DNA and Z-RNA (ZNA), including that formed by expression of endogenous retroelements. Viruses such as the Epstein–Barr “kissing virus” inhibit ICD, RCD and other cell death signaling pathways to produce persistent infection. EBV undergoes lytic replication in plasma cells, which maintain detectable levels of basal ZBP1 expression, leading us to suggest a new role for ZBP1 in maintaining EBV latency, one of benefit for both host and virus. We provide an overview of the pathways that are involved in establishing latent infection, including those regulated by MYC and NF-κB. We describe and provide a synthesis of the evidence supporting a role for ZNA in these pathways, highlighting the positive and negative selection of ZNA forming sequences in the EBV genome that underscores the coadaptation of host and virus. Instead of a fight to the death, a state of détente now exists where persistent infection by the virus is tolerated by the host, while disease outcomes such as death, autoimmunity and cancer are minimized. Based on these new insights, we propose actionable therapeutic approaches to unhost EBV.

Virus–Host Interplay Between Poly (ADP-Ribose) Polymerase 1 and Oncogenic Gammaherpesviruses

The gammaherpesviruses, include the Epstein–Barr virus, Kaposi’s sarcoma-associated herpesvirus, and murine gammaherpesvirus 68. They establish latent infection in the B lymphocytes and are associated with various lymphoproliferative diseases and tumors. The poly (ADP-ribose) polymerase-1 (PARP1), also called ADP-ribosyltransferase diphtheria-toxin-like 1 (ARTD1) is a nuclear enzyme that catalyzes the transfer of the ADP-ribose moiety to its target proteins and participates in important cellular activities, such as the DNA-damage response, cell death, transcription, chromatin remodeling, and inflammation. In gammaherpesvirus infection, PARP1 acts as a key regulator of the virus life cycle: lytic replication and latency. These viruses also develop various strategies to regulate PARP1, facilitating their replication. This review summarizes the roles of PARP1 in the viral life cycle as well as the viral modulation of host PARP1 activity and discusses the implications. Understanding the interactions between the PARP1 and oncogenic gammaherpesviruses may lead to the identification of effective therapeutic targets for the associated diseases.

Andrographolide Inhibits Lytic Reactivation of Epstein-Barr Virus by Modulating Transcription Factors in Gastric Cancer

Andrographolide is the principal bioactive chemical constituent of Andrographis paniculata and exhibits activity against several viruses, including Epstein–Barr virus (EBV). However, the particular mechanism by which andrographolide exerts an anti-EBV effect in EBV-associated gastric cancer (EBVaGC) cells remains unclear. We investigated the molecular mechanism by which andrographolide inhibits lytic reactivation of EBV in EBVaGC cells (AGS-EBV cell line) using proteomics and bioinformatics approaches. An andrographolide treatment altered EBV protein-expression patterns in AGS-EBV cells by suppressing the expression of EBV lytic protein. Interestingly cellular transcription factors (TFs), activators for EBV lytic reactivation, such as MEF2D and SP1, were significantly abolished in AGS-EBV cells treated with andrographolide and sodium butyrate (NaB) compared with NaB-treated cells. In contrast, the suppressors of EBV lytic reactivation, such as EZH2 and HDAC6, were significantly up-regulated in cells treated with both andrographolide and NaB compared with NaB treatment alone. In addition, bioinformatics predicted that HDAC6 could interact directly with MEF2D and SP1. Furthermore, andrographolide significantly induced cell cytotoxicity and apoptosis of AGS-EBV cells by induction of apoptosis-related protein expression. Our results suggest that andrographolide inhibits EBV lytic reactivation by inhibition of host TFs, partially through the interaction of HDAC6 with TFs, and induces apoptosis of EBVaGC cells.

Molecular Basis of Epstein-Barr Virus Latency Establishment and Lytic Reactivation

Epstein–Barr virus (EBV) is a causative agent of infectious mononucleosis and several types of cancer. Like other herpesviruses, it establishes an asymptomatic, life-long latent infection, with occasional reactivation and shedding of progeny viruses. During latency, EBV expresses a small number of viral genes, and exists as an episome in the host–cell nucleus. Expression patterns of latency genes are dependent on the cell type, time after infection, and milieu of the cell (e.g., germinal center or peripheral blood). Upon lytic induction, expression of the viral immediate-early genes, BZLF1 and BRLF1, are induced, followed by early gene expression, viral DNA replication, late gene expression, and maturation and egress of progeny virions. Furthermore, EBV reactivation involves more than just progeny production. The EBV life cycle is regulated by signal transduction, transcription factors, promoter sequences, epigenetics, and the 3D structure of the genome. In this article, the molecular basis of EBV latency establishment and reactivation is summarized.

