Activation and repression of Epstein-Barr Virus and Kaposi's sarcoma-associated herpesvirus lytic cycles by short- and medium-chain fatty acids

Transcriptome analysis of Burkitt lymphoma cells treated with anti-convulsant drugs that are inhibitors of Epstein-Barr virus lytic reactivation

Herpesviruses have two distinct life cycle stages, latency and lytic replication. Epstein-Barr virus (EBV), a gamma-herpesvirus, establishes latency in vivo and in cultured cells. Cell lines harboring latent EBV can be induced into the lytic cycle by treatment with chemical inducing agents. In the Burkitt lymphoma cell line HH514-16 the viral lytic cycle is triggered by butyrate, a histone deacetylase (HDAC) inhibitor. Butyrate also alters expression of thousands of cellular genes. However, valproic acid (VPA), another HDAC inhibitor with global effects on cellular gene expression blocks EBV lytic gene expression in Burkitt lymphoma cell lines. Valpromide (VPM), an amide derivative of VPA, is not an HDAC inhibitor, but like VPA blocks induction of the EBV lytic cycle. VPA and VPM are the first examples of inhibitors of initial stages of lytic reactivation. We compared the effects of VPA and VPM, alone and in combination with butyrate, on host cellular gene expression using whole transcriptome analysis (RNA-seq). Gene expression was analyzed 6 h after addition of the compounds, a time before the first EBV lytic transcripts are detected. The results address two alternative, yet possibly complementary, mechanisms for regulation of EBV lytic reactivation. First, cellular genes that were up- or down-regulated by butyrate, but no longer altered in the presence of VPA or VPM, represent genes that correlated with EBV lytic reactivation. Second, genes regulated similarly by VPA and VPM in the absence and presence of butyrate are candidates for suppressors of EBV reactivation. Two genes upregulated by the lytic cycle inhibitors, CHAC1 and SLC7A11, are related to redox status and the iron-dependent cell death pathway ferroptosis. This study generates new hypotheses for control of the latency to lytic cycle switch of EBV and provides the first description of effects of the anti-convulsant drug VPM on global human cellular gene expression.

Impact of the Microbiota on Viral Infections

The mammalian gastrointestinal tract (GIT) hosts a diverse and highly active microbiota composed of bacteria, eukaryotes, archaea, and viruses. Studies of the GIT microbiota date back more than a century, although modern techniques, including mouse models, sequencing technology, and novel therapeutics in humans, have been foundational to our understanding of the roles of commensal microbes in health and disease. Here, we review the impacts of the GIT microbiota on viral infection, both within the GIT and systemically. GIT-associated microbes and their metabolites alter the course of viral infection through a variety of mechanisms, including direct interactions with virions, alteration of the GIT landscape, and extensive regulation of innate and adaptive immunity. Mechanistic understanding of the full breadth of interactions between the GIT microbiota and the host is still lacking in many ways but will be vital for the development of novel therapeutics for viral and nonviral diseases alike.

Role of the Microbiota in Skin Neoplasms: New Therapeutic Horizons

The skin and the gut are regularly colonized by a variety of microorganisms capable of interacting with the immune system through their metabolites and influencing the balance between immune tolerance and inflammation. Alterations in the composition and diversity of the skin microbiota have been described in various cutaneous diseases, including skin cancer, and the actual function of the human microbiota in skin carcinogenesis, such as in progression and metastasis, is currently an active area of research. The role of Human Papilloma Virus (HPV) in the pathogenesis of squamous cell carcinoma is well consolidated, especially in chronically immunosuppressed patients. Furthermore, an imbalance between Staphylococcus spp., such as Staphylococcus epidermidis and aureus, has been found to be strongly related to the progression from actinic keratosis to squamous cell carcinoma and differently associated with various stages of the diseases in cutaneous T-cell lymphoma patients. Also, in melanoma patients, differences in microbiota have been related to dissimilar disease course and prognosis and may affect the effectiveness and tolerability of immune checkpoint inhibitors, which currently represent one of the best chances of a cure. From this point of view, acting on microbiota can be considered a possible therapeutic option for patients with advanced skin cancers, even if several issues are still open.

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.

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.

Epigenetic Reprogramming of Kaposi's Sarcoma-Associated Herpesvirus during Hypoxic Reactivation

The biphasic life cycle (latent and lytic) of Kaposi's sarcoma-associated Herpesvirus (KSHV) is regulated by epigenetic modification of its genome and its associated histone proteins. The temporal events driving epigenetic reprogramming of the KSHV genome on initial infection to establish latency has been well studied, but the reversal of these epigenetic changes during lytic replication, especially under physiological conditions such as hypoxia, has not been explored. In this study, we investigated epigenetic reprogramming of the KSHV genome during hypoxic reactivation. Hypoxia induced extensive enrichment of both transcriptional activators and repressors on the KSHV genome through H3K4Me3, H3K9Me3, and H3K27Me3, as well as histone acetylation (H3Ac) modifications. In contrast to uniform quantitative enrichment with modified histones, a distinct pattern of RTA and LANA enrichment was observed on the KSHV genome. The enrichment of modified histone proteins was due to their overall higher expression levels, which was exclusively seen in KSHV-positive cells. Multiple KSHV-encoded factors such as LANA, RTA, and vGPCR are involved in the upregulation of these modified histones. Analysis of ChIP-sequencing for the initiator DNA polymerase (DNAPol1α) combined with single molecule analysis of replicated DNA (SMARD) demonstrated the involvement of specific KSHV genomic regions that initiate replication in hypoxia.

Epstein-Barr virus infection, B-cell dysfunction and other risk factors converge in gut-associated lymphoid tissue to drive the immunopathogenesis of multiple sclerosis: a hypothesis

Multiple sclerosis is associated with Epstein-Barr virus (EBV) infection, B-cell dysfunction, gut dysbiosis, and environmental and genetic risk factors, including female sex. A disease model incorporating all these factors remains elusive. Here, we hypothesise that EBV-infected memory B cells (MBCs) migrate to gut-associated lymphoid tissue (GALT) through EBV-induced expression of LPAM-1, where they are subsequently activated by gut microbes and/or their products resulting in EBV reactivation and compartmentalised anti-EBV immune responses. These responses involve marginal zone (MZ) B cells that activate CD4⁺ T-cell responses, via HLA-DRB1, which promote downstream B-cell differentiation towards CD11c⁺/T-bet⁺ MBCs, as well as conventional MBCs. Intrinsic expression of low-affinity B-cell receptors (BCRs) by MZ B cells and CD11c⁺/T-bet⁺ MBCs promotes polyreactive BCR/antibody responses against EBV proteins (e.g. EBNA-1) that cross-react with central nervous system (CNS) autoantigens (e.g. GlialCAM). EBV protein/autoantigen-specific CD11c⁺/T-bet⁺ MBCs migrate to the meningeal immune system and CNS, facilitated by their expression of CXCR3, and induce cytotoxic CD8⁺ T-cell responses against CNS autoantigens amplified by BAFF, released from EBV-infected MBCs. An increased abundance of circulating IgA⁺ MBCs, observed in MS patients, might also reflect GALT-derived immune responses, including disease-enhancing IgA antibody responses against EBV and gut microbiota-specific regulatory IgA⁺ plasma cells. Female sex increases MZ B-cell and CD11c⁺/T-bet⁺ MBC activity while environmental risk factors affect gut dysbiosis. Thus, EBV infection, B-cell dysfunction and other risk factors converge in GALT to generate aberrant B-cell responses that drive pathogenic T-cell responses in the CNS.

