Functional Epstein-Barr virus reservoir in plasma cells derived from infected peripheral blood memory B cells

Epstein-Barr Virus Monitoring after an Allogeneic Hematopoietic Stem Cell Transplant: Review of the Recent Data and Current Practices in Canada

Epstein-Barr virus-related post-transplantation lymphoproliferative disorder (EBV-PTLD) is a serious complication following hematopoietic stem cell transplantation (HSCT). A pre-emptive strategy using rituximab, which aims to manage patients early at the time of EBV reactivation to avoid PTLD, has been recommended by the most recent ECIL-6 guidelines in 2016. However, there is still a great heterogeneity of viral-load monitoring protocols, targeted patient populations, and pre-emptive treatment characteristics between centers, making precise EBV monitoring recommendations difficult. We conducted a literature review from the most recent publications between 1 January 2015 and 1 August 2023, to summarize the emerging data on EBV-PTLD prevention strategies in HSCT recipients, including the EBV-DNA threshold and use of rituximab. We also present the results of a survey of current practices carried out in 12 of the main HSCT centers across Canada. We confirm that pre-emptive rituximab remains an efficient strategy for EBV-PTLD prevention. However, there is an urgent need to perform prospective, randomized, multicentric trials with larger numbers of patients reflecting current practices to determine the best clinical conduct with regards to rituximab dosing, timing of treatment, and criteria to initiate treatments. Longer follow-ups will also be necessary to assess patients' long-term outcomes.

Increased circulating fibronectin, depletion of natural IgM and heightened EBV, HSV-1 reactivation in ME/CFS and long COVID

Myalgic Encephalomyelitis/ Chronic Fatigue syndrome (ME/CFS) is a complex, debilitating, long-term illness without a diagnostic biomarker. ME/CFS patients share overlapping symptoms with long COVID patients, an observation which has strengthened the infectious origin hypothesis of ME/CFS. However, the exact sequence of events leading to disease development is largely unknown for both clinical conditions. Here we show antibody response to herpesvirus dUTPases, particularly to that of Epstein-Barr virus (EBV) and HSV-1, increased circulating fibronectin (FN1) levels in serum and depletion of natural IgM against fibronectin ((n)IgM-FN1) are common factors for both severe ME/CFS and long COVID. We provide evidence for herpesvirus dUTPases-mediated alterations in host cell cytoskeleton, mitochondrial dysfunction and OXPHOS. Our data show altered active immune complexes, immunoglobulin-mediated mitochondrial fragmentation as well as adaptive IgM production in ME/CFS patients. Our findings provide mechanistic insight into both ME/CFS and long COVID development. Finding of increased circulating FN1 and depletion of (n)IgM-FN1 as a biomarker for the severity of both ME/CFS and long COVID has an immediate implication in diagnostics and development of treatment modalities.

The interaction between Epstein-Barr virus and multiple sclerosis genetic risk loci: insights into disease pathogenesis and therapeutic opportunities

Multiple sclerosis (MS) is a chronic neurodegenerative autoimmune disease, characterised by the demyelination of neurons in the central nervous system. Whilst it is unclear what precisely leads to MS, it is believed that genetic predisposition combined with environmental factors plays a pivotal role. It is estimated that close to half the disease risk is determined by genetic factors. However, the risk of developing MS cannot be attributed to genetic factors alone, and environmental factors are likely to play a significant role by themselves or in concert with host genetics. Epstein-Barr virus (EBV) infection is the strongest known environmental risk factor for MS. There has been increasing evidence that leaves little doubt that EBV is necessary, but not sufficient, for developing MS. One plausible explanation is EBV may alter the host immune response in the presence of MS risk alleles and this contributes to the pathogenesis of MS. In this review, we discuss recent findings regarding how EBV infection may contribute to MS pathogenesis via interactions with genetic risk loci and discuss possible therapeutic interventions.

EBV dUTPase: A Novel Modulator of Inflammation and the Tumor Microenvironment in EBV-Associated Malignancies

There is increasing evidence that put into question the classical dogma that the Epstein-Barr virus (EBV) exists in cells as either a lytic virus in which new progeny is produced or in a latent state in which no progeny is produced. Notably, a third state has now been described, known as the abortive-lytic phase, which is characterized by the expression of some immediate early (IE) and early (E) genes, but no new virus progeny is produced. While the function of these IE and E gene products is not well understood, several recent studies support the concept they may contribute to tumor promotion by altering the tumor microenvironment (TME). The mechanisms by which these viral gene products may contribute to tumorigenesis remain unclear; however, it has been proposed that some of them promote cellular growth, immune evasion, and/or inhibit apoptosis. One of these EBV early gene products is the deoxyuridine triphosphate nucleotidohydrolase (dUTPase) encoded by BLLF3, which not only contributes to the establishment of latency through the production of activin A and IL-21, but it may also alter the TME, thus promoting oncogenesis.

