Research Advances in Infectious Mononucleosis Caused by Epstein-Barr Virus

Infectious mononucleosis (IM), primarily caused by the Epstein-Barr virus (EBV), manifests as the classic triad of fever, pharyngitis, and cervical lymphadenopathy. Severe cases may involve organ damage, most commonly affecting the liver. Diagnosis relies on a combination of clinical presentation and laboratory parameters, with commonly used indicators including EBV-specific antibodies, EBV-DNA load, and the ratio of atypical lymphocytes. Treatment primarily involves symptomatic supportive care, with a cautious approach to the routine use of antiviral medications. In recent years, significant research in traditional Chinese medicine has been conducted in China, showing promising advancements. This article provides a comprehensive review of EBV-induced infectious mononucleosis, offering insights for clinical diagnosis and treatment.

CHARACTERIZATION OF A HUMAN HERPES VIRUS－6（HHV－6） AND EPSTEIN－BARR VIRUS（EBV） ASSOCIATED LEUKEMIC CELL LINE，J6－1

This report characterizes the J6-1 cell line derived from a Chinese acute myelomonocytic leukemia patient and previously reported to be associated with EBV. These studies showed that J6-1 cells were also infected with HHV-6 as demonstrate at the DNA level by PCR and Southern blot hybridization and by expression of HHV-6 early membrane antigen on the J6-1 cell surface. Further characterization showed J6-1 was co-infected with EBV type 2. Generally, cells infected with EBV type 2 do not grow well in vitro. However, J6-1 , although difficult to maintain in vitro, has been grown for 15 years. Possibly, co-infection with HHV6 confers this property. In this regard, J6-1 cells exhibited density dependent growth which could be inhibited with an anti-HHV-6-MA monoclonal antibody(MAb). In contrast, anti-HHV-6-VCA MAb stimulated the J6-1 cell proliferation. Electron microscopic analysis showed that, morphologically, there were two types of J6-1 cell, one with lymphoblastoid features and one with a monocytoid appearance. Accordingly, the flow profile of the J6-1 cell line showed heterogeneity. with two populations comprised of CD15-, CD19+ cells with low light scatter(small cells) and a population with greater light scatter(larger cells) which was CD15+ , CD19+. The population was negative for progenitor cell markers(CD33, 34 ), and T cell markers. Southern analysis showed no T cell receptor rearrangement, however there was a clonal JH and kappa light chain expressing population. Glycocytochemical analysis showed several endogenous lectin receptors on the J6-1 cell surface: BSA-Xylose, BSA-Rhamnose, BSAGal. BSA-Lac. This cell line shares many characteristics with other monocytic/ lymphoblastoid cell lines isolated elsewhere and provides circumstantial evidence linking Herpes viruses, as least as co- factors,to leukemia cell growth.

STUDIES ON THE RELATIONSHIP BETWEEN EPSTEIN BARR VIRUS (EBV) AND PATHOGENESIS OF MULTIPLE MYELOMA

In order to explore the relationship between Epstein Barr virus (EBV) and pathogenesis of multiple myeloma (MM), the presence of EBV DNA in mononuclear cells of bone marrow (BMMC) and peripheral blood (PBMC) taken from 23 multiple myeloma patients who were neither posttransplanted nor HIV positive were examined by polymerase chain reaction (PCR). Meanwhile the presence of EBV EBERs in bioptic bone marrow's specimens of 4 MM patients were examined by in situ hybridization (ISH). Acute leukemia, aplastic anemia and malnourished anemia patients were taken as control. It showed EBV DNA detective rate in BMMC (69 6%) and in PBMC (39 1%) of MM patients were higher significantly than control groups (P<0 05). The positive signals of EBERs were located in BMMC and the EBV positive samples detected by ISH were consistent with those by PCR. The results indicate that EBV is closely correlated to pathogenesis of MM.