Prophylactic and Therapeutic EBV Vaccines: Major Scientific Obstacles, Historical Progress, and Future Direction

The Epstein-Barr virus (EBV) infects more than 95% of adults worldwide and is associated with various malignant tumors and immune diseases, imparting a huge disease burden on the human population. Available EBV vaccines are imminent. Prophylactic vaccines can effectively prevent the spread of infection, whereas therapeutic vaccines mainly stimulate cell-mediated immunity and kill infected cells, thus curbing the development of malignant tumors. Nevertheless, there are still no approved EBV vaccines after decades of effort. The complexity of the EBV life cycle, the lack of appropriate animal models, and the limited reports on adjuvant selection and immune responses are gravely impeding progress in EBV vaccines. The soluble gp350 vaccine could reduce the incidence of infectious mononucleosis (IM), which seemed to offer hope, but could not prevent EBV infection. Continuous research and vaccine trials provide deep insights into the structural biology of viruses, the designs for immunogenicity, and the evolving vaccine platforms. Moreover, the new vaccine candidates are expected to achieve further success via combined immunization to elicit both a dual protection of B cells and epithelial cells, and sustainable immunization against infected cells at several phases of infection.

Epstein-Barr virus reactivation induced myeloperoxidase-specific antineutrophil cytoplasmic antibody (MPO-ANCA)-associated vasculitis

We present a patient with systemic symptoms including 4 months of dyspnoea worsened with exertion, fatigue, rhinorrhoea, intermittent facial swelling, generalised lymphadenopathy and weight loss. Laboratory studies demonstrated proteinuria and eosinophilia. His serology was consistent with Epstein-Barr Virus (EBV) reactivation. A lymph node biopsy was consistent with EBV-associated reactive lymphoid hyperplasia. He was told to continue symptomatic treatment for EBV infection. After several admissions, vasculitis workup and myeloperoxidase-antineutrophil cytoplasmic autoantibody (ANCA) studies were positive. Evolution of clinical symptoms, laboratory parameters and our literature review suggested the diagnosis of EBV-associated ANCA vasculitis. Steroids were started after the patient continued to deteriorate; the viral load started increasing, so we added valganciclovir with favourable clinical response and no relapse during the follow-up for 6 months. This suggests that with evidence of viraemia (primary or reactivation), antiviral treatment likely has clinical benefit while immunosuppression is being considered.

A STING inhibitor suppresses EBV-induced B cell transformation and lymphomagenesis

Epstein‐Barr virus‐associated lymphoproliferative disease (EBV‐LPD) is frequently fatal. Innate immunity plays a key role in protecting against pathogens and cancers. The stimulator of interferon genes (STING) is regarded as a key adaptor protein allowing DNA sensors recognizing exogenous cytosolic DNA to activate the type I interferon signaling cascade. In terms of EBV tumorigenicity, the role of STING remains elusive. Here we showed that treatment with the STING inhibitor, C‐176, suppressed EBV‐induced transformation in peripheral blood mononuclear cells. In an EBV‐LPD mouse model, C‐176 treatment also inhibited tumor formation and prolonged survival. Treatment with B cells alone did not affect EBV transformation, but suppression of EBV‐induced transformation was observed in the presence of T cells. Even without direct B cell‐T cell contact in a transwell system, the inhibitor reduced the transformation activity, indicating that intercellular communication by humoral factors was critical to prevent EBV‐induced transformation. These findings suggest that inhibition of STING signaling pathway with C‐176 could be a new therapeutic target of EBV‐LPD.

The Epstein-Barr virus deubiquitinating enzyme BPLF1 regulates the activity of topoisomerase II during productive infection

Topoisomerases are essential for the replication of herpesviruses but the mechanisms by which the viruses hijack the cellular enzymes are largely unknown. We found that topoisomerase-II (TOP2) is a substrate of the Epstein-Barr virus (EBV) ubiquitin deconjugase BPLF1. BPLF1 co-immunoprecipitated and deubiquitinated TOP2, and stabilized SUMOylated TOP2 trapped in cleavage complexes (TOP2ccs), which halted the DNA damage response to TOP2-induced double strand DNA breaks and promoted cell survival. Induction of the productive virus cycle in epithelial and lymphoid cell lines carrying recombinant EBV encoding the active enzyme was accompanied by TOP2 deubiquitination, accumulation of TOP2ccs and resistance to Etoposide toxicity. The protective effect of BPLF1 was dependent on the expression of tyrosyl-DNA phosphodiesterase 2 (TDP2) that releases DNA-trapped TOP2 and promotes error-free DNA repair. These findings highlight a previously unrecognized function of BPLF1 in supporting a non-proteolytic pathway for TOP2ccs debulking that favors cell survival and virus production.