Cytomegalovirus infection disrupts the influence of short-chain fatty acid producers on Treg/Th17 balance

BACKGROUND

Both the gut microbiota and chronic viral infections have profound effects on host immunity, but interactions between these influences have been only superficially explored. Cytomegalovirus (CMV), for example, infects approximately 80% of people globally and drives significant changes in immune cells. Similarly, certain gut-resident bacteria affect T-cell development in mice and nonhuman primates. It is unknown if changes imposed by CMV on the intestinal microbiome contribute to immunologic effects of the infection.

RESULTS

We show that rhesus cytomegalovirus (RhCMV) infection is associated with specific differences in gut microbiota composition, including decreased abundance of Firmicutes, and that the extent of microbial change was associated with immunologic changes including the proliferation, differentiation, and cytokine production of CD8+ T cells. Furthermore, RhCMV infection disrupted the relationship between short-chain fatty acid producers and Treg/Th17 balance observed in seronegative animals, showing that some immunologic effects of CMV are due to disruption of previously existing host-microbe relationships.

CONCLUSIONS

Gut microbes have an important influence on health and disease. Diet is known to shape the microbiota, but the influence of concomitant chronic viral infections is unclear. We found that CMV influences gut microbiota composition to an extent that is correlated with immunologic changes in the host. Additionally, pre-existing correlations between immunophenotypes and gut microbes can be subverted by CMV infection. Immunologic effects of CMV infection on the host may therefore be mediated by two different mechanisms involving gut microbiota. Video Abstract.

Fatty acids role in multiple sclerosis as "metabokines"

Multiple sclerosis (MS), as an autoimmune neurological disease with both genetic and environmental contribution, still lacks effective treatment options among progressive patients, highlighting the need to re-evaluate disease innate properties in search for novel therapeutic targets. Fatty acids (FA) and MS bear an interesting intimate connection. FA and FA metabolism are highly associated with autoimmunity, as the diet-derived circulatory and tissue-resident FAs level and composition can modulate immune cells polarization, differentiation and function, suggesting their broad regulatory role as “metabokines”. In addition, FAs are indeed protective factors for blood–brain barrier integrity, crucial contributors of central nervous system (CNS) chronic inflammation and progressive degeneration, as well as important materials for remyelination. The remaining area of ambiguity requires further exploration into this arena to validate the existed phenomenon, develop novel therapies, and confirm the safety and efficacy of therapeutic intervention targeting FA metabolism.

Environmental factors for Epstein-Barr virus reactivation in a high-risk area of nasopharyngeal carcinoma: a population-based study

Background

Epstein-Barr virus (EBV) reactivation from latent to lytic infection has been considered as a key step in nasopharyngeal carcinoma oncogenesis. However, epidemiological evidence regarding environmental risk factors for EBV reactivation on a population level remains largely lacking.

Methods

We enrolled 1916 randomly selected adults from the general population of Guangdong and Guangxi, China, from 2010 to 2014. Information on environmental factors was collected via a structured interview. Serum immunoglobulin A antibodies against EBV viral capsid antigen and nuclear antigen 1 were measured by enzyme-linked immunosorbent assay to evaluate EBV reactivation status. We used logistic regression to calculate odds ratios (ORs) with 95% confidence intervals (CIs) for the associations of EBV reactivation with various environmental factors.

Results

No associations were observed between EBV reactivation and extensive environmental factors, including alcohol or tea drinking, a history of chronic ear/nose/throat diseases, use of medications or herbs, consumption of salted fish or preserved foods, oral hygiene, sibship structure, and various residential and occupational exposures. Only cigarette smoking was associated with EBV reactivation (current smokers vs never smokers; OR = 1.37; 95% CI = 1.02–1.83), with positive exposure-response trends with increasing intensity, duration, and pack-years of smoking.

Conclusions

Consistent with previous studies, we found an association between cigarette smoking and EBV reactivation. Other examined exposures were not associated with EBV reactivation. These null results could suggest either more complex interactions between exposures and EBV reactivation or a predominant role of host and/or viral genetic variation.

Bacterial-Viral Interactions in Human Orodigestive and Female Genital Tract Cancers: A Summary of Epidemiologic and Laboratory Evidence

Infectious agents, including viruses, bacteria, fungi, and parasites, have been linked to pathogenesis of human cancers, whereas viruses and bacteria account for more than 99% of infection associated cancers. The human microbiome consists of not only bacteria, but also viruses and fungi. The microbiome co-residing in specific anatomic niches may modulate oncologic potentials of infectious agents in carcinogenesis. In this review, we focused on interactions between viruses and bacteria for cancers arising from the orodigestive tract and the female genital tract. We examined the interactions of these two different biological entities in the context of human carcinogenesis in the following three fashions: (1) direct interactions, (2) indirect interactions, and (3) no interaction between the two groups, but both acting on the same host carcinogenic pathways, yielding synergistic or additive effects in human cancers, e.g., head and neck cancer, liver cancer, colon cancer, gastric cancer, and cervical cancer. We discuss the progress in the current literature and summarize the mechanisms of host-viral-bacterial interactions in various human cancers. Our goal was to evaluate existing evidence and identify gaps in the knowledge for future directions in infection and cancer.

Cancer Microbiology

Microbes play important roles in cancer from direct carcinogenic effects to their use in treatment. Cancers caused by microorganisms account for approximately 15% of cancers, mostly in low- and middle-income countries. Unique features of infectious carcinogens include their transmissibility, mutability, and specific immune interactions, which provide challenges and opportunities for cancer prevention and treatment. For these agents, infection control through exposure reduction, antivirals, antibiotics, and vaccines is cancer control. In addition, developing evidence suggests that microorganisms including the human microbiome can indirectly modulate cancer formation and influence the effectiveness and toxicity of cancer treatments. Finally, microorganisms themselves can be used to prevent or treat cancer. The convergence of these factors signals the emergence of a new field, Cancer Microbiology. Recognition of Cancer Microbiology will spur research, stimulate cross-disciplinary training, inform drug development, and improve public health.

