Epstein-Barr virus: induction and control of cell transformation

Exploring the nuclear proteins, viral capsid protein, and early antigen protein using immunoinformatic and molecular modeling approaches to design a vaccine candidate against Epstein Barr virus

The available Epstein Barr virus vaccine has tirelessly harnessed the gp350 glycoprotein as its target epitope, but the result has not been preventive. Right here, we designed a global multi-epitope vaccine for EBV; with special attention to making sure all strains and preventive antigens are covered. Using a robust computational vaccine design approach, our proposed vaccine is armed with 6-16 mers linear B-cell epitopes, 4-9 mer CTL epitopes, and 8-15 mer HTL epitopes which are verified to induce interleukin 4, 10 & IFN-gamma. We employed deep computational mining coupled with expert intelligence in designing the vaccine, using human Beta defensin-3-which has been reported to induce the same TLRs as EBV-as the adjuvant. The tendency of the vaccine to cause autoimmune disorder is quenched by the assurance that the construct contains no EBNA-1 homolog. The protein vaccine construct exhibited excellent physicochemical attributes such as Aliphatic index 59.55 and GRAVY - 0.710; and a ProsaWeb Z score of - 3.04. Further computational analysis revealed the vaccine docked favorably with EBV indicted TLR 1, 2, 4 & 9 with satisfactory interaction patterns. With global coverage of 85.75% and the stable molecular dynamics result obtained for the best two interactions, we are optimistic that our nontoxic, non-allergenic multi-epitope vaccine will help to ameliorate the EBV-associated diseases-which include various malignancies, tumors, and cancers-preventively.

How I Diagnose EBV-Positive B- and T-Cell Lymphoproliferative Disorders

OBJECTIVES

Epstein-Barr virus (EBV)-associated lymphoproliferative disorders (LPDs) encompass a group of well-defined entities of B-, T-, and natural killer (NK)-cell derivation. The diagnosis of these disorders is challenging because of clinical and morphologic features that may overlap with other benign and malignant EBV+ lymphoproliferations. This review describes our approach to the diagnosis of EBV-associated LPDs.

METHODS

Two cases are presented that illustrate how we diagnose EBV-associated LPDs. The first case represents a systemic EBV+ T-cell lymphoma of childhood and the second case an EBV+ mucocutaneous ulcer. The clinicopathologic features that help distinguish these entities from biological and morphologic mimickers are emphasized.

RESULTS

The accurate diagnosis of EBV-associated LPDs requires the incorporation of histologic and immunophenotypic features, the assessment of the EBV latency program, and, most important, complete clinical findings. Clonality analysis is not helpful in distinguishing benign from malignant EBV+ LPDs.

CONCLUSIONS

The better understanding of EBV-associated LPDs has resulted in the recognition of well-defined entities of B-, T-, and NK-cell derivation and consequently improvement of their treatment with curative intent. It is critical to distinguish benign from malignant EBV+ LPDs to avoid overtreatment.

Evaluation of HPV and EBV in OSCC and the expression of p53, p16, E-cadherin, COX-2, MYC, and MLH1

OBJECTIVE

This study aimed to evaluate the presence of human papillomavirus (HPV) and Epstein-Barr virus (EBV) and the expression of p53, p16, E-cadherin, COX-2, MLH1, and MYC in oral squamous cell carcinoma (OSCC).

MATERIALS AND METHODS

One hundred OSCC specimens were submitted to in situ hybridization for HPV and EBV, and immunohistochemistry for detection of the human proteins.

RESULTS

Thirty-one cases showed HPV in tumor tissue. EBV was not detected in any case investigated. The HPV(+) group demonstrated an increase of staining scores for nuclear p16 (p = .047), cytoplasmic MYC (p = .002), while a decrease for nuclear MLH1 (p = .048), suggesting that HPV may upregulate the expression of the first two proteins and down-regulate the latter.

CONCLUSION

Our findings reinforce the hypothesis of the HPV-related oral carcinogenesis involving the expression of p16 and MYC, and MLH1 suppression. Exclusively cytoplasmic stainings for p16, MLH1, and MYC were also associated with more advanced tumors. Finally, in view of the lack of studies correlating the HPV or EBV infection to the expression of oncoproteins, more researches assessing a broader panel of markers and employing different approaches are still necessary in order to understand the role of these viruses as well as the molecular mechanisms involved in the development and progression of oral carcinomas.

Epstein-Barr virus and risk of breast cancer: a systematic review and meta-analysis

Despite the numerous publications regarding the role of Epstein-Barr virus (EBV) in breast cancer development, the topic has still remained controversial. The aim of the meta-analysis was to estimate the overall prevalence of EBV in the breast cancer population, and to investigate the association between EBV and breast cancer risk. The overall prevalence of EBV was calculated 26.37% (95% CI: 22-31%) from the 44 included studies. Meta-analysis of 30 case-control studies showed that the pooled association between EBV and risk of breast cancer is odds ratio 4.74 (95% CI: 2.92-7.69; Z = 6.30; p < 0.0001). Our analyses indicate a strong statistical relationship between EBV infection and risk of breast cancer, suggesting a potential role of EBV infection in the development of breast cancer.

Herpesvirus deconjugases inhibit the IFN response by promoting TRIM25 autoubiquitination and functional inactivation of the RIG-I signalosome

The N-terminal domains of the herpesvirus large tegument proteins encode a conserved cysteine protease with ubiquitin- and NEDD8-specific deconjugase activity. The proteins are expressed during the productive virus cycle and are incorporated into infectious virus particles, being delivered to the target cells upon primary infection. Members of this viral enzyme family were shown to regulate different aspects of the virus life cycle and the innate anti-viral response. However, only few substrates have been identified and the mechanisms of these effects remain largely unknown. In order to gain insights on the substrates and signaling pathways targeted by the viral enzymes, we have used co-immunoprecipitation and mass spectrometry to identify cellular proteins that interact with the Epstein-Barr virus encoded homologue BPLF1. Several members of the 14-3-3-family of scaffold proteins were found amongst the top hits of the BPLF1 interactome, suggesting that, through this interaction, BPLF1 may regulate a variety of cellular signaling pathways. Analysis of the shared protein-interaction network revealed that BPLF1 promotes the assembly of a tri-molecular complex including, in addition to 14-3-3, the ubiquitin ligase TRIM25 that participates in the innate immune response via ubiquitination of cytosolic pattern recognition receptor, RIG-I. The involvement of BPLF1 in the regulation of this signaling pathway was confirmed by inhibition of the type-I IFN responses in cells transfected with a catalytically active BPLF1 N-terminal domain or expressing the endogenous protein upon reactivation of the productive virus cycle. We found that the active viral enzyme promotes the dimerization and autoubiquitination of TRIM25. Upon triggering of the IFN response, RIG-I is recruited to the complex but ubiquitination is severely impaired, which functionally inactivates the RIG-I signalosome. The capacity to bind to and functionally inactivate the RIG-I signalosome is shared by the homologues encoded by other human herpesviruses.