The N-terminal domains of the herpesvirus large tegument proteins encode a conserved cysteine protease with ubiquitin- and NEDD8-specific deconjugase activity. Members of the viral enzyme family regulate different aspects of the virus life cycle including virus replication, the assembly of infectious virus particles and the host innate anti-viral response. However, only few substrates have been validated under physiological conditions of expression and very little is known on the mechanisms by which the enzymes contribute to the reprograming of cellular functions that are required for efficient infection and virus production. Cellular type I and type II topoisomerases (TOP1 and TOP2) resolve topological problems that arise during DNA replication and transcription and are therefore essential for herpesvirus replication. We report that the Epstein-Barr virus (EBV) ubiquitin deconjugase BPLF1 selectively regulates the activity of TOP2 in cells treated with the TOP2 poison Etoposide and during productive infection. Using transiently transfected and stable cell lines that express catalytically active or inactive BPLF1, we found that BPLF1 interacts with both TOP2α and TOP2β in co-immunoprecipitation and in vitro pull-down assays and the active enzyme stabilizes TOP2 trapped in TOP2ccs, promoting a shift towards TOP2 SUMOylation. This hinders the activation of DNA-damage responses and reduces the toxicity of Etoposide. The physiological relevance of this finding was validated using pairs of EBV carrying HEK-293T cells and EBV immortalized lymphoblastoid cell lines (LCLs) expressing the wild type or catalytic mutant enzyme. Using knockout LCLs we found that the capacity of BPLF1 to rescue of Etoposide toxicity is dependent on the expression of tyrosyl-DNA phosphodiesterase 2 (TDP2) that releases DNA-trapped TOP2 and promotes error-free DNA repair.

Stress-Induced Epstein-Barr Virus Reactivation

Epstein-Barr virus (EBV) is typically found in a latent, asymptomatic state in immunocompetent individuals. Perturbations of the host immune system can stimulate viral reactivation. Furthermore, there are a myriad of EBV-associated illnesses including various cancers, post-transplant lymphoproliferative disease, and autoimmune conditions. A thorough understanding of this virus, and the interplay between stress and the immune system, is essential to establish effective treatment. This review will provide a summary of the interaction between both psychological and cellular stressors resulting in EBV reactivation. It will examine mechanisms by which EBV establishes and maintains latency and will conclude with a brief overview of treatments targeting EBV.

Recent advancements in our understanding of equid gammaherpesvirus infections

Equid gammaherpesviruses are ubiquitous and widespread in the equine population. Despite their frequent detection, their contribution to immune system modulation and the pathogenesis of several diseases remains unclear. Genetic variability and the combination of equid gammaherpesvirus strains a horse is infected with might be clinically significant. Initial gammaherpesvirus infection occurs in foals peripartum with latency then established in peripheral blood mononuclear cells. A novel EHV-5 study suggests that following inhalation equid gammaherpesviruses might obtain direct access to T and B lymphocytes via the tonsillar crypts to establish latency. EHV-5 is associated with equine multinodular pulmonary fibrosis, however, unlike with EHV-2 there is currently minimal evidence for its role in milder cases of respiratory disease and poor performance. Transmission is presumed to be via the upper respiratory tract with periodic reactivation of the latent virus in adult horses. Stress of transport has been identified as a risk factor for reactivation and shedding of equine gammaherpesviruses. There is currently a lack of evidence for the effectiveness of antiviral drugs in the treatment of equine gammaherpesvirus infections.

An Ancestral Retrovirus Envelope Protein Regulates Persistent Gammaherpesvirus Lifecycles

Human gammaherpesviruses Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV) persist as life-long infections alternating between latency and lytic replication. Human endogenous retroviruses (HERVs), via integration into the host genome, represent genetic remnants of ancient retroviral infections. Both show similar epigenetic silencing while dormant, but can reactivate in response to cell signaling cues or triggers that, for gammaherpesviruses, result in productive lytic replication. Given their co-existence with humans and shared epigenetic silencing, we asked if HERV expression might be linked to lytic activation of human gammaherpesviruses. We found ERVW-1 mRNA, encoding the functional HERV-W envelope protein Syncytin-1, along with other repeat class elements, to be elevated upon lytic activation of EBV. Knockdown/knockout of ERVW-1 reduced lytic activation of EBV and KSHV in response to various lytic cycle triggers. In this regard, reduced expression of immediate early proteins ZEBRA and RTA for EBV and KSHV, respectively, places Syncytin-1's influence on lytic activation mechanistically upstream of the latent-to-lytic switch. Conversely, overexpression of Syncytin-1 enhanced lytic activation of EBV and KSHV in response to lytic triggers, though this was not sufficient to induce lytic activation in the absence of such triggers. Syncytin-1 is expressed in replicating B cell blasts and lymphoma-derived B cell lines where it appears to contribute to cell cycle progression. Together, human gammaherpesviruses and B cells appear to have adapted a dependency on Syncytin-1 that facilitates the ability of EBV and KSHV to activate lytic replication from latency, while promoting viral persistence during latency by contributing to B cell proliferation.

Association between HLA alleles and Epstein-Barr virus Zta-IgA serological status in healthy males from southern China

Background

Nasopharyngeal carcinoma (NPC), an Epstein–Barr virus (EBV) associated cancer, exhibits an extremely high incidence in southern Chinese. Given that human leukocyte antigen (HLA) plays critical roles in antigen presentation and relates to NPC susceptibility, it is speculated that certain HLA variants may affect EBV reactivation, which is a key pathogenic factor of NPC. Therefore, we attempted to identify HLA alleles associated with the indicator of EBV reactivation, Zta‐IgA, in healthy males from NPC endemic area.

