Epstein-Barr virus and Hodgkin's disease: transcriptional analysis of virus latency in the malignant cells

Epstein-Barr virus (EBV) gene expression in lymphoid B cells during acute infectious mononucleosis (IM) and clonality of the directly growing cell lines

We examined the patterns of viral gene expression in acute infectious mononucleosis (IM) patients and the clonality of the directly growing EBV-carrying cell lines. Both low- and high-density EBV-carrying B cells obtained from the patients' tonsils expressed EBNA1, EBNA2 and LMP1. Like LCLs and immunoblastic B-cell lymphomas, the in vivo EBV-carrying low-density cells used only the latency III program for viral gene expression. The in vivo EBV-carrying high-density B cells used both the latency I program, as indicated by the QUK-, and the latency III program, as indicated by the YUK-EBNA1. This suggests that the lymphoid tissues contained not only proliferating immunoblasts but also cells programmed for latent viral persistence in vivo. EBV-carrying cells that grew directly into permanent cell lines in the presence of virus-neutralizing antibody and a late viral inhibitor were polyclonal, as indicated by JH rearrangement. Two of the high-density-derived lines had identical JH and TR patterns, indicating a common parental origin. Our investigation indicates that EBV-carrying cells divide and survive in a fully competent immune system during the outbreak of acute IM.

Epstein-Barr virus BMRF-2 and BDLF-3 expression in hairy leukoplakia

Hairy leukoplakia (HL) is a lesion found on the side of the tongue of immunocompromised individuals, including those with human immunodeficiency virus (HIV) infection. The lesion has unique histopathologic features and is characterised by high-level Epstein-Barr virus (EBV) replication, multiple EBV strains, and extensive inter- and intra-strain recombination. Expression of EBV genes spanning the entire viral life cycle from latency-associated genes to late, replicative genes has been detected in the lesion. HL thus provides a unique opportunity to study EBV expression in oral epithelium, and to study expression of novel EBV genes. We therefore constructed a cDNA library from an HL biopsy and detected expression of two genes not previously described in vivo: BMRF-2 and BDLF-3. Sequence analysis of the cDNAs revealed few amino acid changes from the B95-8 sequence. Expression of both genes was localized to the lower prickle cell layer of the tongue epithelium. BMRF-2 protein expression was primarily detected in the cell nuclei of the upper prickle cell layer. BDLF-3 protein expression was observed in the peri-nuclear space and Golgi compartment. The function of these proteins is currently under investigation.

Epstein-Barr virus in Hodgkin's disease: more than just an innocent bystander

Several lines of evidence suggest that the Epstein-Barr virus (EBV) is an important factor in the pathogenesis of Hodgkin's disease (HD). This Editorial focuses on two pathogenic mechanisms probably influenced by the presence of EBV in the Hodgkin and Reed-Sternberg (H-RS) cells: resistance of the H-RS cells to apoptosis; and escape of H-RS cells from a cytotoxic T lymphocyte (CTL) mediated immune response. In addition, data are summarized implicating the latent membrane protein 1 (LMP1) as the most likely EBV-encoded protein responsible for this putative EBV-mediated pathogenic effect. It is known that, using conventional therapy regimens, the presence of EBV bears little influence on clinical presentation and treatment outcome of HD. However, the differences in regulation of both apoptosis and immune escape mechanisms between EBV+ and EBV- cases may be important determinants of the success of immunotherapy to treat Hodgkin's disease. Thus, clarification of these mechanisms will be essential to the development of successful immunotherapeutic strategies in Hodgkin's disease.

Isolation of Epstein-Barr Virus (EBV)-Specific Cytotoxic T Lymphocytes That Lyse Reed-Sternberg Cells: Implications for Immune-Mediated Therapy of EBV+ Hodgkin's Disease

A subset of Hodgkin's disease (HD) patients have detectable Epstein-Barr virus (EBV) genomes in the malignant Reed-Sternberg (R-S) cells. R-S cells express only a limited set of latent EBV proteins, but only LMP1 and LMP2 can potentially elicit a CD8+ cytotoxic T-lymphocyte (CTL) response. We have evaluated if either of these proteins could be used as targets for specific adoptive T-cell therapy for EBV-positive (EBV+) HD. The success of this strategy requires that R-S cells are susceptible to lysis by CD8+ CTL, and that CTL specific for LMP1 and LMP2 can be detected and potentially amplified in HD patients. Antigen presentation and CTL sensitivity was evaluated with an in vitro maintained, phenotypically representative R-S cell line, HDLM-2. The R-S cells were able to process and present viral proteins, and to be efficiently lysed by specific CTL in a Class I–restricted manner. Since CTL responses to LMP1 and LMP2 do not represent the dominant responses to EBV, we examined if CTL clones specific for these proteins could be isolated despite the presence of weak or nondetectable responses in polyclonal T-cell lines. LMP-specific clones were generated from individuals either by cloning from the polyclonal EBV-reactive T-cell lines or by direct stimulation of peripheral blood mononuclear cells (PBMC) with cells expressing LMP1 or LMP2 as the only EBV protein. Our ability to isolate CTL specific for LMP proteins from individuals with HD and the sensitivity of R-S cells for CTL-mediated lysis suggest that the pursuit of specific adoptive immunotherapy represents a viable strategy for the subset of HD patients with EBV+ tumors.

Epstein-Barr virus-associated Hodgkin's disease: epidemiologic characteristics in international data

Hodgkin's disease (HD) has long been suspected to have an infectious precursor, and indirect evidence has implicated Epstein-Barr virus (EBV), a ubiquitous herpesvirus, as a causal agent. Recent molecular studies using EBER in situ hybridization or latency membrane protein-I (LMP-I) immunohistochemistry have identified EBV latent infection in up to 50% of HD tumors. However, the epidemiologic features of these cases have not been examined in detail. To explore the epidemiology of EBV-positive HD so as to understand the role of EBV in HD etiology more clearly, this project accumulated patient data from 14 studies that had applied these EBV assays to HD tumors. With information on age at diagnosis, sex, ethnicity, histologic subtype, country of residence, clinical stage and EBV tumor status from 1,546 HD patients, we examined risk for EBV-positive disease using logistic regression. Forty percent of subjects had EBV-positive tumors, and EBV prevalence varied significantly across groups defined by the study variables. Odds ratios (OR) for EBV-associated HD were significantly elevated for Hispanics vs. whites (OR = 4.1), mixed cellularity vs. nodular sclerosis histologic subtypes (OR = 7.3, 13.4, 4.9 for ages 0-14, 15-49, 50+ years), children from economically less-developed vs. more-developed regions and young adult males vs. females (OR = 2.5). These findings suggest that age, sex, ethnicity and the physiologic effects of poverty may represent biologic modifiers of the EBV association and confirm that this association is strongly but variably linked to histologic subtype. The data augment biologic evidence that EBV is actively involved in HD pathogenesis in some cases but describe epidemiologic complexity in this process.