Human immunodeficiency virus (HIV) and Epstein-Barr virus (EBV) related lymphomas, pathology view point

The contribution of Epstein Barr virus (EBV) and Kaposi sarcoma herpes virus (KSHV) to the development of specific types of malignant lymphomas occurring in the human immunodeficiency virus (HIV) setting has been extensively studied since the beginning of the HIV epidemic 35 years ago. The introduction of highly active antiretroviral therapies (HAART) in 1996 has changed dramatically the incidence of HIV-related malignancies. Nevertheless, malignant lymphomas continue to be the major group of malignances observed in HIV infected individuals, and the most common cause of cancer related-deaths. Common features of the predominant B-cell lymphomas in the HIV⁺ setting are the frequent plasmacytoid morphology of the neoplastic cells, advanced stage, aggressive disease and frequent extranodal involvement. In this article, we review the evolving concepts and definitions of the various EBV-associated lymphomas in HIV⁺ patients, including diffuse large B-cell lymphoma, Burkitt lymphoma, classical Hodgkin lymphoma, plasmablastic lymphoma and primary effusion lymphoma. The current knowledge regarding the pathogenesis of these malignancies, the interplay between HIV and EBV co-infection in the development of certain HIV related lymphomas, and the emerging paradigm that suggests that HIV may play a direct role in lymphomagenesis are explored as well.

Epstein-Barr virus and cytomegalovirus infections and their clinical relevance in Egyptian leukemic pediatric patients

Background

Epstein-Barr virus (EBV) and human cytomegalovirus (CMV) infections are environmental risk factors affecting the outcome of cancer due to an impairment in the cell-mediated immunity. Therefore, this study aimed to detect the frequency of EBV and CMV DNA and their association with clinical characteristics and outcome of pediatric leukemic patients.

Methods

Samples of 50 immunocompromised pediatric leukemic patients and 30 apparently healthy children were subjected to the amplification of EBV DNA by one version of PCR targeting the Bam H1 W region of the genomic region of EBV, and the amplification of CMV DNA by targeting the CMV UL97 genomic region by a second round PCR. All investigations were performed on WBCs and sera. Results were correlated with the clinical and laboratory characteristics of the disease, and with overall survival.

Results

EBV and CMV DNA were detected in 20 and 54% of leukemic patients, respectively. Nine out of ten patients with EBV DNA (90%) were positive for CMV DNA in their sera. The presence of EBV DNA or CMV DNA was associated with neutropenia and a low total leukocyte count (TLC) (p = 0.02, 0.03, respectively). The presence of severe CMV disease, longer duration of febrile neutropenia, neutropenia, lymphopenia, thrombocytopenia and the presence of EBV DNA in patients’ sera were significantly associated with worse overall survival.

Conclusion

The detection of CMV disease and EBV DNA is relatively common in leukemic children and is significantly associated with a decline in the overall survival.

An EBV recombinant deleted for residues 130-159 in EBNA3C can deregulate p53/Mdm2 and Cyclin D1/CDK6 which results in apoptosis and reduced cell proliferation

Epstein-Barr virus (EBV), a gamma herpes virus is associated with B-cell malignancies. EBNA-3C is critical for in vitro primary B-cell transformation. Interestingly, the N terminal domain of EBNA3C which contains residues 130–159, interacts with various cellular proteins, such as p53, Mdm2, CyclinD1/Cdk6 complex, and E2F1. In the current reverse genetics study, we deleted the residues 130-159 aa within EBNA3C open reading frame (ORF) by BACmid recombinant engineering methodology. Our experiments demonstrated that deletion of the 130-159 aa showed a reduction in cell proliferation. Also, this recombinant virus showed with higher infectivity of human peripheral blood mononuclear cells (PBMCs) compared to wild type EBV. PBMCs- infected with recombinant EBV deleted for 130-159 residues have differential expression patterns for the p53/Mdm2, CyclinD1/Cdk6 and pRb/E2F1 pathways compared to wild type EBV-infected PBMCs. PBMCs infected with recombinant virus showed increased apoptotic cell death which further resulted in activation of polymerase 1 (PARP1), an important contributor to apoptotic signaling. Interestingly, cells infected with this recombinant virus showed a dramatic decrease in chromosomal instability, indicated by the presence of increased multinucleation and micronucleation. In addition infection with recombinant virus have increased cells in G0/G1 phase and decreased cells in S-G2M phase when compared to wild type infected cells. Thus, these differences in signaling activities due to 29 amino acid residues of EBNA3C is of particular significance in deregulation of cell proliferation in EBV-infected cells.

Telomerase Activation in Hematological Malignancies

Telomerase expression and telomere maintenance are critical for cell proliferation and survival, and they play important roles in development and cancer, including hematological malignancies. Transcriptional regulation of the rate-limiting subunit of human telomerase reverse transcriptase gen (hTERT) is a complex process, and unveiling the mechanisms behind its reactivation is an important step for the development of diagnostic and therapeutic applications. Here, we review the main mechanisms of telomerase activation and the associated hematologic malignancies.

Dissecting the contribution of EBNA3C domains important for EBV-induced B-cell growth and proliferation

Epstein-Barr virus (EBV) is an oncogenic gammaherpes virus which is linked to pathogenesis of several human lymphatic malignancies. The EBV essential latent antigen EBNA3C is critical for efficient conversion of primary human B-lymphocytes to lymphoblastic cell lines and for continued LCL growth. EBNA3C, an EBV latent antigen with oncogenic potential can bind and regulate the functions of a wide range of cellular transcription factors. In our current reverse genetics study, we deleted the full length EBNA3C, and independently the RBP-Jκ and Nm23-H1 binding sites within EBNA3C using BACmid recombinant engineering methodology. Our experiments demonstrated that deletion of the EBV EBNA3C open reading frame (ORF) and more specifically the residues 621–675 which binds Nm23H1 and SUMO-1 showed a significant reduction in the ability of the cells to proliferate. Furthermore, they exhibited lower infectivity of human peripheral blood mononuclear cells (PBMCs). We also showed that recombinant EBV with deletions of the EBNA3C ORF, as well as a recombinant with residues 621–675 within EBNA3C ORF deleted had diminished abilities to activate CD40. Our study also revealed that the full length (1–992) and 621–675 aa deletions of EBNA3C when compared to wild type EBV infected PBMCs had differential expression patterns for the phosphorylation of MAP kinases specifically p38, JNK and ERK. Regulation of β-catenin also differed among wild type and EBNA3C deleted mutants. These temporal differences in signaling activities of these recombinant viruses in PBMCs is likely important in defining their functional importance in EBV-mediated B-cell transformation.