Methods

HLA alleles of 1078 healthy males in southern China from the 21‐RCCP study were imputed using genome‐wide single nucleotide polymorphism data. EBV Zta‐IgA in blood samples were measured using an enzyme‐linked immunosorbent assay. Multiple logistic regression analysis was used to evaluate the effect of HLA allele on Zta‐IgA serological status and its potential joint association with smoking. The binding affinity for Zta‐peptide was predicted using NetMHCIIpan 4.0.

Results

HLA‐DRB1*09:01 was found to be associated with a higher risk of Zta‐IgA seropositivity (odds ratio = 1.80, 95% confidence interval = 1.32–2.45; p = 1.82 × 10⁻⁴). Compared with non‐smokers without HLA‐DRB1*09:01, the effect size increased to 2.19‐ and 3.70‐fold for the light and heavy smokers carrying HLA‐DRB1*09:01, respectively. Furthermore, HLA‐DRB1*09:01 showed a stronger binding affinity to Zta peptide than other HLA‐DRB1 alleles.

Conclusions

Our study highlighted the pivotal role of genetic HLA variants in EBV reactivation and the etiology of NPC. Smokers with HLA‐DRB1*09:01 have a significantly higher risk of being Zta‐IgA seropositive, which indicates the necessity of smoking cessation in certain high‐risk populations and also provide clues for further research on the etiology of NPC.

Epstein-Barr virus: Current questions and challenges

Epstein-Barr virus (EBV) infects most people worldwide and persists for life due to complicated interplay between lytic infection and multiple types of latent infections. While usually asymptomatic, EBV is a causative agent in several types of cancer and has a strong association with multiple sclerosis. Exactly how EBV promotes these diseases and why they are rare consequences of infection are incompletely understood. Here I will discuss current ideas on disease induction by EBV, including the importance of lytic protein expression in the context of latent infection as well as the possible importance of specific EBV variants in disease induction.

RNAseq analysis identifies involvement of EBNA2 in PD-L1 induction during Epstein-Barr virus infection of primary B cells

Epstein-Barr virus (EBV) is a causative agent of infectious mononucleosis and several types of malignancy. RNAseq of peripheral blood primary B cell samples infected with wild-type EBV revealed that expression of programmed cell death ligand-1 (PD-L1) is markedly induced by infection. This induction of PD-L1 was alleviated by knockout of the EBNA2 gene, but knockout of LMP1 had little effect. ChIPseq, ChIA-PET, and reporter assays further confirmed that EBNA2-binding sites in the promoter region and at 130 kb downstream of the PD-L1 gene played important roles in PD-L1 induction. Our results indicate that EBV mainly utilizes the EBNA2 gene for induction of PD-L1 and to evade host immunity on infection of primary B cells. Furthermore, pathway analysis revealed that genes involved in the cell cycle, metabolic processes, membrane morphogenesis, and vesicle regulation were induced by EBNA2, and that EBNA2 suppressed genes related to immune signaling.

(-)-Epigallocatechin-3-gallate inhibits EBV lytic replication via targeting LMP1-mediated MAPK signal axes

Epstein–Barr virus (EBV)-encoded latent membrane protein 1 (LMP1) plays an important oncogenic role in the viral latent infection. Recently, increasing evidence indicates that the high expression of LMP1 during EBV lytic cycle is related to the viral lytic replication. However, the mechanism by which LMP1 regulates EBV lytic replication remains unclear. (−)-Epigallocatechin-3-gallate (EGCG) prevents carcinogenesis by directly targeting numerous membrane proteins and effectively inhibits EBV lytic cascade. Here, we demonstrated that LMP1 promotes EBV lytic replication through the downstream signal molecules MAPKs, including ERKs, p38, and JNKs. LMP1 induces the phosphorylation of p53 through MAPKs to enhance the ability of wild-type p53 (wt-p53) to activate expression of BZLF1 gene, while the JNKs/c-Jun signal axis appears to be involved in EBV lytic replication induced by LMP1 in p53 mutant manner. We provided the first evidence that EGCG directly targets the viral membrane LMP1 (K_d = 0.36 μM, n = 1) using fluorescence quenching, isothermal titration calorimetry (ITC) assay, and CNBR-activated Sepharose 4B pull-down affinity chromatography. Furthermore, we revealed that EGCG inhibits EBV lytic replication via suppressing LMP1 and thus blocking the downstream MAPKs/wt-p53 signal axis in AGS-EBV cells and JNKs/c-Jun signal axis in p53 mutant B95.8 cells. Our study, for the first time, reports the binding and inhibitory efficacy of EGCG to the LMP1, which is a key oncoprotein encoded by EBV. These findings suggest the novel function of LMP1 in the regulation of EBV lytic cycle and reveal the new role of EGCG in EBV-associated malignancies through suppressing viral reactivation.

