EBNA size polymorphism can be used to trace Epstein-Barr virus spread within families

Childcare attendance and risk of infectious mononucleosis: A population-based Danish cohort study

BACKGROUND

The risk of infectious mononucleosis (IM) is affected both by crowding and by sibship structure, i.e., number and signed age differential between an index child and a sibling. Siblings provide protection against IM by pre-empting delayed primary Epstein-Barr virus infection with its associated high risk of IM. The association between childcare attendance and risk of IM, on the other hand, has never been studied in a large, well-characterized cohort.

METHODS

Danish children born in July 1992 through 2016 with a completely known simple childcare attendance history before age 1.5 years (n = 908,866) were followed up for a hospital contact with an IM diagnosis at ages 1.5-26 years. Hazard ratios (HRs) of IM for an additional year of exposure were obtained from stratified Cox regression analyses, stratified by sex and year of birth, with age as the underlying time scale, adjusted for sibship structure, and sociodemographic variables including parental ethnicity and maternal age.

RESULTS

An additional year of exclusively attending a daycare home (max 5 children) yielded HR = 0.90 (95% confidence interval 0.81-1.00), and similarly, each year of exclusively attending a childcare institution (e.g., crèche) yielded HR = 0.94 (0.84-1.06).

CONCLUSIONS

Forwarding enrollment in childcare by a year lowers the risk of IM later in life much less than having an additional sibling of comparable age and has no practical public health implications. We find our results suggestive of a random threshold for successful Epstein-Barr virus infection that is more easily reached by a sibling than the collective of playmates in daycare homes or childcare institutions.

Epstein-Barr Virus Infection in the Development of Neurological Disorders

Epstein-Barr Virus (EBV) is a ubiquitous human herpesvirus that contributes to the etiology of diverse human cancers and auto-immune diseases. EBV establishes a relatively benign, long-term latent infection in over 90 percent of the adult population. Yet, it also increases risk for certain cancers and auto-immune disorders depending on complex viral, host, and environmental factors that are only partly understood. EBV latent infection is found predominantly in memory B-cells, but the natural infection cycle and pathological aberrations enable EBV to infect numerous other cell types, including oral, nasopharyngeal, and gastric epithelia, B-, T-, and NK-lymphoid cells, myocytes, adipocytes, astrocytes, and neurons. EBV infected cells, free virus, and gene products can also be found in the CNS. In addition to the direct effects of EBV on infected cells and tissue, the effect of chronic EBV infection on the immune system is also thought to contribute to pathogenesis, especially auto-immune disease. Here, we review properties of EBV infection that may shed light on its potential pathogenic role in neurological disorders.

Infectious mononucleosis with atypical manifestations accompanied by transient IgM antibody response for cytomegalovirus

Infectious mononucleosis (IM) is a clinical syndrome caused by primary infection with Epstein-Barr virus (EBV) that is common in adolescents. In adults, particularly in elderly people, the clinical picture of IM tends to be atypical, often leading to a diagnostic challenge. Diagnosis is also complicated because infection with EBV can induce the synthesis of cross-reacting immunoglobulin M antibodies for other herpesviruses. We report an unusual case of infectious mononucleosis in a 34-year-old immunocompetent adult. Epidemiological studies indicate that the average age of primary EBV infection in developed countries is increasing. IM with atypical presentation will be a diagnostic challenge in the future as the number of EBV-naïve adults increases.

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.

Active Epstein-Barr virus infection after allogeneic stem cell transplantation: re-infection or reactivation?