Circadian Rhythm Modulation of Microbes During Health and Infection

Circadian rhythms, referring to 24-h daily oscillations in biological and physiological processes, can significantly regulate host immunity to pathogens, as well as commensals, resulting in altered susceptibility to disease development. Furthermore, vaccination responses to microbes have also shown time-of-day-dependent changes in the magnitude of protective immune responses elicited in the host. Thus, understanding host circadian rhythm effects on both gut bacteria and viruses during infection is important to minimize adverse effects on health and identify optimal times for therapeutic administration to maximize therapeutic success. In this review, we summarize the circadian modulations of gut bacteria, viruses and their interactions, both in health and during infection. We also discuss the importance of chronotherapy (i.e., time-specific therapy) as a plausible therapeutic administration strategy to enhance beneficial therapeutic responses.

The Gastrointestinal Microbiota of the Common Marmoset (Callithrix jacchus)

The microbiota is heavily involved in both health and disease pathogenesis, but defining a normal, healthy microbiota in the common marmoset has been challenging. The aim of this review was to systematically review recent literature involving the gastrointestinal microbiome of common marmosets in health and disease. Twelve sources were included in this review. The gut microbiome composition was reviewed across institutions worldwide, and taxonomic shifts between healthy individuals were described. Unlike the human gut microbiome, which is dominated by Firmicutes and Bacteroidetes, the marmoset gut microbiome shows great plasticity across institutions, with 5 different phyla described as dominant in different healthy cohorts. Genera shared across institutions include Anaerobiospirillum, Bacteroides, Bifidobacterium, Collinsella, Fusobacterium, Megamonas, Megasphaera, Phascolarctobacterium, and Prevotella. Shifts in the abundance of Prevotella or Bifidobacterium or invasion by pathogens like Clostridium perfringens may be associated with disease. Changes in microbial composition have been described in healthy and diseased marmosets, but factors influencing the severe changes in microbial composition have not been established. Multi-institutional, prospective, and longitudinal studies that utilize multiple testing methodologies are required to determine sources of variability in the reporting of marmoset microbiomes. Furthermore, methods of microbial manipulation, whether by diet, enrichment, fecal microbiome transplantation, etc, need to be established to modulate and maintain robust and resilient microbiome communities in marmoset colonies and reduce the incidence of idiopathic gastrointestinal disease.

Pseudomonas aeruginosa Stimulates Inflammation and Enhances Kaposi's Sarcoma Herpesvirus-Induced Cell Proliferation and Cellular Transformation through both Lipopolysaccharide and Flagellin

Inflammation triggered by innate immunity promotes carcinogenesis in cancer. Kaposi's sarcoma (KS), a hyperproliferative and inflammatory tumor caused by Kaposi's sarcoma-associated herpesvirus (KSHV) infection, is the most common cancer in AIDS patients. KSHV infection sensitizes cells to pathogen-associated molecular patterns (PAMPs). We examined the role of Pseudomonas aeruginosa, an opportunistic bacterium that can affect AIDS patients, in inflammation and cell proliferation of KSHV-transformed cells. P. aeruginosa stimulation increased cell proliferation and efficiency of colony formation in soft agar of KSHV-transformed rat primary mesenchymal precursor (KMM) cells but had no significant effect on the untransformed (MM) cells. P. aeruginosa stimulation also increased cell proliferation of KSHV-infected human B cells, BJAB, but not the uninfected cells. Mechanistically, P. aeruginosa stimulation resulted in increased inflammatory cytokines and activation of p38, ERK1/2, and JNK mitogen-activated protein kinase (MAPK) pathways in KMM cells while having no obvious effect on MM cells. P. aeruginosa induction of inflammation and MAPKs was observed with and without inhibition of the Toll-like receptor 4 (TLR4) pathway, while a flagellin-deleted mutant of P. aeruginosa required a functional TLR4 pathway to induce inflammation and MAPKs. Furthermore, treatment with either lipopolysaccharide (LPS) or flagellin alone was sufficient to induce inflammatory cytokines, activate MAPKs, and increase cell proliferation and efficiency of colony formation in soft agar of KMM cells. These results demonstrate that both LPS and flagellin are PAMPs that contribute to P. aeruginosa induction of inflammation in KSHV-transformed cells. Because AIDS-KS patients are susceptible to P. aeruginosa infection, our work highlights the preventive and therapeutic potential of targeting P. aeruginosa infection in these patients.IMPORTANCE Kaposi's sarcoma (KS), caused by infection with Kaposi's sarcoma-associated herpesvirus (KSHV), is one of the most common cancers in AIDS patients. KS is a highly inflammatory tumor, but how KSHV infection induces inflammation remains unclear. We have previously shown that KSHV infection upregulates Toll-like receptor 4 (TLR4), sensitizing cells to lipopolysaccharide (LPS) and Escherichia coli In the current study, we examined the role of Pseudomonas aeruginosa, an opportunistic bacterium that can affect AIDS patients, in inflammation and cell proliferation of KSHV-transformed cells. P. aeruginosa stimulation increased cell proliferation, inflammatory cytokines, and activation of growth and survival pathways in KSHV-transformed cells through two pathogen-associated molecular patterns, LPS and flagellin. Because AIDS-KS patients are susceptible to P. aeruginosa infection, our work highlights the preventive and therapeutic potential of targeting P. aeruginosa infection in these patients.

Herpesviral Latency-Common Themes

Latency establishment is the hallmark feature of herpesviruses, a group of viruses, of which nine are known to infect humans. They have co-evolved alongside their hosts, and mastered manipulation of cellular pathways and tweaking various processes to their advantage. As a result, they are very well adapted to persistence. The members of the three subfamilies belonging to the family Herpesviridae differ with regard to cell tropism, target cells for the latent reservoir, and characteristics of the infection. The mechanisms governing the latent state also seem quite different. Our knowledge about latency is most complete for the gammaherpesviruses due to previously missing adequate latency models for the alpha and beta-herpesviruses. Nevertheless, with advances in cell biology and the availability of appropriate cell-culture and animal models, the common features of the latency in the different subfamilies began to emerge. Three criteria have been set forth to define latency and differentiate it from persistent or abortive infection: 1) persistence of the viral genome, 2) limited viral gene expression with no viral particle production, and 3) the ability to reactivate to a lytic cycle. This review discusses these criteria for each of the subfamilies and highlights the common strategies adopted by herpesviruses to establish latency.