SERO-EPIDEMIOLOGICAL STUDIES OF EPSTEIN-BARR VIRUS(EBV) INFECTION BY TESTING ANTIBODIES AGAINST EBV SPECIFIC DNASE(EDAb) AS A METHOD FOR EARLY DETECTION OF NASOPHARYNGEAL CARCINOMA(NPC)

In 1987, a mass survey of EDAb was carried out in Sihui county of Gunagdong Province (the highest incidence area of NPC in China) and the city of Guangzhou using the methods previously established by our lab. In order to study the correlation between EDAb level and NPC, the titre of DEAb and their distribution in sera from 430 patients with NPC and 5030 normal persons were detected. It was found that the AER (level of EDAb was represented by the anti enzyme rate) of NPC patients gave a negative skew distribution and the Md=65.3% while the natural population (30 59 years old) gave a serious positive skew distribution and the Md is 7.9%. According to the pattern of EDAb distribution curve of 430 NPC patients and 2060 natural population. AER≥30% was defined as a cut off point between EDAb positive and negative. Using this value we got a rate of 90.7% (390/430) positive diagnosis in NPC patients, while in natural population the positive rate was 3.3% (68/2060), and in the IgA/VCA positive (1:5) normal person the positive rate was 6.0% (41/681). As to the other tumors including head and neck tumors the positive rate was 3.4% (7/204), similar to the natural population. After a period of 62 months of follow up surveillance, 15 of 224 EDAb positive normal persons found in the mass survey were diagnosed as NPC by histopathological examination. While in 4806 EDAb negative normal person only one case NPC patient was found in this period. 60% of these patients were diag nosed in their early stage of NPC. From these patients it was found that EDAb could appear in the sera of the patients as early as 62 months before NPC was definitely diagnosed. 2 of these patients were shown IgA/VCA negative and EDAb positive in mass survey. This suggested that in some of the precancerous patients EDAb could appear earlier than IgA/VCA. The signifi cance of the sera EDAb positivity of normal person was discussed.

A Case Report of Pediatric Epstein Barr Virus (EBV) Related Cholestasis from Al-Adan Hospital, Kuwait

Infectious mononucleosis is an acute illness due to Epstein Barr virus infection, which occurs commonly in young adults. Liver involvement in acute EBV infection occurs in up to 95% of patients between the 6th and 15th day of illness and is usually mild [1]. Here we report on a 7-year-old girl treated by Gastroenterology, Hepatology, and Nutrition Unit of Al-Adan Hospital pediatric Department, presented with prolonged fever, lymphadenopathy, generalized edema, hyperbilurubi- nemia and elevated liver enzymes secondary to EBV infection. This case represents a rare presentation of common viral infection in pediatric population.

Chronic Physical Stress Does Not Interact with Epstein-Barr Virus (EBV)-Encoded Dutpase to Alter the Sickness Response

Most adult humans have been infected with Epstein-Barr virus (EBV), which is thought to contribute to the development of chronic fatigue syndrome. Stress is known to influence the immune system and can exacerbate the sickness response. Although a role for psychological stress in the sickness response, particularly in combination with EBV-encoded deoxyuridine triphosphate nucleotidohydrolase (dUTPase) has been established, and the role of physical stressors in these interactions remains unspecified. In this study, we seek to determine the interaction of chronic physical (swim) stress and EBV-encoded dUTPase injection. We hypothesize that a chronic physical stressor will exacerbate the sickness response following EBV-encoded dUTPase injection. To test this hypothesis mice receive daily injections of EBV-encoded dUTPase or vehicle and are subjected to 15 min of swim stress each day for 14 days or left unmanipulated. On the final evening of injections mice undergo behavioral testing. EBV-encoded dUTPase injection alone produces some sickness behaviors. The physical swimming stress does not alter the sickness response.