Multiprimed cDNA synthesis followed by PCR is the most suitable method for Epstein-Barr virus transcript analysis in small lymphoma biopsies

In this study, the reverse transcriptase-polymerase chain reaction (RT-PCR) for the reliable detection of multiple Epstein-Barr virus (EBV) transcripts was optimized and subsequently evaluated on lymphoma specimens. Since often only small lymphoma biopsies are available for analysis of EBV transcripts, several RT-protocols to generate cDNA from multiple targets were applied. These were multi-primer, oligo-dT primed and random hexamer primed cDNA synthesis. Multi-primer cDNA synthesis appeared to be the most suitable method for subsequent PCR analysis of EBV targets; simultaneous priming with up to 10 specific antisense primers (for EBNA1 and 2, LMP1 and 2, BARF0, BHRF1, BZLF1, C promoter activity and the RNA control genes U1A and c-abl) followed by PCR showed no loss of sensitivity compared to single-specific antisense priming. Transcripts were specifically detected in up to one EBV-positive JY cell in a background of 50,000 EBV-negative BJAB cells, with the exception of BZLF1 and QK spliced EBNA1 transcripts which could only be detected in 1000 and 10,000 EBV-positive cells, respectively. The analytical sensitivities of all the primers used in PCR, including BZLF1 and QK EBNA1 primers, were 1-10 copies of cloned RT-PCR products. The multi-primed RT-PCR was evaluated on lymphomas (n = 13). In cases with proper RNA quality, EBV expression patterns found were identical to those found in previous studies using single-primed RT-PCR assays. In conclusion, this study shows that multi-primed RT-PCR analysis can be used efficiently for EBV transcript analysis in small lymphoma biopsies, thereby facilitating studies concerning the role of EBV in lymphomagenesis.

The Epstein-Barr virus EBNA-1 promoter Qp requires an initiator-like element

Expression of the Epstein-Barr virus (EBV) EBNA-1 protein within EBV-positive tumor cells and subpopulations of latently infected B lymphocytes in vivo is mediated by the promoter Qp. Previous studies have established that Qp is a TATA-less promoter whose activation requires only proximal regulatory elements and that it is negatively autoregulated through two EBNA-1 binding sites downstream of the transcription initiation sites. The objective of this study was to better define the properties of an essential positive regulatory element (QRE-2) adjacent to a major transcription start site of Qp and to evaluate the contributions of other potential regulatory elements proximal to the Qp start site. Using DNA affinity purification and UV cross-linking, we have identified the QRE-2-binding protein as a single polypeptide of approximately 40 kDa. The DNA-binding properties of this protein are clearly distinct from those of the TATA-binding protein, suggesting that in the absence of a TATA box, QRE-2 may function as an initiator element to direct assembly of TFIID near the transcription start site. Mutational analysis of potential regulatory elements, furthermore, indicated that the putative E2F binding sites within the EBNA-1 binding domain can exert a positive influence on Qp that is EBNA-1 independent, suggesting that these regulatory elements play an additional if not different role in Qp regulation than previously proposed. A model for the regulation of Qp consistent with the current and previous findings which provides for a simple but efficient mechanism of ensuring the EBNA-1 expression necessary to sustain long-term latency is presented.

Host-cell-determined methylation of specific Epstein-Barr virus promoters regulates the choice between distinct viral latency programs

Epstein-Barr virus (EBV) is capable of adopting three distinct forms of latency: the type III latency program, in which six EBV-encoded nuclear antigens (EBNAs) are expressed, and the type I and type II latency programs, in which only a single viral nuclear protein, EBNA1, is produced. Several groups have reported heavy CpG methylation of the EBV genome in Burkitt's lymphoma cell lines which maintain type I latency, and loss of viral genome methylation in tumor cell lines has been correlated with a switch to type III latency. Here, evidence that the type III latency program must be inactivated by methylation to allow EBV to enter the type I or type II restricted latency program is provided. The data demonstrates that the EBNA1 gene promoter, Qp, active in types I and II latency, is encompassed by a CpG island which is protected from methylation. CpG methylation inactivates the type III latency program and consequently allows the type I or II latency program to operate by alleviating EBNA1-mediated repression of Qp. Methylation of the type III latency EBNA gene promoter, Cp, appears to be essential to prevent type III latency, since EBNA1 is expressed in all latently infected cells and, as shown here, is the only viral antigen required for activation of Cp. EBV is thus a pathogen which subverts host-cell-determined methylation to regulate distinct genetic programs.

Nasal NK- and T-cell lymphomas share the same type of Epstein-Barr virus latency as nasopharyngeal carcinoma and Hodgkin's disease

Nasal T/NK-cell lymphomas can be further separated into those of natural killer (NK) cell lineage or of T-cell lineage, with differences in cellular phenotype, T-cell receptor (TcR) gene rearrangement and TcR transcript expression. Both NK- and T-cell subtypes are closely associated with Epstein-Barr virus (EBV). In this study, EBV gene expression was determined in 23 cases of nasal lymphoma (NL) by in situ hybridisation (ISH), reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry (IH). Of the 23 cases, 19 were classified as NK-cell and 4 as T-cell tumours. ISH for EBV-encoded small non-polyadenylated RNAs showed that all cases, whether NK or T, harboured EBV in virtually all tumour cells. RT-PCR demonstrated that NL of both subtypes expressed EBNAI of the QUK splice pattern, the latent membrane proteins, LMP1 and 2 and the BamHI A rightward transcripts in the absence of EBNA2 mRNAs, compatible with the latency type II pattern. In addition, analysis of EBV protein expression by IH revealed a heterogeneous pattern of EBV gene expression at the single-cell level consisting of both LMP1+ and LMP1- tumour cells, suggesting a mixture of latency I and II. Although 2 early lytic transcripts, BZLF1 and BHRF1, were also detected in 13 and 10 cases, respectively, the lack of ZEBRA staining in any case indicates that these lytic transcripts are most likely expressed by rare cells in the biopsies entering lytic cycle. The viral transcriptional pattern similar to that of nasopharyngeal carcinoma and Hodgkin's disease suggests that EBV can exploit common regulatory mechanisms for gene transcription in diverse host cell types. Down-regulation of immunogenic proteins (EBNA2-EBNA6) in nasal lymphoma may enable tumour cells to evade host cytotoxic T-cell surveillance.

Expression of epstein-barr virus encoded nuclear antigen 1 in benign and malignant tissues harbouring EBV

AIMS

To determine levels of expression of Epstein-Barr virus (EBV) nuclear antigen 1 (EBNA1) in benign and malignant tissues harbouring EBV in relation to EBNA1 promoter usage.

METHODS

Expression of EBNA1 was investigated by means of immunohistochemistry using a mixture of two EBNA1 specific monoclonal antibodies, 1H4-1 and 2B4-1. The presence of EBV was detected by EBER1/2 RNA in situ hybridisation. Detection of promoter specific EBNA1 transcripts was by RT-PCR analysis.

RESULTS

EBNA1 positive cells were detected in all 20 EBV associated B cell lymphomas, 18 of which had arisen in immunocompromised patients; in eight of nine EBV associated T cell lymphomas; in 11 of 27 EBV positive cases of Hodgkin's disease; and in reactive lymphoid tissue harbouring EBV, including four cases of infectious mononucleosis. A diffuse EBNA1 staining pattern was observed in most of the EBV associated B cell lymphomas and was comparable with the EBER1/2 staining pattern. In the T cell lymphomas the number of EBNA1 positive cells was usually considerably less than the number of EBER1/2 positive ones. RT-PCR analysis revealed that in tumours with restricted EBNA1 expression-that is, T cell lymphomas and Hodgkin's disease lesions, EBNA1 transcripts were usually generated only by the F/Q promoter, whereas in B cell lymphomas EBNA1 transcripts were usually generated by both the C/W and F/Q promoters.

CONCLUSIONS

EBNA1 is expressed in all types of tissue harbouring EBV, but the level of expression varies greatly. This may be the result of differential promoter usage.

