Epstein-Barr Virus Variants Research Articles

Unusually Strong Positive Cooperativity in Binding of Peptides to Latent Membrane Protein‐1 DNA Fragments of the Epstein–Barr Viral Gene

The DNA-binding preferences of two oligopeptide amides, (His-Pro-Arg-Lys)(3)NH(2) (HR-12) and (Ser-Pro-Arg-Lys)(3)NH(2) (SP-12), have been examined by quantitative DNase I footprinting studies. Two different DNA fragments were investigated: a pair of 5'-(32)P-labeled duplexes from pBR322 with one or other of the complementary strands labeled and a corresponding pair of 5'-(32)P-labeled duplexes representing fragments of the latent membrane protein (LMP-1) gene from a pathogenic Epstein-Barr virus variant derived from nasopharyngeal carcinoma. The major objective was to examine molecular recognition and cooperative features associated with sequence-selective binding of synthetic peptides to the LMP-1 fragments. At various binding sites on the pBR322 fragments, Hill coefficients (n(H)) ranging from 1.9-2.2 were observed; these results indicate modest positive cooperativity between binding sites for both peptides. By contrast, unusually high values of n(H), ranging from 4.0-9.3, were observed at various binding sites on the LMP-1 fragments. Allosteric models can be constructed to interpret the observed cooperative interactions between different DNA recognition sites in the LMP-1 gene upon binding of the peptide ligands. It is noteworthy that these models feature a novel network of cooperativity interconnecting multiple DNA allosteric sites. The evidence of sequence selectivity and strong cooperativity discovered in this work may prove to be a general feature of peptide interactions with some nucleic acids.

Analysis of LMP1 variants of EBV in Southern Thailand: Evidence for strain-associated T-cell tropism and pathogenicity

Background The latent membrane protein 1 (LMP1) of Epstein–Barr virus (EBV) has sequence heterogeneity. Some of the variants are associated with altered tumorigenic activity and show geographically specific localization. In Thailand, the EBV genome is frequently detected in circulating T cells of T-cell diseases. Objective To determine the role of EBV LMP1 variation in the genesis of T-cell diseases, we focused on virus factors and analyzed EBV strains in Thailand. Study design EBV DNA was extracted from 18 healthy individuals and 45 patients with T-cell diseases in Southern Thailand and 30 healthy individuals in Central Thailand. By using PCR-direct sequencing method, nucleotide sequences corresponding to the carboxyl terminus of the LMP1 were determined. Results Four known strains, B95-8 prototype, China 1, China 2 and Mediterranean (Med) and two novel strains, Southeast Asia 1 (SEA 1) and Southeast Asia 2 (SEA 2) were identified. The prevalence of China 2 strain was significantly different ( p = 0.006) between Central and Southern Thailand. Higher prevalence ( p = 0.026) of 30-bp deletion type in the Southern Thais was observed. The LMP1 Med strain was associated with the worse prognosis ( p = 0.029). Among T-cell diseases patients, CD3 +-cell oriented infection was recognized in SEA1 strain ( p = 0.025). Conclusion The distribution of EBV strains may be associated with geographic/ethnic and clinical background in the Thai population. Certain EBV strains defined by their LMP1 sequence may influence cell tropism, disease association, or disease severity.

Association of a distinctive strain of Epstein‐Barr virus with gastric cancer

Epstein-Barr virus (EBV) has been linked to gastric carcinoma (GC) with worldwide geographical variations attributable to types and variants of EBV. Here, we compare EBV strains between EBVaGC and healthy donors in Latin America, a high frequency area for EBVaGC. Tumor samples from 73 EBVaGC cases and throat washings from 329 healthy adults were examined for types 1 and 2 EBV and polymorphism at BamHI-F and BamHI-W1/I1 boundary regions and XhoI restriction site in LMP1 gene. Type 1 and prototype F of BamHI- F polymorphism accounted 59 (81%) and 69 (95%) of EBVaGC cases and 257 (78%) and 267 (81%) of healthy donors, respectively. Types I and "i" of BamHI W1/I1 polymorphism accounted 2 (3%) and 62 (85%) of EBVaGC and 85 (26%) and 170 (52%) of healthy donors, respectively (p<0.001). XhoI+ and - polymorphism accounted 60 (82%) and 4 (5%) of EBVaGC and 142 (43%) and 92 (28%) of healthy donors, respectively (p<0.001). Cosegregation analysis demonstrated that most of the 62 type "i" EBVaGC cases harbor XhoI+ strain (81%). However, among 143 type "i" healthy adults, both XhoI polymorphism were present in relatively similar frequencies (XhoI+ 58% and XhoI- 42%) (OR 9.0; 95% CI 1.2-69). Our findings are against to the proposed hypothesis that EBV strains are geographically but not disease-restricted. We conclude that most of the EBVaGC cases harbor a distinctive EBV strain (type "i"/XhoI +), but in healthy donors, this strain was as common as other strains. This finding is contrary to the proposed hypothesis that EBV strains are geographically but not disease-restricted and identified a healthy population group that share the same strain that predominate in EBVaGC cases.