Restraint Induces Sickness Responses Independent of Injection with Epstein-Barr Virus (EBV)-Encoded dUTPase

Most adult humans have been infected by Epstein-Barr virus (EBV), a putative cause of chronic fatigue syndrome, and carry latent EBV. The EBV-encoded dUTPase can induce sickness responses in mice and chronic stress exacerbates this response. Because individuals often adapt to chronic stress, we tested the hypothesis that acute restraint stress would potentiate these sickness responses elicited by EBV-encoded dUTPase. Male CD-1 mice were injected daily for one or three days with either saline or EBV-encoded dUTPase. Additionally, mice from each condition were either restrained for three hours daily or left undisturbed during the light phase when mice are inactive. Restraint decreased weight gain during the one- and three-day experiments. Restraint in saline injected mice increased anxiety-like behavior in the open field during the three-day experiment. There were no behavioral differences during the one-day experiment. Restraint stress had no effect when experienced acutely on one day, but did produce a sickness response after three days of exposure regardless of saline or dUTPase injection. In contrast to the effects of chronic stress and EBV-encoded dUTPase on the sickness response, acute stress did not affect sickness responses in association with EBV-encoded dUTPase. Thus, dUTPase does not appear to provoke the same sickness responses after acute stress as compared to chronic stress.

Prognostic value of plasma Epstein-Barr virus DNA level during posttreatment follow-up in the patients with nasopharyngeal carcinoma having undergone intensity-modulated radiotherapy

Background: The value of Epstein-Barr virus(EBV) DNA assay during posttreatment follow-up of the patients with nasopharyngeal carcinoma(NPC) presenting with different pretreatment plasma EBV DNA levels remains unclear. In the present study, we aimed to evaluate the prognostic value of plasma EBV DNA assay during posttreatment followup in the patients with NPC who have undergone intensity-modulated radiotherapy.Methods: The medical records of 385 NPC patients treated with intensity-modulated radiotherapy between November 2009 and February 2012 were reviewed. All patients underwent plasma EBV DNA assays before treatment, within3 months after treatment, and then every 3-12 months during posttreatment follow-up period. The recurrence rates for patients with different pretreatment and posttreatment follow-up plasma EBV DNA levels were analyzed.Results: Of the 385 patients, 267(69.4%) had detectable pretreatment plasma EBV DNA(> 0 copy/mL) and 93(24.2%) had detectable posttreatment EBV DNA during a median follow-up of 52.8 months(range 9.3-73.8 months).Detectable EBV DNA during posttreatment follow-up was found in 14.4%(17/118) and 28.5%(76/267) of patients with undetectable and detectable pretreatment EBV DNA, respectively, and was significantly associated with tumor recurrence in both patient groups. EBV DNA was detectable in 12.8%(40/313) of patients who remained disease-free,56.4%(22/39) of patients with locoregional recurrence alone, and 93.9%(31/33) of patients with distant metastasis as the first recurrence event(P < 0.001); 6.5%(19/292) of patients with undetectable EBV DNA and 57.0%(53/93) of patient with detectable EBV DNA during posttreatment follow-up experienced tumor recurrence. Compared with other cut-off values, the cut-off value of 0 copy/mL for EBV DNA during posttreatment follow-up had the highest area under the ROC curve(AUC) value(0.804,95% confidence interval 0.741-0.868) for predicting tumor recurrence(sensitivity, specificity, and accuracy: 73.6%, 87.2%, and 84.7%, respectively).Conclusion: Plasma EBV DNA level during posttreatment follow-up is a good marker for predicting distant metastasis but not locoregional recurrence in the patients with NPC irrespective of the pretreatment EBV DNA levels.

Prognostic values of the integrated model incorporating the volume of metastatic regional cervical lymph node and pretreatment serum Epstein-Barr virus DNA copy number in predicting distant metastasis in patients with N1 nasopharyngeal carcinoma

