Inhibition of Epstein-Barr virus (EBV) release from P3HR-1 and B95-8 cell lines by monoclonal antibodies to EBV membrane antigen gp350/220

Epstein-Barr Virus Reactivation-Induced Immunoglobulin Production: Significance on Autoimmunity

Epstein–Barr virus (EBV) mainly persists in B cells, which differentiate into antibody-producing cells, and thus, EBV has been implicated in autoimmune diseases. We aimed to describe the EBV reactivation and its relevance to autoimmune disease, focusing on Graves’ disease, which is an autoimmune hyperthyroidism caused by thyrotropin receptor antibodies. Circulating autoreactive B cells that have evaded from the selection have difficulties differentiating to produce antibodies. However, once EBV infects such B cells and reactivates, the B cells may become plasma cells and produce autoantibody. We herein proposed an EBV reactivation-induced Ig production system, which is a distinct pathway from the antibody production system through germinal centers and bone marrow and has the following characteristics: 1. IgM dominance, 2. ubiquitous Ig production, and 3. the rescue of autoreactive B cells, which skews Ig production toward autoantigens. IgM autoantibodies induced by EBV reactivation may activate the classical complement pathway and injure healthy tissue, which supply autoantigens for the production of affinity-matured IgG autoantibodies. Antibodies induced by EBV reactivation may play important roles in the development and exacerbation of autoimmune diseases.

Epstein-Barr Virus Lytic Reactivation Induces IgG4 Production by Host B Lymphocytes in Graves' Disease Patients and Controls: A Subset of Graves' Disease Is an IgG4-Related Disease-Like Condition

Immunoglobulin (Ig) G4-related disease (IgG4-RD) is a newly recognized systemic fibroinflammatory disease with characteristic histological findings and high serum IgG4 levels. Epstein–Barr virus (EBV) is a persistent herpesvirus in B lymphocytes, and we previously reported EBV reactivation-induced Ig production. We showed that EBV reactivation induced the production of thyrotropin receptor antibodies, the causative antibodies of Graves' disease. In the present study, we investigated whether EBV reactivation induced IgG4 production and if EBV-positive B cells or IgG4-positive plasma cells are present in the thyroid tissues of Graves' disease patients with lymphoplasmacytic infiltration. EBV-encoded small RNA1 (EBER1) in situ hybridization and immunohistochemistry for IgG and IgG4 were performed on seven resected thyroid tissues with lymphoplasmacytic infiltration collected from the thyroids of 11 Graves' disease patients. We then cultured the lymphocytes of 13 Graves' disease patients and 14 controls and induced EBV reactivation to measure IgG4 levels in culture fluids. We detected EBER1-positive cells and IgG4-positive plasma cells in the same area of thyroid tissues. EBV-reactivated cells with IgG4 on their surface were observed in culture cells, and IgG4 production was detected in culture fluids. The IgG4/IgG percentage was higher than that in normal serum level. A subset of Graves' disease is an IgG4-RD-like condition, not an IgG4-RD. EBV reactivation stimulates IgG4 production, which may result in high serum IgG4 levels and promote IgG4-positive plasma cell infiltration. EBER1 needs to be examined when an increase in IgG4-positive plasma cell numbers is noted.

Epstein-Barr Virus Lytic Reactivation Activates B Cells Polyclonally and Induces Activation-Induced Cytidine Deaminase Expression: A Mechanism Underlying Autoimmunity and Its Contribution to Graves' Disease

Graves' disease is an autoimmune disease that results in and is the most common cause of hyperthyroidism, and the reactivation of persisting Epstein–Barr virus (EBV) in B lymphocytes induces the differentiation of host B cells into plasma cells. We previously reported that some EBV-infected B cells had thyrotropin receptor antibodies (TRAbs) as surface immunoglobulins (Igs), and EBV reactivation induced these TRAb+EBV+ cells to produce TRAbs. EBV reactivation induces Ig production from host B cells. The purpose of the present study was to examine total Ig productions from B cell culture fluids and to detect activation-induced cytidine deaminase (AID), nuclear factor kappa B (NF-κB), and EBV latent membrane protein (LMP) 1 in culture B cells during EBV reactivation induction and then we discussed the mechanisms of EBV reactivation-induced Ig production in relation to autoimmunity. We showed that the EBV reactivation induces the production of every isotype of Ig and suggested that the Ig production was catalyzed by AID through LMP1 and NF-κB. The results that the amount of IgM was significantly larger compared with IgG suggested the polyclonal B cell activation due to LMP1. We proposed the pathway of EBV reactivation induced Ig production; B cells newly infected with EBV are activated by polyclonal B cell activation and produce Igs through plasma cell differentiation induced by EBV reactivation. LMP1-induced AID enabled B cells to undergo class-switch recombination to produce every isotype of Ig. According to this mechanism, EBV rescues autoreactive B cells to produce autoantibodies, which contribute to the development and exacerbation of autoimmune diseases.