Recipients of allogeneic stem cell transplants (SCT) often show active Epstein-Barr virus (EBV) infection, which may progress to EBV-associated lymphoproliferative disorders. It is not known whether these EBV infections are true reactivations of the endogenous EBV strain or re-infections with an exogenous EBV strain. Fifty-three recipients of matched related or matched unrelated donor grafts were studied. EBV monitoring was based on a realtime TaqMan EBV DNA polymerase chain reaction (PCR) assay in plasma. In 17 patients, EBV DNA PCR monitoring was performed in peripheral blood mononuclear cells (PBMCs) as well. Mouth washings (MWs) were collected pre-transplant from all patients and family donors. Both pre-transplant EBV DNA from MWs and post-transplant EBV DNA from plasma or PBMCs were successfully obtained in 6 patients. A nested PCR targeting the EBV latent membrane protein-1 C-terminus gene was used to determine sequence variations enabling EBV strain typing. In 3 of 6 patients, the post-transplant EBV sequence pattern differed from the pre-transplant pattern, indicating a re-infection post-transplant with an exogenous strain instead of a reactivation of the original endogenous EBV strain. In the other 3 patients, the endogenous strain was identified. Active EBV infection resulting from re-infection was more severe compared with active EBV infection because of reactivation. In conclusion, active EBV infections after allogeneic SCT frequently result from re-infection with an exogenous EBV strain instead of a true reactivation of the endogenous strain and are potentially more severe.

Maintenance of serum immunoglobulin G antibodies to Epstein-Barr virus (EBV) nuclear antigen 2 in healthy individuals from different age groups in a Japanese population with a high childhood incidence of asymptomatic primary EBV infection

Immunoglobulin G (IgG) antibodies to Epstein-Barr virus (EBV) nuclear antigens 2 and 1 (EBNA-2 and EBNA-1, respectively) were studied using sera from healthy individuals of a population with a high incidence of asymptomatic primary EBV infections during infancy or childhood in Japan. Two CHO-K1 cell lines expressing EBNA-2 and EBNA-1 were used for anticomplement and indirect immunofluorescence assays. The positivity rate for EBNA-2 IgG rose in the 1- to 2-year age group, increased and remained at a plateau ( approximately 45%) between 3 and 29 years of age (3- to 4-, 5- to 9-, 10- to 14-, and 15- to 29-year age groups), and then reached 98% by age 40 (>/== 40-year age group). Both seropositivity for EBNA-1 and seropositivity for EBNAs in Raji cells (EBNA/Raji) were detected in the 1- to 2-year age group, remained high, and finally reached 100% by age 40. The geometric mean titer (GMT) of EBNA-2 IgG reached a plateau in the 5- to 9- and 10- to 14-year-old groups and remained elevated in the older age groups (15 to 29 and >/== 40 years). The GMT of EBNA-1 IgGs increased to a plateau in the 1- to 2-year-old group and remained unchanged in the older age groups. The GMT of EBNA/Raji IgGs also reached a plateau in the 1- to 2-year-old group, remained level throughout the 3- to 14-year age groups, and decreased in the 15- to 29-year-olds. EBNA-2 IgGs emerged earlier than EBNA-1 IgGs in 8 of 10 patients with infectious mononucleosis, who were between 1 and 27 years old, and declined with time in three of eight cases. These results suggest that EBNA-2 IgG antibodies evoked in young children by asymptomatic primary EBV infections remain elevated throughout life, probably because of reactivation of latent and/or exogenous EBV superinfection.

Epstein-Barr virus-recent advances

Epstein-Barr virus is a tumorigenic herpes virus that is ubiquitous in the adult population. The virus is generally spread to and between young children through salivary contact, and only causes clinical illness where primary infection is delayed until adolescence or beyond, when an intense immunopathological reaction leads to the symptoms of infectious mononucleosis in roughly 50% of cases. More than 90% of the world's population carry Epstein-Barr virus as a life-long, latent infection of B lymphocytes. Recent data show that by mimicking B-cell antigen-activation pathways the virus enters the long-lived memory B lymphocyte pool where it evades immune elimination by severely restricting its own gene expression. By influencing B-cell survival mechanisms Epstein-Barr virus may induce tumours such as B lymphoproliferative disease and Hodgkin's disease. Vaccines are being developed to prevent and/or treat these conditions, but an animal model is required to study pathogenesis before a rational vaccine strategy can be formulated.

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.