Background: According to the 7 th edition of the American Joint Committee on Cancer(AJCC) staging system, over50% of patients with nasopharyngeal carcinoma(NPC) have N1 disease at initial diagnosis. However, patients with N1 NPC are relatively under-researched, and the metastasis risk of this group is not well-stratified. This study aimed to evaluate the prognostic values of gross tumor volume of metastatic regional lymph node(GTVnd) and pretreatment serum copy number of Epstein-Barr virus(EBV) DNA in predicting distant metastasis of patients with N1 NPC, and to develop an integrated prognostic model that incorporates GTVnd and EBV DNA copy number for this group of patients.Methods: The medical records of 787 newly diagnosed patients with nonmetastatic, histologically proven N1 NPC who were treated at Sun Yat-sen University Cancer Center between November 2009 and February 2012 were analyzed. Computed tomography-derived GTVnd was measured using the summation-of-area technique. Blood samples were collected before treatment to quantify plasma EBV DNA. The receiver operating characteristic(ROC) curve analysis was used to evaluate the cut-off point for GTVnd, and the area under the ROC curve was used to assess the predicted validity of GTVnd. The survival rates were assessed by Kaplan-Meier analysis, and the survival curves were compared using a log-rank test. Multivariate analysis was conducted using the Cox proportional hazard regression model.Results: The 5-year distant metastasis-free survival(DMFS) rates for patients with GTVnd > 18.9 vs.≤ 18.9 mL were82.2% vs. 93.2%(P < 0.001), and for patients with EBV DNA copy number > 4000 vs. < 4000 copies/mL were 83.5% vs.93.9%(P < 0.001). After adjusting for GTVnd, EBV DNA copy number, and T category in the Cox regression model, both GTVnd > 18.9 mL and EBV DNA copy number > 4000 copies/mL were significantly associated with poor prognosis(both P < 0.05). According to combination of GTVnd and EBV DNA copy number, all patients were divided into low-,moderate-, and high-risk groups, with the 5-year DMFS rates of 96.1,87.4, and 73.8%, respectively(P < 0.001). Multivariate analysis confirmed the prognostic value of this model for distant metastatic risk stratification(hazard ratio [HR],4.17; 95% confidence interval [CI] 2.34-7.59; P < 0.001).Conclusions: GTVnd and serum EBV DNA copy number are independent prognostic factors for predicting distant metastasis in NPC patients with N1 disease. The prognostic model incorporating GTVnd and EBV DNA copy number may improve metastatic risk stratification for this group of patients.

Plasma Epstein-Barr virus DNA as a biomarker for nasopharyngeal carcinoma

Nasopharyngeal carcinoma(NPC)is common in southern China and Southeast Asia.Epstein-Barr virus(EBV)infection is an important etiology for NPC,and EBV genome can be detected in almost all tumor tissues of NPC in this region.Plasma EBV DNA,when quantitatively analyzed using real-time polymerase chain reaction(PCR),has been developed as a biomarker for NPC.In this review,the different clinical applications of plasma EBV DNA in the management of NPC,including screening,monitoring,and prognostication,are discussed.In addition,the biological issues of circulating EBV DNA,including the molecular nature and clearance kinetics,are also explored.

Epstein Barr virus-positive mucocutaneous ulcer of thecolon associated Hodgkin lymphoma in Crohn＇s disease

Epstein Barr virus （EBV） positive mucocutaneous ulcers（EBVMCU） form part of a spectrum of EBV-associatedlymphoproliferative disease. They have been reportedin the setting of immunosenescence and iatrogenicimmunosuppression, affecting the oropharyngeal mucosa,skin and gastrointestinal tract （GIT）. Case reports andseries to date suggest a benign natural history respondingto conservative management, particularly in the GIT. Wereport an unusual case of EBVMCU in the colon, arisingin the setting of immunosuppression in the treatment ofCrohn＇s disease, with progression to Hodgkin lymphoma18 mo after cessation of infliximab. The patient presentedwith multiple areas of segmental colonic ulceration,histologically showing a polymorphous infiltrate withEBV positive Reed-Sternberg-like cells. A diagnosisof EBVMCU was made. The ulcers failed to regressupon cessation of infliximab and methotrexate for 18mo. Following commencement of prednisolone for herCrohn＇s disease, the patient developed widespreadHodgkin lymphoma which ultimately presented as alife-threatening lower GIT bleed requiring emergencycolectomy. This is the first report of progression ofEBVMCU to Hodgkin lymphoma, in the setting of ongoingiatrogenic immunosuppression and inflammatory boweldisease.