Oxidative stress enables Epstein-Barr virus-induced B-cell transformation by posttranscriptional regulation of viral and cellular growth-promoting factors

Infection of human B lymphocytes by Epstein-Barr virus (EBV) leads to the establishment of immortalized lymphoblastoid cell lines (LCLs) that are widely used as a model of viral oncogenesis. An early consequence of infection is the induction of DNA damage and activation of the DNA damage response, which limits the efficiency of growth transformation. The cause of the DNA damage remains poorly understood. We have addressed this question by comparing the response of B lymphocytes infected with EBV or stimulated with a potent B-cell mitogen. We found that although the two stimuli induce comparable proliferation during the first 10 days of culture, the EBV-infected blasts showed significantly higher levels of DNA damage, which correlated with stronger and sustained accumulation of reactive oxygen species (ROS). Treatment with ROS scavengers decreased DNA damage in both mitogen-stimulated and EBV-infected cells. However, while mitogen-induced proliferation was slightly improved, the proliferation of EBV-infected cells and the establishment of LCLs were severely impaired. Quenching of ROS did not affect the kinetics and magnitude of viral gene expression but was associated with selective downregulation of the viral LMP1 and phosphorylated cellular transcription factor STAT3 that have key roles in transformation. Analysis of the mechanism by which high levels of ROS support LMP1 expression revealed selective inhibition of viral microRNAs that target the LMP1 transcript. Our study provides novel insights into the role of EBV-induced oxidative stress in promoting B-cell immortalization and malignant transformation.

Pre-stimulation of CD81 expression by resting B cells increases proliferation following EBV infection, but the overexpression of CD81 induces the apoptosis of EBV-transformed B cells

Hepatitis C virus (HCV) E2 protein binds to CD81, which is a component of the B cell co-stimulatory complex. The E2-CD81 interaction leads to B cell proliferation, protein tyrosine phosphorylation and to the hypermutation of immunoglobulin genes. Epidemiological studies have reported a high prevalence of B cell non-Hodgkin lymphoma (NHL) in HCV-positive patients, suggesting a potential association between HCV and Epstein-Barr virus (EBV) in the genesis of B lymphocyte proliferative disorders. In the present study, in order to investigate the association between EBV and HCV in B cells, we created an in vitro EBV-induced B cell transformation model. CD81 was gradually overexpressed during transformation by EBV. B cells isolated from HCV-positive patients grew more rapidly and clumped together earlier than B cells isolated from healthy donors following EBV infection. Pre-stimulation of CD81 expressed by resting B cells with anti-CD81 monoclonal antibody (mAb) or HCV E2 accelerated the generation of lymphoblastoid cell lines (LCLs) by EBV infection. These cells proliferated prominently through the early expression of interleukin-10 and intracellular latent membrane protein (LMP)-l. By contrast, the overexpression of CD81 on EBV-transformed B cells by anti-CD81 mAb or HCV E2 protein induced apoptosis through reactive oxygen species (ROS)-mediated mitochondrial dysfunction. These results suggest that the engagement of CD81 expressed by B cells has differential effects on B cell fate (proliferation or apoptosis) according to EBV infection and the expression level of CD81.

EPSTEIN -BARR VIRUS ASSOCIATION WITH MALIGNANT LYMPHOMA SUBGROUPS IN ZARIA, NIGERIA

Epstein-Barr virus (EBV) is said to infect more than 90% of humans worldwide with latent infection for life. A recognized carcinogen, EBV is linked to malignant lymphoma (ML) subtypes of Burkitt's lymphoma (BL), plasmablastic lymphoma, diffuse large cell lymphoma (DLBCL) and Hodgkin's lymphoma (HL). We report the association of EBV with ML in a segment of our patient population. Paraffin blocks from the archives of ABUTH, Zaria were used to construct tissue microarray sections stained using 30 monoclonal antibodies for common Non-Hodgkin's lymphoma/ Hodgkin's lymphoma antigen and chromogenic in situ hybridization (CISH) for EBV-encoded RNA were done. Fewer associations of ML with EBV were found than reported from elsewhere in Africa.

Detection of a specific biomarker for Epstein-Barr virus using a polymer-based genosensor

This paper describes methodology for direct and indirect detections of a specific oligonucleotide for Epstein-Barr virus (EBV) using electrochemical techniques. The sequence of oligonucleotide probe (EBV1) revealed a high sequence identity (100%) with the EBV genome. For the development of the genosensor, EBV1 was grafted to the platform sensitized with poly(4-aminothiophenol). After that, the hybridization reaction was carried out with the complementary target (EBV2) on the modified electrode surface using ethidium bromide as DNA intercalator. The oxidation peak currents of ethidium bromide increased linearly with the values of the concentration of the complementary sequences in the range from 3.78 to 756 μmol·L⁻¹. In nonstringent experimental conditions, this genosensor can detect 17.32 nmol·L⁻¹ (three independent experiments) of oligonucleotide target, discriminating between complementary and non-complementary oligonucleotides, as well as differentiating one-base mismatch, as required for detection of genetic diseases caused by point mutations. The biosensor also displayed high specificity to the EBV target with elimination of interference from mix (alanine, glucose, uric acid, ascorbic acid, bovine serum albumin (BSA), glutamate and glycine) and good stability (120 days). In addition, it was possible to observe differences between hybridized and non-hybridized surfaces through atomic force microscopy.

Hodgkin lymphoma transformation of chronic lymphocytic leukemia: cases report and discussion

B-cell chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) is the most common form of leukemia affecting adults in Europe and North America. Large B-cell lymphoma known as Richter's syndrome (RS) may develop approximately in 3-15 % patients. Furthermore, other hematological malignancies may also occur as RS variants, among them-Hodgkin lymphoma (HL). CLL/SLL transformation into HL is observed in about 0.5 % of patients, and till now, fewer than 100 cases have been reported in the medical literature. We present two cases of HL transformation of CLL/SLL and review the previously published literature.

Human papillomavirus and Epstein-Barr virus co-infection in cervical carcinoma in Algerian women

Background

Despite the fact that the implication of human papillomavirus (HPV) in the carcinogenesis and prognosis of cervical cancer is well established, the impact of a co-infection with high risk HPV (HR-HPV) and Epstein-Barr virus (EBV) is still not fully understood.

Methods

Fifty eight randomly selected cases of squamous cell carcinomas (SCC) of the uterine cervix, 14 normal cervices specimens, 21 CIN-2/3 and 16 CIN-1 cases were examined for EBV and HPV infections. Detection of HR-HPV specific sequences was carried out by PCR amplification using consensus primers of Manos and by Digene Hybrid Capture. The presence of EBV was revealed by amplifying a 660 bp specific EBV sequence of BALF1. mRNA expression of LMP-1 in one hand and protein levels of BARF-1, LMP-1 and EBNA-1 in the other hand were assessed by RT-PCR and immunoblotting and/or immunohischemistry respectively.