Nucleotide Sequences and Functions of the Epstein-Barr Virus Latent Membrane Protein 1 Genes Isolated from Salivary Gland Lymphoepithelial Carcinomas

Epstein-Barr virus (EBV) infection is associated with salivary gland lymphoepithelial carcinoma (SLEC) and nasopharyngeal carcinoma (NPC). EBV is a ubiquitous herpes virus world wide, but EBV-associated SLEC and NPC are prevalent in restricted regions such as south areas of China, Southeastern Asia and Greenland (Eskimos). To examine whether particular EBV variants play roles in the development of SLEC and NPC, we isolated the complete EBV LMP1 genes from 12 paraffin-embedded biopsy samples of SLECs isolated from China, Taiwan and Russia, and compared these LMP1 genes with those of NPC (CAO) and the prototype B95-8 EBV. Nucleotide sequence analysis showed that SLECs LMP1 is more similar to that of CAO than that of prototype B95-8. The analysis also identified several conserved (67-100%) variations in SLEC-LMP1 and CAO-LMP1 distinct from B95-8-LMP1. These included 10-amino acid deletion, 5-amino acid deletion and 12-single amino acid variations. A SLEC-LMP1 gene with the aforementioned conserved variations inhibited the growth of an embryonic kidney cell line (293T), highly activated the NF-kappaB pathway, and these activities were equivalent to those of B95-8 and CAO. These findings suggest that the biological functions of SLEC-LMP 1 are similar to those of B95-8-LMP1 and CAO-LMP1, and that these amino acid variations including the well-known 10-aa deletion did not affect these two prominent activities. While the present results could not uncover functional differences between SLEC-LMP1 and B95-8-LMP1, the nucleotide sequences and the molecular clone of LMP1 directly isolated from SLEC patients will be a useful tool to identify the high-pathogenic EBV strain(s), associated with SLEC and NPC.

Latent Membrane Protein 1 Deletion Mutants Accumulate in Reed-Sternberg Cells of Human Immunodeficiency Virus-Related Hodgkin's Lymphoma

The origin and biological significance of deletions at the 3' end of the Epstein-Barr virus (EBV)-encoded latent membrane protein 1 (LMP-1) gene are still controversial. We herein demonstrate that LMP-1 deletion mutants are highly associated with human immunodeficiency virus-related Hodgkin's lymphoma (HIV-HL) of Italian patients (29 of 31 cases; 93.5%), a phenomenon that is not due to a peculiar distribution of EBV strains in this area. In fact, although HIV-HL patients are infected by multiple EBV variants, we demonstrate that LMP-1 deletion mutants preferentially accumulate within neoplastic tissues. Subcloning and sequencing of the 3' LMP-1 ends of two HIV-HL genes in which both variants were present showed the presence of molecular signatures suggestive of a likely derivation of the LMP-1 deletion mutant from a nondeletion ancestor. This phenomenon likely occurs within tumor cells in vivo, as shown by the detection of both LMP-1 variants in single microdissected Reed-Sternberg cells, and may at least in part explain the high prevalence of LMP-1 deletions associated with HIV-HL.