Potential effect of epigenetic drugs in the treatment of multiple-site extramedullary plasmacytoma involving the respiratory system: a case report and review of the literature

We report the case of a 23-year-old man with a medical history of idiopathic thrombocytopenic purpura (ITP) and newly diagnosed with the Epstein-Barr virus (EBV)-positive multiple-site extramedullary plasmacytoma (EMP), which involves the respiratory system. The patient was referred to our hospital because of progressive nasal congestion and nasal mass. Nasopharyngoscopy and bronchoscopy were performed. The biopsy pathological hematoxylin and eosin (HE) staining indicated plasma cell myeloma, and further immunohistochemistry CD99(+), CD79a(+), CD38(+), MUM-1(+), and Lambda(+) confirmed the diagnosis. The patient's bone marrow was normal, and hypercalcemia, renal insufficiency, anemia, evident bone lesions were not observed. Serum immunoglobulin quantification, serum protein electrophoresis, and blood and urine light chain quantification were all within the normal range. The serum immunofixation electrophoresis was negative, and the serum-free light chain was normal. These results could rule out multiple myeloma (MM) and prove to be EMP involving the nasal cavity, main bronchus, lung, and left hip. No desired effect was achieved after receiving PAD (bortezomib, adriamycin, and dexamethasone) and VRD (bortezomib, lenalidomide, and dexamethasone) treatments. Even if the tumor was remarkably relieved after receiving the 2-course CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone) regimen, secondary resistance to CHOP unfortunately occurred in this case. We attempted to apply epigenetic therapy in the treatment of refractory multiple EMP. Although no complete remission (CR) was achieved, the maximum standard uptake value (SUVmax) in tumor lesions was significantly lower than before, and the patient's symptoms significantly improved. The patient tolerated decitabine and chidamide. We speculated that epigenetic drugs have potential effect in the treatment of multiple-site EMP.

B Cell Receptor-Responsive miR-141 Enhances Epstein-Barr Virus Lytic Cycle via FOXO3 Inhibition

Antigen recognition by the B cell receptor (BCR) is a physiological trigger for reactivation of Epstein-Barr virus (EBV) and can be recapitulated in vitro by cross-linking of surface immunoglobulins. Previously, we identified a subset of EBV microRNAs (miRNAs) that attenuate BCR signal transduction and subsequently dampen lytic reactivation in B cells. The roles of host miRNAs in the EBV lytic cycle are not completely understood. Here, we profiled the small RNAs in reactivated Burkitt lymphoma cells and identified several miRNAs, such as miR-141, that are induced upon BCR cross-linking. Notably, EBV encodes a viral miRNA, miR-BART9, with sequence homology to miR-141. To better understand the functions of these two miRNAs, we examined their molecular targets and experimentally validated multiple candidates commonly regulated by both miRNAs. Targets included B cell transcription factors and known regulators of EBV immediate-early genes, leading us to hypothesize that these miRNAs modulate kinetics of the lytic cascade in B cells. Through functional assays, we identified roles for miR-141 and EBV miR-BART9 and one specific target, FOXO3, in progression of the lytic cycle. Our data support a model whereby EBV exploits BCR-responsive miR-141 and further mimics activity of this miRNA family via a viral miRNA to promote productive lytic replication.

IMPORTANCE EBV is a human pathogen associated with several malignancies. A key aspect of lifelong virus persistence is the ability to switch between latent and lytic replication modes. The mechanisms governing latency, reactivation, and progression of the lytic cycle are only partly understood. This study reveals that specific miRNAs can act to support the EBV lytic phase following BCR-mediated reactivation triggers. Furthermore, this study identifies a role for FOXO3, commonly suppressed by both host and viral miRNAs, in modulating progression of the EBV lytic cycle.