Designing an effective vaccine to prevent Epstein-Barr virus-associated diseases: challenges and opportunities

INTRODUCTION

Epstein-Barr virus (EBV) is a ubiquitous herpesvirus associated with a number of clinical manifestations. Primary EBV infection in young adolescents often manifests as acute infectious mononucleosis and latent infection is associated with multiple lymphoid and epithelial cancers and autoimmune disorders, particularly multiple sclerosis. Areas covered: Over the last decade, our understanding of pathogenesis and immune regulation of EBV-associated diseases has provided an important platform for the development of novel vaccine formulations. In this review, we discuss developmental strategies for prophylactic and therapeutic EBV vaccines which have been assessed in preclinical and clinical settings. Expert commentary: Major roadblocks in EBV vaccine development include no precise understanding of the clinical correlates of protection, uncertainty about adjuvant selection and the unavailability of appropriate animal models. Recent development of new EBV vaccine formulations provides exciting opportunities for the formal clinical assessment of novel formulations.

Reactivation of persistent Epstein-Barr virus (EBV) causes secretion of thyrotropin receptor antibodies (TRAbs) in EBV-infected B lymphocytes with TRAbs on their surface

Epstein-Barr virus (EBV) is a ubiquitous virus that infects most adults latently. It persists in B lymphocytes and reactivates occasionally. Graves' disease is an autoimmune hyperthyroidism caused by thyrotropin receptor antibodies (TRAbs). We have reported that Graves' disease patients and healthy controls have EBV-infected lymphocytes that have TRAbs on their surface (TRAb(+)EBV(+) cells) in peripheral blood mononuclear cells (PBMCs). EBV reactivation is known to be associated with plasma cell differentiation and antibody production of B cells. In this study, we investigated whether TRAb(+)EBV(+) cells really produce TRAbs or not when persistent EBV is reactivated. We cultured PBMCs from 12 Graves' disease patients and 12 healthy controls for several days with cyclosporine A to expand the EBV-infected cell population, and then compared TRAb levels between EBV reactivation by 33 °C culture and EBV nonreactivation by 37 °C culture of PBMCs. Flow cytometry confirmed that all samples at day 0 (reactivation starting point) contained TRAb(+)EBV(+) cells. During 33 °C culture, EBV-reactivated cells with EBV-gp350/220 expression increased from about 1 to 4%. We quantified TRAb levels in culture fluids by radio-receptor assay, and detected an increased concentration for at least one sampling point at 33 °C (from days 0 to 12) for all patients and healthy controls. TRAb levels were significantly higher in supernatants of 33 °C culture than of 37 °C culture, and also significantly higher in supernatants from patients than those from controls. This study revealed TRAb production from TRAb(+)EBV(+) cells in response to reactivation induction of persistent EBV in different efficiencies between patients and controls.

Epstein-barr virus vaccines

Epstein–Barr virus (EBV) is the primary cause of infectious mononucleosis (IM) and is associated with epithelial cell malignancies such as nasopharyngeal carcinoma and gastric carcinoma, as well as lymphoid malignancies including Hodgkin lymphoma, Burkitt lymphoma, non-Hodgkin lymphoma and post-transplant lymphoproliferative disorder. EBV vaccines to prevent primary infection or disease, or therapeutic vaccines to treat EBV malignancies have not been licensed. Most efforts to develop prophylactic vaccines have focused on EBV gp350, which is the major target of neutralizing antibody. A single phase 2 trial of an EBV gp350 vaccine has been reported; the vaccine reduced the rate of IM but not virus infection. The observation that infusion of EBV-specific T cells can reduce disease due to Hodgkin lymphoma and nasopharyngeal carcinoma provides a proof of principle that a therapeutic vaccine for these and other EBV-associated malignancies might be effective. Most therapeutic vaccines have targeted EBV LMP2 and EBV nuclear antigen-1. As EBV is associated with nearly 200 000 new malignancies each year worldwide, an EBV vaccine to prevent these diseases is needed.