Signatures of oral microbiome in HIV-infected individuals with oral Kaposi's sarcoma and cell-associated KSHV DNA

Infection by Kaposi's sarcoma-associated herpesvirus (KSHV) is necessary for the development of Kaposi's sarcoma (KS), which most often develops in HIV-infected individuals. KS frequently has oral manifestations and KSHV DNA can be detected in oral cells. Numerous types of cancer are associated with the alteration of microbiome including bacteria and virus. We hypothesize that oral bacterial microbiota affects or is affected by oral KS and the presence of oral cell-associated KSHV DNA. In this study, oral and blood specimens were collected from a cohort of HIV/KSHV-coinfected individuals all previously diagnosed with KS, and were classified as having oral KS with any oral cell-associated KSHV DNA status (O-KS, n = 9), no oral KS but with oral cell-associated KSHV DNA (O-KSHV, n = 10), or with neither oral KS nor oral cell-associated KSHV DNA (No KSHV, n = 10). We sequenced the hypervariable V1-V2 region of the 16S rRNA gene present in oral cell-associated DNA by next generation sequencing. The diversity, richness, relative abundance of operational taxonomic units (OTUs) and taxonomic composition of oral microbiota were analyzed and compared across the 3 studied groups. We found impoverishment of oral microbial diversity and enrichment of specific microbiota in O-KS individuals compared to O-KSHV or No KSHV individuals. These results suggest that HIV/KSHV coinfection and oral microbiota might impact one another and influence the development of oral KS.

The Commensal Microbiota and Viral Infection: A Comprehensive Review

The human body is inhabited by a diverse microbial community that is collectively coined as commensal microbiota. Recent research has greatly advanced our understanding of how the commensal microbiota affects host health. Among the various kinds of pathogenic infections of the host, viral infections constitute one of the most serious public health problems worldwide. During the infection process, viruses may have substantial and intimate interactions with the commensal microbiota. A plethora of evidence suggests that the commensal microbiota regulates and is in turn regulated by invading viruses through diverse mechanisms, thereby having stimulatory or suppressive roles in viral infections. Furthermore, the integrity of the commensal microbiota can be disturbed by invading viruses, causing dysbiosis in the host and further influencing virus infectivity. In the present article, we discuss current insights into the regulation of viral infection by the commensal microbiota. We also draw attention to the disruption of microbiota homeostasis by several viruses.

Development of a novel inducer for EBV lytic therapy

Epstein-Barr virus (EBV) is a human herpesvirus that infects over 90% of the world's population that persists as a latent infection in various lymphoid and epithelial malignancies. The total number of EBV associated malignancies is estimated to exceed 200,000 new cancers per year. Current chemotherapeutic treatments of EBV-positive cancers include broad-spectrum cytotoxic drugs that ignore the EBV positive status of tumors and have limited safety and selectivity. In an effort to develop new and more efficacious molecules for inducing EBV reactivation, we have developed high-throughput screening assays to identify a class of small molecules (referred to as the C60 series) that efficiently activate the EBV lytic cycle in multiple latency types, including lymphoblastoid and nasopharyngeal carcinoma cell lines. In this paper we report our preliminary structure activity relationship studies and demonstrate reactivation of EBV in the SNU719 gastric carcinoma mouse model and the AGS-Akata gastric carcinoma mouse model.

Inhibition of Epstein-Barr Virus Lytic Reactivation by the Atypical Antipsychotic Drug Clozapine

Epstein–Barr virus (EBV), a member of the Herpesviridae family, maintains a lifelong latent infection in human B cells. Switching from the latent to the lytic phase of its lifecycle allows the virus to replicate and spread. The viral lytic cycle is induced in infected cultured cells by drugs such as sodium butyrate and azacytidine. Lytic reactivation can be inhibited by natural products and pharmaceuticals. The anticonvulsant drugs valproic acid and valpromide inhibit EBV in Burkitt lymphoma cells. Therefore, other drugs that treat neurological and psychological disorders were investigated for effects on EBV lytic reactivation. Clozapine, an atypical antipsychotic drug used to treat schizophrenia and bipolar disorder, was found to inhibit the reactivation of the EBV lytic cycle. Levels of the viral lytic genes BZLF1, BRLF1, and BMLF1 were decreased by treatment with clozapine in induced Burkitt lymphoma cells. The effects on viral gene expression were dependent on the dose of clozapine, yet cells were viable at an inhibitory concentration of clozapine. One metabolite of clozapine—desmethylclozapine—also inhibited EBV lytic reactivation, while another metabolite—clozapine-N-oxide—had no effect. These drugs may be used to study cellular pathways that control the viral lytic switch in order to develop treatments for diseases caused by EBV.

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.

Curbing Lipids: Impacts ON Cancer and Viral Infection

Lipids play a fundamental role in maintaining normal function in healthy cells. Their functions include signaling, storing energy, and acting as the central structural component of cell membranes. Alteration of lipid metabolism is a prominent feature of cancer, as cancer cells must modify their metabolism to fulfill the demands of their accelerated proliferation rate. This aberrant lipid metabolism can affect cellular processes such as cell growth, survival, and migration. Besides the gene mutations, environmental factors, and inheritance, several infectious pathogens are also linked with human cancers worldwide. Tumor viruses are top on the list of infectious pathogens to cause human cancers. These viruses insert their own DNA (or RNA) into that of the host cell and affect host cellular processes such as cell growth, survival, and migration. Several of these cancer-causing viruses are reported to be reprogramming host cell lipid metabolism. The reliance of cancer cells and viruses on lipid metabolism suggests enzymes that can be used as therapeutic targets to exploit the addiction of infected diseased cells on lipids and abrogate tumor growth. This review focuses on normal lipid metabolism, lipid metabolic pathways and their reprogramming in human cancers and viral infection linked cancers and the potential anticancer drugs that target specific lipid metabolic enzymes. Here, we discuss statins and fibrates as drugs to intervene in disordered lipid pathways in cancer cells. Further insight into the dysregulated pathways in lipid metabolism can help create more effective anticancer therapies.

A bacterial genotoxin causes virus reactivation and genomic instability in Epstein-Barr virus infected epithelial cells pointing to a role of co-infection in viral oncogenesis

We have addressed the role of bacterial co‐infection in viral oncogenesis using as model Epstein–Barr virus (EBV), a human herpesvirus that causes lymphoid malignancies and epithelial cancers. Infection of EBV carrying epithelial cells with the common oral pathogenic Gram‐negative bacterium Aggregatibacter actinomycetemcomitans (Aa) triggered reactivation of the productive virus cycle. Using isogenic Aa strains that differ in the production of the cytolethal distending toxin (CDT) and purified catalytically active or inactive toxin, we found that the CDT acts via induction of DNA double strand breaks and activation of the Ataxia Telangectasia Mutated (ATM) kinase. Exposure of EBV‐negative epithelial cells to the virus in the presence of sub‐lethal doses of CDT was accompanied by the accumulation of latently infected cells exhibiting multiple signs of genomic instability. These findings illustrate a scenario where co‐infection with certain bacterial species may favor the establishment of a microenvironment conducive to the EBV‐induced malignant transformation of epithelial cells.