Nasopharyngeal carcinomas and Epstein-Barr virus: from epidemiology and detection to therapy

Nasopharyngeal carcinomas (NPC) challenge clinicians and biologists in various fields including epidemiology, genetics, virology and immunology. These tumours have a striking geographical distribution. They are constantly associated with the Epstein-Barr virus (EBV) and contain a massive lymphocytic infiltrate. Their study has major implications especially at this moment while a pathological role of EBV is suspected in several other human epithelial malignancies (for example gastric, mammary and thyroid carcinomas). The North-South Workshop on Nasopharyngeal Carcinoma was held at the Institut Gustave-Roussy in early December 2003. Its main goal was to support the exchanges between clinical research on NPC in the South and basic research in the North. With regard to epidemiology and genetics, the main information was the possible existence of several susceptibility genes (including two of them on the 4p and 5p chromosomes). In virology, participants have emphasized the selection of peculiar EBV variants within the malignant cells and the expression of novel oncogenic viral proteins : LMP2 and BARF1. Cellular gene alterations also contribute to NPC development, especially inactivation of tumor suppressor genes located on the 3p chromosome. Therapeutic research was not forgotten. Hope of higher rate of cure relies on improved ballistic processes in radiotherapy (IMRT) and on the development of targeted therapeutics : induction of the lytic/productive viral cycle, gene therapy with conditional replicative adenoviruses, antitumor vaccination directed against the viral protein LMP2.

Polymorphism analysis of Epstein-Barr virus isolates of lymphoblastoid cell lines from patients with mycosis fungoides.

In order to determine whether there is an association between the presence of Epstein-Barr virus (EBV) and mycosis fungoides (MF) disease progression, PCR was performed to detect the EBV status of 20 MF patients; six EBV-positive patients were found. EBV variants may differ in their biological properties, such as their ability to transform cells; therefore, the ability of these variants to immortalize B cells in vitro was analysed. Six continuously growing cell lines were obtained from prolonged cultures of unstimulated peripheral blood mononuclear cells that were taken from the six EBV-positive patients with MF. In order to characterize the EBV strains, EBNA-2 and LMP-1/LMP-2 gene polymorphisms in the six cell lines were also analysed. All patients were followed up for 10 years and it was noticed that EBV-positive patients had a poor prognosis with rapid disease progression and high mortality rates, compared to EBV-negative patients. EBV may therefore constitute a co-factor that accelerates the progression of disease.

Epstein-Barr virus-Associated Lymphomas in Malaysia: High Frequency of a 30-bp Deletion in the Viral Latent Membrane Protein-1 (LMP-1) Oncogene

A variant of Epstein-Barr virus (EBV) with a 30-base pair (bp) deletion in the latent membrane protein-1 (LMP-1) gene has been reported in many EBV-associated malignancies at different frequencies in different geographical locations. This study aims to determine the frequency of this variant in Asian EBV-associated lymphomas. We analyzed a total of 81 cases of known EBV-associated lymphomas [20 classical Hodgkin's, 19 Burkitt's, 33 T-and natural killer (NK)/T-cell, and 9 diffuse large B-cell lymphomas (DLBCL)] and 19 reactive lymphoid tissues from the archives. The presence of the 30-bp deletion at the 3' end of the LMP-1 gene was demonstrated by hybridization of polymerase chain reaction (PCR) products after amplification with a pair of primers flanking the deletion region. The DNA from 96.3% (78/81) of the lymphomas and 78.9% (15/19) of the reactive lymphoid tissues were amplified by PCR. The lymphomas showed infection by the deleted variant in 91.0% (71/78) of the cases, including 33.3% (26/78) cases with dual variant infection. The deleted variant was observed in 100% (19/19) of the Burkitt's lymphoma, 89.5% (17/19) of the classical Hodgkin's lymphomas, 90.6% (29/32) of the T-and NK/T-cell lymphomas and 75.0% (6/8) of DLBCL, whereas it was detected in 60.0% (9/15) of the reactive lymphoid tissues. The difference in the frequency of deleted LMP-1 variants observed between the lymphomas and the reactive lymphoid tissues was statistically significant (p=0.006). A significant difference was also observed between childhood and male lymphoma patients and reactive lymphoid controls of comparable age or gender group (p<0.001 and p=0.012 respectively). In conclusion, a high frequency of the 30-bp deletion in the LMP-1 gene was observed in the Malaysian population. The significantly higher percentage of deleted variant observed in EBV-associated lymphomas suggests the possibility of a selection mechanism during malignant transformation.