Presence of Epstein-Barr virus-infected B lymphocytes with thyrotropin receptor antibodies on their surface in Graves' disease patients and in healthy individuals

Graves' disease is an autoimmune hyperthyroidism caused by thyrotropin receptor antibodies (TRAbs). Because Epstein-Barr virus (EBV) persists in B cells and is occasionally reactivated, we hypothesized that EBV contributes to TRAbs production in Graves' disease patients by stimulating the TRAbs-producing B cells. In order for EBV to stimulate antibody-producing cells, EBV must be present in those cells but that have not yet been observed. We examined whether EBV-infected (EBV(+)) B cells with TRAbs on their surface (TRAbs(+)) as membrane immunoglobulin were present in peripheral blood of Graves' disease patients. We analyzed cultured or non-cultured peripheral blood mononuclear cells (PBMCs) from 13 patients and 11 healthy controls by flow-cytometry and confocal laser microscopy, and confirmed all cultured PBMCs from 8 patients really had TRAbs(+) EBV(+) double positive cells. We unexpectedly detected TRAbs(+) cells in all healthy controls, and TRAbs(+) EBV(+) double positive cells in all cultured PBMC from eight healthy controls. The frequency of TRAbs(+) cells in cultured PBMCs was significantly higher in patients than in controls (p = 0.021). In this study, we indicated the presence of EBV-infected B lymphocytes with TRAbs on their surface, a possible player of the production of excessive TRAbs, the causative autoantibody for Graves' disease. This is a basic evidence for our hypothesis that EBV contributes to TRAbs production in Graves' disease patients. Our results further suggest that healthy controls have the potential for TRAbs production. This gives us an important insight into the pathogenesis of Graves' disease.

A virus-like particle-based Epstein-Barr virus vaccine

Epstein-Barr Virus (EBV) is an ubiquitous human herpesvirus which can lead to infectious mononucleosis and different cancers. In immunocompromised individuals, this virus is a major cause for morbidity and mortality. Transplant patients who did not encounter EBV prior to immunosuppression frequently develop EBV-associated malignancies, but a prophylactic EBV vaccination might reduce this risk considerably. Virus-like particles (VLPs) mimic the structure of the parental virus but lack the viral genome. Therefore, VLPs are considered safe and efficient vaccine candidates. We engineered a dedicated producer cell line for EBV-derived VLPs. This cell line contains a genetically modified EBV genome which is devoid of all potential viral oncogenes but provides viral proteins essential for the assembly and release of VLPs via the endosomal sorting complex required for transport (ESCRT). Human B cells readily take up EBV-based VLPs and present viral epitopes in association with HLA molecules to T cells. Consequently, EBV-based VLPs are highly immunogenic and elicit humoral and strong CD8+ and CD4+ T cell responses in vitro and in a preclinical murine model in vivo. Our findings suggest that VLP formulations might be attractive candidates to develop a safe and effective polyvalent vaccine against EBV.

Epstein-Barr virus promotes human monocyte survival and maturation through a paracrine induction of IFN-alpha

The role of monocytes and macrophages during EBV infection is not clear. The interaction of EBV with human monocytes was investigated in terms of cell survival and morphological and phenotypic changes to gain a better understanding of the role of these cells during EBV infection. We show that EBV infection of PBMCs rescues monocytes from undergoing spontaneous apoptosis and dramatically enhances their survival. Results obtained with heat-inactivated virus, neutralizing anti-EBV mAb 72A1 and recombinant gp350, suggest that enhancement of viability by EBV requires both infectious virus and interaction between gp350 and its receptor. IFN-alpha either secreted within 24 h from PBMCs upon infection with EBV or exogenously added to unstimulated monocytes inhibited spontaneous apoptosis, indicating that induction of IFN-alpha is an early important survival signal responsible for the delay in the apoptosis of monocytes. EBV infection also induced acute maturation of monocytes to macrophages with morphological and phenotypic characteristics of potent APCs. Monocytes exposed to EBV became larger in size with increased granularity and expressed considerably higher levels of membrane HLA classes I and II, ICAM-1, CD80, CD86, and CD40 compared with uninfected cultures. These observations provide the first immunoregulatory links among EBV, IFN-alpha, and monocyte survival and maturation and importantly raise the possibility that these cells may serve as a vehicle for the dissemination of the virus as well as being active participants in eliciting anti-EBV T cell responses during acute infection.