Epstein-Barr virus and Burkitt lymphoma

In 1964,a new herpesvirus,Epstein-Barr virus(EBV),was discovered in cultured tumor cells derived from a Burkitt lymphoma(BL)biopsy taken from an African patient.This was a momentous event that reinvigorated research into viruses as a possible cause of human cancers.Subsequent studies demonstrated that EBV was a potent growth-transforming agent for primary B cells,and that all cases of BL carried characteristic chromosomal translocations resulting in constitutive activation of the c-MYC oncogene.These results hinted at simple oncogenic mechanisms that would make Burkitt lymphoma paradigmatic for cancers with viral etiology.In reality,the pathogenesis of this tumor is rather complicated with regard to both the contribution of the virus and the involvement of cellular oncogenes.Here,we review the current understanding of the roles of EBV and c-MYC in the pathogenesis of BL and the implications for new therapeutic strategies to treat this lymphoma.

Epstein-Barr virus:Silent companion or causative agent of chronic liver disease?

The Epstein-Barr virus(EBV)has an important and multifaceted role in liver pathology.As a member of the herpes virus family,EBV establishes a persistent infection in more than 90%of adults.Besides acute hepatitis during primary infection,many clinical syndromes of interest for the hepatologist are associated with EBV infection.The role of EBV in the evolution of chronic hepatitis from hepatotropic viruses is considered.Chronic EBVassociated hepatitis is suspected in immunocompetent adults with compatible serology,suggestive histology and detection of the viral genome in the liver and/or increase of specific circulating cytotoxic T-lymphocytes.EBV is the main cause of post-transplant lymphoproliferative disorders which occur in up to 30%of cases.EBV-driven lymphoproliferative diseases are also recognized in non-immunocompromised patients and liver is involved in up to a third of the cases.Directly implicated in the pathogenesis of different tumors,EBV has a disputable role in hepatocellular carcinoma carcinogenesis.Further research is required in order to establish or reject the role of EBV in human liver cancer.This paper attempts to discuss the range of EBV-associated chronic liver diseases in immunocompetent patients,from mild,self-limiting mononuclear hepatitis to liver cancer.

Epigenetic dysregulation in Epstein-Barr virus-associated gastric carcinoma: Disease and treatments

Epstein-Barr virus(EBV)-associated gastric carcinoma(EBVaGC)comprises nearly 10%of gastric carcinoma cases worldwide.Recently,it was recognised to have unique clinicopathologic characteristics,including male predominance,lower rates of lymph node involvement,and better prognosis.EBVaGC is further characterised by abnormal hypermethylation of tumour suppressor gene promoter regions,causing down-regulation of their expression.In the present review,we critically discuss the role of EBV in gastric carcinogenesis,summarising the role of viral proteins and microRNAs with respect to aberrant methylation in EBVaGC.Given the role of epigenetic dysregulation in tumourigenesis,epigenetic modifiers may represent a novel therapeutic strategy.

The interplay of host genetic factors and Epstein-Barr virus in the development of nasopharyngeal carcinoma

The interplay between host cell genetics and Epstein-Barr virus(EBV) infection contributes to the development of nasopharyngeal carcinoma(NPC). Understanding the host genetic and epigenetic alterations and the influence of EBV on cell signaling and host gene regulation will aid in understanding the molecular pathogenesis of NPC and provide useful biomarkers and targets for diagnosis and therapy. In this review, we provide an update of the oncogenes and tumor suppressor genes associated with NPC, as well as genes associated with NPC risk including those involved in carcinogen detoxification and DNA repair. We also describe the importance of host genetics that govern the human leukocyte antigen(HLA) complex and immune responses, and we describe the impact of EBV infection on host cell signaling changes and epigenetic regulation of gene expression. High-power genomic sequencing approaches are needed to elucidate the genetic basis for inherited susceptibility to NPC and to identify the genes and pathways driving its molecular pathogenesis.