Multiple Viral microRNAs Regulate Interferon Release and Signaling Early during Infection with Epstein-Barr Virus

Epstein-Barr virus (EBV), a human herpesvirus, encodes 44 microRNAs (miRNAs), which regulate many genes with various functions in EBV-infected cells. Multiple target genes of the EBV miRNAs have been identified, some of which play important roles in adaptive antiviral immune responses. Using EBV mutant derivatives, we identified additional roles of viral miRNAs in governing versatile type I interferon (IFN) responses upon infection of human primary mature B cells. We also found that Epstein-Barr virus-encoded small RNAs (EBERs) and LF2, viral genes with previously reported functions in inducing or regulating IFN-I pathways, had negligible or even contrary effects on secreted IFN-α in our model. Data mining and Ago PAR-CLIP experiments uncovered more than a dozen previously uncharacterized, direct cellular targets of EBV miRNA associated with type I IFN pathways. We also identified indirect targets of EBV miRNAs in B cells, such as TRL7 and TLR9, in the prelatent phase of infection. The presence of epigenetically naive, non-CpG methylated viral DNA was essential to induce IFN-α secretion during EBV infection in a TLR9-dependent manner. In a newly established fusion assay, we verified that EBV virions enter a subset of plasmacytoid dendritic cells (pDCs) and determined that these infected pDCs are the primary producers of IFN-α in EBV-infected peripheral blood mononuclear cells. Our findings document that many EBV-encoded miRNAs regulate type I IFN response in newly EBV infected primary human B cells in the prelatent phase of infection and dampen the acute release of IFN-α in pDCs upon their encounter with EBV.IMPORTANCE Acute antiviral functions of all nucleated cells rely on type I interferon (IFN-I) pathways triggered upon viral infection. Host responses encompass the sensing of incoming viruses, the activation of specific transcription factors that induce the transcription of IFN-I genes, the secretion of different IFN-I types and their recognition by the heterodimeric IFN-α/β receptor, the subsequent activation of JAK/STAT signaling pathways, and, finally, the transcription of many IFN-stimulated genes (ISGs). In sum, these cellular functions establish a so-called antiviral state in infected and neighboring cells. To counteract these cellular defense mechanisms, viruses have evolved diverse strategies and encode gene products that target antiviral responses. Among such immune-evasive factors are viral microRNAs (miRNAs) that can interfere with host gene expression. We discovered that multiple miRNAs of Epstein-Barr virus (EBV) control over a dozen cellular genes that contribute to the antiviral states of immune cells, specifically B cells and plasmacytoid dendritic cells (pDCs). We identified the viral DNA genome as the activator of IFN-α and question the role of abundant EBV EBERs, that, contrary to previous reports, do not have an apparent inducing function in the IFN-I pathway early after infection.

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: The Human Herpesviruses Are Back!

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) or Systemic Exertion Intolerance Disease (SEID) is a chronic multisystem illness of unconfirmed etiology. There are currently no biomarkers and/or signatures available to assist in the diagnosis of the syndrome and while numerous mechanisms have been hypothesized to explain the pathology of ME/CFS, the triggers and/or drivers remain unknown. Initial studies suggested a potential role of the human herpesviruses especially Epstein-Barr virus (EBV) in the disease process but inconsistent and conflicting data led to the erroneous suggestion that these viruses had no role in the syndrome. New studies using more advanced approaches have now demonstrated that specific proteins encoded by EBV could contribute to the immune and neurological abnormalities exhibited by a subgroup of patients with ME/CFS. Elucidating the role of these herpesvirus proteins in ME/CFS may lead to the identification of specific biomarkers and the development of novel therapeutics.

Potential anti-EBV effects associated with elevated interleukin-21 levels: a case report

BACKGROUND

Germinal center derived memory B cells and plasma cells constitute, in health and during EBV reactivation, the largest functional EBV reservoir. Hence, by reducing germinal center derived formation of memory B cells and plasma cells, EBV loads may be reduced. Animal and in-vitro models have shown that IL-21 can support memory B and plasma cell formation and thereby potentially contribute to EBV persistence. However, IL-21 also displays anti-viral effects, as mice models have shown that CD4⁺ T cell produced IL-21 is critical for the differentiation, function and survival of anti-viral CD8⁺ T cells able to contain chronic virus infections.

