Tissue distribution of Epstein-Barr virus genotypes

A Systematic Review of Epstein-Barr Virus Latent Membrane Protein 1 (LMP1) Gene Variants in Nasopharyngeal Carcinoma

Nasopharyngeal carcinoma (NPC) is an aggressive tumor with a complex etiology. Although Epstein-Barr virus (EBV) infection is known environmental factor for NPC development, the degree to which EBV naturally infects nasopharyngeal epithelium and the moment when and why the virus actively begins to affect cell transformation remains questionable. The aim of this study was to explore the association between LMP1 gene variability and potential contribution to NPC development. A systematic review was performed through searches of PubMed, Web of Science (WoS) and SCOPUS electronic databases. Additionally, meta-analysis of the difference in the frequency of seven LMP1 gene variants in NPC and control individuals was accomplished. The results from this study give a proof of concept for the association between 30 bp deletion (OR = 3.53, 95% CI = 1.48-8.43) and Xhol loss (OR = 14.17, 95% CI = 4.99-40.20) and NPC susceptibility when comparing biopsies from NPC and healthy individuals. Otherwise, 30 bp deletion from NPC biopsies could not distinguish NPC from EBV-associated non-NPC tumors (OR = 1.74, 95% CI = 0.81-3.75). However, B95-8, China1 and North Carolina variants were uncommon for NPC individuals. Much more efforts remains to be done to verify the biological significance of the differences observed, define so-called "high-risk" EBV variants and make it available for clinical application.

High prevalence of the EBER variant EB-8m in endemic nasopharyngeal carcinomas

Epstein-Barr virus (EBV)-encoded small RNAs (EBERs) are the most highly expressed transcripts in all EBV-associated tumors and are involved in both lymphoid and epithelioid carcinogenesis. Our previous study on Chinese isolates from non-endemic area of nasopharyngeal carcinoma (NPC) identified new EBER variants (EB-8m and EB-10m) which were less common but relatively more frequent in NPC cases than healthy donors. In the present study, we determined the EBER variants in NPC cases and healthy donors from endemic and non-endemic areas of NPC within China and compared the EBER variants, in relation to the genotypes at BamHI F region (prototype F and f variant), between population groups and between two areas. According to the phylogenetic tree, four EBER variants (EB-6m, EB-8m, EB-10m and B95-8) were identified. EB-6m was dominant in all population groups except for endemic NPC group, in which EB-8m was dominant. EB-8m was more common in endemic NPC cases (82.0%, 41/50) than non-endemic NPC cases (33.7%, 32/95) (p<0.0001), and it was also more frequent in healthy donors from endemic area (32.4%, 24/74) than healthy donors from non-endemic area (1.1%, 1/92) (p<0.0001). More importantly, the EB-8m was more prevalent in NPC cases than healthy donors in both areas (p<0.0001). The f variant, which has been suggested to associate with endemic NPC, demonstrated preferential linkage with EB-8m in endemic isolates, however, the EB-8m variant seemed to be more specific to NPC isolates than f variant. These results reveal high prevalence of EBER EB-8m variant in endemic NPC cases, suggesting an association between NPC development and EBV isolates carrying EB-8m variant. Our finding identified a small healthy population group that shares the same viral strain which predominates in NPC cases. It could be interesting to carry extensive cohort studies following these individuals to evaluate the risk to develop NPC.

Epstein-Barr virus BZLF1 gene polymorphisms: malignancy related or geographically distributed variants?

The ubiquitous Epstein-Barr virus (EBV) is related to the development of several lymphoid and epithelial malignancies and is also the aetiological agent for infectious mononucleosis (IM). BZLF1, an immediate early gene, plays a key role in modulating the switch from latency to lytic replication, hence enabling viral propagation. Polymorphic variations in the coded protein have been studied in other geographical regions in a search for viral factors that are inherent to malignancies and differ from those present in benign infections. In the present study, in samples of paediatric patients with benign IM and paediatric patients with malignant lymphomas, we detected previously described sequence variations as well as distinctive sequence polymorphisms from our region. By means of phylogenetic reconstruction, we characterized new phylogenetically distinct variants. Moreover, we described an association between specific variants and the studied pathologies in our region, particularly variant BZLF1-A2 with lymphomas and BZLF1-C with IM. Additionally, length polymorphisms within intron 1 were also assessed and compared between pathologies resulting in an association between 29-bp repeated units and lymphomas. In conclusion, this is the first report to characterize BZLF1 gene polymorphisms in paediatric patients from our geographical region and to suggest the association of these polymorphisms with malignant lymphomas.

Molecular pathogenesis of B-cell posttransplant lymphoproliferative disorder: what do we know so far?