Epstein-Barr virus-associated lymphoepithelioma-like early gastric carcinomas and endoscopic submucosal dissection: Case series

Epstein-Barr virus (EBV)-associated lymphoepithelioma-like gastric carcinoma (LELC) is characterized by a lower lymph node (LN) metastasis rate and a higher survival rate than other forms of gastric cancer. Although current prognosis for LELC is favorable, the most common approach is radical gastrectomy involving an extensive D2 lymph node dissection. Here, we report four cases of EBV-associated early LELC that were treated by an alternative approach, endoscopic submucosal dissection (ESD). The long-term outcome of this procedure is discussed. All patients were treated by ESD en bloc, and all ESD specimens showed tumor-free lateral resection margins. None of the lesions showed lymphovascular invasion. A pathological examination of ESD specimens revealed submucosal invasion of more than 500 &#x003bc;m in all four cases. One patient underwent additional radical surgery post-ESD; no residual tumor or LN metastasis was noted in the surgical specimen. The other three patients did not undergo additional surgery, either because of severe comorbidity or their refusal to undergo operation, but were subjected to medical follow-up. None of the ESD-treated patients reported local recurrence or distant metastases during the 27-32 mo of follow-up after ESD.

Epstein-Barr virus infection and persistence in nasopharyngeal epithelial cells

Epstein-Barr virus(EBV) infection is closely associated with undifferentiated nasopharyngeal carcinoma(NPC), strongly implicating a role for EBV in NPC pathogenesis; conversely, EBV infection is rarely detected in normal nasopharyngeal epithelial tissues. In general, EBV does not show a strong tropism for infecting human epithelial cells, and EBV infection in oropharyngeal epithelial cells is believed to be lytic in nature. To establish life-long infection in humans, EBV has evolved efficient strategies to infect B cells and hijack their cellular machinery for latent infection. Lytic EBV infection in oropharyngeal epithelial cells, though an infrequent event, is believed to be a major source of infectious EBV particles for salivary transmission. The biological events associated with nasopharyngeal epithelial cells are only beginning to be understood with the advancement of EBV infection methods and the availability of nasopharyngeal epithelial cell models for EBV infection studies. EBV infection in human epithelial cells is a highly inefficient process compared to that in B cells, which express the complement receptor type 2(CR2) to mediate EBV infection. Although receptor(s) on the epithelial cell surface for EBV infection remain(s) to be identified, EBV infection in epithelial cells could be achieved via the interaction of glycoproteins on the viral envelope with surface integrins on epithelial cells, which might trigger membrane fusion to internalize EBV in cells. Normal nasopharyngeal epithelial cells are not permissive for latent EBV infection, and EBV infection in normal nasopharyngeal epithelial cells usually results in growth arrest. However, genetic alterations in premalignant nasopharyngeal epithelial cells, including p16 deletion and cyclin D1 overexpression, could override the growth inhibitory effect of EBV infection to support stable and latent EBV infection in nasopharyngeal epithelial cells. The EBV episome in NPC is clonal in nature, suggesting that NPC develops from a single EBV-infected nasopharyngeal epithelial cell, and the establishment of persistent and latent EBV infection in premalignant nasopharyngeal epithelium may represent an early and critical event for NPC development.

Serological diagnosis of Epstein-Barr virus infection: Problems and solutions

Serological tests for antibodies specific for Epstein-Barr virus(EBV) antigens are frequently used to define infection status and for the differential diagnosis of other pathogens responsible for mononucleosis syndrome. Using only three parameters [viral capsid antigen(VCA) Ig G, VCA Ig M and EBV nuclear antigen(EBNA)-1 Ig G],it is normally possible to distinguish acute from past infection: the presence of VCA Ig M and VCA Ig G without EBNA-1 Ig G indicates acute infection, whereas the presence of VCA Ig G and EBNA-1 Ig G without VCA Ig M is typical of past infection. However, serological findings may sometimes be difficult to interpret as VCA Ig G can be present without VCA Ig M or EBNA-1 Ig G in cases of acute or past infection, or all the three parameters may be detected simultaneously in the case of recent infection or during the course of reactivation. A profile of isolated EBNA-1 Ig G may also create some doubts. In order to interpret these patterns correctly, it is necessary to determine Ig G avidity, identify anti-EBV Ig G and Ig M antibodies by immunoblotting, and look for heterophile antibodies, anti-EA(D) antibodies or viral genome using molecular biology methods. These tests make it possible to define the status of the infection and solve any problems that may arise in routine laboratory practice.