A novel monoclonal antibody specific to the C-terminal tail of the gp41 envelope transmembrane protein of human immunodeficiency virus type 1 that preferentially neutralizes virus after it has attached to the target cell and inhibits the production of infectious progeny

SAR1 is a new IgG2a murine monoclonal antibody derived by immunization with a plant virus expressing the sequence GERDRDR from the C-terminal tail of the gp41 transmembrane glycoprotein of human immunodeficiency virus type 1 (HIV-1). SAR1 binds to peptides and proteins carrying the GERDRDR sequence, to some but not all preparations of purified virus, and to cells infected with all viruses tested. In a standard neutralization assay, SAR1 failed to neutralize, or neutralized poorly, a number of T cell line-adapted viruses. However, it was more effective at postattachment neutralization. This was measured by two assays, the inhibition of the syncytium production by input virus, and the inhibition of the production of infectious progeny virus. In general SAR1 was more effective at neutralizing progeny virus than inoculum virus. Fifty percent inhibition of progeny virus production by different HIV-1 strains was obtained with 2-26 microg/ml of SAR1. The SAR1 neutralizing epitope was mapped specifically to the gp41 C-terminal tail. SAR1 is an unusual, if not unique, antibody whose activity supports the view that part of the gp41 C-terminal tail is exposed on the outside of the virion.

High level of transgene expression in primary chronic lymphocytic leukemia cells using helper-virus-free recombinant Epstein-Barr virus vectors

OBJECTIVE

Epstein-Barr virus (EBV)-based vectors have favorable features for gene transfer, including a high transduction efficiency especially for B cells, large packaging capacity up to 150 kb pairs, and ability to infect postmitotic cells. Recombinant EBV was explored for transduction of primary human B-cell chronic lymphocytic leukemia (CLL) cells.

MATERIAL AND METHODS

EBV vectors deleted for all oncogenic sequences and encoding terminal repeats (TR) essential for encapsidation, the lytic origin of replication (oriLyt) for DNA amplification, and the enhanced green fluorescent protein (EGFP) were packaged using an optimized, helper-virus-free method. Infectious EBV virions encoding EGFP (EBV/EGFP) with an infectious titer up to 2 x 10(6) per milliliter were generated. Primary leukemic cells from 14 patients with CLL were successfully transduced with EBV/EGFP at a very low multiplicity of infection (< 1).

RESULTS

Transgene expression was detected in up to 85% of cells 48 hours after infection. Transduction was specifically mediated by EBV vectors because gene transfer was inhibited by an antibody (72A1) directed against the viral envelope glycoprotein gp350/220. Furthermore, transduction of CLL cells with packaged EBV vectors coding for EGFP but deleted for TR sequences (TR-) did not result in EGFP expression compared to TR+ vector constructs (p = 0.009).

CONCLUSION

Helper-virus-free EBV-based gene transfer vectors hold promise for development of genetic therapies for CLL patients.

Down-regulation of spontaneous Epstein-Barr virus reactivation in the P3HR-1 cell line by L-arginine

We tested the hypothesis that inhibition of Epstein-Barr virus (EBV) reactivation is controlled in part by nitric oxide (NO) generated from L-arginine (Arg). The spontaneous reactivation of EBV in the Burkitt's lymphoma (BL) cell line P3HR-1 was inhibited when the cells were cultured in L-Arg-supplemented medium. The expression of EBV early antigen (EA), immediate-early BZLF1 mRNA and the protein ZEBRA, and production of infectious virus were reduced by L-Arg supplementation in a dose-dependent manner. We demonstrated that inducible NO synthase (iNOS) mRNA was constitutively expressed in P3HR-1 cells, as quantitated by the reverse transcription-polymerase chain reaction. L-Arg supplementation enhanced iNOS and NOx expression in the cells. A specific NOS inhibitor, NG-monomethyl-L-Arg enhanced the expression of ZEBRA and early BMRF1 protein EA-D in the cells. L-Arg supplementation also inhibited the spontaneous EBV reactivation in another BL cell line EB1 and a B lymphoblastoid cell line OB. These results indicated that L-Arg induces iNOS and generates NO, which inhibits EBV reactivation in EBV-positive cells.