Posttransplant lymphoproliferative disorder (PTLD) is a potentially fatal disease that arises in 2%-10% of solid organ and hematopoietic stem cell transplants and is most frequently of B-cell origin. This very heterogeneous disorder ranges from benign lymphoproliferations to malignant lymphomas, and despite the clear association with Epstein-Barr Virus (EBV) infection, its etiology is still obscure. Although a number of risk factors have been identified (EBV serostatus, graft type, and immunosuppressive regimen), it is currently not possible to predict which transplant patient will eventually develop PTLD. Genetic studies have linked translocations (involving C-MYC, IGH, BCL-2), various copy number variations, DNA mutations (PIM1, PAX5, C-MYC, RhoH/TTF), and polymorphisms in both the host (IFN-gamma, IL-10, TGF-beta, HLA) and the EBV genome to B-cell PTLD development. Furthermore, the tumor microenvironment seems to play an important role in the course of disease representing a local niche that can allow antitumor immune responses even in an immunocompromised host. Taken together, B-cell PTLD pathogenesis is very complex due to the interplay of many different (patient-dependent) factors and requires thorough molecular analysis for the development of novel tailored therapies. This review aims at giving a global overview of the currently known parameters that contribute to the development of B-cell PTLD.

Direct sequencing and characterization of a clinical isolate of Epstein-Barr virus from nasopharyngeal carcinoma tissue by using next-generation sequencing technology

Epstein-Barr virus (EBV)-encoded molecules have been detected in the tumor tissues of several cancers, including nasopharyngeal carcinoma (NPC), suggesting that EBV plays an important role in tumorigenesis. However, the nature of EBV with respect to genome width in vivo and whether EBV undergoes clonal expansion in the tumor tissues are still poorly understood. In this study, next-generation sequencing (NGS) was used to sequence DNA extracted directly from the tumor tissue of a patient with NPC. Apart from the human sequences, a clinically isolated EBV genome 164.7 kb in size was successfully assembled and named GD2 (GenBank accession number HQ020558). Sequence and phylogenetic analyses showed that GD2 was closely related to GD1, a previously assembled variant derived from a patient with NPC. GD2 contains the most prevalent EBV variants reported in Cantonese patients with NPC, suggesting that it might be the prevalent strain in this population. Furthermore, GD2 could be grouped into a single subtype according to common classification criteria and contains only 6 heterozygous point mutations, suggesting the monoclonal expansion of GD2 in NPC. This study represents the first genome-wide analysis of a clinical isolate of EBV directly extracted from NPC tissue. Our study reveals that NGS allows the characterization of genome-wide variations of EBV in clinical tumors and provides evidence of monoclonal expansion of EBV in vivo. The pipeline could also be applied to the study of other pathogen-related malignancies. With additional NGS studies of NPC, it might be possible to uncover the potential causative EBV variant involved in NPC.

Characterization of variants in the promoter of BZLF1 gene of EBV in nonmalignant EBV-associated diseases in Chinese children

Background

Diseases associated with Epstein-Barr virus (EBV) infections, such as infectious mononucleosis (IM), EBV-associated hemophagocytic lymphohistiocytosis (EBV-HLH) and chronic active EBV infection (CAEBV) are not rare in Chinese children. The association of type 1 or type 2 EBV and variants of the EBV BZLF1 promoter zone (Zp) with these diseases is unclear.

Results

The objective of this study was to investigate the relationship between EBV genotypes (Zp variants and EBV type 1 and 2) and the clinical phenotypes of EBV-associated diseases in Chinese children. The Zp region was directly sequenced in 206 EBV-positive DNA samples from the blood of patients with IM, EBV-HLH, CAEBV, and healthy controls. Type 1 or type 2 EBV was examined by PCR for EBNA2 and EBNA3C subtypes. Four polymorphic Zp variants were identified: Zp-P, Zp-V3, Zp-P4 and Zp-V1, a new variant. The Zp-V3 variant was significantly associated with CAEBV (P ≤ 0.01). The frequency of co-infection with Zp variants was higher in patients with CAEBV and EBV-HLH, compared with IM and healthy controls, mostly as Zp-P+V3 co-infection. Type 1 EBV was predominant in all categories (81.3-95%) and there was no significant difference in the frequency of the EBV types 1 and 2 in different categories (P > 0.05).

Conclusions

Type 1 EBV and BZLF1 Zp-P of EBV were the predominant genotypes in nonmalignant EBV associated diseases in Chinese children and Zp-V3 variant may correlates with the developing of severe EBV infection diseases, such as CAEBV and EBV-HLH.