Frequent presence of subtype A virus in Epstein-Barr virus-associated malignancies

AIMS

Epstein-Barr virus (EBV) is associated with many human malignancies. It is implicated in a pathogenetic role in some of these tumours. Two subtypes, type A and B have been identified on the basis of DNA sequence divergence in the nuclear protein genes (EBNA) 2, 3, 4 and 6. They differ in their transforming efficiency and prevalence pattern in different geographical locations. We aimed to identify the virus subtype infection pattern in our EBV-associated diseases.

METHODS

Paraffin-embedded tissue from 38 lymphomas (17 Hodgkin's, 14 Burkitt's, four T cell and 3 B cell non-Hodgkin's lymphomas) and 14 nasopharyngeal carcinomas (NPC) were studied, with 12 reactive lymph nodes and tonsils as normal control. EBER in situ hybridisation was performed to confirm EBV association in the tumour cells. A nested polymerase chain reaction (PCR) protocol was employed using two pairs of consensus primers which flanked a 105-bp deletion in the type A virus. U2 region encoding for EBNA-2 was chosen as the target of amplification, with cell lines B95.8 and AG876 serving as positive controls for types A and B virus, respectively.

RESULTS

All cases showed presence of type A virus, consistently detected with nested PCR protocol but not with single step PCR. There was no type B virus or mix infections detected.

CONCLUSIONS

Nested PCR technique has successfully increased the sensitivity of EBV subtype detection, and type A virus is the prevalent strain associated with human diseases in Malaysia.

Identification of Epstein-Barr virus strain variants in hairy leukoplakia and peripheral blood by use of a heteroduplex tracking assay

Epstein-Barr virus (EBV) strains can be distinguished by specific sequence variations in the LMP1 gene. In this study, a heteroduplex tracking assay (HTA) specific for LMP1 was developed to precisely identify the prototypic undeleted strain B958, other undeleted strains (Ch2, AL, NC, and Med-), and strains with the 30-bp deletion (Med+ and Ch1). This technique also provides an estimate of the relative abundance of strains in patient samples. In this study, EBV strains were identified in 25 hairy leukoplakia (HLP) biopsies and six matched peripheral blood samples and throat washes with the LMP1-HTA. To investigate the relationship of the virus found in the peripheral blood to that in the HLP lesion, the strain variants in the peripheral blood B lymphocytes and those present within the epithelial cells in the HLP lesion and in throat washes were identified. In many of the subjects, compartmental differences in the EBV strain profiles in the oral cavity and peripheral blood were readily apparent. The throat wash specimens usually had a strain profile similar to that within the corresponding HLP sample, which was distinct from the strain profile detected in the peripheral blood. These analyses reveal that the nature of EBV infection can be very dynamic, with changes in relative strain abundance over time as well as the appearance of new strains. The patterns of abundance in the blood and oral cavity provide evidence for compartmentalization and for the transmission of strains between the blood and oropharynx.

DNA sequence heterogeneity within the Epstein-Barr virus family of repeats in the latent origin of replication

To detect the presence of variability in the tandemly repeated sequences of the Epstein-Barr virus latent origin of replication, we analyzed the length of the family of repeats in 14 lymphoblastoid and Burkitt's lymphoma cell lines by PCR amplification. The gel electrophoresis analysis of the PCR products revealed a broad banding pattern, characteristic of each line, consisting of several fragments, sometimes smeared, of variable length. This finding was interpreted as a result of the hairpin-like structures generated by the palindrome within the family of repeats, able to originate artefacts. Since the banding pattern was different only in strictly non-correlated cell lines, we supposed that the sequence of the repeat units was polymorphic. We therefore sequenced the family of repeats in three healthy bone marrow derived lymphoblastoid cell lines carrying an endogenous EBV as well as in a B95-8 infected cell line as control. The sequence analysis revealed that each line is different both in the number and in the sequence of repeats. At the 3' end of the family of repeats the B95-8 virus was found to have a 252 bp region missing in the GenBank standard sequence. This one is probably a partial sequence since it was shorter than the control specimens obtained from different sources of B95-8 DNA analyzed by Southern blot hybridization. The length analysis of the family of repeats can be used to characterize EBV strains by PCR.