CASE PRESENTATION

We present immunological work-up (flow-cytometry, ELISA and genetics) related to a patient suffering from a condition resembling B cell chronic active EBV infection, albeit with moderately elevated EBV copy numbers. No mutations in genes associated with EBV disease, common variable immunodeficiency or pertaining to the IL-21 signaling pathway (including hypermorphic IL-21 mutations) were found. Increased (> 5-fold increase 7 days post-vaccination) CD4⁺ T cell produced (p < 0.01) and extracellular IL-21 levels characterized our patient and coexisted with: CD8⁺ lymphopenia, B lymphopenia, hypogammaglobulinemia, compromised memory B cell differentiation, absent induction of B-cell lymphoma 6 protein (Bcl-6) dependent peripheral follicular helper T cells (pT_FH, p = 0.01), reduced frequencies of peripheral CD4⁺ Bcl-6⁺ T cells (p = 0.05), compromised plasmablast differentiation (reduced protein vaccine responses (p < 0.001) as well as reduced Treg frequencies. Supporting IL-21 mediated suppression of pT_FH formation, pT_FH and CD4⁺ IL-21⁺ frequencies were strongly inversely correlated, prior to and after vaccination, in the patient and in controls, Spearman's rho: - 0.86, p < 0.001.

CONCLUSIONS

To the best of our knowledge, this is the first report of elevated CD4⁺ IL-21⁺ T cell frequencies in human EBV disease. IL-21 overproduction may, apart from driving T cell mediated anti-EBV responses, disrupt germinal center derived memory B cell and plasma cell formation, and thereby contribute to EBV disease control.

Oncogenic Properties of the EBV ZEBRA Protein

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

A tissue level atlas of the healthy human virome

BACKGROUND

Human-resident microbes can influence both health and disease. Investigating the microbiome using next-generation sequencing technology has revealed examples of mutualism and conflict between microbes and humans. Comparing to bacteria, the viral component of the microbiome (i.e., the "virome") is understudied. Somatic tissues of healthy individuals are usually inaccessible for the virome sampling; therefore, there is limited understanding of the presence and distribution of viruses in tissues in healthy individuals and how virus infection associates with human gene expression and perturbs immunological homeostasis.

RESULTS

To characterize the human virome in a tissue-specific manner, here we performed meta-transcriptomic analysis using the RNA-sequencing dataset from the Genotype-Tissue Expression (GTEx) Project. We analyzed the 8991 RNA-sequencing data obtained from 51 somatic tissues from 547 individuals and successfully detected 39 viral species in at least one tissue. We then investigated associations between virus infection and human gene expression and human disease onset. We detected some expected relationships; for instance, hepatitis C virus infection in the liver was strongly associated with interferon-stimulated gene upregulation and pathological findings of chronic hepatitis. The presence of herpes simplex virus type 1 in one subject's brain strongly associated with immune gene expression. While torque teno virus was detected in a broad range of human tissues, it was not associated with interferon responses. Being notable in light of its association with lymphoproliferative disorders, Epstein-Barr virus infection in the spleen and blood was associated with an increase in plasma cells in healthy subjects. Human herpesvirus 7 was often detected in the stomach; intriguingly, it associated with the proportion of human leukocytes in the stomach as well as digestive gene expression. Moreover, virus infections in the local tissues associated with systemic immune responses in circulating blood.

CONCLUSIONS

To our knowledge, this study is the first comprehensive investigation of the human virome in a variety of tissues in healthy individuals through meta-transcriptomic analysis. Further investigation of the associations described here, and application of this analytical pipeline to additional datasets, will be useful to reveal the impact of viral infections on human health.

Multiparametric flow cytometry analysis of peripheral blood B cell trafficking differences among Epstein-Barr virus infected and uninfected subpopulations

AIMS

Epstein-Barr virus (EBV) targets predominantly B cells and these cells could acquire new phenotype characteristics. Here we analyzed whether EBV-infected and -uninfected B cells from healthy subjects differ in proportion of dominant phenotypes, maturation stage, and homing receptors expression.

METHODS

EBV-infected and -uninfected cells were identified by flow cytometry using fluorophore-labeled EBV RNA-specific DNA probes combined with fluorophore-labeled antibody to surface lineage markers, integrins, chemokine receptors, and immunoglobulin isotypes, including intracellular ones.