Immune Cell Number, Phenotype, and Function in the Elderly with Sepsis

Sepsis is a form of life-threatening organ dysfunction caused by dysregulated host responses to an infection that can be partly attributed to immune dysfunction. Although sepsis affects patients of all ages, elderly individuals display increased susceptibility and mortality. This is partly due to immunosenescence, a decline in normal immune system function associated with physiological aging that affects almost all cell types in the innate and adaptive immune systems. In elderly patients with sepsis, these alterations in immune cells such as endothelial cells, neutrophils, monocytes, macrophages, natural killer cells, dendritic cells, T lymphocytes, and B lymphocytes, are largely responsible for their poor prognosis and increased mortality. Here, we review recent studies investigating the events affecting both innate and adaptive immune cells in elderly mice and patients with sepsis, including alterations in their number, phenotype, and function, to shed light on possible new therapeutic strategies.

Epstein-Barr Virus and Systemic Autoimmune Diseases

Epstein-Barr Virus (EBV) is an extremely successful human herpes virus, which infects essentially all human beings at some time during their life span. EBV infection and the associated immune response results in production of antibodies (seroconversion), which occurs mainly during the first years of life, but may also happen during adolescence or later in life. Infection of adolescents can result in infectious mononucleosis, an acute serious condition characterized by massive lymphocytosis. Transmission of EBV mainly occurs through saliva but can rarely be spread through semen or blood, e.g. through organ transplantations and blood transfusions. EBV transmission through oral secretions results in infection of epithelial cells of the oropharynx. From the epithelial cells EBV can infect B cells, which are the major reservoir for the virus, but other cell types may also become infected. As a result, EBV can shuttle between different cell types, mainly B cells and epithelial cells. Moreover, since the virus can switch between a latent and a lytic life cycle, EBV has the ability to cause chronic relapsing/reactivating infections. Chronic or recurrent EBV infection of epithelial cells has been linked to systemic lupus erythematosus and Sjögren’s syndrome, whereas chronic/recurrent infection of B cells has been associated with rheumatoid arthritis, multiple sclerosis and other diseases. Accordingly, since EBV can shuttle between epithelial cells and B cells, the systemic autoimmune diseases often occur as overlapping syndromes with symptoms and characteristic autoantibodies (e.g. antinuclear antibodies and rheumatoid factors) reflecting epithelial and/or B cell infection.

Epstein-Barr Virus and Multiple Sclerosis

Multiple sclerosis (MS) is a neurologic disease affecting myelinated nerves in the central nervous system (CNS). The disease often debuts as a clinically isolated syndrome, e.g., optic neuritis (ON), which later develops into relapsing-remitting (RR) MS, with temporal attacks or primary progressive (PP) MS. Characteristic features of MS are inflammatory foci in the CNS and intrathecal synthesis of immunoglobulins (Igs), measured as an IgG index, oligoclonal bands (OCBs), or specific antibody indexes. Major predisposing factors for MS are certain tissue types (e.g., HLA DRB1*15:01), vitamin D deficiency, smoking, obesity, and infection with Epstein-Barr virus (EBV). Many of the clinical signs of MS described above can be explained by chronic/recurrent EBV infection and current models of EBV involvement suggest that RRMS may be caused by repeated entry of EBV-transformed B cells to the CNS in connection with attacks, while PPMS may be caused by more chronic activity of EBV-transformed B cells in the CNS. In line with the model of EBV's role in MS, new treatments based on monoclonal antibodies (MAbs) targeting B cells have shown good efficacy in clinical trials both for RRMS and PPMS, while MAbs inhibiting B cell mobilization and entry to the CNS have shown efficacy in RRMS. Thus, these agents, which are now first line therapy in many patients, may be hypothesized to function by counteracting a chronic EBV infection.

Epstein-Barr virus peptides derived from latent cycle proteins alter NKG2A + NK cell effector function

Natural killer (NK) cells control viral infection through the interaction between inhibitory receptors and human leukocyte antigen (HLA) ligands and bound peptide. NK cells expressing the inhibitory receptor NKG2A/CD94 recognize and respond to autologous B cells latently infected with Epstein-Barr virus (EBV). The mechanism is not yet understood, thus we investigated peptides derived from seven latent proteins of EBV in the interaction of NKG2A and its ligand HLA-E. Functional analysis demonstrated that EBV peptides can bind to HLA-E and block inhibition of NK cell effector function. Moreover, analysis of DNA from 79 subjects showed sequence variations in the latent protein, LMP1, which alters NK responses to EBV. We provide evidence that peptides derived from EBV latent cycle proteins can impair the recognition of NKG2A despite being presented by HLA-E, resulting in NK cell activation.