Signature amino acid changes in latent membrane protein 1 distinguish Epstein-Barr virus strains

Sequence variations in the Epstein-Barr virus (EBV) latent membrane protein 1 gene have been described in numerous EBV-associated tumors with some of these variations, most notably a 30-base pair deletion in the cytoplasmic carboxyl-terminal domain, suggested as associated with an increase in tumorigenicity. In this study, EBV DNA sequence was determined from 92 tissue specimens or cell lines, including nasopharyngeal carcinoma, oral hairy leukoplakia, post-transplant lymphoma, post-transplant without pathology, mononucleosis, Burkitt's lymphoma, parotid tumor, and normal from distinct geographical regions. The amino- and carboxyl-terminal sequences and, in some cases, the full-length sequences of latent membrane protein 1 were determined. Characteristic sequence patterns distinguished strains, with the carboxyl-terminal sequence being the most informative in distinguishing among the strains. Phylogenetic relationships between strains were determined, as were signature amino acid changes that discriminate between them. A correlation between strain and disease or strain and geographic location was not detected. The sequence variation and signature sequences identified at least seven distinct strains, as well as hybrid strains that apparently result from recombination.

Epstein-Barr Virus in Nasal Lymphomas Contains Multiple Ongoing Mutations in the EBNA-1 Gene

We have described 5 major subtypes of Epstein-Barr virus (EBV) based on variations in EBNA-1 sequences. These include P-ala (identical to the prototype B95.8 virus), P-thr, V-pro, V-leu, and V-val. Normal individuals often carry multiple EBV subtypes, the most common being P-ala, whereas EBV-associated tumors examined to date always contain a single subtype, which only on rare occasion is P-ala. The primary hypotheses that these observations generate are as follows: (1) Each of these EBV subtypes are naturally occurring, and in normal individuals the multiplicity of subtypes results from multiple infections. (2) EBV subtypes in normal individuals are generated in vivo from a single infecting virus subtype by mutations in EBNA-1. The second hypothesis essentially excludes the possibilities that the nonrandom association of certain subtypes with lymphomas is secondary to the geographic distribution of EBV subtypes and, if proven correct, could provide strong support for a direct role of EBV in tumorigenesis. In this report, we provide evidence for the latter hypothesis. We show that the P-ala EBV subtype present in most nasal lymphomas undergoes and accumulates multiple mutations consistent with the generation of variant species of EBNA-1 in vivo. This phenomenon is similar to the generation of quasispecies in RNA viruses and is the first description of in vivo generation of subtypes in DNA viruses. In RNA-based viruses, including human immunodeficiency virus and hepatitis C virus, the emergence of quasispecies is linked to replication infidelity and significantly influences disease processes through its effect on viral tropism, the emergence of viruses resistant to the host defenses or to therapy, and pathogenicity. The present data thus raise important questions relating to the mechanisms whereby these mutations are generated in EBV and their relevance to the pathogenicity of EBV-associated lymphomas.

Epstein-Barr Virus in Nasal Lymphomas Contains Multiple Ongoing Mutations in the EBNA-1 Gene

We have described 5 major subtypes of Epstein-Barr virus (EBV) based on variations in EBNA-1 sequences. These include P-ala (identical to the prototype B95.8 virus), P-thr, V-pro, V-leu, and V-val. Normal individuals often carry multiple EBV subtypes, the most common being P-ala, whereas EBV-associated tumors examined to date always contain a single subtype, which only on rare occasion is P-ala. The primary hypotheses that these observations generate are as follows: (1) Each of these EBV subtypes are naturally occurring, and in normal individuals the multiplicity of subtypes results from multiple infections. (2) EBV subtypes in normal individuals are generated in vivo from a single infecting virus subtype by mutations in EBNA-1. The second hypothesis essentially excludes the possibilities that the nonrandom association of certain subtypes with lymphomas is secondary to the geographic distribution of EBV subtypes and, if proven correct, could provide strong support for a direct role of EBV in tumorigenesis. In this report, we provide evidence for the latter hypothesis. We show that the P-ala EBV subtype present in most nasal lymphomas undergoes and accumulates multiple mutations consistent with the generation of variant species of EBNA-1 in vivo. This phenomenon is similar to the generation of quasispecies in RNA viruses and is the first description of in vivo generation of subtypes in DNA viruses. In RNA-based viruses, including human immunodeficiency virus and hepatitis C virus, the emergence of quasispecies is linked to replication infidelity and significantly influences disease processes through its effect on viral tropism, the emergence of viruses resistant to the host defenses or to therapy, and pathogenicity. The present data thus raise important questions relating to the mechanisms whereby these mutations are generated in EBV and their relevance to the pathogenicity of EBV-associated lymphomas.