What's new?

Little is known about the influence of coinfections, especially of bacteria, on viral oncogenesis. Here, the authors examined the effect of the cytolethal distending toxin (CDT) of Aggregatibacter actinomycetemcomitans, a common oral pathogen, on epithelial cells infected with Epstein–Barr virus (EBV). Exposure of EBV+ cells to CDT induced viral reactivation, while exposure of EBV‐ cells to low amounts of CDT led to the accumulation of latently infected cells upon infection, pointing to a multi‐layered role of bacterial co‐infection in viral oncogenesis.

Targeted Diet Modification Reduces Multiple Sclerosis-like Disease in Adult Marmoset Monkeys from an Outbred Colony

Experimental autoimmune encephalomyelitis (EAE) in common marmosets is a translationally relevant model of the chronic neurologic disease multiple sclerosis. Following the introduction of a new dietary supplement in our purpose-bred marmoset colony, the percentage of marmosets in which clinically evident EAE could be induced by sensitization against recombinant human myelin oligodendrocyte glycoprotein in IFA decreased from 100 to 65%. The reduced EAE susceptibility after the dietary change coincided with reduced Callitrichine herpesvirus 3 expression in the colony, an EBV-related γ1-herpesvirus associated with EAE. We then investigated, in a controlled study in marmoset twins, which disease-relevant parameters were affected by the dietary change. The selected twins had been raised on the new diet for at least 12 mo prior to the study. In twin siblings reverted to the original diet 8 wk prior to EAE induction, 100% disease prevalence (eight out of eight) was restored, whereas in siblings remaining on the new diet the EAE prevalence was 75% (six out of eight). Spinal cord demyelination, a classical hallmark of the disease, was significantly lower in new-diet monkeys than in monkeys reverted to the original diet. In new-diet monkeys, the proinflammatory T cell response to recombinant human myelin oligodendrocyte glycoprotein was significantly reduced, and RNA-sequencing revealed reduced apoptosis and enhanced myelination in the brain. Systematic typing of the marmoset gut microbiota using 16S rRNA sequencing demonstrated a unique, Bifidobacteria-dominated composition, which changed after disease induction. In conclusion, targeted dietary intervention exerts positive effects on EAE-related parameters in multiple compartments of the marmoset's gut-immune-CNS axis.

Caprylic acid and nonanoic acid upregulate endogenous host defense peptides to enhance intestinal epithelial immunological barrier function via histone deacetylase inhibition

The intestinal epithelial barrier plays a critical role in the etiopathogenesis of ulcerative colitis. This study aims to explore the potential effects and underlying mechanisms of medium chain fatty acids (caprylic acid and nonanoic acid) on intestinal epithelial barrier function. Using the porcine jejunal epithelial cell line IPEC-J2, a well-established model, challenged with Escherichia coli ATCC 43889 (O157:H7), we found that treatment with caprylic acid (C8) and nonanoic acid (C9) significantly reduced bacterial translocation, enhanced antibacterial activity, and remarkably increased the secretion of porcine β-defensins 1 (pBD-1) and pBD-2. Mechanistically, like TSA (a histone deacetylase inhibitor), C8 and C9 attenuated the activity of the classical histone deacetylase pathway to facilitate the acetylation of histone 3 lysine 9 (H3K9) at the promoters pBD-1 and pBD-2, and consequently augmented the gene expression of pBD-1 and pBD-2. In conclusion, with their combined antibacterial and defense peptide-induced roles, the use of C8 and C9 may provide a novel method to protect the intestinal barrier of animals and humans from bacterial infection.

Subclinical Cytomegalovirus Infection Is Associated with Altered Host Immunity, Gut Microbiota, and Vaccine Responses

Subclinical viral infections (SVI), including cytomegalovirus (CMV), are highly prevalent in humans, resulting in lifelong persistence. However, the impact of SVI on the interplay between the host immunity and gut microbiota in the context of environmental exposures is not well defined. We utilized the preclinical nonhuman primate (NHP) model consisting of SVI-free (specific-pathogen-free [SPF]) rhesus macaques and compared them to the animals with SVI (non-SPF) acquired through natural exposure and investigated the impact of SVI on immune cell distribution and function, as well as on gut microbiota. These changes were examined in animals housed in the outdoor environment compared to the controlled indoor environment. We report that SVI are associated with altered immune cell subsets and gut microbiota composition in animals housed in the outdoor environment. Non-SPF animals harbored a higher proportion of potential butyrate-producing Firmicutes and higher numbers of lymphocytes, effector T cells, and cytokine-producing T cells. Surprisingly, these differences diminished following their transfer to the controlled indoor environment, suggesting that non-SPFs had increased responsiveness to environmental exposures. An experimental infection of indoor SPF animals with CMV resulted in an increased abundance of butyrate-producing bacteria, validating that CMV enhanced colonization of butyrate-producing commensals. Finally, non-SPF animals displayed lower antibody responses to influenza vaccination compared to SPF animals. Our data show that subclinical CMV infection heightens host immunity and gut microbiota changes in response to environmental exposures. This may contribute to the heterogeneity in host immune response to vaccines and environmental stimuli at the population level.IMPORTANCE Humans harbor several latent viruses that modulate host immunity and commensal microbiota, thus introducing heterogeneity in their responses to pathogens, vaccines, and environmental exposures. Most of our understanding of the effect of CMV on the immune system is based on studies of children acquiring CMV or of immunocompromised humans with acute or reactivated CMV infection or in ageing individuals. The experimental mouse models are genetically inbred and are completely adapted to the indoor laboratory environment. In contrast, nonhuman primates are genetically outbred and are raised in the outdoor environment. Our study is the first to report the impact of long-term subclinical CMV infection on host immunity and gut microbiota, which is evident only in the outdoor environment but not in the indoor environment. The significance of this study is in highlighting the impact of SVI on enhancing host immune susceptibility to environmental exposures and immune heterogeneity.

