Early virological and immunological events in Epstein–Barr virus infection

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.

Characteristics of immunological events in Epstein-Barr virus infection in children with infectious mononucleosis

BACKGROUNDS & AIMS

Epstein-Barr virus (EBV) infection occurs commonly in children and may cause acute infectious mononucleosis (AIM) and various malignant diseases. Host immune responses are key players in the resistance to EBV infection. We here assessed the immunological events and laboratory indicators of EBV infection, as well as determined the clinical usefulness of evaluating the severity and efficacy of antiviral therapy in AIM patients.

METHODS

We enrolled 88 children with EBV infection. The immune environment was defined by immunological events such as frequencies of lymphocyte subsets, phenotypes of T cells, and their ability to secrete cytokines, and so on. This environment was analyzed in EBV-infected children with different viral loads and in children in different phases of infectious mononucleosis (IM) from disease onset to convalescence.

RESULTS

Children with AIM had higher frequencies of CD3⁺ T and CD8⁺ T cells, but lower frequencies of CD4⁺ T cells and CD19⁺ B cells. In these children, the expression of CD62L was lower and that of CTLA-4 and PD-1 was higher on T cells. EBV exposure induced granzyme B expression, but reduced IFN-γ secretion, by CD8⁺ T cells, whereas NK cells exhibited reduced granzyme B expression and increased IFN-γ secretion. The frequency of CD8⁺ T cells was positively correlated with the EBV DNA load, whereas the frequencies of CD4⁺ T cells and B cells were negatively correlated. During the convalescent phase of IM, CD8⁺ T cell frequency and CD62L expression on T cells were restored. Moreover, patient serum levels of IL-4, IL-6, IL-10, and IFN-γ were considerably lower throughout the convalescent phase than throughout the acute phase.

CONCLUSION

Robust expansion of CD8⁺ T cells, accompanied by CD62L downregulation, PD-1 and CTLA-4 upregulation on T cells, enhanced granzyme B production, and impaired IFN-γ secretion, is a typical characteristic of immunological events in children with AIM. Noncytolytic and cytolytic effector functions of CD8⁺ T cells are regulated in an oscillatory manner. Furthermore, the AST level, number of CD8⁺ T cells, and CD62L expression on T cells may act as markers related to IM severity and the effectiveness of antiviral treatment.

BRLF1 suppresses RNA Pol III-mediated RIG-I inflammasome activation in the early EBV lytic lifecycle

Latent infection with herpesviruses constitutively activates inflammasomes, while lytic replication suppresses their activation through distinct mechanisms. However, how Epstein-Barr virus (EBV) lytic replication inhibits the activation of inflammasomes remains unknown. Here, we reveal that the EBV immediate-early protein BRLF1 inhibits inflammasome activation, and BRLF1 deficiency significantly increases the activation of inflammasomes and pyroptosis during early lytic lifecycle. BRLF1 interacts with RNA polymerase III subunits to suppress immunostimulatory small RNA transcription, RIG-I inflammasome activation, and antiviral responses. Consequently, BRLF1-deficient EBV primary infection induces robust T-cell and NK cell activation and killing through IL-1β and IL-18. A BRLF1-derived peptide that inhibits inflammasome activation is sufficient to suppress T-cell and NK cell responses during BRLF1-deficient EBV primary infection in lymphocytes. These results reveal a novel mechanism involved in the evasion of inflammasome activation and antiviral responses during EBV early lytic infection and provide a promising approach for the manipulation of inflammasomes against infection of oncogenic herpesviruses.

Cigarette smoke-induced lung inflammation in COPD mediated via CCR1/JAK/STAT /NF-κB pathway

Inflammation is an important cause of chronic obstructive pulmonary disease (COPD) and its acute exacerbation. However, the critical role of C-C chemokine receptor (CCR)1 in progression of cigarette smoke-induced chronic inflammation remains unclear. We studied CCR1 expression using immunohistochemistry, immunofluorescence, and real-time polymerase chain reaction (RT-PCR) in COPD patients and controls. Cytokine levels in peripheral blood were measured by enzyme-linked immunosorbent assay (ELISA). In vitro, we investigated Janus kinase/signal transducers and activators of transcription (JAK/STAT)/nuclear factor-κB (NF-κB) signaling in cigarette smoke extract-induced or CCR1 deficiency/overexpressed mouse macrophage cell line MH-S by RT-PCR and western blot, and measured the cytokine levels in the supernatant with ELISA. We found that CCR1 expression was upregulated in COPD patients and there was a negative correlation between CCR1 mRNA levels and predicted % forced expiratory volume in 1 min. Inflammatory cytokine levels in the peripheral blood were higher in COPD patients than controls, and these were positively correlated with CCR1 levels. CCR1 was shown to play a critical role in regulating smoke-induced inflammation via JAK/STAT3/NF-κB signaling in vitro. CCR1 may play a critical role in airway inflammation in COPD. Additionally, understanding the molecular mechanism may help develop novel methods for the treatment of COPD.