RESULTS

Our results show that the trafficking characteristics of EBER^pos B cells are distinct from EBER^neg B cells with most dominant differences detected for α4β1 and α4β7 and CCR5 and CCR7. EBV-positive cells are predominantly memory IgM⁺ B cells or plasmablasts/plasma cells (PB/PC) positive for IgA or less for IgM. In comparison to uninfected B cells, less EBV-positive B cells express α4β7 and almost no cells express α4β1. EBV-positive B cells contained significantly higher proportion of CCR5⁺ and CCR7⁺ cells in comparison to EBV-negative cells. In vitro exposure of blood mononuclear cells to pro-inflammatory cytokine IL-6 reduces population of EBV-positive B cell.

CONCLUSION

Although EBV-infected B cells represent only a minor subpopulation, their atypical functions could contribute in predisposed person to development abnormities such as some autoimmune diseases or tumors. Using multi-parameter flow cytometry we characterized differences in migration of EBV-positive and -negative B cells of various maturation stage and isotype of produced antibodies particularly different targeting to mucosal tissues of gastrointestinal and respiratory tracts.

Discrepancy of Serological and Molecular Patterns of Circulating Epstein-Barr Virus Reactivation in Primary Sjögren's Syndrome

Primary Sjögren's syndrome (pSS) is characterized by B cell hyperactivation, production of autoantibodies and increased risk of B cell lymphomas. Serological profile of Epstein-Barr virus (EBV) reactivation and increase EBV DNA levels in exocrine glands are observed in pSS, but whether these abnormalities are accompanied with disturbed systemic EBV control or have any association with pSS activity remains to be investigated. In this observational study, we initially explored anti-EBV antibodies and cell-free DNA in 395 samples from a cross-sectional plasma collection of pSS patients included in ASSESS French national cohort. Results were assessed in relation with disease activity. Further, to assess cell-associated EBV DNA we organized a case-control study including 20 blood samples from pSS patients followed in University Hospital Center of Montpellier. Results were compared with matched controls. Robust response against EBV early antigen (EA) was observed in pSS patients with anti-SSA/B (Sjögren's syndrome A and B) and anti-SSA autoantibodies compared to anti-SSA/B negatives (P < 0.01 and P = 0.01, respectively). Increased beta-2 microglobulin, kappa and lambda light chains, and immunoglobulin G levels were more frequently observed in anti-EA seropositive pSS subjects compared to anti-EA negative subjects (P < 0.001; P = 0.001; P = 0.003, respectively). Beta-2 microglobulin was independently associated with anti-EA positivity in multivariate analysis (P < 0.001). Plasma cell-free EBV DNA and EBV cellular reservoir was not different between pSS patients and controls. We conclude that serological evidence of EBV reactivation was more frequently observed and more strongly associated with anti-SSA/B status and B cell activation markers in pSS. However, serological profile of EBV reactivation was not accompanied by molecular evidence of systemic EBV reactivation. Our data indicated that EBV infection remains efficiently controlled in the blood of pSS patients.

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

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

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

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

CD3+ CD56+ EBER1+ atypical extraosseous plasmacytoma of the nasal cavity

We present a case of atypical extraosseous plasmacytoma (EP) with a plasmablastic morphology and CD3⁺ CD56⁺ Epstein-Barr virus-encoded RNA-1 (EBER1)⁺ phenotypes of the nasal cavity. A 51-year-old male attended a local hospital with a tumor located in his left nasal cavity that was histologically diagnosed as extranodal NK/T cell lymphoma, nasal type. We reviewed the specimens and re-biopsied the tumor, and confirmed that the tumor was positive for CD3, CD56, and EBER1; however, the tumor showed a plasmablastic morphology without necrosis and angiocentricity, and was positive for CD138, but negative for CD20 and PAX5. Given a plasmablastic morphology and EBER1 positivity, but a relatively low Ki67 index (30%), we diagnosed the case as atypical EP. The CHOP regimen was administered and complete remission achieved. This case indicated that EP should be considered as a differential diagnosis even when a tumor shows large cell morphology and is positive for CD3, CD56, and EBER1.