Results

HR-HPV infection was found in patients with SCC (88%), low-grade (75%) and high grade (95%) lesions compared to only 14% of normal cervix cases. However, 69%, 12.5%, 38.1%, and 14% of SCC, CIN-1, CIN-2/3 and normal cervix tissues, respectively, were EBV infected. The highest co-infection (HR-HPV and EBV) was found in squamous cell carcinoma cases (67%). The latter cases showed 27% and 29% expression of EBV BARF-1 and LMP-1 oncogenes respectively.

Conclusion

The high rate of HR-HPV and EBV co-infection in SCC suggests that EBV infection is incriminated in cervical cancer progression. This could be taken into account as bad prognosis in this type of cancer. However, the mode of action in dual infection in cervical oncogenesis needs further investigation.

Genetic and immunohistochemical characterization of Epstein-Barr virus-associated diffuse large B-cell lymphoma

Epstein-Barr virus (EBV) has a pathogenic role in several lymphomas, including diffuse large B-cell lymphoma (DLBCL). EBV-associated genetic aberrations in DLBCL have not been fully characterized. The aim of this study was to investigate the prevalence of EBV infection in sporadic DLBCL cases in Kuwait and to evaluate their EBV status in relation to demographic data, the anatomical disease site, immunophenotypic features, particularly pertaining to the Choi's DLBCL prognostic classification, and chromosomal aberrations. Using immunohistochemistry (IHC), in situ hybridization (ISH), nested polymerase chain reaction (nPCR) and comparative genomic hybridization techniques, formalin-fixed paraffin-embedded blocks of archived DLBCL cases were included and evaluated in the study. EBV was detected in 6.9, 18.2 and 25% of the studied cases using IHC, ISH and nPCR, respectively, indicating that nPCR is more sensitive in detecting EBV than IHC and ISH. EBV- DLBCL cases showed BCL6 protein expression more frequently than EBV+ DLBCL cases. The reported prevalence of EBV+ DLBCL cases in this study is similar to that reported in the literature using ISH results and higher using nPCR results. There was a significant inverse correlation between BCL6 protein expression and the presence of EBV (p = 0.01).

Thymoquinone efficiently inhibits the survival of EBV-infected B cells and alters EBV gene expression

Epstein--Barr virus (EBV) is a human virus with oncogenic potentials that is implicated in various human diseases and malignancies. In this study, the modulator activity of the potent herbal extract drug thymoquinone on EBV was assessed in vitro. Thymoquinone was tested for cytotoxicity on human cells of lymphoblastoid cells, Raji Burkitt's lymphoma, DG-75 Burkitt's lymphoma, peripheral blood mononuclear cells, and periodontal ligament fibroblast. Apoptosis induction was analyzed via TUNEL assay and activity studies of caspase-3. The effect of thymoquinone on EBV gene expression was determined using real-time polymerase chain reaction. We report here, for the first time, a promising selective inhibitory affect of thymoquinone on EBV-infected B cell lines in vitro, compared with lower activity on EBV negative B cell line and very low toxicity on human peripheral blood mononuclear cells and periodontal ligament fibroblasts. Moreover, the drug was found to efficiently suppress the RNA expression of EBNA2, LMP1, and EBNA1 genes. Specifically, EBNA2 expression levels were the most affected indicating that this gene might have a major contribution to thymoquinone potency against EBV infected cells. Overall, our results suggest that thymoquinone has the potential to suppress the growth of EBV-infected B cells efficiently.

Cross-linking of CD80 and CD86 Diminishes Expression of CD54 on EBV-transformed B Cells through Inactivation of RhoA and Ras

Background

Epstein Barr virus (EBV) infected B cells are transformed into lymphoblastoid cell lines. Some researchers suggested some a few similarities between this process and carcinogenesis. We observed the expression of CD80 and CD86, co-stimulatory molecules on EBV-transformed B cells and changes of CD54 expression after stimulation of CD80 and CD86.

Methods

CD80 and CD86 were stimulated using anti-CD80 and anti-CD86 monoclonal antibodies. To assess apoptosis and surface protein expression, flow cytometric analysis was performed. Intracellular signal molecules were evaluated by RT-PCR and immunoblot. Morphology and localization of proteins were examined using inverted or confocal microscope.

Results

Cross-linking of CD80 and CD86 induced apoptosis and interfered with proliferation of EBV-transformed B cells, and dispersion of clumped cells. We also examined that their stimulation induced ROS accumulation and reduced CD54 expression. Interestingly, we observed that CD80 and CD86 diminished the expression of CD54 in different methods. Both CD80 and CD86 down-regulated activation of focal adhesion kinase. CD80 stimulus inhibited CD54 expression through mainly RhoA inactivation, while CD86 down-regulated Ras and JNK phosphorylation.

Conclusion

These results suggest that co-stimulatory CD80 and CD86 molecules, expressed EBV-transformed B cells, may play a role in apoptosis and cell adhesion.

Exploiting the interplay between innate and adaptive immunity to improve immunotherapeutic strategies for Epstein-Barr-virus-driven disorders

The recent demonstration that immunotherapeutic approaches may be clinically effective for cancer patients has renewed the interest for this strategy of intervention. In particular, clinical trials using adoptive T-cell therapies disclosed encouraging results, particularly in the context of Epstein-Barr-virus- (EBV-) related tumors. Nevertheless, the rate of complete clinical responses is still limited, thus stimulating the development of more effective therapeutic protocols. Considering the relevance of innate immunity in controlling both infections and cancers, innovative immunotherapeutic approaches should take into account also this compartment to improve clinical efficacy. Evidence accumulated so far indicates that innate immunity effectors, particularly NK cells, can be exploited with therapeutic purposes and new targets have been recently identified. We herein review the complex interactions between EBV and innate immunity and summarize the therapeutic strategies involving both adaptive and innate immune system, in the light of a fruitful integration between these immunotherapeutic modalities for a better control of EBV-driven tumors.

Lymphoproliferative disorders after solid organ transplantation-classification, incidence, risk factors, early detection and treatment options

Posttransplant lymphoproliferative disorder (PTLD) is a heterogeneous disease group of benign and malignant entities. The new World Health Organisation classification introduced in 2008 distinguishes early lesions, polymorphic, monomorphic and classical Hodgkin lymphoma-type PTLD. Based on the time of appearance, early and late forms can be identified.PTLDs are the second most frequent posttransplantation tumors in adulthood, and the most frequent ones in childhood. The incidence varies with the transplanted organ-from 1%-2% following kidney transplantation to as high as 10% following thoracic organ transplantation-due to different intensities in immunosuppression. Immunocompromised state and Epstein-Barr virus (EBV) infection are the two major risk factors.In Europe and the US approximately 85% of PTLDs are of B-cell origin, and the majority are EBV-associated. Symptoms are often unspecific; extranodal, organ manifestations and central nervous system involvement is common. Early lesions respond well to a decrease in immunosuppression. Malignant entities are treated with rituximab, chemotherapy, radiotherapy and surgical therapy. Adoptive T-cell transfer represents a promising therapeutic approach. The prognosis is favorable in early PTLD, and poor in late PTLD. Five-year survival is 30% for high-grade lymphomas. The prognosis of EBV-negative lymphomas is worse.Lowering the risk of PTLD may be achieved by low dose maintenance immunosuppression, immunosuppressive drugs inhibiting cell proliferation, and special immunotherapy (e.g. interleukin-2 inhibitors). Early detection is especially important for high risk-e.g. EBV-negative-patients, where the appearance of EBV-DNA and the increase in its titer may help.