Epstein-Barr Virus Mediated Signaling in Nasopharyngeal Carcinoma Carcinogenesis

Simple Summary

Epstein-Barr virus (EBV) infection is known to contribute in nasopharyngeal carcinoma (NPC) carcinogenesis. The oncogenic roles of the EBV proteins and non-coding RNAs in NPC are becoming evident with the aid of current advances in genome-wide and in-depth molecular analyses. This current work provides a comprehensive overview, which covers recent understandings of the pathogenic role of EBV infection in NPC. Perspectives on molecular mechanisms, which are involved in the pathogenesis of NPC, focusing on the connection between EBV and NPC cells and the corresponding signaling pathways are highlighted. Cancer hallmarks associated with EBV in NPC development are also discussed herein.

Abstract

Nasopharyngeal carcinoma (NPC) is one of the most common tumors occurring in China and Southeast Asia. Etiology of NPC seems to be complex and involves many determinants, one of which is Epstein-Barr virus (EBV) infection. Although evidence demonstrates that EBV infection plays a key role in NPC carcinogenesis, the exact relationship between EBV and dysregulation of signaling pathways in NPC needs to be clarified. This review focuses on the interplay between EBV and NPC cells and the corresponding signaling pathways, which are modulated by EBV oncoproteins and non-coding RNAs. These altered signaling pathways could be critical for the initiation and progression of NPC.

Evaluation of Cyprinid Herpesvirus 2 Latency and Reactivation in Carassius gibel

Cyprinid herpesvirus 2 (CyHV-2, species Cyprinid herpesvirus 2) causes severe mortality in ornamental goldfish, crucian carp (Carassius auratus), and gibel carp (Carassius gibelio). It has been shown that the genomic DNA of CyHV-2 could be detected in subclinical fish, which implied that CyHV-2 could establish persistent infection. In this study, the latency of CyHV-2 was investigated in the survival fish after primary infection. CyHV-2 genomic DNA was detected in multiple tissues of acute infection samples; however, detection of CyHV-2 DNA was significantly reduced in fish recovered from the primary infection on day 300 postinfection. No active viral gene transcription, such as DNA polymerase and ORF99, was detected in recovered fish. Following temperature stress, an increase of CyHV-2 DNA copy numbers and gene transcription were observed in tissues examined, which suggests that CyHV-2 was reactivated under stress. In addition, a cell line (GCBLat1) derived from the brain tissue from CyHV-2-exposed fish harbored CyHV-2 genome but did not produce infectious virions under normal culture conditions. However, CyHV-2 replication and viral gene transcription occurred when GCBLat1 cells were treated with trichostatin A (TSA) or phorbol 12-myristate 13-acetate (TPA). It suggests CyHV-2 can remain latent in vitro and can reactivate under stress condition.

Epstein-Barr Virus Infection of Oral Squamous Cells

The Epstein-Barr virus (EBV) is a human herpesvirus associated with various cancers. The number of reports that describe infection of EBV in oral squamous carcinoma cells is increasing. However, there is no available in vitro model to study the possible role of EBV in the development of oral squamous cell carcinoma. Herein, we report establishment of a latent EBV infection of well-differentiated HSC1 cells and poorly differentiated SCC25 cells. Viral copy numbers per cell in EBV-infected HSC1 and SCC25 cells are 2 and 5, respectively. Although the EBV copy number was small, spontaneous viral replication was observed in EBV-infected HSC1 cells. Contrarily, infectious viral production was not observed in EBV-infected SCC25 cells, despite containing larger number of EBV genomes. Chemical activation of cells induced expression of viral lytic BZLF1 gene in EBV-infected HSC1 cells, but not in EBV-infected SCC25 cells. EBV infection activated proliferation and migration of HSC1 cells. However, EBV-infection activated migration but not proliferation in SCC25 cells. In conclusion, EBV can infect squamous cells and establish latent infection, but promotion of cell proliferation and of lytic EBV replication may vary depending on stages of cell differentiation. Our model can be used to study the role of EBV in the development of EBV-associated oral squamous cell carcinoma.

Viral miRNAs as Active Players and Participants in Tumorigenesis

The theory that viruses play a role in human cancers is now supported by scientific evidence. In fact, around 12% of human cancers, a leading cause of morbidity and mortality in some regions, are attributed to viral infections. However, the molecular mechanism remains complex to decipher. In recent decades, the uncovering of cellular miRNAs, with their invaluable potential as diagnostic and prognostic biomarkers, has increased the number of studies being conducted regarding human cancer diagnosis. Viruses develop clever mechanisms to succeed in the maintenance of the viral life cycle, and some viruses, especially herpesviruses, encode for miRNA, v-miRNAs. Through this viral miRNA, the viruses are able to manipulate cellular and viral gene expression, driving carcinogenesis and escaping the host innate or adaptive immune system. In this review, we have discussed the main viral miRNAs and virally influenced cellular pathways, and their capability to drive carcinogenesis.