A simple reverse transcriptase PCR assay to distinguish EBNA1 gene transcripts associated with type I and II latency from those arising during induction of the viral lytic cycle

In Epstein-Barr virus (EBV)-associated tumors that arise in immunocompetent individuals, the pattern of viral gene expression is very restricted compared with that of latently infected B cells in tissue culture. A hallmark of viral gene expression in these tumors is the exclusive expression of only one EBV-encoded nuclear antigen, EBNA1, which is driven from a promoter (Qp) that lies near the junction of the viral BamHI F and Q fragments. During induction of the lytic cycle, a viral promoter, Fp, which lies ca. 200 bp upstream of Qp, gives rise to transcripts which overlap with Qp-initiated EBNA1 gene transcripts. Distinguishing between latency-associated EBNA1 gene transcripts and those associated with the early phase of the viral lytic cycle is critical for correct identification of restricted viral latency. Here we describe a reverse transcriptase PCR protocol which employs a nested set of upstream primers from the BamHI Q region of the viral genome and readily distinguishes Fp-initiated transcripts from Qp-initiated transcripts. A single set of amplification conditions was used for the various PCR primer combinations, which allowed all reactions to be run simultaneously. An in vitro-generated transcript, diluted in RNA from an EBV-negative cell line, was used to demonstrate that the efficiencies of amplification with the different primer combinations were very similar. This protocol was used to demonstrate that EBNA1 gene transcription in two previously uncharacterized EBV-positive epithelial cell lines initiates from Qp. In addition, we assessed the site(s) of initiation of EBNA1 gene transcripts in cell lines exhibiting restricted viral latency. Contrary to the results of Nonkwelo et al. (J. Virol. 70:623-627, 1996), which indicated that EBNA1 gene transcription during restricted viral latency initiates at multiple sites downstream of Fp, we show here that nearly all EBNA1 transcripts start at the previously identified Qp transcription initiation site.

Hodgkin disease occurring in a patient with extremely high serum antibody titers to Epstein-Barr virus--associated antigens without chronic illness

PURPOSE

We described for the first time a patient with long-lasting, extremely high serum antibody titer against Epstein-Barr virus (EBV) viral capsid antigen and early antigen without clinical symptoms suggestive of active EBV infection; the patient finally developed Hodgkin disease (HD) after 7 years of follow-up.

PATIENT AND METHODS

High serum EBV antibody titers were noted at 2 years of age. Immunological evaluation was performed at the age of 7 years. EBV-specific cytotoxic T-lymphocyte activity was normal. None of the other results showed any significant abnormalities except for the abnormal antibody titers against EBV-associated antigens.

RESULTS

The patient developed HD at the age of 9 years. In addition, EBV genomes were found in the nuclei of Hodgkin and Reed-Sternberg cells in the lymph node.

CONCLUSIONS

This case suggests that (a) a patient with extremely high serum antibody titers against EBV-associated antigens may develop HD after a prolonged period, even though no clinical symptom suggestive of active EBV infection is observed; (b) EBV may play an important role in the occurrence of HD.

Adoptive immunotherapy for Epstein-Barr virus-related lymphoma

Epstein-Barr virus (EBV) causes opportunistic B cell lymphomas in patients whose cellular immunity is compromised. We have been investigating whether infusions of donor-derived, EBV-specific cytotoxic T cells can prevent and/or treat EBV-related lymphoproliferative disease in children receiving T cell-depleted bone marrow from HLA-matched, unrelated or HLA-mismatched, related donors. In this review, we discuss the rationale for this therapeutic approach, describe our experiences with the regimen thus far, and consider some future directions in immunotherapy.

Transcriptional analysis of Epstein-Barr virus gene expression in EBV-positive gastric carcinoma: unique viral latency in the tumour cells

Although case-oriented evidence for an association of Epstein-Barr virus (EBV) with gastric carcinoma has been accumulating recently, the interaction(s) between EBV and gastric epithelial cells is/are largely unknown. In this study, we examined seven EBV-positive gastric carcinoma tissues for viral gene expression at the mRNA level, from which studies on the EBV oncogenicity in human epithelial cells will benefit. Reverse transcription-PCR analysis showed that all seven EBV-positive tumour tissues constitutively expressed EBV nuclear antigen (EBNA) 1 mRNA, but not EBNA2 mRNA. The EBNA transcription was initiated from one of three EBNA promoters, Qp: by contrast, both Cp and Wp were silent, thus resulting in the lack of EBNA2 mRNA. Latent membrane protein (LMP) 2A mRNA was detected in three of seven cases; however, neither LMP1 nor LMP2B mRNA was detected in any of the tumours tested. Transcripts from the BamHI-A region of the viral genome were detectable in all cases. BZLF1 mRNA and the product, an immediate-early gene for EBV replication, was not expressed in any of them, thereby suggesting that the tumour cells carried EBV genomes in a tightly latent form. These findings further extended our previous data regarding EBV latency in gastric carcinoma cells at the protein level, and have affirmed that the programme of viral gene expression in the tumour more closely resembles 'latency I' represented by Burkitt's lymphoma than 'latency II' represented by the majority of nasopharyngeal carcinomas.

Peptide transporter (TAP-1 and TAP-2)-independent endogenous processing of Epstein-Barr virus (EBV) latent membrane protein 2A: implications for cytotoxic T-lymphocyte control of EBV-associated malignancies

Major histocompatibility [correction of histocampatability] complex (MHC) class I-restricted cytotoxic T lymphocytes (CTLs) recognizing Epstein-Barr virus (EBV) latent antigens play a pivotal role in restricting the proliferation of EBV-infected normal B cells. However, it is now well established that most of the EBV-associated malignancies escape this potent CTL response in vivo. This resistance to immune surveillance is not due to an obvious CTL dysfunction but has been partly attributed to the down-regulation of the peptide transporters, TAP-1 and TAP-2, thus restricting the endogenous loading of MHC class I molecules with peptides derived from viral nuclear antigens. In the present study we have explored the possibility that EBV latent membrane protein 2A (LMP2A), which is often expressed in many of the EBV-associated malignancies, such as nasopharyngeal carcinoma and Hodgkin's disease tumors, can be endogenously processed through an alternative, TAP-1- and TAP-2-independent pathway. The data presented in this study clearly demonstrate not only that LMP2A can be processed by a TAP-independent mechanism but also that tumor cells with down-regulated TAP expression can be efficiently recognized by LMP2A-specific T cells following infection with recombinant vaccinia virus encoding this protein. We propose that since LMP2A is a membrane protein, it is directly translocated into the secretory pathway and the processing enzymes present in the endoplasmic reticulum are capable of generating the relevant peptide epitopes for MHC binding. The present finding of TAP-1- and TAP-2-independent presentation of LMP2A epitopes suggests a novel mechanism for immune targeting of EBV-positive malignancies, such as nasopharyngeal carcinoma and Hodgkin's disease tumors.