Intralesional EBV-DNA load as marker of prognosis for nasopharyngeal cancer

Nasopharyngeal cancer (NPC) is associated with the Epstein-Barr virus (EBV). The clinical presentation and prognosis of NPC is well described, but not in relation to intralesional EBV-DNA load. In a retrospective design, 48 patients with NPC were examined. Patient history was re-evaluated, and diagnostic biopsies were re-examined. Furthermore, intralesional EBV-DNA was quantitated and HPV status determined. Cancer stage, disease-free survival (DFS), and overall survival (OS) were assessed. Of the 48 patients, 36 (75%) patients featured lesions that were positive for EBER (Epstein-Barr virus-encoded small RNA) and 40 (83%) were positive for EBV-DNA. Seven patients (15%) were HPV positive. The levels of EBV-DNA ranged from 0.0005 to 94617 copies/cell. An EBV-DNA load of more than 70 copies/cell was associated with a prolonged DFS for EBV-DNA positive patients treated with curative intent (p = 0.046). In conclusion, the EBV-DNA load in NPC lesions appears to vary greatly. For patients with EBV-DNA positive NPC treated with curative intent, an EBV-DNA load of more than 70 copies/cell is associated with a better outcome in terms of 7-year DFS.

Endosomal Toll-Like Receptors Mediate Enhancement of Interleukin-17A Production Triggered by Epstein-Barr Virus DNA in Mice

We previously demonstrated that Epstein-Barr virus (EBV) DNA increases the production of the proinflammatory cytokine interleukin-17A (IL-17A) in mice. This property may contribute to the established association between EBV and autoimmune diseases. The objective of the present study was to elucidate mechanisms through which EBV DNA modulates IL-17A levels in mice. To determine whether endosomal Toll-like receptors (TLRs) played a role in this pathway, the expression of TLR3, -7, or -9 was assessed by real-time reverse transcription-PCR in mouse spleens after injection of EBV DNA. Moreover, specific inhibitors were used for these TLRs in mouse peripheral blood mononuclear cells (PBMCs) cultured with EBV DNA and in mice injected with this viral DNA; IL-17A levels were then assessed using an enzyme-linked immunosorbent assay. The expression of the endosomal receptors TLR3, -7, and -9 was increased in mice injected with EBV DNA. When mouse immune cells were cultured with EBV DNA and a TLR3, -7, or -9 inhibitor or when mice were injected with the viral DNA along with either of these inhibitors, a significant decrease in IL-17A levels was detected. Therefore, endosomal TLRs are involved in the EBV DNA-mediated triggering of IL-17A production in mice. Targeting these receptors in EBV-positive subjects with autoimmunity may be useful pending investigations assessing whether they play a similar role in humans.IMPORTANCE Epstein-Barr virus is a pathogen that causes persistent infection with potential consistent viral DNA shedding. The enhancement of production of proinflammatory cytokines by viral DNA itself may contribute to autoimmune disease development or exacerbation. In this project, we identified that endosomal Toll-like receptors are involved in triggering proinflammatory mediators in response to viral DNA. Pathways and receptors involved may serve as future therapeutic targets for autoimmune diseases such as rheumatoid arthritis, multiple sclerosis, and systemic lupus erythematosus.

Viral Interplay with the Host Sumoylation System

Viruses have evolved elaborate means to regulate diverse cellular pathways in order to create a cellular environment that facilitates viral survival and reproduction. This includes enhancing viral macromolecular synthesis and assembly, as well as preventing antiviral responses, including intrinsic, innate, and adaptive immunity. There are numerous mechanisms by which viruses mediate their effects on the host cell, and this includes targeting various cellular post-translational modification systems, including sumoylation. The wide-ranging impact of sumoylation on cellular processes such as transcriptional regulation, apoptosis, stress response, and cell cycle control makes it an attractive target for viral dysregulation. To date, proteins from both RNA and DNA virus families have been shown to be modified by SUMO conjugation, and this modification appears critical for viral protein function. More interestingly, members of the several viral families have been shown to modulate sumoylation, including papillomaviruses, adenoviruses, herpesviruses, orthomyxoviruses, filoviruses, and picornaviruses. This chapter will focus on mechanisms by which sumoylation both impacts human viruses and is used by viruses to promote viral infection and disease.