MHV-68 Open Reading Frame 20 is a nonessential gene delaying lung viral clearance

Recently, it has been demonstrated that the MHV-68 ORF20-encoded gene product induces cell-cycle arrest at the G2/M phase, followed by apoptosis. To study the role of this conserved gene in vivo, two independent ORF20-deficient MHV-68 viruses and their revertants were constructed. As the replication in vitro of both mutants followed similar kinetics to that of the wild-type and revertant viruses, ORF20 is therefore a nonessential virus gene. No cell cycle arrest could be observed upon infection of cells with wild type MHV-68 or mutant viruses. In addition, no major differences were detected between mock- and virus-infected cells when protein and inactivation levels of the mitotic promoter factor cdc2/cyclinB were analyzed. Following intranasal infection, the recovery of mutant, revertant and wild-type viruses in the lungs was similar. With the ORF20-deficient viruses, however, there was a significant delay of four days in clearance of virus from the lungs. Surprisingly, the magnitude and cell population distribution in the exudates of the lung was essentially similar to mice infected with wild-type, revertant or ORF20-deleted viruses. Subsequent establishment of latency was normal for both mutants, demonstrating that ORF20 does not play a critical role in establishment of a persistent infection. These results indicate that while expression of ORF20 may impact on the pathogenicity of the infection, the observed induction of G2/M arrest in ORF20-expressing cells may not be the primary function of ORF20 in the context of viral infection.

Epstein-Barr virus infection and chronic lymphocytic leukemia: a possible progression factor?

Epstein-Barr virus is pathogenically associated with a well defined group of lymphoid and epithelial tumors in which the virus directly drives transformation of infected cells. Recent evidence however indicates that this virus may infect a subpopulation of tumor cells in patients with chronic lymphocytic leukemia (CLL) and EBV infection has been also associated with Richter transformation in a fraction of cases. We herein review available data suggesting a possible role of EBV as a direct or micro-environmental progression factor in a subset of CLL.

Epstein-Barr virus infection in immortalized nasopharyngeal epithelial cells: regulation of infection and phenotypic characterization

Epstein-Barr virus (EBV) infection has been postulated to be an early event involved in the pathogenesis of nasopharyngeal carcinomas (NPC). The lack of representative premalignant nasopharyngeal epithelial cell system for EBV infection has hampered research investigation into the regulation and involvement of EBV infection in NPC pathogenesis. We have compared the efficiency of EBV infection in nasopharyngeal epithelial cells with different biological properties including immortalized, primary and cancerous nasopharyngeal epithelial cells. EBV infection could be achieved in all the nasopharyngeal epithelial cells examined with variable infection rate. TGF-beta effectively enhanced EBV infection into nasopharyngeal epithelial cells both in the immortalized and primary nasopharyngeal epithelial cells. Stable infection of EBV was achieved in a telomerase-immortalized nasopharyngeal epithelial cell line, NP460hTert. The expression pattern of EBV-encoded genes and biological properties of this EBV infected cell line on long-term propagation were monitored. The EBV-infected nasopharyngeal epithelial cells acquired anchorage-independent growth and exhibited invasive growth properties on prolonged propagation. A distinguished feature of this EBV-infected nasopharyngeal epithelial cell model was its enhanced ability to survive under growth factor and nutrient starvation. This was evidenced by the suppressed activation of apoptotic markers and sustained activation of pAkt of EBV-infected cells compared to control cells under nutrient starvation. Examination of cytokine profiles of EBV-infected NP460hTert cells to nutrient and growth factor deprivation revealed upregulation of expression of MCP-1 and GRO-alpha. The establishment of a stable EBV infection model of premalignant nasopharyngeal epithelial cells will facilitate research investigation into the pathogenic role of EBV in NPC development.

Telomere/telomerase interplay in virus-driven and virus-independent lymphomagenesis: pathogenic and clinical implications

Telomerase is a ribonucleoprotein complex critically involved in extending and maintaining telomeres. Unlike the majority of somatic cells, in which hTERT and telomerase activity are generally silent, normal lymphocytes show transient physiological hTERT expression and telomerase activity according to their differentiation/activation status. During lymphomagenesis, induction of persistent telomerase expression and activity may occur before or after telomere shortening, as a consequence of the different mechanisms through which transforming factors/agents may activate telomerase. Available data indicate that the timing of telomerase activation may allow the distinction of two different lymphomagenetic models: (i) an early activation of telomerase via exogenous regulators of hTERT, along with an increased lymphocyte growth and a subsequent selection of cells with increased transforming potential may characterize several virus-related lymphoid malignancies; (ii) a progressive shortening of telomeres, leading to genetic instability which favors a subsequent activation of telomerase via endogenous regulators may occur in most virus-unrelated lymphoid tumors. These models may have clinically relevant implications, particularly for the tailoring of therapeutic strategies targeting telomerase.

Cell cycle regulation distinguishes lymphocytes from sporadic and familial Alzheimer's disease patients

Cell cycle (CC) reactivation in neurons seems to underlie the development of Alzheimer's disease (AD). We analyzed whether CC alterations can be detected in immortalized lymphocytes from patients with the sporadic and the familial form of AD (SAD and FAD). Real-time polymerase chain reaction (PCR)-arrays, immunoblotting, and flow cytometry demonstrated differences in the regulation of G1/S phases between SAD lymphocytes and cells from nondemented subjects, as well as between SAD and FAD cells. SAD compared to FAD lymphocytes showed differences in expression profiles of the 90 CC genes, and a marked increase in the level of the p21 protein, which promotes G1-arrest. Accordingly, SAD but not FAD cells had a prolonged G1-phase. γ-secretase inhibition did not change the CC profiles of the cell lines. These data show that SAD involves a prolongation of the G1 phase driven by p21 pathway, which is not activated in FAD cells. Thus, the mechanism in SAD differs from FAD. Moreover, disturbances of the CC in lymphocytes have a potential diagnostic value.