The extent of genetic diversity of Epstein-Barr virus and its geographic and disease patterns: a need for reappraisal

Epstein-Barr virus (EBV) is a ubiquitous, gamma-1 lymphotrophic virus etiologically linked to nasopharyngeal carcinoma (NPC), endemic to Southern China, and Burkitt lymphoma (BL), endemic to equatorial Africa, both of which are rare elsewhere in the world. Why EBV is associated with different malignancies in different geographic regions remains puzzling and may be related to EBV genotypic variability through specific disease and geographic associations. We review the literature on sequence variation in EBV genes, focusing on LMP-1, EBNA-1, and BZLF-1 and their distribution by geography and disease. Given the limitations of current studies, definitive conclusions regarding the link between EBV genotypes, disease and geography are not possible. We suggest that the true extent of EBV diversity is likely to be greater than is currently recognized. Additional studies conducted in carefully selected populations, that are sufficiently powered to provide robust estimates, and that utilize testing approaches that permit full characterization of viral diversity are needed to further our understanding of patterns of EBV genetic variation and their association with malignancies in different regions.

Distribution of Epstein-Barr virus genotypes in throat washings, sera, peripheral blood lymphocytes and in EBV positive tumor biopsies from Slovenian patients with nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a malignancy closely associated with Epstein-Barr virus (EBV). It is prevalent among the Chinese of Southern China, whereas outside China, the position seems to be different. The aim of this study was to determine the distribution of EBV genotypes in the patients with NPC in Slovenia, which is a nonendemic area. Detection of EBV was undertaken by testing the throat washes, sera, peripheral blood lymphocytes (PBLs), and biopsies of primary tumors of 48 patients with NPC in Slovenia. The sera of 20 patients with serologically confirmed primary EBV infection served as a control clinical material. The analysis of genotypes was carried out on three regions of EBV genome; BamHI WYH, BamHI I, and BamHI F, using the polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP). The results show that, in Slovenia, the predominant combination of EBV genotypes based on the differences in the three genomic regions is ADF. This combination was found in 56 out of 103 different EBV positive clinical samples (throat washes, sera, PBLs, and tumor biopsies) of patients with NPC and in 15 out of 17 sera of patients with primary EBV infection. Very low number of genotypes C and f were detected, in spite of the fact that these two genotypes were considered to be associated with the development and/or maintenance of NPC in Southern China. Genotype f was found in only two tumor biopsies; in all other clinical samples (throat washes, sera and PBLs), genotype F was detected. Genotype C was proven in 31/103 clinical samples, with the highest percentage in tumor biopsies (37.5%). As in the NPC patients from other countries (Alaska is an exception), genotype A was predominant and was detected in 86/103 clinical samples. Genotype B was found in 15 clinical samples of patients with NPC and in 3 the two genotypes A and B were found. In comparison to China, these results show different EBV genotypes distribution. It seems that the genetic disposition of human population is an important factor that may contribute to different susceptibility for specific EBV genotypes.

Cytomegalovirus and Epstein-Barr virus subtypes—The search for clinical significance

Cytomegalovirus (CMV) as well as Epstein Barr virus (EBV) genomes include regions which show in part substantial polymorphisms. Characterization of several polymorphic regions led to the identification of various CMV and EBV subtypes. Within the last years there have been undertaken numerous efforts to find out whether the diverse subtypes differentially contribute to clinical manifestations. However, although some associations have been described so far between a certain virus subtype and the development of individual diseases these analyses were greatly complicated by the huge genomic background of CMV and EBV, by the large variety of individual host-virus relations and by differences in the geographic or demographic subtype distribution. In addition, it was shown meanwhile that a substantial proportion of virus infections is due to mixed infections with different subtypes. In this review we will give an overview of the current knowledge concerning the clinical significance of individual CMV and EBV subtypes, defined by characterization of selected polymorphisms. In addition, we also focus on recent analyses which show that infection with mixed virus subtype populations may be disadvantageous compared to single virus subtype infections.

Characterization of variants in the promoter of EBV gene BZLF1 in normal donors, HIV-positive patients and in AIDS-related lymphomas

OBJECTIVE

The aim of this study was to determine the occurrence of polymorphic variants of EBV BamHI fragment Z (BZLF1) promoter zone Zp in tumor and non-tumor-associated EBV. We characterized the Zp region in type A and type B EBV, infecting AIDS-related non-Hodgkin's lymphomas (AIDS-NHL) and non-malignant lymphoid tissues derived from HIV-positive patients and from healthy individuals.

METHODS

The Zp region was directly sequenced in 133 EBV-positive DNA samples: 63 AIDS-NHL (32 systemic AIDS-NHL and 31 AIDS-primary central nervous system lymphoma [AIDS-PCNSL]), 30 lymphoid tissues derived from HIV-positive individuals and 40 lymphoid samples derived from healthy individuals. The chi square test was used to assess for statistically significant differences among proportions, and a two-tailed P value </=0.05 was chosen as statistically significant.