Expression of the chemokine receptors CCR1 and CCR2B is up-regulated in peripheral blood B cells upon EBV infection and in established lymphoblastoid cell lines

In immunocompetent individuals, EBV establishes in B cells an asymptomatic lifelong latent infection controlled by the immune system. Chemokine receptors regulate immune system function. CCR1 and CCR2 share protein sequence similarity and exert responses to multiple chemokines. The role of these receptors in B cells is largely unknown. We show that the mRNA and functional protein expression of CCR1 and CCR2 is induced in ex vivo B cells upon EBV infection and in established lymphoblastoid cell lines (LCLs). The CCR1 and CCR2B ORF transcripts were determined in LCLs. In contrast, in both the EBV-negative and EBV-positive Burkitt lymphoma cell lines, neither the CCR1, CCR2A, and CCR2B ORF transcripts nor their corresponding proteins were detected. Our data suggest that CCR1/CCR2B could be involved in clearing EBV-infected latency III B cells in immunocompetent individuals via directing the migration of these cells and attracting the chemokines-expressing immune cells.

Presencia del marcador lmp-1 del virus epstein barr en linfomas de caninos

Epstein Barr virus (EBV) is a humans’ high prevalent virus associated with lymphoid B cells tumors development. In canines, few reports have been published regarding the presence of the virus in dogs but its role in this species remain unclear.  The aim of this study was to determine the presence of LMP-1 protein of EBV in 20 canine lymphomas tissues which were previously diagnosed in a period of time between 2004 -2014.  Lymphomas were reclassified in accordance with the new histopathological classifications for lymphomas and were stained by IHQ with anti-CD79a, anti-CD3 and anti-LMP1; specific antibodies for B lymphocytes, T lymphocytes and EBV biomarker respectively.  As a result, it was found that the most common lymphoma was T-zone lymphoma in 75% of the cases of the study. The distribution of the cases regarding the immunostaining were: 18 positive cases with anti- CD3, 2 positive cases with anti-CD79a and 6 positive cases with anti-LMP-1.  Positive cases of LMP1 as a biomarker of the presence of EBV corresponded to the 30% of the cases of the study. Chi-square test showed statistical significance between the presence of the virus and the presence of lymphomas, which suggests not only that the virus is circulating in the canine population but also that could have implications in the development of the disease. Regarding demographic parameters, only the Golden Retriever breed showed a relationship with the presence of lymphoma, but not with the presence of the virus.

Associations of Epstein-Barr Virus DNA in PBMCs and the Subtypes with Breast Cancer Risk

Objective: Epstein-Barr virus (EBV) has been found to be implicated in the development of breast cancer. The purpose of the present study was to identify the associations of EBV DNA and the subtypes in peripheral blood mononuclear cells (PBMCs) with the risk of breast cancer. Material and Methods: A case-control study with 671 breast cancer cases and 859 age-matched controls was conducted in Guangzhou, China. Face-to-face interviews were performed and blood samples were collected immediately after admission to the hospital for patients or after the interview for controls. EBV DNA in PBMCs and the subtypes were detected using Polymerase Chain Reaction (PCR) and restricted fragment length polymorphisms (RFLP). IgA antibodies against EBV VCA-p18 and EBNA-1 were examined using commercial enzyme-linked immunosorbent assay kits. Unconditional logistic regression analysis was applied to evaluate the associations of the DNA positivity and subtypes of EBV with the risk of breast cancer. Results: Among the 1530 subjects, 164 cases (24.4 %) and 206 controls (24.0 %) were positive for EBV DNA in PBMCs and no significant difference occurred between cases and controls. The presence of EBV DNA was related to the positivity of EBV IgA antibodies. Of the DNA positive samples, 71 cases and 109 controls for F/f subtype and 58 cases and 112 controls for C/D subtype were successfully obtained. The D subtype was associated with an increased breast cancer risk compared with the C subtype [OR (95% CI): 2.86 (1.25~6.53)]. We did not find an association of the F/f polymorphism with breast cancer risk. Conclusions: The present study suggested that the presence of EBV DNA in PBMCs may not be an appropriate biomarker for breast cancer risk. The subtype D of EBV was likely to be related to breast tumorigenesis.