Hodgkin's disease after transplantation

Hodgkin's disease (HD) has seldom been reported after transplantation. Epstein-Barr virus (EBV) is present in about 50% of Reed-Sternberg cells in HD developing in immunocompetent individuals, but is more frequently found in HD of acquired immune deficiency syndrome patients. We report 7 cases of HD that occurred in transplant recipients. Clinical and pathological data and studies of EBV reveal specific features of HD after transplantation. Six patients received kidney transplants and 1 patient received combined kidney and pancreas transplantation. Immunosuppressive therapy consisted of cyclosporine, steroids, azathioprine, and antilymphocyte globulins. One patient received, in addition, anti-CD3 mAb therapy and an EBV+ B cell lymphoma developed. Retrospective EBV serological data from patients were collected. Tumors were classified according to pathology. EBV studies were conducted by immunohistochemical methods with monoclonal antibodies to EBV-latent membrane protein (LMP) or EBV-nuclear antigen 2 (EBNA2), and by in situ hybridization for latent nuclear EBV-early RNAs (EBERs). The mean lapse of time between transplantation and HD was 49 months. Six patients presented with enlarged lymph nodes and 1 patient presented with liver involvement. HD was classified as IA in 2 patients, IIA in 3 patients, IIIB in 1 patient, and IVB in 1 patient. Four patients had primary EBV infection after graft, before HD, and the others reactivated latent EBV infection. Histological subtypes were mixed cellularity in 6 cases and lymphocytic depletion in 1 case. Latent EBV infection was detected with EBERs in all tumors. Reed-Sternberg cells expressed LMP, and were negative for EBNA2 expression. Six patients were treated: 2 patients at stage I received radiotherapy, and relapsed within 1 year with a more advanced stage of HD; chemotherapy was indicated as primary therapy in 5 patients, and as salvage therapy in 2 patients; it was associated with radiotherapy in 4 patients. Immunosuppressive therapy was reduced in all patients. Four patients were alive and in complete remission 18, 25, 31, and 67 months after chemotherapy, with a functioning graft in 3 patients. Two patients died of infection. Mixed cellularity is the most frequent histological subtype observed in HD occurring in transplant patients. EBV is present in all Reed-Sternberg cells. Posttransplant HD shows similarities with human immunodeficiency virus-associated HD. These facts argue for a role of EBV infection and immunosuppression in the progression of HD after transplantation.

Transcription start sites downstream of the Epstein-Barr virus (EBV) Fp promoter in early-passage Burkitt lymphoma cells define a fourth promoter for expression of the EBV EBNA-1 protein

In Epstein-Barr virus (EBV)-transformed B lymphoblastoid and many Burkitt lymphoma cell lines, the EBV EBNA-1 protein is one of six viral nuclear antigens expressed from a common transcription unit under the control of one of two promoters, Wp or Cp. In contrast, EBNA-1 is the only EBV nuclear antigen expressed in Burkitt and other EBV-positive tumors. We previously identified a promoter of EBNA-1 transcription, designated Fp, in early-passage Mutu Burkitt tumor cells, and this promoter is also active in long-term Mutu and Akata Burkitt cell lines which maintain the exclusive expression of EBNA-1 characteristic of the tumor. However, transcription initiation within Fp reporter gene plasmids in EBV-negative cells occurs at positions 100 to 200 bases downstream of the Fp start site in the BamHI-Q restriction fragment. Here we demonstrate that transcription initiation within newly established Burkitt lymphoma cell lines is consistent with the transcription initiation we observed in reporter plasmids. Furthermore, previous observations of transcription from Fp to generate EBNA-1 transcripts can be attributed to lytic-cycle gene expression. These data, in conjunction with our previous characterization of promoter regulatory elements, define a fourth EBNA-1 promoter, Qp, that is active in latently infected Burkitt tumor cells.

The association of the Epstein-Barr virus with malignant lymphoma

The Epstein-Barr virus, a human herpesvirus, has been found in the neoplastic cells of numerous lymphoid malignancies, including Burkitt's lymphoma, immunodeficiency-associated lymphoproliferative disorders, nasal T/NK lymphoma, and Hodgkin's disease. The available data suggest that Epstein-Barr virus contributes to the pathogenesis of many of these neoplasms but is not directly linked to the etiology of any of these lymphomas.

Expression of Epstein-Barr virus encoded latent genes in nasal T cell lymphomas

AIMS

To determine the expression of Epstein-Barr (EB) virus encoded latent genes in nasal T-cell lymphomas in The Netherlands.

METHODS

Seven europid (Dutch) cases of nasal T cell lymphoma were investigated for the presence of EB virus by RNA in situ hybridisation (EBER). The expression of the EB virus encoded genes BARF0, EBNA1, EBNA2, LMP1, LMP2A, LMP2B, and ZEBRA was studied at the mRNA level using reverse transcriptase polymerase chain reaction. At the protein level the expression was investigated of EBNA2 and LMP1 by immunohistochemistry.

RESULTS

In all seven nasal T cell lymphomas EBER was detected in the nuclei of virtually all tumour cells. BARF0 mRNA was detected in all samples. EBNA1 mRNA was found in six cases, LMP1 mRNA in five, LMP2A mRNA in three, LMP2B mRNA in one, and ZEBRA mRNA in one. EBNA2 mRNA was not found in any case. At the protein level occasional LMP1 positive tumour cells were seen in only one case. The EBNA2 protein was not detected.

CONCLUSIONS

Nasal T cell lymphomas in The Netherlands are strongly associated with EB virus. The virus shows a type II latency pattern (EBNA1+, LMP1+, EBNA2-) that seems to be similar to the EB virus associated nasal T cell lymphomas in oriental countries.

The role of Epstein-Barr virus in the pathogenesis of Hodgkin's disease

Hodgkin's disease represents a phenotypically and genotypically heterogeneous lymphoma of CD30-positive tumour cells. Infection of the putative tumour cell population with Epstein-Barr virus (EBV) represents the most common genetic abnormality detectable in HD, yet the role of EBV in the pathogenesis of HD is only poorly understood. In virus-associated HD cases, monoclonal EBV genomes are detectable in all Hodgkin and Reed-Sternberg (HRS) cells, indicating that EBV infection takes place before expansion of the HRS cell population and, by implication, supporting the concept of a monoclonal origin of HRS cells. EBV infection does not define a distinct subgroup of HD but is detectable in different histotypes and in HRS cells expressing lymphocyte differentiation antigens of different cell lineages. Through the EBV-encoded protein, LMP1, the virus may superimpose an activated phenotype on genotypically immature lymphocytes. EBV-induced modulation of the cytokine expression pattern of HRS cells may contribute to the local inhibition of EBV-specific immunity observed in EBV-positive cases.

In situ detection of the Epstein-Barr virus-encoded nuclear antigen 1 in oral hairy leukoplakia and virus-associated carcinomas

A new monoclonal antibody has been used to examine immunohistochemically the expression of the Epstein-Barr virus (EBV)-encoded nuclear antigen (EBNA) 1 in virus-associated epithelial lesions. EBNA1 was detected in the tumour cell nuclei of 10/13 undifferentiated nasopharyngeal carcinomas and of 10/10 EBV-associated gastric carcinomas. EBNA1 was also detected in 13 of 16 oral hairy leukoplakia (HL) samples, where its expression was confined to nuclei in the upper epithelial cell layers whilst basal epithelial cells were negative. This observation is in agreement with previous studies demonstrating the absence of latent EBV infection in the basal cell compartment of HL and suggests an essential role for EBNA1, not only in latent EBV infection but also in virus replication.

The ecology and pathology of Epstein-Barr virus

Epstein-Barr virus achieves its ubiquitous and uniform epidemiological distribution by a dual strategy of latency to guarantee lifelong persistence and intermittent replication to guarantee transmission. These two functions appear to dictate residence in different cell types: latency in B lymphocytes and replication in epithelial cells. Both of these cell compartments are potential sites for EBV-associated malignancies.

Epstein Barr virus (EBV)-carrying cells of a chronic lymphocytic leukemia (CLL) subpopulation express EBNA1 and LMPs but not EBNA2 in vivo

We have previously described an exceptional CLL patient, P.G., whose leukemic cell population contained a small fraction of Epstein-Barr virus (EBV)-carrying cells. These cells grow directly into permanent cell lines in vitro. Using RT-PCR analysis, we now show that the in vivo EBV-carrying CLL cells expressed EBNAI, LMPI, LMP2a and 2b, but not EBNA2, in 4 of 4 blood samples obtained during the last 3 years of the patient's life. Our data also show that the CLL cells used a promoter in the F/Q, but not the W or C, region. This is consistent with the fact that CLL cells resemble resting lymphocytes rather than immunoblasts. Expression of LMP1 and LMP2b differs from the exclusive EBNAI and LMP2a expression of normal resting B cells, however, and corresponds to the state defined as latency II. This form of latency was until now detected only in EBV-carrying non-B cells in vivo. Our data show that a B-cell subtype can also show this expression pattern in vivo.