RESULTS

We found three polymorphic Zp variants: Zp-P, considered to be the prototype sequence; Zp-V3, that differs from Zp-P for three nucleotide substitutions; and a new variant, Zp-PV, that differs from Zp-P for a single nucleotide substitution. Zp-V3 was significantly associated with AIDS-PCNSL (P<0.001) and with systemic AIDS-NHL (P=0.007), in particular with AIDS-related immunoblastic lymphoma (P<0.001). Moreover, in malignant samples, this variant was also significantly associated with type B EBV (P<0.001). Finally, the new identified Zp-PV variant was isolated in 7 AIDS-PCNSL.

CONCLUSIONS

The frequency of polymorphisms in the regulatory zone of BZLF1 is different between malignant and non-malignant samples in AIDS patients and may identify EBV subtypes with different transforming activities, including those associated to the pathogenesis of B cell lymphoma.

Mutational events in LMP1 gene of Epstein-Barr virus in salivary gland lymphoepithelial carcinomas

It is still unknown what kinds of roles Epstein-Barr virus (EBV) infection that are highly specific to salivary gland lymphoepithelial carcinomas (LECs) play in their tumorigenesis. To clarify the significance of EBV in LECs, we paid particular attention to the LMP1 gene, which is responsible for triggering several pathways for activating transcription factors. Sixty-one cases of EBV positive LECs confirmed by PCR and in-situ hybridization were collected from various areas of the world and studied immunohistochemically for latent membrane protein-1. Furthermore, PCR for the LMP1 carboxyl (C)-terminus region was performed, and the PCR products were sequenced for detection of other mutational events. LMP1 gene products were immunohistochemically demonstrated in 51% of the cases, while PCR amplification of the LMP1 gene was successful in 41 cases (67%). Among them, a 30 bp deletion in the C-terminus of the LMP1 gene, which had been shown to be characteristic to EBV in Chinese nasopharyngeal carcinomas, was found in 20 cases (32%). Most of them were from Guangzhou, Chengdu and Taiwan, while most of the cases from Shanghai and other areas exhibited no 30 bp deletion. In addition, several point mutations including codon 338 of LMP1 were commonly shared by the cases with or without the 30 bp deletion. These results indicate that there are 2 major genomic variations of EBV infecting salivary gland LECs. The frequent mutational events in the C-terminus in addition to the 30 bp deletion also seem to be critical for the pathogenesis because such mutational events may possibly promote cellular proliferation.

Coinfection by multiple strains of Epstein-Barr virus in infectious mononucleosis in immunocompetent patients

OBJECTIVE

A molecular study of Epstein-Barr virus (EBV)-induced infectious mononucleosis (IM) was performed. The presence of a 30-bp deletion on the latent membrane protein-1 (LMP-1) oncogene from EBV in Caucasian IM patients was evaluated.

MATERIAL AND METHODS

Peripheral blood mononuclear cells were obtained from 27 IM patients and 18 adenoids, 28 tonsils and 16 EBV-related reactive lymphadenitis specimens were used as controls. DNA isolation, EBV polymerase chain reaction (PCR) and LMP-1 oncogene PCR analysis were performed.

RESULTS

The 30-bp deletion on LMP-1 was identified in 29.6% of IM patients, but was always seen in conjunction with full-length LMP-1. Although the LMP-1-deleted strain seemed to be more prevalent in IM (29.6%) and EBV-related reactive lymphadenitis (37.5%,) than in adenoid (0%) or tonsil specimens (21.4%), these differences were not significant (p > 0.05; chi2). Thus, a 30-bp deletion on LMP-1 was present in almost a third of Caucasian IM patients.

CONCLUSION

The finding of coinfections in IM patients confirms that primary infection by more than one EBV strain is possible.

Compartmentalization and transmission of multiple epstein-barr virus strains in asymptomatic carriers

Infection with the Epstein-Barr virus (EBV) is often subclinical in the presence of a healthy immune response; thus, asymptomatic infection is largely uncharacterized. This study analyzed the nature of EBV infection in 20 asymptomatic immunocompetent hosts over time through the identification of EBV strain variants in the peripheral blood and oral cavity. A heteroduplex tracking assay specific for the EBV gene LMP1 precisely identified the presence of multiple EBV strains in each subject. The strains present in the peripheral blood and oral cavity were often completely discordant, indicating the existence of distinct infections, and the strains present and their relative abundance changed considerably between time points. The possible transmission of strains between the oral cavity and peripheral blood compartments could be tracked within subjects, suggesting that reactivation in the oral cavity and subsequent reinfection of B lymphocytes that reenter the periphery contribute to the maintenance of persistence. In addition, distinct virus strains persisted in the oral cavity over many time points, suggesting an important role for epithelial cells in the maintenance of persistence. Asymptomatic individuals without tonsillar tissue, which is believed to be an important source of virus for the oral cavity, also exhibited multiple strains and a cyclic pattern of transmission between compartments. This study revealed that the majority of patients with infectious mononucleosis were infected with multiple strains of EBV that were also compartmentalized, suggesting that primary infection involves the transmission of multiple strains. Both the primary and carrier states of infection with EBV are more complex than previously thought.