Polymorphisms of Epstein-Barr virus BHRF1 gene, a homologue of bcl-2

Background and Objective: EBV BamHI fragment H rightward open reading frame 1 (BHRF1), the Epstein-Barr virus (EBV) early gene, is structurally and functionally homologous to the oncogene bcl-2 and may play an important role in the development of EBV-associated tumors. To characterize the polymorphisms of BHRF1 in EBV-associated tumors, we analyzed the sequences of BHRF1 in isolates from nasopharyngeal carcinoma (NPC) and EBV-associated gastric carcinoma (EBVaGC) biopsies as well as throat washing (TW) samples from healthy donors. Methods: BHRF1 DNA sequences were analyzed by polymerase chain reaction (PCR) and sequencing for 39 NPC samples, 40 EBVaGC samples, and 53 EBV-positive TW samples from healthy donors. The variants of BHRF1 gene were classified according to the signature changes. The EBV types 1 and 2 at nuclear antigen (EBNA) 3C locus were determined by PCR. Results: Compared with EBV standard cell line B95-8, all isolates carried a silent mutation at amino acid (AA) 80 (nucleotide 54616 T→C), the AA88 L→V mutation was found in most isolates, and the AA79 V→L mutation in a few isolates. Other mutations were sporadically distributed. Based on the mutations at AA88 and AA79, 3 distinct variants of BHRF1 genes, designated as 79V88V, 79L88L, and 79V88L, were identified. The 79V88V was the most common variant. The distribution of the BHRF1 variants among the NPC, EBVaGC, and TW samples was not significant. The corresponding regions of bcl-2 homologues were conserved in all isolates except for 3 samples. The distribution of BHRF1 variants in type 1 and type 2 strains was significant different (P < 0.001, contingency coefficient was 0.554). Conclusions: The 79V88V is the dominant variant in NPC, EBVaGC, and TW samples from healthy donors and preferential linkages between BHRF1 and EBNA3C variants exist. Conserved BHRF1 in Bcl-2 homologous domains is helpful to remain the important role of BHRF1.

Cancer stem-like cells in Epstein-Barr virus-associated nasopharyngeal carcinoma

Although the Epstein-Barr virus(EBV) has spread to all populations in the world, EBV-associated nasopharyngeal carcinoma(NPC) is prevalent only in South China and Southeast Asia. The role of EBV in the malignant transformation of nasopharyngeal epithelium is the main focus of current researches. Radiotherapy and chemoradiotherapy have been successful in treating early stage NPC, but the recurrence rates remain high. Unfortunately, local relapse and metastasis are commonly unresponsive to conventional treatments. These recurrent and metastatic lesions are believed to arise from residual or surviving cells that have the properties of cancer stem cells. These cancer stem-like cells(CSCs) have the ability to selfrenew, differentiate, and sustain propagation. They are also chemo-resistant and can form spheres in anchorage-independent environments. This review summarizes recent researches on the CSCs in EBVassociated NPC, including the findings regarding cell surface markers, stem cell-related transcription factors, and various signaling pathways. In particular, the review focuses on the roles of EBV latent genes [latent membrane protein 1(LMP1) and latent membrane protein 2A(LMP2A)], cellular microRNAs, and adenosine triphosphate(ATP)-binding cassette chemodrug transporters in contributing to the properties of CSCs, including the epithelial-mesenchymal transition, stem-like transition, and chemo-resistance. Novel therapeutics that enhance the efficacy of radiotherapy and chemoradiotherapy and inhibitors that suppress the properties of CSCs are also discussed.