Epidemiology of infection with Epstein-Barr virus types 1 and 2: lessons from the study of a T-cell-immunocompromised hemophilic cohort

In apparent contrast to earlier work on Epstein-Barr virus (EBV) carriage in the general Caucasian population, in vitro virus isolations from human immunodeficiency virus (HIV)-positive male homosexual cohorts have shown frequent examples of multiple EBV infection and an overall prevalence of type 2 EBV strains exceeding 30%. Here we ask to what extent these findings might hold true in another T-cell-immunocompromised cohort, HIV-positive hemophilic patients. Resident EBV strains were rescued within lymphoblastoid cell lines derived from the blood and throat washings of 39 such individuals, using the same in vitro protocols of virus isolation as for the homosexual cohort. A mean of 19 independent cell lines was made per patient, and in each case the resident virus was characterized by PCR-based viral genomic analysis and by immunoblotting to reveal the viral "EBNAprint." By these criteria a significant proportion (14 of 39) of the hemophilic cohort carried more than one EBV strain, suggesting that T-cell impairment does indeed sensitize virus carriers to reinfection with new strains of exogenously transmitted virus. However, the overall incidence of type 2 EBV infection was 10%, which is close to that observed in the earlier work with healthy carriers and substantially lower than that seen in HIV-positive homosexuals. We infer that type 2 EBV is relatively rare in the general Caucasian population but has become endemic in the homosexual community.

Epstein-Barr virus strain characterization

The Epstein-Barr virus (EBV), a ubiquitous human herpesvirus originally described in cultured lymphoblasts from African Burkitt's lymphoma, is the causative agent of infectious mononucleosis, but appears to be involved in the pathogenesis of a variety of diseases. EBV has the ability to establish lifelong persistent infection, where only a restricted pattern of the viral proteins is expressed. Periodic reactivation of EBV occurs, where mature EBV particles are produced. Strain variation is potentially important in the biology and epidemiology of EBV, and in attempts to relate EBV to associated diseases. Analysis of the EBV genomes isolated from patients with EBV-associated diseases and from various parts of the world has so far failed to identify conclusive disease-specific viral subtypes. This review focuses on the different strategies which have been used for strain characterization or subtyping of EBV.

Frequency of multiple Epstein-Barr virus infections in T-cell-immunocompromised individuals

The Epstein-Barr virus (EBV) carrier state is characterized by latent infection of the general B-cell pool and by chronic virus replication at oropharyngeal sites. In Caucasian populations, most healthy carriers seem to harbor one dominant transforming virus strain, usually of type I rather than type 2, which persists over time and is detectable both in the blood and in the throat. This finding implies that once the virus carrier state is established, both viral reservoirs are largely if not completely protected from infection with additional strains. However, it is not known which facets of the immune response offer that protection. Here we address this question by a detailed study of EBV carriage in patients T-cell immunocompromised as a result of chronic human immunodeficiency virus (HIV) infection. Resident EBV strains were rescued from blood and from throat washings by using an in vitro transformation assay which aims to minimize bias toward faster-growing transformants; in this way, a mean of 16 independent isolations were made from each of 35 HIV-positive (predominantly male homosexual) patients. These virus isolates were characterized first at the DNA level by PCR amplification across type-specific polymorphisms in the EBNA2 and EBNA3C genes and across the 30-bp deletion and 33-bp repeat loci in the LMP1 gene and then at the protein level by immunoblotting for the strain-specific "EBNAprint" of EBNA1, -2, and -3C molecular weights. By these criteria, 18 of 35 patients harbored only one detectable EBV strain, usually of type 1, as do healthy carriers. However, the other 17 patients showed clear evidence of multiple infection with different EBV strains. In eight cases these strains were of the same type, again usually type 1, and were more often found coresident in throat washings than in the blood. By contrast, a further nine patients gave evidence of coinfection with type 1 and type 2 strains, and in these cases both virus types were detectable in the blood as well as in the throat. Immunological assays on these HIV-positive patients as a group showed a marked impairment of T-cell responses, reflected in reduced levels of EBV-specific cytotoxic T-cell memory, but an elevation of humoral responses, reflected in raised antibody titers to the EBV envelope glycoprotein gp340 and by the maintenance of virus neutralizing antibodies in serum. We infer that selective impairment of the T-cell system predisposes the host to infection with additional exogenously transmitted EBV strains.