The Relationship Between Environmental Factors and the Profile of Epstein-Barr Virus Antibodies in the Lytic and Latent Infection Periods in Healthy Populations from Endemic and Non-Endemic Nasopharyngeal Carcinoma Areas in China

Our previous study found that smoking was associated with an elevated level of the antibody against VCA in the Epstein-Barr virus (EBV) lytic phase, which was an important predictive marker of the risk of nasopharyngeal carcinoma (NPC). It remained unknown whether environmental factors were associated with the levels of other EBV antibodies, such as Zta-IgA, EA-IgA, EBNA1-IgA, and LMP1-IgA, in the lytic and latent infection periods. We aimed to investigate the possible environmental inducers that could affect EBV antibody levels in two independent healthy male populations from endemic NPC areas in South China (N=1498) and non-endemic NPC areas in North China (N=1961). We performed ELISA and immunoenzymatic assays to test the levels of antibodies specific to the EBV antigens. The seropositive rates of antibodies against the antigens expressed in both the EBV latent and lytic infection periods, namely, LMP1-IgA, EBNA1-IgA, and Zta-IgA, in endemic areas (28.65%, 5.43% and 14.49%, respectively) were significantly higher than those in non-endemic areas (14.43%, 1.07% and 6.32%, respectively). Smoking was associated with higher seropositivity for EBNA1-IgA (OR=1.47, 95% CI=1.12-1.93) and Zta-IgA (OR=1.28, 95% CI=0.99-1.66), with dose-response effects, while not associated with the levels of LMP1-IgA. In conclusion, smoking was an important environmental factor, which associated with increased levels of EBNA1-IgA, and Zta-IgA.

Rapamycin enhances lytic replication of Epstein-Barr virus in gastric carcinoma cells by increasing the transcriptional activities of immediate-early lytic promoters

Epstein-Barr virus (EBV), a human herpesvirus, is linked to both epithelial and lymphoid malignancies. Induction of EBV reactivation is a potential therapeutic strategy for EBV-associated tumors. In this study, we assessed the effects of rapamycin on EBV reactivation in gastric carcinoma cells. We found that rapamycin upregulated expression of EBV lytic proteins and increased the viral proliferation triggered by the EBV lytic inducer sodium butyrate. Reverse transcription-qPCR, luciferase activity assays, chromatin immunoprecipitation and western blotting were employed to explore the mechanism by which rapamycin promotes EBV reactivation. Our results showed that rapamycin treatment resulted in increased mRNA levels of EBV immediate-early genes. Rapamycin also enhanced the transcriptional activities of the EBV immediate-early lytic promoters Zp and Rp by strengthening Sp1 binding. Repression of the cellular ataxia telangiectasia-mutated/p53 pathway by siRNA-mediated knockdown of the ataxia telangiectasia-mutated gene significantly abrogated virus reactivation by rapamycin/sodium butyrate treatment, indicating that the ataxia telangiectasia-mutated/p53 pathway is involved in rapamycin-promoted EBV reactivation. Taken together, these findings demonstrate that rapamycin might have the potential to enhance the effectiveness of oncolytic viral therapies developed for EBV-associated malignancies.

Lipids, lipid metabolism and Kaposi's sarcoma-associated herpesvirus pathogenesis

Lipids are essential for mammalian cells to maintain many physiological functions. Emerging evidence has shown that cancer cells can develop specific alterations in lipid biosynthesis and metabolism to facilitate their survival and various malignant behaviors. To date, the precise role of cellular lipids and lipid metabolism in viral oncogenesis is still largely unclear with only a handful of literature covering this topic to implicate lipid metabolism in oncogenic virus associated pathogenesis. In this review, we focus on the role of lipid biosynthesis and metabolism in the pathogenesis of the Kaposi's sarcoma-associated herpesvirus, a common causative factor for cancers arising in the immunocompromised settings.

Hypoxia-inducible factor-1α plays roles in Epstein-Barr virus's natural life cycle and tumorigenesis by inducing lytic infection through direct binding to the immediate-early BZLF1 gene promoter

When confronted with poor oxygenation, cells adapt by activating survival signaling pathways, including the oxygen-sensitive transcriptional regulators called hypoxia-inducible factor alphas (HIF-αs). We report here that HIF-1α also regulates the life cycle of Epstein-Barr virus (EBV). Incubation of EBV-positive gastric carcinoma AGS-Akata and SNU-719 and Burkitt lymphoma Sal and KemIII cell lines with a prolyl hydroxylase inhibitor, L-mimosine or deferoxamine, or the NEDDylation inhibitor MLN4924 promoted rapid and sustained accumulation of both HIF-1α and lytic EBV antigens. ShRNA knockdown of HIF-1α significantly reduced deferoxamine-mediated lytic reactivation. HIF-1α directly bound the promoter of the EBV primary latent-lytic switch BZLF1 gene, Zp, activating transcription via a consensus hypoxia-response element (HRE) located at nt -83 through -76 relative to the transcription initiation site. HIF-1α did not activate transcription from the other EBV immediate-early gene, BRLF1. Importantly, expression of HIF-1α induced EBV lytic-gene expression in cells harboring wild-type EBV, but not in cells infected with variants containing base-pair substitution mutations within this HRE. Human oral keratinocyte (NOK) and gingival epithelial (hGET) cells induced to differentiate by incubation with either methyl cellulose or growth in organotypic culture accumulated both HIF-1α and Blimp-1α, another cellular factor implicated in lytic reactivation. HIF-1α activity also accumulated along with Blimp-1α during B-cell differentiation into plasma cells. Furthermore, most BZLF1-expressing cells observed in lymphomas induced by EBV in NSG mice with a humanized immune system were located distal to blood vessels in hypoxic regions of the tumors. Thus, we conclude that HIF-1α plays central roles in both EBV’s natural life cycle and EBV-associated tumorigenesis. We propose that drugs that induce HIF-1α protein accumulation are good candidates for development of a lytic-induction therapy for treating some EBV-associated malignancies.

Most adults throughout the world are infected with Epstein-Barr virus (EBV), a human herpesvirus frequently associated in a latent state with some cancers of epithelial and B-cell origin such as nasopharyngeal carcinoma and Burkitt lymphoma, respectively. To develop an oncolytic therapy for treating patients with EBV-associated cancers, we need a method to efficiently induce synthesis of lytic EBV proteins. The EBV protein encoded by its immediate-early BZLF1 gene usually mediates the switch into lytic viral infection. We show here that HIF-1α, a cellular transcription factor that accumulates in cells when deprived of normal levels of oxygen, can induce lytic EBV infection. HIF-1α mediates this switch by directly binding to a specific sequence located within the BZLF1 gene promoter, activating its expression. Importantly, we also show that deferoxamine, an FDA-approved drug that inhibits degradation of HIF-1α, can induce synthesis of lytic EBV proteins in some EBV-positive epithelial and lymphocytic cell lines. These findings indicate that HIF-1α-stabilizing drugs, administered in combination with nucleoside analogues such as ganciclovir, may be helpful as part of a lytic-induction therapy for treating some patients with EBV-positive malignancies.

Chemical signaling between gut microbiota and host chromatin: What is your gut really saying?