Epstein-Barr virus in the pathogenesis of NPC

Epstein-Barr virus (EBV) is consistently detected in nasopharyngeal carcinoma (NPC) from regions of high and low incidence. EBV DNA within the tumor is homogeneous with regard to the number of terminal repeats. The detection of a single form of viral DNA suggests that the tumors are clonal proliferations of a single cell that was initially infected with EBV. Specific EBV genes are consistently expressed within the NPC tumors and in early, dysplastic lesions. The viral proteins, latent membrane protein 1 and 2, have profound effects on cellular gene expression and cellular growth, resulting in the highly invasive, malignant growth of NPC tumors. In addition to potential genetic changes, the establishment of a latent, transforming infection in epithelial cells is likely to be a major contributing factor to the development of this tumor.

Quantitative CSF PCR in Epstein-Barr virus infections of the central nervous system

Acute Epstein-Barr virus (EBV) infection of the central nervous system (CNS) is associated with meningoencephalitis and other neurological syndromes and with CNS lymphomas (CNSLs). Diagnosis is based on serological studies and more recently on detection of EBV DNA in cerebrospinal fluid (CSF) by polymerase chain reaction (PCR). We measured EBV DNA by quantitative PCR and EBV mRNA by RT-PCR in the CSF in patients with EBV-associated neurological disorders. EBV was identified as the cause of CNS infection in 28 patients: 14 with CNSL, 10 with encephalitis, and 4 with postinfectious neurological complications. CSF analysis showed that patients with CNSL had high EBV load (mean +/- standard error of 4.8 +/- 0.2 log(10) DNA copies/ml) and low leukocyte counts (22 +/- 7 cells/microl); encephalitis was characterized by high EBV load (4.2 +/- 0.3 log(10) DNA copies/ml) and high leukocyte counts (143 +/- 62 cells/microl); and patients with postinfectious complications showed low EBV load (3.0 +/- 0.2 log(10) DNA copies/ml) with high leukocyte counts (88 +/- 57 cells/microl). Lytic cycle EBV mRNA, a marker of viral replication, was identified in 10 CSF samples from patients with CNSL and encephalitis. These studies demonstrate the utility of quantitative CSF PCR and establish the presence of lytic cycle EBV mRNA in CSF of patients with EBV-associated neurological disease.

Tissue specific distribution of Epstein-Barr virus (EBV) BZLF1 gene variants in nasopharyngeal carcinoma (NPC) bearing patients

Using EBV BNLF1 gene polymorphism, we have recently shown that, in NPC bearing patients, lymphocytes and tumor cells of the same individual were infected by different viruses. It appeared as a rule that EBV infection was by multiple strains in these immunocompetent, HIV negative patients. Our data did not detect any evident association between tumor cells and a particular BNLF1 variant. In the present paper, we extend our analysis to the BZLF1 gene of the viruses present in different sites of the same patients. Only two main variants of the BZLF1 gene were identified. Despite this very weak polymorphism of this locus, our results entirely confirm the very frequent occurrence of multistrain infections in these patients, and the presence of different EBV strains in tumor cells and lymphocytes from the same individual. However, in contrast to our results concerning the BNLF1 gene, the BZLF1 variants appeared to be cell type specific, one being associated mainly with epithelial or tumor cells and the other with lymphocytes. The possible reasons for this distribution are discussed.

Heterogeneous distribution of TT virus of distinct genotypes in multiple tissues from infected humans

TT virus (TTV) DNA was quantitated in the serum and nine autopsy tissues (bone marrow, lymph node, muscle, thyroid gland, lung, liver, spleen, pancreas, and kidney) obtained from each of three TTV-infected subjects by real-time polymerase chain reaction (PCR), which can detect all TTV genotypes. TTV DNA was detected in all examined tissues, with the viral load being equal to or up to 300 times higher than that in the corresponding serum (2.1 x 10(5) to 5.3 x 10(7) copies/g vs 1.2-3.9 x 10(5) copies/ml). Generally, the TTV viral load was higher in the bone marrow, lung, spleen, and liver than in the other tissues, although it varied by individual. Restriction fragment length polymorphism (RFLP) analysis of the PCR-amplified TTV DNA of 3.3 kilobases (kb) revealed considerable differences among the TTVs in the serum and tissue specimens from each subject. Further, the 3.3-kb amplicons from the serum and tissue specimens from one subject were molecularly cloned, and 30 clones each from the serum and each tissue specimen were subjected to RFLP and sequence analysis (total, 300 clones): the TTV clones were classified into six genotypes including four novel genotypes. The genotypic variability was remarkable: each specimen had one to five TTV genotypes at different frequencies. TTV DNA in replicative intermediate forms and TTV mRNA were detectable in all tissues tested. These results indicate the broad, uneven distribution of TTV genotypes in tissues and suggest that viral replication takes place in multiple tissues at distinct levels in infected individuals.