Circulating Antibodies against Epstein-Barr Virus (EBV) and p53 in EBV-Positive and -Negative Gastric Cancer

BACKGROUND

Epstein-Barr virus (EBV)-positive gastric cancers have clinicopathologic differences from EBV-negative tumors and lack TP53 mutation. Serologic profiles may inform viral contribution to carcinogenesis.

METHODS

We compared humoral responses of EBV-positive (n = 67) and EBV-negative (n = 137) patients with gastric cancer from the International EBV-Gastric Cancer Consortium. Serum antibodies against four EBV proteins, nuclear (EBNA), viral capsid (VCA), early-diffuse (EA-D), and Zta replication activator (ZEBRA), and to p53 were assessed by multiplex assays. OR of antibody level tertiles (T1-T3) were adjusted by logistic regression. We also conducted a meta-analysis of reported anti-p53 seropositivity in gastric cancer.

RESULTS

Consistent with EBV's ubiquity, 99% of patients were seropositive for anti-EBNA and 98% for anti-VCA, without difference by tumor EBV status. Seropositivity varied between patients with EBV-positive and EBV-negative tumors for anti-EA-D (97% vs. 67%, respectively, P < 0.001) and anti-ZEBRA (97% vs. 85%, respectively, P = 0.009). Adjusted ORs (vs. T1) for patients with EBV-positive versus EBV-negative tumors were significantly elevated for higher antibodies against EBNA (2.6 for T2 and 13 for T3), VCA (1.8 for T2 and 2.4 for T3), EA-D (6.0 for T2 and 44 for T3), and ZEBRA (4.6 for T2 and 12 for T3). Antibodies to p53 were inversely associated with EBV positivity (3% vs. 15%; adjusted OR = 0.16, P = 0.021). Anti-p53 prevalence from the literature was 15%.

CONCLUSIONS

These serologic patterns suggest viral reactivation in EBV-positive cancers and identify variation of p53 seropositivity by subtype.

IMPACT

Anti-EBV and anti-p53 antibodies are differentially associated with tumor EBV positivity. Serology may identify EBV-positive gastric cancer for targeted therapies.

Identifying the Cellular Interactome of Epstein-Barr Virus Lytic Regulator Zta Reveals Cellular Targets Contributing to Viral Replication

The human gammaherpesvirus Epstein-Barr virus (EBV) (human herpesvirus 4 [HHV4]) infects most adults and is an important contributor to the development of many types of lymphoid and epithelial cancers. Essential contributions of viral genes to viral replication are known, but the potential contributions of cell genes are less well delineated. A key player is the viral protein Zta (BZLF1, ZEBRA, or Z). This sequence-specific DNA-binding protein can disrupt EBV latency by driving the transcription of target genes and by interacting with the EBV lytic origin of replication. Here, we used an unbiased proteomics approach to identify the Zta-interactome in cells derived from Burkitt's lymphoma. Isolating Zta and associated proteins from Burkitt's lymphoma cells undergoing EBV replication, followed by tandem mass tag (TMT) mass spectrometry, resulted in the identification of 39 viral and cellular proteins within the Zta interactome. An association of Zta with the cellular protein NFATc2 was validated in independent experiments. Furthermore, the ability of Zta to attenuate the activity of an NFAT-dependent promoter was shown, which suggests a functional consequence for the association. The expression of Zta is itself regulated through NFAT activity, suggesting that Zta may contribute to a feedback loop that would limit its own expression, thus aiding viral replication by preventing the known toxic effects of Zta overexpression.IMPORTANCE Epstein-Barr virus infects most people across the world and causes several kinds of cancer. Zta is an important viral protein that makes the virus replicate by binding to its DNA and turning on the expression of some genes. We used a sensitive, unbiased approach to isolate and identify viral and cellular proteins that physically interact with Zta. This revealed 39 viral and cellular proteins. We found that one protein, termed NFATc2, was already known to be important for a very early step in viral replication. We identify that once this step has occurred, Zta reduces the effectiveness of NFATc2, and we suggest that this is important to prevent cells from dying before viral replication is complete and the mature virus is released from the cells.

[Dynamic changes of cellular environment during Epstein-Barr virus productive replication]

Productive (lytic) replication of DNA viruses elicits host cell DNA damage responses, which cause both beneficial and detrimental effects on viral replication. Viruses utilize them and selectively cancel the 'noisy' downstream signaling pathways, leading to maintain high S-phase CDK activities required for viral replication. To achieve this fine tuning of cellular environment, herpesviruses encode many (>70) genes in their genome, which are expressed in a strictly regulated temporal cascade (immediate-early, early, and late). Here, I introduce and discuss how Epstein-Barr virus, an oncogenic herpesvirus, hijacks the cellular environment and adapt it for the progeny production.