Use of ELISpot assay to study HBs-specific B cell responses in vaccinated and HBV infected humans

Hepatitis B surface antibody (HBsAb) plays a critical role in protecting against infection of hepatitis B virus (HBV) and were extensively studied in literature. At the same time, the status of hepatitis B surface antigen (HBs)-specific B cells in both vaccinated and HBV infected people received limited attention. In the current study, we adopted a highly specific B-cell Enzyme Linked ImmunoSpot (ELISpot) assay to analyze HBs-specific B cells in various clinical settings: healthy individuals with the history of HBV vaccination before and after receiving an extra HBV vaccine boost, people chronically infected with HBV (CHB) in various clinical stages, with or without a particular type anti-viral treatment, or whether receiving a dose of HBV vaccine. In all of these cases, B-cell ELISpot assay was used effectively in enumerating the frequency of HBs-specific B cells. While the focus of the current report was to establish the utility of this assay for HBV research, a number of interesting observations were made in this pilot study based on the profiles and dynamics of HBs-specific B cells in various conditions. Such information is useful to guide the future work in designing novel therapeutic strategies against CHB.

Lytic EBV infection investigated by detection of Soluble Epstein-Barr virus ZEBRA in the serum of patients with PTLD

The ZEBRA protein (encoded by the BZLF1 gene), is the major transcription factor of EBV, expressed upon EBV lytic cycle activation. Several studies highlighted the critical role of EBV lytic infection as a risk factor for lymphoproliferative disorders like post-transplant lymphoproliferative disease (PTLD). Here, we use an antigen-capture ELISA assay specifically designed to detecting the circulating soluble ZEBRA (sZEBRA) in serum samples (threshold value determined at 40ng/mL). We retrospectively investigated a population of 66 transplanted patients comprising 35 PTLD. All the samples from a control population (30 EBV-seronegative subjects and 25 immunocompetent individuals with EBV serological reactivation), classified as sZEBRA < 40ng/mL were assigned as negative. At PTLD diagnosis, EBV genome (quantified by qPCR with EBV DNA>200 copies/mL) and sZEBRA were detectable in 51% and 60% of cases, respectively. In the patients who developed a pathologically-confirmed PTLD, the mean sZEBRA value in cases, was 399 ng/mL +/− 141 versus 53ng/mL +/− 7 in patients who did not (p  < 0,001). This is the first report relating to the detection of the circulating ZEBRA in serum specimens, as well as the first analysis dealing with the lytic cycle of EBV in PTLD patients with this new biomarker.

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

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

Human herpesviruses-encoded dUTPases: a family of proteins that modulate dendritic cell function and innate immunity

We have previously shown that Epstein-Barr virus (EBV)-encoded dUTPase can modulate innate immune responses through the activation of TLR2 and NF-κB signaling. However, whether this novel immune function of the dUTPase is specific for EBV or a common property of the Herpesviridae family is not known. In this study, we demonstrate that the purified viral dUTPases encoded by herpes simplex virus type 2 (HSV-2), human herpesvirus-6A (HHV-6A), human herpesvirus-8 (HHV-8) and varicella-zoster virus (VZV) differentially activate NF-κB through ligation of TLR2/TLR1 heterodimers. Furthermore, activation of NF-κB by the viral dUTPases was inhibited by anti-TLR2 blocking antibodies (Abs) and the over-expression of dominant-negative constructs of TLR2, lacking the TIR domain, and MyD88 in human embryonic kidney 293 cells expressing TLR2/TLR1. In addition, treatment of human dendritic cells and PBMCs with the herpesviruses-encoded dUTPases from HSV-2, HHV-6A, HHV-8, and VZV resulted in the secretion of the inflammatory cytokines IL-1β, IL-6, IL-8, IL-12, TNF-α, IL-10, and IFN-γ. Interestingly, blocking experiments revealed that the anti-TLR2 Ab significantly reduced the secretion of cytokines by the various herpesviruses-encoded dUTPases (p < 0.05). To our knowledge, this is the first report demonstrating that a non-structural protein encoded by herpesviruses HHV-6A, HHV-8, VZV and to a lesser extent HSV-2 is a pathogen-associated molecular pattern. Our results reveal a novel function of the virus-encoded dUTPases, which may be important to the pathophysiology of diseases caused by these viruses. More importantly, this study demonstrates that the immunomodulatory functions of dUTPases are a common property of the Herpesviridae family and thus, the dUTPase could be a potential target for the development of novel therapeutic agents against infections caused by these herpesviruses.