Epstein--Barr virus gene polymorphisms in Chinese Hodgkin's disease cases and healthy donors: identification of three distinct virus variants

Epstein--Barr virus (EBV) is associated with several malignancies. Specific EBV gene variants, e.g. the BamHI f configuration, a C-terminal region 30 bp deletion in the latent membrane protein-1 (LMP1) gene (del-LMP) and the loss of an XhoI site in LMP1 (XhoI-loss), are found in Chinese cases of nasopharyngeal carcinoma (NPC), suggesting that EBV sequence variation may be involved in oncogenesis. In order to understand better the epidemiology of these EBV variants, they were studied in virus isolates from EBV-positive Chinese cases of Hodgkin's disease (HD; n=71) and donor throat washings from healthy CHINESE: Sequencing was performed of 15 representative EBV isolates, including the first analysis of the LMP1 promoter in Asian wild-type EBV isolates. The following observations were made. (i) Three EBV LMP1 variants were identified, designated Chinese groups (CG) 1--3. In both EBV-associated HD and in healthy Chinese, CG1-like viruses showing del-LMP1 and XhoI-loss were predominant. (ii) CG1viruses were distinct from European and African variants, suggesting that this profile is useful for epidemiological studies. (iii) Specific patterns of mutations were present in the LMP1 promoter in both CG1 and CG2. (iv) The BamHI f variant was not found in Chinese HD, in contrast to Chinese NPC and European HD. This study confirms that EBV isolates in Chinese HD and other tumours differ from those reported in Western cases. However, this reflects the predominant virus strain present in the healthy Chinese population, suggesting that these are geographically restricted polymorphisms rather than tumour-specific strains.

In nasopharyngeal carcinoma-bearing patients, tumors and lymphocytes are infected by different Epstein-Barr virus strains

Despite the fact that most adult humans worldwide are latently infected by the Epstein-Barr virus (EBV), only a very small percentage of them will develop an EBV-associated malignancy. We do not know whether this situation reflects the existence of more sensitive individuals or of particularly tumorigenic EBV strains. We postulated that if highly tumorigenic EBV strains did exist, they would be preferentially found in consistently EBV-associated tumors, such as nasopharyngeal carcinoma (NPC), and differ significantly from the strains present in other, non-pathological sites of the same patients. To test this hypothesis, we compared the BNLF1 gene of the EBV strains present in tumors and in "reservoir lymphocytes" of 6 NPC-bearing patients from Tunisia. Our results show that all of these patients were infected by more than 1 (and up to 7) EBV strains. Moreover, lymphocytes and tumor cells from the same individual were systematically infected by different viral strains. The origin and biological significance of these multistrain infections are discussed.

Analysis of the Epstein-Barr virus (EBV) latent membrane protein 1 (LMP-1) gene and promoter in Hodgkin's disease isolates: selection against EBV variants with mutations in the LMP-1 promoter ATF-1/CREB-1 binding site

AIMS

To study the distribution of Epstein-Barr virus (EBV) variants containing mutations in the latent membrane protein 1 (LMP-1) oncogene and promoter in EBV associated Hodgkin's disease and infectious mononucleosis compared with previous findings in asymptomatic EBV carriers.

METHODS

Sequence analysis of the EBV LMP-1 promoter and gene in isolates from Danish patients with Hodgkin's disease (n = 61) and infectious mononucleosis (n = 10).

RESULTS

Viruses (previously designated group D) that contain two mutations in the activating transcription factor/cAMP response element (ATF/CRE) in the LMP-1 promoter, which are known to decrease promoter activity greatly, were significantly less frequent in Hodgkin's disease than in both infectious mononucleosis (p = 0.0081) and asymptomatic EBV carriers (p = 0.0084). In some cases, the LMP-1 gene contained mutations in a recently identified cytotoxic T cell (CTL) epitope. Most viral isolates contained mutations shown to increase nuclear factor kappa B (NF-kappa B) activation and had one of two newly identified C-terminal activation regions 3 (CTAR-3) deleted. The exon 1 Xho-I restriction site in the LMP-1 gene could be lost through a range of different mutations.

CONCLUSIONS

These findings indicate selection pressure against EBV strains with weak LMP-1 promoter activity in Hodgkin's disease and thus provide further strong circumstantial evidence for the pathogenic role of EBV (and LMP-1) in this disease. Mutation of the CTL epitope suggests immune selection of EBV strains. Many EBV isolates contain functionally important mutations in the LMP-1 gene. Loss of the Xho-I restriction site should not be used as a marker of specific LMP-1 variants.