Redefining the Epstein-Barr virus-encoded nuclear antigen EBNA-1 gene promoter and transcription initiation site in group I Burkitt lymphoma cell lines

The Epstein-Barr virus-encoded nuclear antigen EBNA-1 gene promoter for the restricted Epstein-Barr virus (EBV) latency program operating in group I Burkitt lymphoma (BL) cell lines was previously identified incorrectly. Here we present evidence from RACE (rapid amplification of cDNA ends) cloning, reverse transcription-PCR, and S1 nuclease analyses, which demonstrates that the EBNA-1 gene promoter in group I BL cell lines is located in the viral BamHI Q fragment, immediately upstream of two low-affinity EBNA-1 binding sites. Transcripts initiated from this promoter, referred to as Qp, have the previously reported Q/U/K exon splicing pattern. Qp is active in group I BL cell lines but not in group III BL cell lines or in EBV immortalized B-lymphoblastoid cell lines. In addition, transient transfection of Qp-driven reporter constructs into both an EBV-negative BL cell line and a group I BL cell line gave rise to correctly initiated transcripts. Inspection of Qp revealed that it is a TATA-less promoter whose architecture is similar to the promoters of housekeeping genes, suggesting that Qp may be a default promoter which ensures EBNA-1 expression in cells that cannot run the full viral latency program. Elucidation of the genetic mechanism responsible for the EBNA-1-restricted program of EBV latency is an essential step in understanding control of viral latency in EBV-associated tumors.

Epstein-Barr virus is detected in undifferentiated nasopharyngeal carcinoma but not in lymphoepithelioma-like carcinoma of the urinary bladder

The Epstein-Barr virus (EBV) is associated with nasopharyngeal carcinoma (NPC) and with lymphoepithelioma-like carcinomas developing in certain anatomic sites. In this study, an in situ hybridization was used to identify EBV-encoded ribonucleic acid (RNA) (EBER1) transcripts in 32 of 45 cases of NPC but not in any of the 11 lymphoepithelioma-like carcinomas developing in the urinary bladder. EBER1 was most commonly detected in those NPCs having undifferentiated or nonkeratinizing squamous histology rather than the keratinizing squamous cell subtype of NPC. The EBV-encoded latent membrane protein 1 (LMP1) was expressed focally in only seven of 21 EBER1-positive NPCs by an immunohistochemical technique. These findings imply that EBER1 hybridization is more sensitive than LMP1 immunohistochemistry on paraffin sections in detecting carcinoma-associated virus. Previous in vitro studies have suggested that LMP1 expression might be a function of differentiation, but this study of naturally infected NPCs showed no strong correlation between LMP1 positivity and degree of tumor differentiation, albeit a limited spectrum of differentiation that could be examined. In two cases in which frozen tissue was available, the NPCs were monoclonal with respect to viral DNA structure, implying that the virus was present before malignant transformation. Unlike NPCs, the lymphoepithelioma-like carcinomas of the bladder were uniformly EBV negative, lending further evidence to the growing body of literature linking EBV with lymphoepithelial carcinomas of foregut-derived tissues but not with similar-appearing tumors developing in other anatomic sites.

Infection of human endothelial cells with Epstein-Barr virus

Interleukin-6 (IL-6) promotes growth and tumorigenicity of Epstein-Barr virus (EBV)-immortalized B cells, and is abnormally elevated in the serum of solid organ transplant recipients who develop EBV-positive posttransplant lymphoproliferative disease (PTLD), but not in control transplant recipients. Endothelial cells derived from PTLD lesions were found to secrete spontaneously high levels of IL-6 in vitro for up to 4 mo. We examined possible mechanisms for sustained IL-6 production by endothelial cells. Here, we show that EBV can infect endothelial cells in vitro. After 3-4 wk incubation with lethally irradiated EBV-positive, but not EBV-negative cell lines, a proportion of human umbilical cord-derived endothelial cells (HUVECs) expressed in situ the EBV-encoded small RNAs (EBER). Southern blot analysis after polymerase chain reaction showed EBV DNA in HUVEC that had been incubated with lethally irradiated EBV-positive cells, but not in the controls. Exposure of HUVECs to lethally irradiated EBV-positive but not EBV-negative cell lines induced IL-6 production that was sustained for up to 120 d of culture. These studies identify endothelial cells as targets for EBV infection and raise the possibility that this infection may be important in the life cycle and pathology of EBV.

Human immunodeficiency virus-associated Hodgkin's disease contains latent, not replicative, Epstein-Barr virus

Severe immunodeficiency is associated with reactivation of latent Epstein-Barr virus (EBV) that is manifested by virus replication. It is unknown whether EBV replication also occurs in the Hodgkin's disease (HD) tissue of patients infected with the human immunodeficiency virus (HIV). Therefore, we studied paraffin-embedded lymph nodes from 13 cases of HIV-associated HD to determine the latent or replicative state of EBV infection. All patients were seropositive HIV-infected men; additional clinical information was available for 12 patients. The risk factor(s) for HIV infection were homosexuality (n = 7), intravenous drug abuse (n = 2), homosexuality and intravenous drug abuse (n = 1), sexual promiscuity (n = 1), or hemophilia (n = 1). Advanced clinical stage and B symptoms were common at the time of initial diagnosis of HD. The histological subtype of Hodgkin's disease was universally mixed cellularity, except for a single case classified as nodular sclerosis. Seven cases exhibited foci of relative lymphoid depletion. Five cases contained foci of necrosis. Reed-Sternberg (RS) cells and RS cell variants were positive for CD30/BerH2 and negative for CD45/LCA, CD45RO/UCHL1, and CD20/L26 in all cases. Tumor cells were positive for CD15/LeuM1 in seven cases. In all 13 cases, RS cells and RS cell variants were infected by latent EBV as shown by in situ hybridization to EBV-encoded ribonucleic acid (EBER1). In 12 of 13 cases neoplastic cells coexpressed EBV latent membrane protein 1 (LMP1). EBV replication was examined by two different methods: immunohistochemistry to identify EBV-encoded BZLF1 protein and in situ hybridization to detect EBV BHLF1 transcripts. No positivity in RS or RS cell variants was detected with either assay of EBV replication (95% confidence interval [CI] = 0% to 23%). The findings confirm that EBV is detected more frequently in HIV-associated HD when compared with immunocompetent patients with HD. The findings also suggest that EBV is tightly latent within RS and RS cell variants of HIV-associated HD. It appears that factors other than host immune status are important in maintaining EBV latency in HIV-associated HD.