Characterization of T-cell Non-Hodgkin's Lymphoma and its Association with Epstein-Barr Virus in Pakistani Patients

This study analyzes the prevalence of T-cell non-Hodgkin's lymphoma (T-NHL) in a major referral center of Pakistan and its association with Epstein-Barr virus (EBV). Ninety-two cases of T-NHL were characterized on the basis of morphology, immunohistochemistry and genetic features. The prevalence of T-NHL was 22.2% of the total NHLs diagnosed during the eight years period (1992-1999). Polymerase chain reaction (PCR) technique was used to assess T-cell clonality in paraffin-embedded tissues of known T-NHL. Amplifiable DNA was isolated from all the cases, which were further studied for T-cell receptor (TcR)- β, γ, δ, and IgH chain gene rearrangements. Out of 92 cases 51 cases showed clonal product and 33 demonstrated polyclonal smear for β, γ, or δ chain genes, respectively, whereas 8 cases exhibited IgH chain gene rearrangement for FR2 region. This study demonstrated frequent presence of EBV in T-NHL (55.4%) by PCR, which were further tested for the localization of the virus by in situ hybridization (ISH). The extent of polymorphism in EBV genome was studied by single stranded conformation polymorphism (SSCP) technique for Bam HI E, K, N and Z regions. Hyper-variability in Bam HI K, and N regions was noticeably higher compared to E or Z regions. In conclusion, our study demonstrated that the prevalence of T-NHL in Pakistan is slightly higher to that reported for Western communities. In addition, the frequency of EBV genome in T-NHL is intermediate as compared to other studies. No association was established between EBV variants differentiated on the basis of sequence heterogeneity in Bam HI K, N, E and Z regions with the manifestation of different subsets of T-NHL.

Analyses of Epstein-Barr virus latent membrane protein-1 in Malaysian nasopharyngeal carcinoma: high prevalence of 30-bp deletion, Xho1 polymorphism and evidence of dual infections.

Nasopharyngeal carcinoma, a malignancy associated closely with Epstein-Barr virus (EBV), is prevalent among Chinese of Southern China origin. Epidemiological studies indicate a high prevalence of EBV in Asia with viral isolates having typical characteristics of the putative viral oncogene, latent membrane protein 1 (LMP-1), such as the loss of the Xho1 restriction site in Exon 1 and the 30-bp deletion in Exon 3. The EBV LMP-1 gene from throat washings of 120 nasopharyngeal carcinoma patients and 14 healthy individuals were analyzed. Similar analyses were also carried out on 30 and 12 postnasal space biopsies from nasopharyngeal carcinoma patients and healthy individuals, respectively. The 30-bp deletion was detected in 20% of nasopharyngeal carcinoma throat washes and in 100% of nasopharyngeal carcinoma postnasal space biopsies. Interestingly, 16% of the nasopharyngeal carcinoma biopsies possessed both the deleted and the undeleted variants, suggestive of dual infections. The notion of dual infections in nasopharyngeal carcinoma was further supported by the coexistence of both "F" and "f" (BamH1F region) EBV variants in 11% of the nasopharyngeal carcinoma biopsies. All of the throat washes and biopsies from the healthy controls showed the undeleted variant. The loss of the Xho1 restriction site was found with higher frequency both in throat washes and biopsies from patients with nasopharyngeal carcinoma. The discrepancy in the frequency of the 30-bp deletion between throat washes (20%) and postnasal space biopsies (100%) was an indication that this deletion is specific for viral isolates from primary tumour sites.

Biophysical Analysis of Natural Variants of the Multimerization Region of Epstein-Barr Virus Lytic-Switch Protein BZLF1

BZLF1 plays a key role in the induction of Epstein-Barr virus (EBV) replication. On the basis of limited sequence homology and mutagenesis experiments, BZLF1 has been described as a member of the bZip family of transcription factors, but this prospect has not been rigorously tested to date. Here, we present biophysical analysis of the multimerization domain of BZLF1, from three natural variants of EBV, and demonstrate for the first time that the region between amino acids 196 and 227 is sufficient to direct folding as a coiled-coil dimer in vitro.

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.

Epstein-Barr virus detection in ductal carcinoma of the breast.

Epstein-Barr virus detection in ductal carcinoma of the breast.

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...

Molecular profile of Epstein-Barr virus infection in HHV-8-positive primary effusion lymphoma.