Coinfection of multiple strains of Epstein-Barr virus in immunocompetent normal individuals: reassessment of the viral carrier state

This study reassesses the occurrence of Epstein-Barr virus (EBV) diversity and coinfection versus dominance of a single viral strain within immunocompetent normal carriers. Polymerase chain reaction analysis of several different polymorphic loci of the EBV genome was performed on collections of peripheral blood mononuclear cells and multiple lymphoid and epithelial tissues of the same individuals. Autopsy specimens from 15 individuals who died of causes unrelated to EBV infection served as normal viral carriers. Unexpectedly, coinfection of multiple distinct strains of EBV of the same type (usually type 1) and less frequently of both types 1 and 2 was found to be very high within individual viral carriers. These data indicate that coinfection with multiple EBV strains is much more prevalent in normal carriers than previously appreciated, which in turn has direct implications on EBV persistence, host–viral interaction and pathogenesis.

Coinfection of multiple strains of Epstein-Barr virus in immunocompetent normal individuals: reassessment of the viral carrier state

This study reassesses the occurrence of Epstein-Barr virus (EBV) diversity and coinfection versus dominance of a single viral strain within immunocompetent normal carriers. Polymerase chain reaction analysis of several different polymorphic loci of the EBV genome was performed on collections of peripheral blood mononuclear cells and multiple lymphoid and epithelial tissues of the same individuals. Autopsy specimens from 15 individuals who died of causes unrelated to EBV infection served as normal viral carriers. Unexpectedly, coinfection of multiple distinct strains of EBV of the same type (usually type 1) and less frequently of both types 1 and 2 was found to be very high within individual viral carriers. These data indicate that coinfection with multiple EBV strains is much more prevalent in normal carriers than previously appreciated, which in turn has direct implications on EBV persistence, host–viral interaction and pathogenesis.

Tissue distribution of Epstein-Barr virus genotypes in hosts coinfected by HIV

BACKGROUND

In healthy people, oral and pharyngeal epithelium preferentially carries Epstein-Barr virus (EBV) belonging to a genotype that possesses three copies of a 29 base-pair repeat in the first intron of the BZLF-1 gene, while peripheral blood mostly carries a genotype that bears two copies. Whether EBV shows differential tropism in HIV-1-coinfected hosts, who are prone to develop oral hairy leukoplakia, has not been studied.

METHODS

Tongue scrapings and CD45+-enriched peripheral blood cells of 20 HIV1-infected patients and 40 healthy controls were examined. EBV-specific DNA was amplified from segments in the first intron of the BZLF-1 gene, in exon C of the LMP-1 gene, and the type A/B-specifying domain of the EBNA-3C gene. Size polymorphisms of these amplicons were assessed by agarose gel electrophoresis, and DNA sequence differences among BZLF-1 gene amplicons by single-strand conformation polymorphism analysis.

RESULTS

The predominant EBV genotype in peripheral blood as well as tongue carried two copies of the BZLF-1 repeat. In controls, although the BZLF-1 genotype with two copies was exclusively detected in the blood, the genotype with three copies predominated in the tongue. The findings could not be correlated with EBV genotyped according size polymorphisms in the EBNA-3C or LMP-1 genes. DNA sequences of a proportion or all of the clones derived from the BZLF-1 amplicons in the tongues of HIV-1-infected patients were identical to those in the blood.

CONCLUSIONS

These findings are consistent with EBV haematogenous superinfection of the tongue of HIV-positive individuals. Such superinfection may precede or lead to the development of oral hairy leukoplakia.

Paediatric Hodgkin's disease in Spain: association with Epstein-Barr virus strains carrying latent membrane protein-1 oncogene deletions and high frequency of dual infections

The present report analyses the distribution of 30-base pair (bp) latent membrane protein-1 (LMP-1) oncogene deletions in 24 cases of Epstein-Barr virus (EBV)-positive paediatric Hodgkin's disease (HD) and 39 normal controls. The 30 bp deletion was identified in 19/24 paediatric HD cases (79.2%), of which seven (29.2%) showed the deleted fragment alone, whereas in the remaining 12 (50%) it was accompanied by the nondeleted fragment. Conversely, the deletion was found in 8/22 (36.4%) EBV-positive healthy children, in two (9.1%) of whom the deleted fragment was alone, and was coinfecting with the nondeleted fragment in the other six (27.3%). The LMP-1 deletion was significantly associated with paediatric HD, both including dual infections (P=0.006) or excluding them (P=0.01). Type 2 EBV was carried by 25% of HD children, whereas all controls harboured type 1 EBV. The 30 bp deletion was present in all the paediatric HD specimens that contained type 2 EBV, suggesting that a deleted type 2 EBV strain may be more tumourigenic than a nondeleted type 2 EBV strain. These findings indicate that EBV strains carrying a 30 bp deletion in the third exon of the LMP-1 oncogene may have a more important role in the pathogenesis of paediatric HD than full-length EBV strains. Dual infection by LMP-1 deleted and nondeleted EBV strains is a frequent event both in healthy children and in the paediatric HD population.