Mammals and their gut microbial communities share extensive and tightly coordinated co-metabolism of dietary substrates. A large number of microbial metabolites have been detected in host circulation and tissues and, in many cases, are linked to host metabolic, developmental, and immunological states. The presence of these metabolites in host tissues intersects with regulation of the host's epigenetic machinery. Although it is established that the host's epigenetic machinery is sensitive to levels of endogenous metabolites, the roles for microbial metabolites in epigenetic regulation are just beginning to be elucidated. This review focuses on eukaryotic chromatin regulation by endogenous and gut microbial metabolites and how these regulatory events may impact host developmental and metabolic phenotypes.

Epstein-Barr Virus: Diseases Linked to Infection and Transformation

Epstein–Barr virus (EBV) was first discovered in 1964, and was the first known human tumor virus now shown to be associated with a vast number of human diseases. Numerous studies have been conducted to understand infection, propagation, and transformation in various cell types linked to human diseases. However, a comprehensive lens through which virus infection, reactivation and transformation of infected host cells can be visualized is yet to be formally established and will need much further investigation. Several human cell types infected by EBV have been linked to associated diseases. However, whether these are a direct result of EBV infection or indirectly due to contributions by additional infectious agents will need to be fully investigated. Therefore, a thorough examination of infection, reactivation, and cell transformation induced by EBV will provide a more detailed view of its contributions that drive pathogenesis. This undoubtedly expand our knowledge of the biology of EBV infection and the signaling activities of targeted cellular factors dysregulated on infection. Furthermore, these insights may lead to identification of therapeutic targets and agents for clinical interventions. Here, we review the spectrum of EBV-associated diseases, the role of the encoded latent antigens, and the switch to latency or lytic replication which occurs in EBV infected cells. Furthermore, we describe the cellular processes and critical factors which contribute to cell transformation. We also describe the fate of B-cells and epithelial cells after EBV infection and the expected consequences which contribute to establishment of viral-associated pathologies.

Establishing and characterizing a new primary effusion lymphoma cell line harboring Kaposi's sarcoma-associated herpesvirus

BACKGROUND

Primary effusion lymphoma is a rare distinct large B-cell neoplasm that is associated with Kaposi's sarcoma-associated herpesvirus (KSHV) infection. Over recent years, 9 KSHV-positive/Epstein-Barr virus (EBV)-negative PEL cell lines have been established.

METHODS

Tumor cells were collected from the pleural effusion of a 49-year-old male with AIDS. Cells were grown in RPMI1640 culture medium supplemented with 10 % fetus bovine serum. Single cell cloning was performed successfully by a limiting dilution method in a 96-well plate. The cell line obtained was designated SPEL.

RESULTS

SPEL cells showed gourd-shaped morphology with a polarized nucleus, expressing CD38, CD138, and Blimp-1, but not B cell markers such as CD19 and CD20. Polymerase chain reaction analysis revealed that SPEL cells were positive for KSHV but negative for EBV. Tetradecanoylphorbol acetate induced expression of KSHV lytic proteins and the production of KSHV particles in SPEL cells. Subcutaneous inoculation of SPEL cells into severe combined immunodeficiency mice resulted in the formation of solid tumors. Next-generation sequencing revealed the 138 kbp genome sequence of KSHV in SPEL cells. Suberic bishydroxamate, a histone deacetylase inhibitor, induced the expression of KSHV-encoded lytic proteins and cell death in SPEL cells.

CONCLUSIONS

A new KSHV-positive and EBV-negative PEL cell line, SPEL was established. This cell line may contribute to furthering our understanding of the pathogenesis of PEL and KSHV infection.

The Microbiome, Systemic Immune Function, and Allotransplantation

Diverse effects of the microbiome on solid organ transplantation are beginning to be recognized. In allograft recipients, microbial networks are disrupted by immunosuppression, nosocomial and community-based infectious exposures, antimicrobial therapies, surgery, and immune processes. Shifting microbial patterns, including acute infectious exposures, have dynamic and reciprocal interactions with local and systemic immune systems. Both individual microbial species and microbial networks have central roles in the induction and control of innate and adaptive immune responses, in graft rejection, and in ischemia-reperfusion injury. Understanding the diverse interactions between the microbiome and the immune system of allograft recipients may facilitate clinical management in the future.

Rapidly progressive Kaposi's Sarcoma in an Iraqi boy received Valproic acid: a case report and review of literature

Background

Kaposi’s sarcoma (KS), an endothelial neoplasm, is associated with human herpes virus (HHV) -8 infection. KS has four clinical sub-types: Mediterranean/classic, African/endemic, human immunodeficiency virus (HIV) -associated/epidemic, and transplantation-related/iatrogenic. Immunosuppression is an important cofactor in KS process. Classic KS (CKS) is exceedingly rare in children and when occurs, it is much more disseminated than adults. The epidemic, HIV-associated and the iatrogenic forms of childhood KS are a result of a profound and acquired T-cell deficiency. To our knowledge, this is the first paediatric KS case report from Iraq. Our patient was showing an unusual aggressive course of the disease while receiving Valproic acid (VPA) of the potential immune-suppressive effect.

Case presentation

A six-year-old Iraqi boy, who had cerebral palsy (CP) and epilepsy since the age of 9-months, had received VPA to control his seizures. He developed skin discoloration followed by nodules that disseminated proximally from the lower extremities to the groin, face, ears and oral cavity, and then he died from severe respiratory distress after 110 days from the disease evolution. KS diagnosis was proved by a skin biopsy. As the patient was of Arab-Asian ethnicity and was HIV-seronegative status, accordingly, his condition best fitted the classic form of KS. However, recent studies showed the link of VPA with the reactivation of HHV-8. Moreover, accumulated experimental and clinical data elucidated that VPA induces T-cell suppression. Given that there was a lack of facilities to perform the laboratory immunological diagnostic tests in Iraq, the VPA-induced effect on immunity in our case (iatrogenic KS) could not be evaluated.

Conclusions

Our report demonstrates a rare, rapidly progressing paediatric KS case and highlights the possible role of the 5-years’ administration of VPA and its challenging effect on cellular immunity based on recent studies. Thus, VPA could have promoted the development of the KS in our patient. This report also recalls the need of paediatricians to consider KS especially when the skin lesion appears at the child’s foot even in countries outside the geographical map of the disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s12887-016-0653-3) contains supplementary material, which is available to authorized users.