3D Telomere FISH defines LMP1-expressing Reed-Sternberg cells as end-stage cells with telomere-poor 'ghost' nuclei and very short telomeres

In Epstein-Barr virus (EBV) negative Hodgkin's cell lines and classical EBV-negative Hodgkin's lymphoma (HL), Reed-Sternberg cells (RS cells) represent end-stage tumor cells, in which further nuclear division becomes impossible because of sustained telomere loss, shortening and aggregation. However, the three-dimensional (3D) telomere organization in latent membrane protein 1 (LMP1)-expressing RS cells of EBV-associated HL is not known. We performed a 3D telomere analysis after quantitative fluorescent in situ hybridization on 5 mum tissue sections on two LMP1-expressing HL cases and showed highly significant telomere shortening (P<0.0001) and formation of telomere aggregates in RS cells (P<0.0001), when compared with the mononuclear precursor Hodgkin cells (H cells). Telomere-poor or telomere-free 'ghost' nuclei were a regular finding in these RS cells. These nuclei and their telomere content strongly contrasted with the corona of surrounding lymphocytes showing numerous midsized telomere hybridization signals. Both H cells and RS cells of two EBV-negative HL cases analyzed in parallel showed 3D telomere patterns identical to those of LMP1-expressing cases. As a major advance, our 3D nuclear imaging approach allows the visualization of hitherto unknown profound changes in the 3D nuclear telomere organization associated with the transition from LMP1-positive H cells to LMP1-positive RS cells. We conclude that RS cells irrespective of LMP1 expression are end-stage tumor cells in which the extent of their inability to divide further is proportional to the increase of very short telomeres, telomere loss, aggregate formation and the generation of 'ghost' nuclei.

Commentary: mechanistic considerations for associations between formaldehyde exposure and nasopharyngeal carcinoma

Occupational exposure to formaldehyde has been linked to nasopharyngeal carcinoma. To date, mechanistic explanations for this association have primarily focused on formaldehyde-induced cytotoxicity, regenerative hyperplasia and DNA damage. However, recent studies broaden the potential mechanisms as it is now well established that formaldehyde dehydrogenase, identical to S-nitrosoglutathione reductase, is an important mediator of cGMP-independent nitric oxide signaling pathways. We have previously described mechanisms by which formaldehyde can influence nitrosothiol homeostasis thereby leading to changes in pulmonary physiology. Considering evidences that nitrosothiols govern the Epstein-Barr virus infection cycle, and that the virus is strongly implicated in the etiology of nasopharyngeal carcinoma, studies are needed to examine the potential for formaldehyde to reactivate the Epstein-Barr virus as well as additively or synergistically interact with the virus to potentiate epithelial cell transformation.

Chromosomal rearrangements after ex vivo Epstein-Barr virus (EBV) infection of human B cells

The Epstein-Barr virus (EBV) is carried by more than 90% of the adult world population and has been implicated in several human malignancies. Its ability to induce unlimited in vitro proliferation of B cells is frequently used to generate lymphoblastoid cell lines (LCLs). In this study, we have investigated the evolution of two LCLs up to 25 weeks after EBV infection. LCLs were karyotyped once a month by spectral karyotyping (SKY). LCLs but not mitogen-activated B cells showed evidence of DNA damage and DNA damage response within the first 2 weeks. After 4 weeks, the former, but not the latter, showed a high level of non-clonal structural aberrations, mainly deletions, fragments, dicentric chromosomes and unbalanced translocations. Genomic instability decreased thereafter over time. Nonrandom aneuploidy 12 weeks after infection showed clonal evolution in culture. After 25 weeks post-infection, most cells exhibited karyotypic stability. Chromosomal aberrations were compatible with telomere dysfunction, although in the absence of telomere shortening. The telomere capping protein TRF2 was partially displaced from telomeres in EBV-infected cells, suggesting an EBV-mediated uncapping problem. In conclusion, this study suggests that DNA damage and telomere dysfunction contribute to EBV-related chromosomal instability in early LCLs.

CD40 signaling activated by Epstein-Barr virus promotes cell survival and proliferation in gastric carcinoma-derived human epithelial cells

CD40 signaling plays a critical role in the survival and proliferation of EBV-infected lymphocytes. Here we show that CD40 is constitutively expressed in the human gastric carcinoma-derived cell lines AGS, MKN28, and MKN74, and expression of CD40L is induced by in vitro infection with EBV. Blocking the interaction between CD40 and CD40L with CD40Ig, a fusion protein of CD40 and IgG, impaired proliferation of EBV-infected AGS cells and enhanced their calcium ionophore-induced apoptosis. These results suggest that CD40 signaling plays a critical role in the survival and proliferation of EBV-infected epithelial cells, as well as in the virus-infected lymphocytes.

Latent membrane protein 1 of Epstein-Barr virus activates the hTERT promoter and enhances telomerase activity in B lymphocytes

Transformation of primary B lymphocytes by Epstein-Barr virus requires the establishment of a strictly latent infection, the expression of several latent viral proteins, and sustained telomerase activity. Our previous findings indicated that induction of hTERT, the rate-limiting catalytic unit of the telomerase complex, was associated with the expression of the viral latent membrane protein 1 (LMP1). In the present study, we demonstrate that ectopic expression of LMP1 in BJAB and Ramos B cells resulted in an increase of hTERT transcripts, thus suggesting that LMP1 acts at the transcriptional level. This was confirmed by transient expression of a luciferase reporter plasmid containing the hTERT promoter cotransfected with an LMP1-expressing vector or transfected into B cells in which LMP1 expression was inducible. Consistently, silencing of LMP1 by small interfering RNA resulted in a reduction of hTERT transcripts. We also provide evidence indicating that LMP1-induced hTERT activation is independently mediated by NF-kappaB and by mitogen-activated protein kinase and extracellular signal-regulated kinase 1/2 pathways, whereas CD40, Akt, and mTOR signaling has no involvement. Moreover, our results do not support a role for c-Myc in mediating these effects on hTERT, since ectopic expression of LMP1 did not upregulate c-Myc and silencing of this oncogene or E box mutagenesis failed to inhibit LMP1-induced hTERT activation. These findings indicate that LMP1 simultaneously modulates multiple signal transduction pathways in B cells to transactivate the hTERT promoter and enhance telomerase activity, thus confirming the pleiotropic nature of this viral oncoprotein.

B lymphocytes and Epstein-Barr virus: the lesson of post-transplant lymphoproliferative disorders

Epstein-Barr virus (EBV) is a ubiquitous human gamma-herpes virus that establishes a life-long asymptomatic infection in immunocompetent hosts by colonizing memory B lymphocytes and hijacking cellular signaling pathways that regulate antigen-dependent B-cell activation and differentiation. In patients with solid organ or hematopoietic stem cell transplantation, the defect in EBV-specific immune responses may allow the outgrowth of EBV-carrying B lymphocytes that may give rise to a spectrum of different clinico-pathologic entities encompassed by the term post-transplantation lymphoproliferative disorders (PTLD). EBV-driven immortalization of B-cells is mediated by the cooperative activity of viral proteins that derange critical cellular pathways controlling growth and/or survival of B lymphocytes. Full transformation of infected B-cells is achieved by the contribution of poorly defined additional co-factors, including microenvironmental stimuli, genetic and epigenetic alterations. The quantification of circulating EBV DNA and EBV-specific T cells are valuable tools in the clinical monitoring of EBV-associated PTLD. The recent advances in elucidation of the mechanisms underlying EBV-induced growth transformation will be instrumental in guiding the design of novel approaches for the treatment of these often life-threatening lymphoproliferative disorders.