Epstein-Barr virus expression within keratinizing nasopharyngeal carcinoma

Three stages of maturation can be seen in keratinizing nasopharyngeal carcinomas. These stages are similar morphologically to basal cells, intermediate and superficial squamous cells seen in normal squamous epithelium. Taking advantage of such a diverse tumour cell population, 10 keratinizing nasopharyngeal carcinoma (NPC) were examined by in situ hybridization for the presence of latent Epstein-Barr Virus (EBV) using EBV encoded RNAs (EBERs) and by immunohistology for the presence of EBV early antigen-diffuse (EA-D) and the 350/220 kd membrane glycoprotein of the EBV. The basal cell-like tumour cells are mainly infected latently with the virus; viral replication was found in isolated intermediate squamous cells, whilst superficial squamous cells are largely depleted of all the viral markers. We used a control series of nonkeratinizing nasopharyngeal carcinomas composed of undifferentiated and poorly differentiated tumour cells and EBV latency was present in these tumours. Viral replication was detected by RT-PCR, in the undifferentiated tumours but viral replication was not seen by immunohistology. The possible relationship between EBV life cycle in these tumours and tumour cell differentiation is discussed in the light of these findings.

Epstein-Barr viral gene expression in B-lymphocytes

The strategy of the Epstein-Barr virus to persist lifelong in the host depends on establishing a reservoir, which cannot be detected by the immune system but allows reactivation of the virus for shedding and transmission to a new host. Epithelial cells and B-cells play a major role in this viral strategy of EBV, since differentiating epithelial tissues were shown to be permissive for lytic replication in vivo, whereas the B-lymphocytes become predominantly latently infected. However, which cells are the reservoir and which the sites of lytic replication are not quite clear. With the technique of reverse transcription, PCR and immunohistochemistry, we demonstrated that the B-cells of the peripheral blood are a major site of virus production during the primary infection during infectious mononucleosis. These permissive B-cells were also detected after convalescence, however, the absence of any lytic transcripts suggested an efficient immunological control very early in the viral lytic cycle. Serological data on reactivation of EBV correlated with the detection of lytic cycle transcripts in the blood and thus demonstrated that the site of virus production during infectious mononucleosis must be different from that of the persistent state. In those cases, where the infection takes a chronic active course, control of lytic replication is insufficient, either on the level of immune surveillance or of viral gene regulation. We have demonstrated a virus strain with a lytic phenotype in an individual suffering chronic active infection. The impaired capability of this virus to immortalise B-cells correlated with an enhanced expression of the lytic switch gene BZLF-1 and down-regulation of latent regulatory genes in the early phase of infection.

Prevalence of mutations and 30-bp deletion in the C-terminal region of Epstein-Barr virus latent membrane protein-1 oncogene in reactive lymphoid tissue and non-nasopharyngeal EBV-associated carcinomas in Hong Kong Chinese

A specific variant of Epstein-Barr virus (EBV) with a 30-bp deletion in the C-terminal region of the LMP1 gene has been found in some EBV-associated malignancies. To better understand the tumorigenic role of this LMP1 variant, we used PCR and sequencing to examine the LMP1 gene in 38 EBV-associated carcinomas (EBV-CAs) occurring in various organs (6 lung, 10 salivary gland, 5 sino-nasal, 16 gastric and 1 metastatic NPC), 55 reactive lymphoid tissues from tonsils (TON) and 67 EBV-negative tumours in various organs (22 adenolymphoma of salivary gland, 14 gastric and 31 colonic adenocarcinomas), where the virus was demonstrated in lymphocytes. The TON showed prevalence of both deleted and non-deleted variants of LMP1, with dual infection being common. Significantly more of the LMP1 variant was deleted in EBV-CA and in EBV-negative tumours. Sequencing showed that the deleted and non-deleted variants have different sets of amino acid mutation. Mutations in codon 344 and 355 in the non-deleted variant disrupted the 9 nucleotide repeat flanking the deletion and thus may have conferred resistance to the deletion. The prevalence of both variants in the TON, with enrichment for the deleted variant in various organs, argues for the existence of an immune selection pressure in our population. The deleted variant, which may have a higher tumorigenic potential, may contribute to the high incidence of NPC, as well as the occurrence of EBV-CA in organs outside the nasopharynx in our locality.