Primary effusion lymphoma (PEL) selectively involves the serous body cavities, occurs predominantly in immunodeficient patients and is infected consistently by human herpesvirus type-8. PEL is also frequently infected by Epstein-Barr virus (EBV). The precise pathogenetic role of EBV coinfection in PEL is not fully understood. The lymphoma fails to express the EBV transforming proteins EBNA-2 and LMP-1, whereas it expresses EBNA-1 (latency I phenotype). Some studies have hypothesized that other EBV-positive lymphomas expressing the latency I phenotype may associate with specific molecular variants of EBNA-1, although this issue has not been addressed in PEL. On this basis, this study is aimed at a detailed molecular characterization of EBV in PEL. Fifteen EBV positive PEL (12 AIDS-related, one post-transplant, two arising in immunocompetent hosts) were subjected to molecular characterization of the viral genes EBNA-1 and LMP-1, as well as definition of EBV type-1/type-2. The EBNA-1 gene displayed a high degree of heterogeneity in different cases of PEL, with seven distinct recognizable variants and subvariants. A wild-type LMP-1 gene was detected in 10/15 cases, whereas in 5/15 cases the LMP-1 gene harbored a deletion spanning codons 346-355. EBV type-1 occurred in 11/15 PEL whereas EBV type-2 occurred in 4/15 cases. Despite a high degree of genetic variability of the virus in different PEL cases, each single PEL harbored only one EBV variant, consistent with monoclonality of infection and suggesting that infection preceded clonal expansion. Overall, our results indicate that: (1) individual PEL cases consistently harbor a single EBV strain; (2) EBNA-1 displays a high degree of heterogeneity in different PEL cases; (3) no specific EBV genotype preferentially associates with PEL.

Characterization of Intertypic Recombinants of the Epstein–Barr Virus from the Body-Cavity-Based Lymphomas Cell Lines BC-1 and BC-2

Epstein–Barr Virus (EBV) can infect and transform human B-lymphocytes and has been associated with numerous human malignancies. Two distinct types of EBV have been described, EBV-1 and EBV-2. Whereas type 1 is known to be most widespread throughout the healthy adult population, type 2 EBV has been shown to be significantly present in certain T-cell immunocompromised patients. Some evidence also suggests that such immune impairment promotes coinfection with multiple strains of EBV and fosters the development of intertypic recombinant viruses. In this work, we have analyzed two established body-cavity-based lymphoma or primary effusion lymphoma cell lines, BC-1 and BC-2, for the presence of intertypic EBV recombinants. Using PCR primers to amplify across several markers in the genome, we have typed the BC-1 and BC-2 EBV at these loci. Immunoblot analysis of the EBNA1 protein expressed by these cell lines also suggests a change in EBV typing at this locus in these genomes. Additionally, we have analyzed the expression patterns of the latent EBNA proteins from these viruses and performed Southern blot analysis of the BamHI- and EcoRI-digested genomes to detect variations occurring from type I and II genomes. On the basis of these data, we suggest that the genomes of EBV in BC-1 and BC-2 are intertypic recombinants of type 1 and type 2 EBV genomes. This work corroborates other reports that intertypic EBV recombinants occur in the immunocompromised population. It is likely that intertypic recombination is a mechanism by which novel variants of EBV emerge having selective advantages over a strictly type 1 or type 2 strain.

Different distribution of H1-H2 Epstein-Barr virus variant in oropharyngeal virus and in biopsies of Hodgkin's disease and in nasopharyngeal carcinoma from Algeria. Int. J. Cancer77, 205-210 (1998)

Different distribution of H1-H2 Epstein-Barr virus variant in oropharyngeal virus and in biopsies of Hodgkin's disease and in nasopharyngeal carcinoma from Algeria. Int. J. Cancer77, 205-210 (1998)

Diversity of naturally occurring Epstein-Barr virus revealed by nucleotide sequence polymorphism in hypervariable domains in the BamHI K and N subgenomic regions.