Immunodominance of lytic cycle antigens in Epstein-Barr virus-specific CD4+ T cell preparations for therapy

BACKGROUND

Epstein-Barr virus (EBV) is associated with a number of human malignancies. EBV-positive post-transplant lymphoproliferative disease in solid organ and hematopoietic stem cell transplant recipients has been successfully treated by the adoptive transfer of polyclonal EBV-specific T cell lines containing CD4+ and CD8+ T cell components. Although patients receiving T cell preparations with a higher CD4+ T cell proportion show better clinical responses, the specificity of the infused CD4+ component has remained completely unknown.

METHODOLOGY/PRINCIPAL FINDINGS

We generated LCL-stimulated T cell lines from 21 donors according to clinical protocols, and analyzed the antigen specificity of the CD4+ component in EBV-specific T cell preparations using a genetically engineered EBV mutant that is unable to enter the lytic cycle, and recombinantly expressed and purified EBV proteins. Surprisingly, CD4+ T cell lines from acutely and persistently EBV-infected donors consistently responded against EBV lytic cycle antigens and autoantigens, but barely against latent cycle antigens of EBV hitherto considered principal immunotherapeutic targets. Lytic cycle antigens were predominantly derived from structural proteins of the virus presented on MHC II via receptor-mediated uptake of released viral particles, but also included abundant infected cell proteins whose presentation involved intercellular protein transfer. Importantly, presentation of virion antigens was severely impaired by acyclovir treatment of stimulator cells, as currently performed in most clinical protocols.

CONCLUSIONS/SIGNIFICANCE

These results indicate that structural antigens of EBV are the immunodominant targets of CD4+ T cells in LCL-stimulated T cell preparations. These findings add to our understanding of the immune response against this human tumor-virus and have important implications for the improvement of immunotherapeutic strategies against EBV.

Rescue of the immunotherapeutic potential of a novel T cell epitope in the Epstein–Barr virus latent membrane protein 2

Epstein-Barr virus (EBV)-associated tumors express a limited number of viral antigens but most of them express the latent membrane protein 2 (LMP2). This article describes a peptide derived from LMP2 (residues 396-404, designated LLL) as a potentially useful vaccine. This peptide could at first be defined as an unlikely T cell target as it could not stabilize MHC surface expression in transporter associated with antigen-processing (TAP)-deficient cells. Nevertheless, T lymphocytes reactive to LLL were detected in the peripheral blood of four EBV-seropositive healthy individuals. We have constructed a chimeric molecule in which LLL was fused to the amino-terminal end of the beta(2) microglobulin (beta(2)m). Autologous dendritic cells constitutively expressing the LLLbeta(2)m molecule were capable of expanding in vitro HLA-A2-restricted anti-LLL T lymphocytes from the peripheral blood of one of the donors. These T lymphocytes exhibited cytolytic activity against target cells expressing the chimeric molecules as well as against EBV-infected lymphoblastoid cells expressing natural LLL-MHC complexes.

Epstein-Barr virus promotes genomic instability in Burkitt's lymphoma

Epstein-Barr virus (EBV) has been implicated in the pathogenesis of human malignancies but the mechanisms of oncogenesis remain largely unknown. Genomic instability and chromosomal aberrations are hallmarks of malignant transformation. We report that EBV carriage promotes genomic instability in Burkitt's lymphoma (BL). Cytogenetic analysis of EBV- and EBV+ BL lines and their sublines derived by EBV conversion or spontaneous loss of the viral genome revealed a significant increase in dicentric chromosomes, chromosome fragments and chromatid gaps in EBV-carrying cells. Expression of EBV latency I was sufficient for this effect, whereas a stronger effect was observed in cells expressing latency III. Telomere analysis by fluorescent in situ hybridization revealed an overall increase of telomere size and prevalence of telomere fusion and double strand-break fusion in dicentric chromosomes from EBV+ cells. Phosphorylated H2AX, a reporter of DNA damage and ongoing repair, was increased in virus-carrying cells in the absence of exogenous stimuli, whereas efficient activation of DNA repair was observed in both EBV+ and EBV- cells following treatment with etoposide. These findings point to induction of telomere dysfunction and DNA damage as important mechanisms for EBV oncogenesis.

Multiple sclerosis is linked to Epstein-Barr virus infection

The aetiology and pathogenesis of MS are unknown, but environmental agents, genetic susceptibility and stochastic events are likely to be involved. In order to evaluate the possibility that MS is linked to EBV infection, we here evaluate studies on MS- and EBV-epidemiology, prospective and retrospective analysis of EBV-serology, investigations of EBV DNA sequences in blood and tissues, specificity of antibodies in oligoclonal bands in MS patients and results from antiviral chemotherapy of MS patients. It could be demonstrated that EBV is complying with the epidemiological observations in MS and that all MS patients are seropositive to EBV in contrast to healthy controls. Importantly, despite difficulties in diagnosing child-MS, the vast majority of these patients are also EBV seropositive. In contrast to control groups, recent EBV infections have never been observed in children or adults with MS. Further prospective studies indicate a 2.8 times higher tendency for development of MS after infectious mononucleosis. In MS patients, unbiased analyses pull out EBV antigens as high-affinity targets for the antibodies in the oligoclonal bands. Humans are the exclusive natural host for EBV, a finding that may explain why MS is unique to humans. Together these unique observations strongly suggest a linkage between MS and EBV infection. Infection by EBV offers numerable mechanisms to perturb the immune system, including mimicry and superantigen induction, which may potentially participate in the disease mechanisms. In contrast, studies demonstrating higher IgG titres and occurrence of viral DNA in serum/plasma are likely to reflect a consequence of the disease. An explanation for a potential role of respiratory diseases in MS is discussed. It is concluded that the ultimate test to the hypothesis of MS and EBV is the development and application of an EBV vaccine, which is predicted to eradicate the disease.