Effect of interleukin-7 on the in vitro development and maturation of monocyte derived human dendritic cells

We have compared the cell phenotype and functional properties of monocyte/macrophage derived dendritic cells (DCs) obtained by culture of human adherent peripheral blood mononuclear cells (PBMCs) in medium containing granulocyte macrophage colony stimulating factor (GM-CSF) either alone (GM-CSF-DCs), or in combination with interleukin (IL)-4 (IL4-DCs) or IL-7 (IL7-DCs). The cell surface phenotype of GM-CSF-DCs and IL-7-DCs was characterized by a high expression of major histocompatibility complex (MHC) class I and II, CD80, CD86 and CD40. In contrast to 'classical' IL-4-DCs, these two types of DCs expressed CD14 and a CD21-like molecule detected by two out of four CD21-specific monoclonal antibodies (MoAb) tested. The same pattern of reactivity with CD21 specific antibodies was observed in freshly isolated adherent PBMCs but not in B lymphocytes. This reactivity was upregulated by IL-7 in a dose dependent manner. Lipopolysaccharide (LPS) treatment induced the upregulation of CD40, CD80, CD86 and the T-cell stimulatory capacity in IL-4-DCs and, to a lesser extent, in the IL-7-DCs whereas GM-CSF-DCs responded very poorly to such treatment. Our data indicate that, together with GM-CSF, the IL-7 drives macrophage precursors to a differentiation stage that is close to but distinct from the phenotype of IL-4-DCs. Comparison of DC development in the presence of IL-7 or IL-4 may help in dissecting signalling pathways that regulate the expression of functionally relevant DC markers.

Retrieval of human cytomegalovirus glycoprotein B from the infected cell surface for virus envelopment

Surface biotinylation of human cytomegalovirus (HCMV)-infected fibroblasts under pulse-chase conditions was used to define the cellular route of the dominant viral envelope glycoprotein gB into the cytoplasmic compartment of viral maturational envelopment. The results showed that a major fraction of gB was re-internalized from the infected cell surface prior to incorporation into the viral envelope. Viral particles carrying biotinylated gB were subsequently released into the culture medium. Viral release appeared to be inhibited in the presence of gB-specific antibody or when infected cultures were incubated at room temperature, but was not reduced by inhibitors of cellular glycoprotein transport. To our knowledge this is the first report describing that HCMV gB is retrieved from the infected cell surface prior to viral envelopment.

Subcellular distribution and life cycle of Epstein-Barr virus in keratinocytes of oral hairy leukoplakia

The authors investigated the life cycle of Epstein-Barr virus (EBV) in keratinocytes of oral hairy leukoplakia by combining immunohistochemistry. DNA in situ hybridization, and lectin histochemistry with electron microscopy. Diffuse-staining components of the EBV early antigen complex (EA-D), EBV 150-kd capsid antigen (VCA), EBV membrane antigen (gp350/220), and double-stranded DNA were labeled with monoclonal antibodies. An EBV-DNA probe was used to locate EBV DNA. Wheat-germ agglutinin (WGA) was employed to distinguish Golgi-associated compartments. The authors found EBV proteins and EBV DNA only in keratinocytes with apparent viral assembly. In situ hybridization showed EBV DNA in free corelike material and in electron-dense cores of mature nucleocapsids. Monoclonal antibodies to nonspecific double-stranded DNA attached to the same structures and to marginated chromatin. Components of EA-D were dispersed throughout the nuclei but accumulated near condensed chromatin and in 'punched-out' regions of the chromatin. Epstein-Barr virus 150-kd capsid antigen was found only in the nuclei, where it appeared preferentially on mature nucleocapsids. As yet unexplained arrays of intranuclear particles that remained unlabeled with all EBV-specific probes reacted intensely with an antiserum against common papillomavirus antigen. Gp350/220 was detectable in various cellular membrane compartments and was highly concentrated on EBV envelopes in peripheral Golgi-associated secretory vesicles. It was less abundant on the extracellular EBV, indicating that viral membrane antigen partly dissociates from the mature virus. Combined lectin-binding histochemistry and electron microscopy demonstrated for the first time that EBV is processed in the Golgi apparatus, which eventually releases the virus by fusion with the plasma membrane. These results provide insight into the biologic events that occur during complete EBV replication in vivo.

Epstein-Barr virus (EBV) antigens processed and presented by B cells, B blasts, and macrophages trigger T-cell-mediated inhibition of EBV-induced B-cell transformation

The ability of B cells, B blasts, and macrophages to present Epstein-Barr virion antigens to autologous T cells and trigger their capacity to inhibit Epstein-Barr virus-induced B-cell transformation was tested. Macrophages were as efficient as B cells and B blasts in presenting the virus to T lymphocytes. This function required antigen processing, because it was inhibited by chloroquine treatment and by fixation of the antigen-presenting cells immediately after viral exposure but not 18 h later. T cells exposed to the purified Epstein-Barr virus envelope antigen gp350 coupled to immunostimulating complexes also showed inhibitory function. These results suggest that recognition of processed virion antigens elicits the generation of T-cell-mediated inhibition of Epstein-Barr virus-induced B-cell transformation.