Epstein-Barr Virus BBRF2 Is Required for Maximum Infectivity

Epstein-Barr virus (EBV) is a member of the gammaherpesvirinae, which causes infectious mononucleosis and several types of cancer. BBRF2 is an uncharacterized gene of EBV and is expressed during the lytic phase. To evaluate its function, BBRF2-knockout EBV was prepared using bacterial artificial chromosome (BAC) technology and the CRISPR/Cas9 system. Although viral gene expression, DNA synthesis, and progeny secretion were not affected, the infectivity of progeny viruses was significantly reduced by the disruption of BBRF2. When expressed alone, BBRF2 protein localized to the nucleus and cytoplasm, while the coexpression of an interacting partner, BSRF1, resulted in its relocalization to the cytoplasm. Interestingly, the coexpression of BBRF2 protected BSRF1 from proteasome/ubiquitin-dependent degradation. Therefore, BBRF2, together with BSRF1, augments viral infectivity.

Antitumor activity of cyclin-dependent kinase inhibitor alsterpaullone in Epstein-Barr virus-associated lymphoproliferative disorders

Epstein‐Barr virus (EBV) is a well‐established tumor virus that has been implicated in a wide range of immunodeficiency‐associated lymphoproliferative disorders (LPDs). Although rituximab, a CD20 mAb, has proven effective against EBV‐associated LPDs, prolonged use of this drug could lead to resistance due to the selective expansion of CD20⁻ cells. We have previously shown that cyclin‐dependent kinase (CDK) inhibitors are able to specifically suppress the expression of viral late genes, particularly those encoding structural proteins; however, the therapeutic effect of CDK inhibitors against EBV‐associated LPDs is not clear. In this study, we examined whether CDK inhibitors confer a therapeutic effect against LPDs in vivo. Treatment with alsterpaullone, an inhibitor of the CDK2 complex, resulted in a survival benefit and suppressed tumor invasion in a mouse model of LPDs. Inhibition of CDK efficiently induced G₁ cell cycle arrest and apoptosis in EBV‐positive B cells. These results suggest that alsterpaullone suppresses cell cycle progression, resulting in the antitumor effect observed in vivo.

Epstein-Barr Virus BALF0 and BALF1 Modulate Autophagy

Autophagy is an essential catabolic process that degrades cytoplasmic components within the lysosome, therefore ensuring cell survival and homeostasis. A growing number of viruses, including members of the Herpesviridae family, have been shown to manipulate autophagy to facilitate their persistence or optimize their replication. Previous works showed that the Epstein–Barr virus (EBV), a human transforming gammaherpesvirus, hijacked autophagy during the lytic phase of its cycle, possibly to favor the formation of viral particles. However, the viral proteins that are responsible for an EBV-mediated subversion of the autophagy pathways remain to be characterized. Here we provide the first evidence that the BALF0/1 open reading frame encodes for two conserved proteins of the Bcl-2 family, BALF0 and BALF1, that are expressed during the early phase of the lytic cycle and can modulate autophagy. A putative LC3-interacting region (LIR) has been identified that is required both for BALF1 colocalization with autophagosomes and for its ability to stimulate autophagy.

New Viral Facets in Oral Diseases: The EBV Paradox

The oral cavity contributes to overall health, psychosocial well-being and quality of human life. Oral inflammatory diseases represent a major global health problem with significant social and economic impact. The development of effective therapies, therefore, requires deeper insights into the etiopathogenesis of oral diseases. Epstein–Barr virus (EBV) infection results in a life-long persistence of the virus in the host and has been associated with numerous oral inflammatory diseases including oral lichen planus (OLP), periodontal disease and Sjogren’s syndrome (SS). There is considerable evidence that the EBV infection is a strong risk factor for the development and progression of these conditions, but is EBV a true pathogen? This long-standing EBV paradox yet needs to be solved. This review discusses novel viral aspects of the etiopathogenesis of non-tumorigenic diseases in the oral cavity, in particular, the contribution of EBV in OLP, periodontitis and SS, the tropism of EBV infection, the major players involved in the etiopathogenic mechanisms and emerging contribution of EBV-pathogenic bacteria bidirectional interaction. It also proposes the involvement of EBV-infected plasma cells in the development and progression of oral inflammatory diseases. A new direction for preventing and treating these conditions may focus on controlling pathogenic EBV with anti-herpetic drugs.

Molecular Interactions between Pathogens and the Circadian Clock

The daily periodicity of the Earth's rotation around the Sun, referred to as circadian (Latin "circa" = about, and "diem" = day), is also mirrored in the behavior and metabolism of living beings. The discovery that dedicated cellular genes control various aspects of this periodicity has led to studies of the molecular mechanism of the circadian response at the cellular level. It is now established that the circadian genes impact on a large network of hormonal, metabolic, and immunological pathways, affecting multiple aspects of biology. Recent studies have extended the role of the circadian system to the regulation of infection, host-pathogen interaction, and the resultant disease outcome. This critical review summarizes our current knowledge of circadian-pathogen interaction at both systemic and cellular levels, but with emphasis on the molecular aspects of the regulation. Wherever applicable, the potential of a direct interaction between circadian factors and pathogenic macromolecules is also explored. Finally, this review offers new directions and guidelines for future research in this area, which should facilitate progress.