Ligation of centrocyte/centroblast marker 1 on Epstein-Barr virus--transformed B lymphocytes induces cell death in a reactive oxygen species--dependent manner

After primary infection of B cells with Epstein-Barr virus (EBV), infected B cells express several viral homologs of human genes that promote activation (LMP1 and CD40) or survival (BHRF and BCL2). EBV-infected B cells also express germinal center phenotype markers, such as CD77, PNA, CD95, and CD38. This transformation of B cells by EBV infection resembles normal B-cell activation and differentiation arising in the germinal center. In the present study, we found that EBV-transformed B cells expressed centrocyte/centroblast marker 1 (CM1), a possible marker of GC B cells and an inducer of their apoptosis. Moreover, ligation of CM1 on EBV-transformed B cells by immobilized anti-CM1 monoclonal antibody induced cell death. The ligation of CM1 immediately increased the generation of intracellular reactive oxygen species (ROS) and disrupted the mitochondrial membrane potential. Pretreatment with N-acetyl cystein (an ROS inhibitor) almost completely blocked this cell death, but Z-VAD-fmk (a caspase inhibitor) did not. We further investigated whether apoptosis-inducing factor (AIF) and endonuclease G (EndoG), which are both related to caspase-independent cell death, would be translocated to the nucleus during the ligation of CM1. We found that AIF and EndoG were released to the cytosplam but not translocated to the nucleus. Moreover, cytochalasin D, a cytoskeleton disruptor, rescued the cells from CM1-mediated cell death and blocked ROS generation. Therefore, it is conceivable that CM1 signaling might provoke cytoskeleton polymerization and trigger ROS generation. Taking these observations together, we conclude that the ligation of CM1 on EBV-transformed B cells can cause cell death via the ROS produced by F-actin polymerization in a caspase-independent manner, although this cell death might be unrelated to AIF and EndoG release from the mitochondria.

Viruses and human breast cancer

There are well-established risk factors for breast cancer, most of which relate to estrogens and growth hormones in females. These include early-age menarche, late-age menopause, postmenopausal obesity and use of hormone therapy. However, these factors do not account for the sixfold difference in breast cancer incidence and mortality between countries and the fact that these differences dramatically lessen after migration; nor do they account for male breast cancer. Accordingly, hormone-responsive viruses have become major suspects as etiological agents for human breast cancer. Human papillomaviruses, mouse mammary tumor virus and Epstein-Barr virus are the prime candidate viruses as causes of human breast cancer. Human papillomaviruses and the mouse mammary tumor virus have hormone responsive elements that appear to be associated with enhanced replication of these viruses in the presence of corticosteroid and other hormones. This biological phenomenon is particularly relevant because of the hormone dependence of breast cancer. Viral genetic material for each of these candidate viruses has been identified by polymerase chain reaction in breast tumors but rarely in normal breast tissue controls. Pooled data from controlled studies show substantial odds ratios for the presence of viral genetic material in breast tumors compared with normal controls. These and additional data provide substantial, but not conclusive, evidence that human papillomavirus, the mouse mammary tumor virus and Epstein-Barr virus may have a role in the etiology of human breast cancer. If conclusive evidence for a role of these viruses in breast carcinogenesis can be developed, there is a practical possibility of primary prevention.

Lymphoproliferative disorder of the airway of an adolescent without immunodeficiency

Epstein-Barr virus (EBV) is a ubiquitous viral pathogen in humans that has a unique ability to immortalize B-cells. In immunosuppressed individuals, EBV can produce non-neoplastic lymphoproliferative disorders involving various organs. We describe a case report of EBV-associated lymphoproliferative disorder in an immunocompetent 14-year-old male. The case provides a description of EBV-associated lymphoproliferation affecting the upper and lower respiratory tract. The massive submucosal infiltration of B-cells in the lingual tonsils, trachea, and bronchi produced near-complete airway obstruction resulting in tracheotomy. Neither surgical reduction of lingual tonsils nor treatment with steroids was of benefit. An extensive evaluation for immunodeficiency and neoplasia was normal. Treatment with rituximab, an anti-CD20 antibody, resulted in near-complete resolution of the infiltrative process, sufficient to allow decannulation. Rituximab is a treatment option for the rare occurrence of non-neoplastic, EBV-associated, lymphoproliferative disorders.

Structure of the p53 binding domain of HAUSP/USP7 bound to Epstein-Barr nuclear antigen 1 implications for EBV-mediated immortalization

USP7/HAUSP is a key regulator of p53 and Mdm2 and is targeted by the Epstein-Barr nuclear antigen 1 (EBNA1) protein of Epstein-Barr virus (EBV). We have determined the crystal structure of the p53 binding domain of USP7 alone and bound to an EBNA1 peptide. This domain is an eight-stranded beta sandwich similar to the TRAF-C domains of TNF-receptor associated factors, although the mode of peptide binding differs significantly from previously observed TRAF-peptide interactions in the sequence (DPGEGPS) and the conformation of the bound peptide. NMR chemical shift analyses of USP7 bound by EBNA1 and p53 indicated that p53 binds the same pocket as EBNA1 but makes less extensive contacts with USP7. Functional studies indicated that EBNA1 binding to USP7 can protect cells from apoptotic challenge by lowering p53 levels. The data provide a structural and conceptual framework for understanding how EBNA1 might contribute to the survival of Epstein-Barr virus-infected cells.

Mitochondria as Functional Targets of Proteins Coded by Human Tumor Viruses

Molecular analyses of tumor virus-host cell interactions have provided key insights into the genes and pathways involved in neoplastic transformation. Recent studies have revealed that the human tumor viruses Epstein-Barr virus (EBV), Kaposi's sarcoma-associated herpesvirus (KSHV), human papillomavirus (HPV), hepatitis B virus (HBV), hepatitis C virus (HCV), and human T-cell leukemia virus type 1 (HTLV-1) express proteins that are targeted to mitochondria. The list of these viral proteins includes BCL-2 homologues (BHRF1 of EBV; KSBCL-2 of KSHV), an inhibitor of apoptosis (IAP) resembling Survivin (KSHV K7), proteins that alter mitochondrial ion permeability and/or membrane potential (HBV HBx, HPV E[wedge]14, HCV p7, and HTLV-1 p13(II)), and K15 of KSHV, a protein with undefined function. Consistent with the central role of mitochondria in energy production, cell death, calcium homeostasis, and redox balance, experimental evidence indicates that these proteins have profound effects on host cell physiology. In particular, the viral BCL-2 homologues BHRF1 and KSBCL-2 inhibit apoptosis triggered by a variety of stimuli. HBx, p7, E1[wedge]4, and p13(II) exert powerful effects on mitochondria either directly due to their channel-forming activity or indirectly through interactions with endogenous channels. Further investigation of these proteins and their interactions with mitochondria will provide important insights into the mechanisms of viral replication and tumorigenesis and could aid in the discovery of new targets for anti-tumor therapy.

Epstein–Barr virus oncogenesis and the ubiquitin–proteasome system

Epstein-Barr virus (EBV), a human herpesvirus associated with lymphoid and epithelial cell tumors, encodes several proteins that exploit the ubiquitin-proteasome system to regulate latency and allow the persistence of infected cells in immunocompetent hosts. Further modifications of ubiquitin-dependent proteolysis by activated cellular oncogenes contribute to malignant transformation. A detailed understanding of these processes may lead to the development of new therapeutic strategies for EBV-associated cancers.