Detection of heterogeneous Epstein-Barr virus gene expression patterns within individual post-transplantation lymphoproliferative disorders

Using RT-PCR analysis of Epstein-Barr virus (EBV) latent gene transcription in EBV-harboring cell lines (JY and RAJI) and in post-transplantation lymphoproliferative disorders (PT-LPDs), we detected transcription of all tested latent genes (EBNA1, EBNA2, LMP1, LMP2A, and BARF0) in all cases, suggesting the presence of similar EBV expression patterns in both PT-LPDs and cell lines. In addition, the detection of immediate early (ZEBRA) and early gene (BHRF1) transcripts in cell lines and PT-LPDs indicates that activation of the virus lytic cycle occurs. To investigate EBV expression patterns at the single-cell level, a combination of immunohistochemistry and RNA in situ hybridization (including double-staining procedures) was used. In the JY and RAJI cell lines, the latency type 3 expression pattern was detected in 80 to 90% of the cells as shown by the co-expression of EBNA2 and LMP1. In contrast, in the three PT-LPDs that could be analyzed by double staining, cells expressing both EBNA2 and LMP1 were rarely detected. A mixture of at least three different cell populations were identified: (1) cells exclusively expressing EBER1/2 and EBNA1 (latency type 1); (2) cells expressing EBER1/2, EBNA1, and LMP1 (latency type 2); and (3) cells expressing EBER1/2, EBNA1, and EBNA2 in the absence of LMP1. Activation of the lytic cycle was observed in a small minority of cells, as demonstrated by detection of ZEBRA and EA-D in all cases and GP350/220 in two cases. Thus, in contrast to EBV-transformed cell lines, the observed EBV gene expression pattern in PT-LPDs reflects a mixture of multiple EBV-harboring subpopulations expressing different subsets of EBV-encoded proteins. These data indicate that the operational definitions of EBV latencies in vitro cannot easily be applied to PT-LPDs but that a continuum of different latency expression patterns can be detected at the single cell level in these lymphomas with, in a small minority of cells, progression to the virus lytic cycle.

Down-regulation of Epstein-Barr virus nuclear antigen 1 in Reed-Sternberg cells of Hodgkin's disease

AIMS

To demonstrate Epstein-Barr virus (EBV) encoded nuclear antigen 1 (EBNA-1) gene expression in EBV associated disorders using a new monoclonal antibody (1H4-1) on routinely processed tissues.

METHODS

The pressure cooker antigen retrieval method was used for the immunohistochemical demonstration of EBNA-1 gene expression in formalin fixed, EBV positive tissues from Hodgkin's disease, infectious mononucleosis, HIV associated non-Hodgkin's lymphomas, post-transplant lymphomas, and undifferentiated nasopharyngeal carcinoma (NPC). EBV encoded EBNA-2, latent membrane protein 1 (LMP-1) and BZLF-1 gene expression was also examined using commercially available monoclonal antibodies.

RESULTS

Of the 34 EBER in situ hybridisation positive cases of Hodgkin's disease examined, none expressed EBNA-1 in the Reed-Sternberg cells. These cells were nevertheless strongly LMP-1 positive in all cases. Strong EBNA-1 staining was seen in all cases of EBER positive HIV associated non-Hodgkin's lymphoma (five of five), nasopharyngeal carcinoma (five of five), infectious mononucleosis (three of three), and post-transplant lymphoma (one of one). These cases also expressed LMP-1, EBNA-2 and BZLF-1, but at differing levels.

CONCLUSION

The pressure cooker antigen retrieval procedure is a sensitive and reliable adjunct to immunohistochemistry, especially with antibodies which are otherwise ineffective on routinely processed tissues. The EBNA-1 gene is not expressed at detectable levels in the malignant cells of Hodgkin's disease, but is consistently expressed in other EBV associated disorders. This finding has important implications for the role of EBNA-1 in the biology of EBV.

Expression of bcl-2 protein and transcription of the Epstein-Barr virus bcl-2 homologue BHRF-1 in Hodgkin's disease: implications for different pathogenic mechanisms

Epstein-Barr virus (EBV) is frequently found in Hodgkin and Reed-Sternberg cells in Hodgkin's disease. Epstein-Barr virus has transforming properties in vitro and might be involved in the pathogenesis of certain types of Hodgkin's disease. One of the possible mechanisms is the upregulation of the human proto-oncogene bcl-2 by the latent membrane protein 1 of EBV in vitro. Another possibility might be the expression of the viral 'bcl-2 homologue' BHRF-1. In the present study of 64 cases of Hodgkin's disease we investigated the expression of bcl-2 at the protein level in relation to the presence of EBV. Moreover, in 10 EBV positive cases we investigated, the expression of the bcl-2 homologue, BHRF-1, by reverse-transcriptase PCR. bcl-2 was detected in 14 of 22 (64%) EBV positive and in 37 of 42 (88%) EBV negative cases. In 17 of 22 (77%) EBV positive cases Reed-Sternberg cells were negative (n = 8) or expressed the bcl-2 protein in a very low percentage ( < 5%) of cells (n = 9), whereas in 20 of 42 (43%) of the EBV negative cases the majority ( > 50%) of the neoplastic cells were bcl-2 positive. Using the reverse-transcriptase PCR with primers amplifying transcripts of BHRF-1 we were able to detect BHRF-1 transcripts in only one of the 10 tested cases of EBV positive Hodgkin's disease. Our data indicate that in EBV positive Hodgkin's disease growth advantage of Reed-Sternberg cells is not obtained by upregulation of bcl-2 or by the EBV homologue BHRF-1.

Dominance of a single Epstein-Barr virus strain in SCID-mouse tumors induced by injection of peripheral blood mononuclear cells from healthy human donors

Severe Combined Immune Deficiency mouse tumors, induced by inoculating peripheral blood mononuclear cells from 11 healthy human donors (hu-PBMC-SCID tumors), were used to analyse Epstein-Barr virus (EBV) type and strain variations. PCR analysis of EBNA 2- and EBNA 3C-specific sequences showed that EBV type A was present in SCID-mouse tumors induced by PBMC from all donors but one, while, using amplimers for a highly polymorphic region within the latent membrane protein (LMP) coding sequence, 5 different strains could be detected among the samples examined. The same LMP fragment was present in different tumors arising in the same animal, as well as in different mice injected with PBMC from any donor. Compared to B95.8 and AG876 prototype viruses, sequence analysis of LMP variants disclosed a higher homology to the latter, with 33 bp additional repetitions and a few point mutations in specific sites. This study confirms and extends previous data on the presence of a single EBV type and strain in the peripheral blood of most normal healthy subjects using the SCID-mouse system.

Epstein-Barr virus as an agent of haematological disease

Epstein-Barr virus (EBV) encodes genes that permit its persistence in human B lymphocytes and genes that ensure its replication in epithelial cells. Immune restraints on the virus are usually so effective that most EBV infections are limited to a minute fraction of B lymphocytes and of epithelial cells. As a result, most EBV infections are never symptomatic. Occasionally, the virus causes disease, often with the cooperation of the immune system or other less characterized cofactors. Infectious mononucleosis, a generally self-limited lymphoproliferative illness common in adolescents and young adults, is due to primary EBV infection and to the brisk cellular immune response it elicits. Lymphoproliferative disorders of EBV-infected B cells arise almost exclusively when cellular immunity is grossly compromised. EBV-positive Burkitt's lymphoma contain a translocated and deregulated c-myc oncogene and EBV-positive non-Hodgkin's lymphomas are characterized by the presence of Reed-Sternberg's and Hodgkin's cells, features that have not been directly linked to EBV. Many recent observations, however, including evidence that virus infection precedes malignant transformation and is often associated with a characteristic pattern of viral gene expression, provide continued interest in the relationship between the virus and these haematological malignancies.

Epstein-Barr virus-associated non-Hodgkin's lymphoma in HIV-infected patients

Epstein-Barr virus (EBV) has been implicated in the pathogenesis of many lymphoproliferations arising in diverse settings, including HIV-infection. The precise roles of EBV may differ between these settings. For example, both the frequencies of EBV-association and the specific c-MYC translocations differ between sporadic and African Burkitt's lymphoma. Similarly, the frequencies of EBV-association in HIV-infected patients differs between anatomical sites, types of NHL, and geographic locations. HIV-related NHL have genetic alterations similar to NHL arising in the general population, and have less in common with the lymphoproliferations which arise in the setting of transplantation. However, the patterns of latent EBV transcription in systemic HIV-related NHL is unique among NHL, suggesting that EBV may contribute differently to their pathogenesis.