Epstein-Barr virus infection transforms CD25+ B cells into antibody-secreting cells in rheumatoid arthritis patients

Epstein-Barr virus (EBV) infection may initiate production of autoantibodies and development of cancer and autoimmune diseases. Here we outline phenotypic and functional changes in B cells of patients with rheumatoid arthritis (RA) related to EBV infection. The B-cell phenotype was analysed in blood and bone marrow (BM) of RA patients who had EBV transcripts in BM (EBV(+) , n = 13) and in EBV(-) (n = 22) patients with RA. The functional effect of EBV was studied in the sorted CD25(+) and CD25(-) peripheral B cells of RA patients (n = 18) and healthy controls (n = 9). Rituximab treatment results in enrichment of CD25(+) B cells in peripheral blood (PB) of EBV(+) RA patients. The CD25(+) B-cell subset displayed a more mature phenotype accumulating IgG-expressing cells. It was also enriched with CD27(+) and CD95(+) cells in PB and BM. EBV stimulation of the sorted CD25(+) B cells in vitro induced a polyclonal IgG and IgM secretion in RA patients, while CD25(+) B cells of healthy subjects did not respond to EBV stimulation. CD25(+) B cells were enriched in PB and synovial fluid of RA patients. EBV infection affects the B-cell phenotype in RA patients by increasing the CD25(+) subset and by inducing their immunoglobulin production. These findings clearly link CD25(+) B cells to the EBV-dependent sequence of reactions in the pathogenesis of RA.

Epstein-Barr virus infection induces aberrant TLR activation pathway and fibroblast-myofibroblast conversion in scleroderma

Scleroderma (SSc) is a complex and heterogeneous connective tissue disease mainly characterized by autoimmunity, vascular damage, and fibrosis that mostly involve the skin and lungs. Epstein–Barr virus (EBV) is a lymphotropic γ-herpesvirus that has co-evolved with human species, infecting >95% of the adult population worldwide, and has been a leading candidate in triggering several autoimmune diseases. Here we show that EBV establishes infection in the majority of fibroblasts and endothelial cells in the skin of SSc patients, characterized by the expression of the EBV noncoding small RNAs (EBERs) and the increased expression of immediate-early lytic and latency mRNAs and proteins. We report that EBV is able to persistently infect human SSc fibroblasts in vitro, inducing an aberrant innate immune response in infected cells. EBV–Toll-like receptor (TLR) aberrant activation induces the expression of selected IFN-regulatory factors (IRFs), IFN-stimulated genes (ISGs), transforming growth factor-β1 (TGFβ1), and several markers of fibroblast activation, such as smooth muscle actin and Endothelin-1, and all of these genes play a key role in determining the profibrotic phenotype in SSc fibroblasts. These findings imply that EBV infection occurring in mesenchymal, endothelial, and immune cells of SSc patients may underlie the main pathological features of SSc including autoimmunity, vasculopathy, and fibrosis, and provide a unified disease mechanism represented by EBV reactivation.

Pivotal role of HIV and EBV replication in the long-term persistence of monoclonal gammopathy in patients on antiretroviral therapy

A high prevalence of monoclonal gammopathy (MG) has been observed in HIV-infected patients. We explored the conditions associated with long-term persistence of serum monoclonal protein (M protein) in HIV-infected patients on antiretroviral therapy (ART). Of 21 patients with MG, M protein disappeared in 12 patients (58%) over 5 years of ART. Higher level of serum γ-globulin and higher percentages of circulating plasmablasts and plasma cells were observed in patients with persistent MG compared with patients with transient MG. MG persistence was associated with the cumulative time of detectable plasma HIV RNA after ART initiation, detection of Epstein-Barr virus (EBV) DNA in plasma, and a high level of EBV DNA in B cells. Poor control of HIV replication and detectable EBV replication in plasma were both associated with long-term MG persistence in patients on ART. In the case of viral control, MG associated with HIV infection is usually transient.

Epstein-Barr virus encoded dUTPase containing exosomes modulate innate and adaptive immune responses in human dendritic cells and peripheral blood mononuclear cells