The Epstein-Barr virus EBNA-2 gene in oral hairy leukoplakia: strain variation, genetic recombination, and transcriptional expression

Oral hairy leukoplakia (HLP) lesions frequently contain defective Epstein-Barr virus (EBV) genomes with deletions in the EBNA-2 gene that abundantly replicate and persist within the lesion. To characterize these viral strains and recombinant variants, the EBNA-2 gene in EBV DNA from several different HLP biopsy specimens was analyzed. Amplification of EBNA-2 coding sequences by PCR demonstrated the presence in HLP of intact EBNA-2 genes as well as a variety of internally deleted variants of both EBNA-2A and EBNA-2B. Some of the deletion variants evolved within the HLP lesion from intact EBNA-2 genes, while other variants appeared to be transmissible strains that directly infected the lesion. Intrastrain recombination within the HLP lesion also generated variation within the EBNA-2 polyproline region. Cloning and sequencing of HLP cDNA demonstrated transcription from the internally deleted EBNA-2 open reading frame, indicating that these variant genes are expressed in HLP. Comparative analysis of the HLP EBNA-2 sequences confirmed previous findings of EBV coinfection with multiple types and strains. Sequence variation of these wild-type genes demonstrated that EBNA-2A sequences distinguish at least two separate strains and a variety of substrains of EBV type 1. Two of the HLP EBNA-2A sequences contained amino acid changes in a cytotoxic T-cell epitope within an otherwise highly conserved region of the gene. These data indicate that EBV coinfection, strain variation, and recombination within the EBNA-2 gene are common features of HLP and suggest that the expression of internally deleted EBNA-2 variants could contribute to EBV pathogenesis in permissive infection.

Epstein-Barr virus intrastrain recombination in oral hairy leukoplakia

In laboratory lymphoblastoid cell lines and in natural human infections, Epstein-Barr virus (EBV) strains have been identified by DNA restriction fragment length polymorphisms of the BamHI H fragment. Multiple, heterogeneous BamHI H fragments have been detected in oral hairy leukoplakia (HLP), raising the question of EBV coinfection with multiple strains. To investigate whether the heterogeneous BamHI H fragments represent different EBV strains or recombinant variants of the same strain, EBV DNA from HLP lesions was analyzed to characterize the viral strains and determine the source of possible recombinant variants. Clones of heterogeneous BamHI H fragments from a single HLP lesion were determined to have strain identity on the basis of sequence identity of the EBNA-2 genes. Intrastrain homologous recombination within the IR2 internal repeat region and nonhomologous recombination of other sequences accounted for the heterogeneity of the BamHI H fragments. PCR amplification from additional HLP specimens detected similar recombinant variants. A possible example of site-specific recombination joining the BamHI Y portion of the EBNA-2 gene to sequences within the BamHI S fragment was also detected in multiple HLP specimens. These data indicate that intrastrain recombination during productive replication confounds the use of restriction fragment length polymorphism analysis of the BamHI Y and H fragments to identify EBV strains in HLP. In patients with permissive epithelial EBV infections, EBV strains could be more accurately distinguished by sequence identity or divergence within known regions of genetic strain variation.