Speculations on the clinical significance of asymptomatic viral infections

A detailed understanding of asymptomatic chronic viral infections is critical to analyse their pathogenesis, assess the severity and burden of disease and, where required, optimize public health control measures. Recent studies on herpesviruses showed that the host-virus interactions are modulated by co-infections, emphasizing the relevance of co-infections in determining the clinical expression (from asymptomatic to symptomatic infections) and the severity of herpesvirus-associated diseases (either neoplastic or infectious diseases). To demonstrate causality between viruses (virome) and diseases, Koch's postulates should be adapted adding new knowledge on host-microbe relationship and microbial interactions. In the present review we aim to provide an update on asymptomatic chronic infections and criteria for causality and on the virological, immunological and host-virus interactions in asymptomatic chronic infections in human hosts, focusing on herpetic infections.

Valpromide Inhibits Lytic Cycle Reactivation of Epstein-Barr Virus

Reactivation of Epstein-Barr virus (EBV) from latency into the lytic phase of its life cycle allows the virus to spread among cells and between hosts. Valproic acid (VPA) inhibits initiation of the lytic cycle in EBV-infected B lymphoma cells. While VPA blocks viral lytic gene expression, it induces expression of many cellular genes, because it is a histone deacetylase (HDAC) inhibitor. Here we show, using derivatives of VPA, that blockade of EBV reactivation is separable from HDAC inhibition. Valpromide (VPM), an amide derivative of valproic acid that is not an HDAC inhibitor, prevented expression of two EBV genes, BZLF1 and BRLF1, that mediate lytic reactivation. VPM also inhibited expression of a viral late gene, but not early genes, when BZLF1 was exogenously expressed. Unlike VPA, VPM did not activate lytic expression of Kaposi's sarcoma-associated herpesvirus. Expression of cellular immediate-early genes, such as FOS and EGR1, is kinetically upstream of the EBV lytic cycle. VPM did not activate expression of these cellular immediate-early genes but decreased their level of expression when induced by butyrate, an HDAC inhibitor. VPM did not alter expression of several other cellular immediate-early genes, including STAT3, which were induced by the HDAC inhibitors in cells refractory to lytic induction. Therefore, VPM selectively inhibits both viral and cellular gene expression. VPA and VPM represent a new class of antiviral agents. The mechanism by which VPA and VPM block EBV reactivation may be related to their anticonvulsant activity.

IMPORTANCE

Epstein-Barr virus, (EBV), a human tumor virus, establishes a life-long latent infection. Reactivation of EBV into the lytic phase of its life cycle allows the virus to spread. Previously, we showed that EBV reactivation was blocked by valproic acid (VPA), an inhibitor of cellular histone deacetylases (HDACs). VPA alters the expression of thousands of cellular genes. In this study, we demonstrate that valpromide (VPM), an amide derivative of valproic acid that is not an HDAC inhibitor, prevented initiation of the EBV lytic cycle. VPA induced lytic reactivation of Kaposi's sarcoma-associated herpesvirus (KSHV), but VPM did not. Unlike VPA, VPM did not activate cellular immediate-early gene expression. VPM is a new type of antiviral agent. VPM will be useful in probing the mechanism of EBV lytic reactivation and may have therapeutic application.

The Role of Gammaherpesviruses in Cancer Pathogenesis

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

Sodium butyrate down-regulates tristetraprolin-mediated cyclin B1 expression independent of the formation of processing bodies

Butyrate regulates multiple host cellular events including the cell cycle; however, little is known about the molecular mechanism by which butyrate induces a global down-regulation of the expression of genes associated with the cell cycle. Here, we demonstrate that treating HEK293T cells and the non-small-cell lung cancer cell line A549 with a high concentration of sodium butyrate reduces cyclin B1 expression. The underlying mechanism is related to the destabilization of its mRNA by tristetraprolin, which is up-regulated in response to sodium butyrate. Specifically, the sodium butyrate stimulation reduces the mRNA and protein expression of cyclin B1 and, conversely, upregulates tristetraprolin expression. Importantly, the overexpression of tristetraprolin in HEK293T decreases the mRNA and protein expression of cyclin B1; in contrast, knockdown of tristetraprolin mediated by small interfering RNA increases its expression in response to sodium butyrate treatment for both HEK293T and A549 cells. Furthermore, results from luciferase reporter assays and RNA immunoprecipitation indicate that sodium butyrate accelerates 3' UTR-dependent cyclin B1 decay by enhancing the binding of tristetraprolin to the 3' untranslated region of cyclin B1. Surprisingly, the overexpression of tristetraprolin prevents the formation of processing bodies, and the siRNA-mediated silencing of EDC4 does not restore the sodium butyrate-induced reduction of cyclin B1 expression. Thus, we confirm that NaBu regulates ZFP36-mediated cyclin B1 expression in a manner that is independent of the formation of P-bodies. The above findings disclose a novel mechanism of sodium butyrate-mediated gene expression regulation and might benefit its application in tumor treatment.

Importance of investigating epigenetic alterations for industry and regulators: An appraisal of current efforts by the Health and Environmental Sciences Institute

Recent technological advances have led to rapid progress in the characterization of epigenetic modifications that control gene expression in a generally heritable way, and are likely involved in defining cellular phenotypes, developmental stages and disease status from one generation to the next. On November 18, 2013, the International Life Sciences Institute (ILSI) Health and Environmental Sciences Institute (HESI) held a symposium entitled "Advances in Assessing Adverse Epigenetic Effects of Drugs and Chemicals" in Washington, D.C. The goal of the symposium was to identify gaps in knowledge and highlight promising areas of progress that represent opportunities to utilize epigenomic profiling for risk assessment of drugs and chemicals. Epigenomic profiling has the potential to provide mechanistic information in toxicological safety assessments; this is especially relevant for the evaluation of carcinogenic or teratogenic potential and also for drugs that directly target epigenetic modifiers, like DNA methyltransferases or histone modifying enzymes. Furthermore, it can serve as an endpoint or marker for hazard characterization in chemical safety assessment. The assessment of epigenetic effects may also be approached with new model systems that could directly assess transgenerational effects or potentially sensitive stem cell populations. These would enhance the range of safety assessment tools for evaluating xenobiotics that perturb the epigenome. Here we provide a brief synopsis of the symposium, update findings since that time and then highlight potential directions for future collaborative efforts to incorporate epigenetic profiling into risk assessment.

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus (KSHV; also known as human herpesvirus 8 (HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.

Chromatin Structure of Epstein-Barr Virus Latent Episomes

EBV latent infection is characterized by a highly restricted pattern of viral gene expression. EBV can establish latent infections in multiple different tissue types with remarkable variation and plasticity in viral transcription and replication. During latency, the viral genome persists as a multi-copy episome, a non-integrated-closed circular DNA with nucleosome structure similar to cellular chromosomes. Chromatin assembly and histone modifications contribute to the regulation of viral gene expression, DNA replication, and episome persistence during latency. This review focuses on how EBV latency is regulated by chromatin and its associated processes.