Epstein-Barr virus association with early cancers found together with gastric medullary carcinomas demonstrating lymphoid infiltration

Seven early gastric cancers obtained from patients also demonstrating Epstein-Barr virus (EBV)-positive gastric medullary carcinoma with lymphoid infiltration were investigated using a combined polymerase chain reaction (PCR) and in situ hybridization (ISH) approach. Sharing the same background mucosa as gastric medullary cancers, they comprised four intramucosal carcinomas, predominantly well-differentiated adenocarcinomas, and three submucosal carcinomas, histologically showing mixtures of well and poorly differentiated adenocarcinoma. In the three cases of submucosal carcinoma, the presence of EBV was proven by means of both PCR and ISH. However, not all cancer cells were positive for EBV on the basis of ISH examination, in contrast to the large series of gastric carcinoma with lymphoid infiltration previously investigated. All four mucosal carcinomas were EBV-negative. Lymphocyte-determined membrane antigen (LYDMA) monoclonality, performed by PCR, and latent membrane protein-1 (LMP-1) and Epstein-Barr virus (EBNA2) expression, assessed immunohistochemically, were negative in all seven cases. The results suggest that EBV becomes associated with gastric medullary carcinoma with lymphoid infiltration (GMCL) at a relatively early stage of the disease, shortly after the tumour has initially progressed to an invasive form, and plays some role in the manifestation as GMCL.

Epstein-Barr virus latency in blood mononuclear cells: analysis of viral gene transcription during primary infection and in the carrier state

Epstein-Barr virus (EBV) can display different forms of latent infection in B-cell lines in vitro; however, the types of infection normally established by the virus in vivo remain largely unexplored. Here we have approached this question by analyzing the types of viral RNAs present in mononuclear cells freshly isolated from the blood of 14 infectious mononucleosis patients undergoing primary EBV infection and 6 long-term virus carriers. Reverse transcription-PCR amplifications were carried out with a panel of oligonucleotide primers and probes which specifically detect (i) the EBER1 RNA common to all forms of latency, (ii) transcripts either from the Cp and Wp promoters generating all six nuclear antigen (EBNA1, -2, -3A, -3B, -3C, -LP) mRNAs or from the Fp promoter generating a uniquely spliced EBNA1 mRNA, (iii) the latent membrane protein (LMP1 and 2A) mRNAs, and (iv) the BZLF1 mRNA, an immediate-early marker of lytic cycle. Viral transcription in infectious mononucleosis mononuclear cells (and in the B-cell-enriched fraction) regularly included the full spectrum of latent RNAs seen during EBV-induced B-cell growth transformation in vitro, i.e., EBER1, Cp/Wp-initiated EBNA mRNAs, and LMP1/LMP2 mRNAs, in the absence of lytic BZLF1 transcripts. In addition, transcripts with the splice pattern of Fp-initiated EBNA1 mRNA, hitherto seen only in vivo in certain EBV-positive tumors, were frequently detected. In long-term virus carriers, the mononuclear cells were again positive for latent (EBER1) and negative for lytic (BZLF1) markers; Cp/Wp-initiated RNAs were not detected in these samples, but in several individuals it was possible to amplify both Fp-initiated EBNA1 mRNA and LMP2A mRNA signals. We suggest (i) that primary infection is associated with a transient virus-driven expansion of the infected B-cell pool through a program of virus gene expression like that seen in in vitro-transformed cells and (ii) that long-term virus carriage is associated with a switch from Cp/Wp to Fp usage and thus to a more restricted form of latent protein expression that may render the infected cells less susceptible to recognition by the virus-specific cytotoxic T-cell response.

A strategy for precision of genotyping of Epstein-Barr virus by polymerase chain reaction: application for studying Hodgkin's lymphoma

Previous studies on the genotyping of Epstein-Barr virus (EBV) have been based on the analysis of a single gene locus. The assignment of genotype of an isolate could easily be over-looked with this assay. Our strategy for precision of EBV genotyping has exploited the existence of two families of EBV strains (type A and B) that can be distinguished at three divergent gene loci (EBNA-2, EBNA-3C, and EBER). To precisely determine the genotype of EBV in Hodgkin's disease (HD), we designed primers and simultaneously analysed these three gene loci that distinguish type A and B viruses by the polymerase chain reaction (PCR) technique. The primers designed to amplify these three gene loci encompass either type-specific deletion sequences (EBNA-2 and EBNA-3C) or type-specific point mutations (EBER) that identify the virus strain based on the sizes of PCR-amplified products or the mobility shifts in single-strand conformation polymorphism (SSCP) analysis. The locations of point mutations were identified by direct sequencing of the PCR-amplified DNA. Fifteen EBV-infected cell lines were analysed and a good correlation between EBNA-2 and EBNA-3C typing results was found. In contrast, approximately 33% of the cell lines analysed maintained type A sequences in EBNA-2 and EBNA-3C genes while carrying type B sequences in the EBER region. Data obtained from analysis of cell lines served as a reference for studying HD samples. EBV DNA was detected in about 70% of HD. Among the EBV-positive samples, 56% were associated with type A virus, 13% with type B, and 31% with dual viral sequences.(ABSTRACT TRUNCATED AT 250 WORDS)

Lymphoproliferative disease in mice infected with murine gammaherpesvirus 68

Murine gammaherpesvirus is a natural pathogen of wild rodents. In the laboratory it establishes an infection of epithelial cells and persists in B lymphocytes in a latent form. Inbred mice chronically infected with the virus develop a lymphoproliferative disease (LPD) similar to that seen in patients infected with Epstein-Barr virus. The frequency of LPD over a period of 3 years was 9% of all infected animals, with 50% of these displaying high grade lymphomas. The incidence of LPD was greatly increased when infected mice were treated with cyclosporin A. The majority of mice used in the experiments were BALB/c, although lymphomas were detected in mice on other genetic backgrounds, ie, CBA and B10Br. Lymphomas were associated with both lymphoid and nonlymphoid tissues (liver, lung, and kidney). In all cases of lymphomas studied thus far, there was a mixed B cell (B220+ve) and T cell (CD3+ve) phenotype. The B cells were light chain restricted, indicative of a clonal origin. Variable numbers of virus genome-positive cells were detected by in situ hybridization in and around the lymphomas. In contrast, no lytic antigen-positive cells were detected, indicating that genome-positive cells were either latently infected or undergoing an abortive infection. These observations suggest that murine gammaherpesvirus-infected mice may be an important model to study the pathogenesis of LPD associated with other gammaherpesviruses, such as Epstein-Barr virus.

Latent Epstein-Barr virus infection in cottontop tamarins. A possible model for Epstein-Barr virus infection in humans

The association of Epstein-Barr virus (EBV) with a growing number of human malignancies underlines the importance of efforts aimed at preventing the infection with this potential carcinogen and of establishing animal models for human virus-associated tumors. Cottontop tamarins have been used in EBV vaccine studies because virus infection regularly induces lymphomas similar to those seen in human immunocompromised individuals. In recent years, several vaccines based on the gp340/220 envelope protein of EBV have been developed and shown to prevent the development of EBV-associated lymphomas in this model. Using in situ hybridization and immunohistology, we have characterized EBV infection in one nonimmunized and three immunized animals after challenge with a standard tumorigenic dose of EBV. In the nonimmunized animal, EBV-infected lymphoid cells were detected in numerous tissues showing no obvious lymphoma infiltration. Surprisingly, variable numbers of virus-carrying cells were also found in all three immunized animals that were protected against the development of virus-associated lymphoma. This observation demonstrates that vaccination does not induce sterilizing immunity against EBV infection in this model. Double labeling suggested a B cell phenotype of the majority of these cells. EBV infection of nonlymphoid cells was not observed. Analysis of viral gene expression in immunized animals suggested a restricted form of virus latency different from that seen in EBV-driven lymphomas in nonimmunized cottontop tamarins. These results raise the possibility that immunized cottontop tamarins protected against the development of EBV-driven lymphoma or animals exposed to a sublymphomagenic dose of virus may serve as a model for EBV infection in humans.