The extent of nucleotide sequence microheterogeneity varies among subgenomic regions of Epstein-Barr virus (EBV). We examined, in EBV-carrying lymphoid cell lines, the extent of polymorphism in EBV DNA fragments amplified from the BamHI E, K, N and Z regions, and then investigated the diversity of the more hypervariable regions in tissues and body fluids. In cell lines, sequence dissimilarities in a genotype-specifying fragment of the EBNA-3C gene varied from < 1-4% within each genotype; dissimilarities in the first intron of the BZLF- 1 gene were < 2% within each genotype. By contrast, dissimilarities in a C-terminal unique domain of the EBNA-1 gene, and in a fragment that encompasses and is upstream of the LMP-1 start codon, varied between 2 and 7% and were not genotype-specific. The sequence diversity in BamHI K and N regions was then examined in tissues and body fluids by single-strand conformation polymorphism (SSCP) analysis and cycle sequencing. Extensive inter-host diversity was observed, whether the host was co-infected by human immunodeficiency virus (HIV) or not. In the oral cavity of HIV-infected patients, inter-compartmental EBV diversity could be demonstrated, even between sites that were anatomically proximate. Studies of BamHI K clones derived from EBV in oral lesions revealed infection by multiple variants. Identification of hypermutable loci within the EBV genome such as those located in the BamHI K and N regions should permit fine discrimination of individual EBV variants.

Different distribution of H1-H2 Epstein-Barr virus variant in oropharyngeal virus and in biopsies of Hodgkin's disease and in nasopharyngeal carcinoma from Algeria.

In a previous study of Epstein-Barr virus (EBV) strains in North African nasopharyngeal carcinoma (N PC) biopsies, we have found that the viral strain present was of A/F/W'-I'/Xhol kept/H1-H2 type, while the strain associated with Chinese NPC was the A/"f"/W'I'/Xhol lost/H type. Using the restriction fragment length polymorphism (RFLP) and PCR-RFLP methods, the present study analyzed the H1-H2 variant in different clinical samples from Algeria, including the saliva of healthy EBV-positive individuals and patients with NPC or Hodgkin's disease (HD), as well as HD biopsies and lymphoblastoid cell lines (LCLs) established from the oropharyngeal virus-infected cells. Our results demonstrate that, in contrast to the H1-H2 variant found in NPC biopsies, the H genotype was dominant in HD biopsies. Moreover, H genotype was also dominant in the oropharynx of healthy EBV-positive individuals, of patients with NPC and with HD. Our results clearly indicate that in North Africa the EBV strain present of NPC biopsies is different from that shed in the oropharynx. This may suggest a specific distribution of the H1-H2 variant in the NPC epithelial tumor, whereas the H genotype is dominant in HD biopsies and in the oropharynx. The specific association of both viral strains with these 2 distinct diseases in North Africa may reflect a difference in tumorigenicity.

The 30-base-pair deletion in Chinese variants of the Epstein-Barr virus LMP1 gene is not the major effector of functional differences between variant LMP1 genes in human lymphocytes.

One group of sequence variants of Epstein-Barr virus is characterized by a 10-amino-acid deletion within the CTAR-2 functional domain of the latent membrane protein, LMP1. A role for this deletion in enhancing the tumorigenicity of the viral oncogene in rodent fibroblasts was recently demonstrated. We examined the effect of this deletion upon LMP1 function in four human lymphoid cell lines by using three natural variants of LMP1: the prototype B95.8 gene and the CAO and AG876 genes, both of which have codons 343 to 352 of the B95.8-LMP1 deleted. These experiments revealed that LMP1-mediated upregulation of CD40 and CD54 was markedly impaired (by 60 to 90%) with CAO-LMP1 compared with B95.8-LMP1. In contrast, the function of AG876-LMP1 was indistinguishable from that of B95.8-LMP1 in two lines and was only slightly impaired in the other two lines. Activation of NF-kappaB by CAO-LMP1 was not impaired in any of the lines; rather, activation of an NF-kappaB reporter by CAO-LMP1 was consistently about twofold greater than the activation with B95.8- or AG876-LMP1. Therefore, while the CAO-LMP1 is functionally distinct from the prototype B95.8-LMP1 in human lymphocytes, the 10-amino-acid deletion appears not to be directly responsible. This conclusion was confirmed by using a B95.8-LMP1 mutant with codons 343 to 352 deleted and chimerae of CAO- and B95.8-LMP1 in which the CTAR-2 domains of these genes were exchanged. Sequences outside the CTAR-2 domain were implicated in the distinct functional characteristics of CAO-LMP1 in human lymphoid cells.