Detection and characterization of Epstein-Barr virus in clinical specimens

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

Characterization of Epstein-Barr viral strains in parotid gland saliva and peripheral blood of patients with primary Sjögren's syndrome and healthy EBV carriers

Increased Epstein-Barr virus (EBV) replication has been reported in the salivary and lacrimal glands in Sjögren's syndrome (SS). We studied whether or not certain EBV strains would occur preferentially in the peripheral blood and parotid gland saliva of 18 EBV-seropositive patients with primary Sjögren's syndrome (pSS) and 12 EBV-seropositive control persons. Transforming EBV was detected in the blood of 11 of 18 (61%) pSS patients and 9 of 12 controls (75%). Unexpectedly, neither transforming nor Raji-superinfecting EBV strains were detected in SS parotid saliva, whereas these EBV types were detected in control saliva in 7 and 8 cases, respectively (P < 0.001). Transforming EBV strains were further characterized by 'Ebno-typing,' i.e., analysis of the size spectrum of the viral antigens EBNA 1, 2, 3, and 6 in immunoblots of lymphoblastoid cell lines (LCL). Previous work has shown that a single EBV strain (Ebnotype) dominates the blood and oropharynx of healthy carriers and that unrelated individuals carry different EBV strains, reflecting the vast polymorphism of Ebnotypes in the general population. Two unexpected observations were made. First, an identical Ebnotype was detected in 4 unrelated individuals, i.e., in the blood of 1 pSS patient and in the saliva of 3 control persons. Second, carriage of 2 to 4 different Ebnotypes by a single individual was observed in 4 cases, i.e., in the blood of 1 pSS patient, and in the blood and saliva of 3 control persons.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of Epstein-Barr virus nuclear antigen 1,2A and 2B in the baculovirus expression system: serological evaluation of human antibodies to these proteins

The Epstein-Barr virus encoded nuclear antigens 1,2A, and 2B (EBNA 1, EBNA 2A, and EBNA 2B) were expressed in a baculovirus system. The full length recombinant proteins were recognized by polyclonal rabbit sera and by human sera. An immunofluorescence (IF) test for the differentiation between EBNA 1 and EBNA 2 antibodies in human sera was established with the expressed proteins. None of 55 sera of patients with infectious mononucleosis (IM) had anti-EBNA 1 antibodies while 36 of these sera had anti-EBNA 2A antibodies. Conversely, 47 of 51 sera from EBV-positive healthy carriers had anti-EBNA 1 antibodies and 18 of these sera had anti-EBNA 2A antibodies. The sensitivity and specificity of the EBNA 1 IF for the diagnosis of IM were higher as compared to conventional anti-complement immunofluorescence (ACIF). In the IF test differentiation between type A and type B EBV infection was only possible in sera from the IM patients. An immunoblot (IB) with low amounts of baculovirus expressed EBNA 2A and EBNA 2B antigen was carried out. Twenty-nine of 31 sera from IM patients or from healthy carriers with EBNA 2 antibodies reacted predominantly with EBNA 2A, whereas a known type B serum reacted strongly with EBNA 2B than with EBNA 2A.

Direct detection of Epstein-Barr virus in peripheral blood and comparison of Epstein-Barr virus genotypes present in direct specimens and lymphoblastoid cell lines established from nasopharyngeal carcinoma patients and healthy carriers in Hong Kong

By means of a PCR assay, EBV was demonstrated directly in peripheral blood of previously infected individuals. The virus was detected in approximately 80% of specimens from EBV-seropositive individuals, but not in cord-blood lymphocytes by this method. When virus present in peripheral blood was compared to that observed directly in NPC biopsies or throat washings, it was distinct from that seen in biopsies in 4/15 cases (27%) and from that seen in throat washes in 1/22 cases (5%). The throat-wash virus differed from the biopsy virus in 3/20 cases (15%). The prototype F virus was found in 7/10 LCLs (70%) established from NPC patients' peripheral blood, but was only detected in 2/9 specimens (22%) directly analyzed by the PCR assay. This finding suggests selective isolation of prototype F EBV in spontaneous LCLs established from NPC patients.