We have recently demonstrated that Epstein-Barr virus (EBV)-encoded deoxyuridine triphosphate nucleotidohydrolase (dUTPase) modulates innate immunity in human primary monocyte-derived macrophages through toll-like receptor (TLR) 2 leading to NF-κB activation and the production of pro-inflammatory cytokines. Our previous depletion studies indicated that dendritic cells (DCs) may also be a target of the EBV-encoded dUTPase. However, the role of EBV-encoded dUTPase in DC activation/function and its potential contribution to the inflammatory cellular milieu characteristic of EBV-associated diseases remains poorly understood. In the present study, we demonstrate that EBV-encoded dUTPase significantly altered the expression of genes involved in oncogenesis, inflammation and viral defense mechanisms in human primary DCs by microarray analysis. Proteome array studies revealed that EBV-encoded dUTPase modulates DC immune responses by inducing the secretion of pro-inflammatory T_H1/T_H17 cytokines. More importantly, we demonstrate that EBV-encoded dUTPase is secreted in exosomes from chemically induced Raji cells at sufficient levels to induce NF-κB activation and cytokine secretion in primary DCs and peripheral blood mononuclear cells (PBMCs). Interestingly, the production of pro-inflammatory cytokines in DCs and PBMCs was TLR2-dependent. Together these findings suggest that the EBV-encoded dUTPase may act as an intercellular signaling molecule capable of modulating the cellular microenvironment and thus, it may be important in the pathophysiology of EBV related diseases.

Large-scale in vitro expansion of polyclonal human switched-memory B lymphocytes

Polyclonal preparations of therapeutic immunoglobulins, namely intravenous immunoglobulins (IVIg), are essential in the treatment of immunodeficiency and are increasingly used for the treatment of autoimmune and inflammatory diseases. Currently, patients’ accessibility to IVIg depends exclusively upon volunteer blood donations followed by the fractionation of pooled human plasma obtained from thousands of individuals. Presently, there are no in vitro cell culture procedures allowing the preparation of polyclonal human antibodies. All in vitro human therapeutic antibodies that are currently generated are based on monoclonal antibodies, which are mostly issued from genetic engineering or single cell antibody technologies. Here, we describe an in vitro cell culture system, using CD40-CD154 interactions, that leads to a 1×10⁶-fold expansion of switched memory B lymphocytes in approximately 50 days. These expanded cells secrete polyclonal IgG, which distribution into IgG₁, IgG₂, IgG₃ and IgG₄ is similar to that of normal human serum. Such in vitro generated IgG showed relatively low self-reactivity since they interacted moderately with only 24 human antigens among a total of 9484 targets. Furthermore, up to one liter of IgG secreting cells can be produced in about 40 days. This experimental model, providing large-scale expansion of human B lymphocytes, represents a critical step toward the in vitro production of polyclonal human IgG and a new method for the ex vivo expansion of B cells for therapeutic purposes.

Investigation of memory B cell responses to hepatitis B surface antigen in health care workers considered as non-responders to vaccination

Up to 20% of health care workers are considered as non-responders to hepatitis B vaccination (anti-HBs<10 m UI/ml in serum). We have explored memory B cells differentiated in vitro into anti-HBs antibody-secreting cells (anti-HBs-SCs) by ELISPOT assay. Anti-HBs-SCs were detected in vaccinated responders (n = 11) and non-responders (n = 10) but IgG anti-HBs-SCs were significantly lower in the non-responder group (p<0.001). Low amounts of HBs antibodies were also quantified by ELISA in non-responders' sera. These results indicate that a suboptimal B cell response exists in non-responders to HBV vaccination. This B cell response may mediate a protection against clinically significant breakthrough hepatitis B infection.

Downregulation of RUNX1 by RUNX3 requires the RUNX3 VWRPY sequence and is essential for Epstein-Barr virus-driven B-cell proliferation

Cross-regulation of RUNX1 expression by RUNX3 plays a critical role in regulating proliferation of human B cells infected with Epstein-Barr virus (EBV). When EBV infection induces RUNX3, the consequent reduction in RUNX1 levels is required for the ensuing cell proliferation because forced expression of RUNX1 in an EBV lymphoblastoid cell line prevented cell proliferation. The TEL-RUNX1 fusion gene from acute B-lymphocytic leukemia retains almost all of the RUNX1 sequence but does not prevent B-cell proliferation in the same assay. B-cell maturation antigen (BCMA) was found to be induced by conditionally expressed RUNX3 in a lymphoma cell line. Chromatin immunoprecipitation assays confirmed that RUNX3 binds to the RUNX1 promoter in a lymphoblastoid cell line and a Burkitt's lymphoma cell line. The TLE binding VWRPY sequence from the C terminus of RUNX3 was found to be required for repression of the RUNX1 P1 promoter in a B-lymphoma cell line. The mechanism of repression in B-cell lines most likely involves recruitment of corepressor TLE3 or TLE4 to the RUNX1 promoter. The results demonstrate the importance of RUNX3-mediated repression of RUNX1 for EBV-driven B-cell proliferation and identify functional differences between human RUNX family proteins.