Antibody-Dependent NK Cell Activation Differentially Targets EBV-Infected Cells in Lytic Cycle and Bystander B Lymphocytes Bound to Viral Antigen-Containing Particles

NK cells have been reported to respond against EBV-infected B cells in the lytic cycle and to control the viral infection involving IFN-γ secretion. Early reports proposed a role for NK cell Ab-dependent cellular cytotoxicity (ADCC) triggered via FcγR-IIIA (CD16) in the response to EBV. In the current study, we revisited this issue, showing that serum from EBV⁺ individuals triggered vigorous NK cell degranulation and cytokine production (i.e., TNF-α and IFN-γ) against EBV-infected cells, enhancing NK cell activation. The effect was preferentially directed against cells in the lytic phase and was associated with surface expression of the gp350/220 envelope Ag. In contrast, binding of gp350⁺ particles, released by EBV-infected cells, to B cell lines or autologous primary B lymphocytes also promoted specific Ab-dependent NK cell degranulation and TNF-α production but induced minimal IFN-γ secretion. In that case, target cell damage appeared marginal compared with the effect of a control anti-CD20 Ab (rituximab) at concentrations that triggered similar NK cell activation, indicating that cell-associated gp350⁺ particles may divert the cytolytic machinery, impairing its direct action on the plasma membrane. These observations support that Ab-dependent NK cell activation plays an important role in the control of EBV, enhancing NK cell effector functions against infected B cells in the lytic cycle. In contrast, the data reveal that gp350⁺ particles bound to bystander B cells trigger Ab-dependent NK cell degranulation and TNF-α but not cytotoxicity or IFN-γ production, potentially favoring the progression of viral infection.

Type I Interferons and NK Cells Restrict Gammaherpesvirus Lymph Node Infection

Gammaherpesviruses establish persistent, systemic infections and cause cancers. Murid herpesvirus 4 (MuHV-4) provides a unique window into the early events of host colonization. It spreads via lymph nodes. While dendritic cells (DC) pass MuHV-4 to lymph node B cells, subcapsular sinus macrophages (SSM), which capture virions from the afferent lymph, restrict its spread. Understanding how this restriction works offers potential clues to a more comprehensive defense. Type I interferon (IFN-I) blocked SSM lytic infection and reduced lytic cycle-independent viral reporter gene expression. Plasmacytoid DC were not required, but neither were SSM the only source of IFN-I, as IFN-I blockade increased infection in both intact and SSM-depleted mice. NK cells restricted lytic SSM infection independently of IFN-I, and SSM-derived virions spread to the spleen only when both IFN-I responses and NK cells were lacking. Thus, multiple innate defenses allowed SSM to adsorb virions from the afferent lymph with relative impunity. Enhancing IFN-I and NK cell recruitment could potentially also restrict DC infection and thus improve infection control.

IMPORTANCE

Human gammaherpesviruses cause cancers by infecting B cells. However, vaccines designed to block virus binding to B cells have not stopped infection. Using a related gammaherpesvirus of mice, we have shown that B cells are infected not via cell-free virus but via infected myeloid cells. This suggests a different strategy to stop B cell infection: stop virus production by myeloid cells. Not all myeloid infection is productive. We show that subcapsular sinus macrophages, which do not pass infection to B cells, restrict gammaherpesvirus production by recruiting type I interferons and natural killer cells. Therefore, a vaccine that speeds the recruitment of these defenses might stop B cell infection.

Malaria - how this parasitic infection aids and abets EBV-associated Burkitt lymphomagenesis

Burkitt lymphoma (BL) is >90% EBV-associated when this pediatric cancer is diagnosed in regions heavily burden by endemic Plasmodium falciparum malaria and thus has been geographically classified as endemic BL. The incidence of endemic BL is 10-fold higher compared to BL diagnosed in non-malarious regions of the world. The other forms of BL have been classified as sporadic BL which contain EBV in ∼30% of cases and immunodeficiency BL which occurs in HIV-infected adults with ∼40% of tumors containing EBV. Within malaria endemic regions, epidemiologic studies replicating Denis Burkitt's seminal observation continue to show differences in endemic BL incidence linked to intensity of malaria transmission. However, the mechanisms by which malaria contributes to B cell tumorigenesis have not been resolved to the point of designing cancer prevention strategies. The focus of this review is to summarize our current knowledge regarding the influence of prolonged, chronic malaria exposure on defects in immunosurveillance that would otherwise control persistent EBV infections. And thus, set the stage for ensuing mechanisms by which malaria could instigate B cell activation and aberrant activation-induced cytidine deaminase expression initiating somatic hypermutation and thereby increasing the likelihood of an Ig/Myc translocation, the hallmark of all BL tumors. Malaria appears to play multiple, sequential and simultaneous roles in endemic BL etiology; the complexity of these interactions are being revealed by applying computational methods to human immunology. Remaining questions yet to be addressed and prevention strategies will also be discussed.