Epstein-Barr virus infection in allogeneic marrow grafting: lessons for transplant physicians and virologists

The relationship between Epstein-Barr virus (EBV) and the host is profoundly disturbed by allogeneic bone marrow transplantation (BMT) because EBV resides in the recipient's hematopoietic system, which has to be destroyed in the majority of cases, and in the donor's hematopoietic system, i.e., the marrow graft. We have shown that EBV may be eradicated from some BMT recipients and that the virus may be transferred with the marrow graft. During the immediate post-transplant period oropharyngeal EBV excretion may occur which, by infecting passing B lymphocytes, may act as co-factor for acute graft-versus-host disease and help the virus to survive, despite the temporary depletion of its reservoir. The coexistence of totally different EBV strains in BMT recipients but not in healthy, untransfused controls, suggests that superinfection may by possible in case of immunodeficiency; alternatively, transfer of the virus by the reservoir itself (the B lymphocytes) might be the only effective route for superinfection. The generation of 'variant' strains during viral replication may form the basis of the vast polymorphism between wild-type EBV isolates in the population.

Detection of multiple Epstein-Barr viral strains in allogeneic bone marrow transplant recipients

We have previously shown in 3 allogeneic bone-marrow transplant (BMT) recipients that complete replacement of recipient marrow was associated with the elimination of the pretransplant Epstein-Barr virus (EBV) strain of the recipient. To study the kinetics of EBV elimination and reinfection in more detail, we have performed a longitudinal study of BMT recipients combining serology, virus isolation from mouthwashes and peripheral blood, and EBV strain characterization. Oropharyngeal EBV excretion was found to persist after the cytoreductive therapy prior to BMT, whereas EBV-carrying cells in the blood were detected only after 5 weeks following BMT. During the first month post-BMT, 2 different EBV strains could be isolated from sequential mouth-washes of 3 patients. The initial strains were found to persist up to 7, 21, and 29 days post-BMT, whereas the subsequent strains appeared at 21, 42, and 34 days post-BMT, respectively. Thus, the original EBV strain may persist only for a limited time after BMT, and the oropharyngeal epithelium may be reinfected by a new EBV strain from the blood within 3 weeks. With respect to the coexistence of multiple EBV strains, 2 patterns were evident. From the day 62 mouthwash of 1 patient, 1 Type A and 1 Type B strain were isolated. From the day 180 mouthwash of a second patient, a dominant Type A strain was recovered, together with 6 "variant" strains that differed from each other by only a single EBNA protein (EBNA 1). This pattern may be explained by viral recombinations during replication, which may form the basis for the vast polymorphism of EBV observed in unrelated individuals.

Detection and prevalence of the "f" variant of Epstein-Barr virus in southern China

The "f" variant of Epstein-Barr virus (EBV) may have an association with the development and/or maintenance of nasopharyngeal carcinoma (NPC) among Southern Chinese. This variant is detected at a higher frequency among individuals with elevated IgA antibody levels against EBV capsid antigen who have no detectable NPC and in NPC patients as compared to healthy individuals or patients who are in remission for NPC for over 3 years. Conversion or replacement of the f variant by the prototype BamHI F virus usually occurs by 3 to 4 years after radiotherapy. By 5 years post-therapy the majority of people in remission for NPC no longer harbor the f variant in their oropharynx. Eradication of this f variant, however, does not appear essential for maintenance of a disease-free state since several patients harboring this variant were in remission for NPC for up to 21 years. The virus strain detected directly in the nasopharynx is not always identical to that seen in the oropharynx. Dual infection was commonly observed in throat washings of NPC patients although the biopsy from tumors harbored unique strains of EBV.

Immunovirology of transforming viruses

The paradigmatic shift in cellular immunology, initiated by the realization that cytotoxic T lymphocytes recognize major histocompatibility complex class I antigens that carry endogenous (including virally encoded) protein-derived peptides in a special groove, has made a strong impact on the immunopathology of virus-associated tumors.