Decreased expression of cellular markers in Epstein-Barr virus-positive Hodgkin's disease

Epstein-Barr virus (EBV) has been demonstrated in the Reed-Sternberg cells and their mononuclear variants (Hodgkin cells; H-RS cells) in a substantial number of Hodgkin's disease (HD) cases. Moreover, EBV can modulate both in vivo and in vitro the expression of several cellular genes, including lymphoid differentiation markers. Therefore we investigated, in 64 cases of HD, the relationship between the presence of EBV and the expression of lymphoid (CD45RB), T- (CD3, CD45RO), B- (CD20, MB2 antigen, CDw75), and myeloid-cell lineage markers (CD15), and of activation markers (CD30, EMA, and the 115D8 antigen) on the H-RS cells. EBV-positive cases, as demonstrated by the presence of EBER-1 and -2 RNA and LMP-1 protein expression, showed a significant reduction in the expression on H-RS cells of T-cell lineage (CD3, P < 0.02), B-cell lineage (CD20; P < 0.005), and activation markers (EMA; P < 0.002 and the 115D8 antigen; P < 0.001) as compared with EBV-negative cases. No differences were found in the expression of CD15, CD30, CD45RO, CD45RB, CDw75, or the MB2 antigen on H-RS cells in EBV-positive and EBV-negative HD cases. Interestingly, in 11 cases of EBV-negative HD, B- as well as T-cell lineage markers could be found on some H-RS cells. These data suggest that EBV in H-RS cells is able to down-regulate the expression of T- (CD3) and B- (CD20) cell lineage markers and lymphoid activation markers (EMA and the 115D8 antigen).(ABSTRACT TRUNCATED AT 250 WORDS)

Detection and characterization of Epstein-Barr virus in clinical specimens

Epstein-Barr virus (EBV) is associated with a wide spectrum of benign and malignant diseases. Recent additions to the list include oral hairy leukoplakia; a subset of Hodgkin's lymphomas, particularly those with mixed cellularity histology or those occurring in underdeveloped countries; a subset of diffuse large cell/immunoblastic lymphoma in the immunocompromised, particularly primary central nervous system lymphoma; a subset of peripheral T cell lymphomas; and a subset of gastric carcinomas, particularly undifferentiated carcinomas. There are several distinctive aspects of the biology of the virus that are important in investigations of virus in clinical specimens. The presence of repeated elements in the genome facilitates detection of viral nucleic acids by a variety of hybridization techniques as well as the characterization of the clonality of virus-infected tissues. Latent viral infection is associated with several different patterns of viral gene expression in infected cells. Latent gene products are important because of their growth-regulating and -transforming properties as well as the potent cytotoxic T cell response they elicit. The abundant expression of the EBER RNA transcripts makes possible the sensitive detection of latent infection in EBV-associated tumors. Lytic infection can be inhibited by antiviral nucleoside analogues. Two lytic gene products are of special interest because of their homology to the cellular proteins BCL-2 and interleukin-10. Two viral biotypes or strains with different properties in terms of lymphocyte immortalization and transformation have recently been characterized. Current evidence suggests a differential biotype association with particular malignancies. Characterization of the association of EBV with various disease processes promises to be important for diagnosis and treatment as well as for a better understanding of the epidemiology and pathogenesis of these diabetes.

Epstein-Barr virus positivity in Hodgkin's disease does not correlate with an HLA A2-negative phenotype

BACKGROUND

Epstein-Barr virus- (EBV) related DNA and RNA can be found in tissues involved with Hodgkin's disease, specifically in the Reed-Sternberg cells. These cells also express the membrane antigens LMP1 and LMP 2A and 2B. Studies in normal individuals indicate that cellular immunity against LMP2 was frequently mediated through human leukocyte antigen (HLA) A2, whereas responses to LMP1 appeared to be relatively infrequent. Assuming that LMP2-positive Reed-Sternberg cells would be sensitive to a CD8-positive cellular immune response, the hypothesis can be made that EBV-positive Hodgkin's disease should be more common in individuals not expressing HLA A2. To test this hypothesis, the authors have studied the frequency of HLA A2 in EBV-positive versus EBV-negative patients with Hodgkin's disease.

METHODS

All 72 patients diagnosed with Hodgkin's disease in Northern and Central Alberta, Canada, during 1990 and 1991 were studied. A nonisotopic in situ hybridization method with an oligonucleotide probe specific for EBER 1 and 2 was used. In addition, sections were stained for the EBV-latent protein LMP1, HLA A2, and a monomorphic HLA class I determinant and beta 2-microglobulin.

RESULTS

EBER-positive Reed-Sternberg cells were found in 26% of the patients. The percentage of positive patients was 86% in mixed cellularity, 13% in nodular sclerosis, and 0% in lymphocyte predominance. The number of those who were HLA-A2 positive was approximately 50% in the EBV-positive and -negative patients.

CONCLUSIONS

Therefore, no correlation between HLA A2 expression and presence or absence of EBV in the R-S cells of Hodgkin's disease was identified.

Expression of hepatitis C virus in hepatocellular carcinoma

BACKGROUND

Epidemiologic studies have suggested a strong association between chronic hepatitis C virus (HCV) infection and the development of hepatocellular carcinoma (HCC). To investigate the possible role of HCV in the pathobiology of HCC, the authors studied the expression of HCV in 10 cases of HCC with chronic HCV infection.

METHODS

The core, envelope, and nonstructural (NS) 3 and 5 proteins were localized in liver and tumor tissues by the immunoperoxidase technique using mouse monoclonal antibodies to recombinant proteins or synthetic peptide of HCV. In addition, the positive and negative strands of HCV RNA were detected in the tissues by strand-specific reverse transcription/double polymerase chain reaction using primers for the 5'-nontranslated region.

RESULTS

The HCV proteins were expressed in three of nine HCC specimens tested (the core protein in three HCC, the envelope, NS3 and NS5 proteins in one HCC) and in two of nine nontumorous liver specimens adjacent to the HCC (the core protein in two specimens, envelope, NS3 and NS5 proteins in one specimen). Positive-stranded HCV RNA was detected in all tumorous and nontumorous specimens except in one tumor. Negative-stranded HCV RNA was found in six of nine HCC tested and in all nontumorous livers.

CONCLUSIONS

These findings suggest that HCV persists in hepatocytes during malignant transformation, although secondary infection of tumor cells by HCV cannot be excluded. Some HCC appear to support replication and expression of HCV.

Localization of predisposition to Hodgkin disease in the HLA class II region

Molecular typing of HLA class II loci has been performed on a sample of 196 patients with Hodgkin lymphoma. Division of patients into two histological categories--nodular sclerosing Hodgkin disease versus all other types--shows significant overall association of the nodular sclerosing group with the HLA class II region. Haplotypes and alleles defined for the four loci typed--DRB1, DQA1, DQB1, and DPB1--were present in both excess and deficit in the nodular sclerosing sample. Some of the effects are attributable to particular DRB1 and DQB1 alleles, while other effects are best explained by haplotypes marking the entire class II region. The latter effects might be due to variation in additional, as-yet-unexamined loci in the class II region or to particular combinations of alleles from two or more loci. These data also explain why earlier studies showed HLA linkage but not association, and they substantiate the specific involvement of the immune system in certain neoplastic diseases.