Lymphoid tissues from patients with infectious mononucleosis lack monoclonal B and T cells

In typical cases of infectious mononucleosis (IM), lymphoid tissue is rarely submitted for pathological examination. When lymphoid tissues from IM cases are examined, the histological appearance of IM may be difficult to distinguish from malignant lymphoma. The purpose of this study was to address the utility of clinical molecular assays for T and B cell clonality in distinguishing IM from lymphoid malignancy. DNA was recovered from paraffin-embedded archival lymphoid tissues of 18 cases of IM and 13 control cases representing other reactive lymphoid hyperplasias. T cell receptor gamma (TCR-gamma) and immunoglobulin heavy chain (IgH) gene rearrangements were assayed using our standard clinical polymerase chain reaction procedures targeting each of the four functional variable (V) families and the three joining (J) families of the TCR-gamma gene, and framework III of the IgH gene, respectively. In 17 of 18 cases of IM, no monoclonal T or B cell populations were detectable. One case, the only spleen specimen in the study, had an oligoclonal pattern of TCR-gamma rearrangements. The control cases representing other reactive hyperplasias also lacked monoclonality. The assays used were sensitive to clonal populations as small as 5% of cells. In this case series, no monoclonal lymphoid populations were identified in any case of IM. This finding suggests that molecular studies are useful in distinguishing IM from lymphoid neoplasms.

[Nucleic acid content in peripheral blood lymphocytes from patients with infectious mononucleosis]

An increase in RNA content in peripheral blood lymphocytes and increased number of macronuclear weakly basophilic cells (presumably due to increased content of B-lymphocytes which, in contrast to sharply basophilic T-lymphocytes, are characterized by light basophilic cytoplasm) are observed in patients with infectious mononucleosis. Macronuclear forms represented equally by hyper- and hypobasophilic elements predominate the structure of atypical mononuclears. Increased content of DNA in the peripheral blood lymphocytes is due to increased number of cells with high DNA content in the patient's blood and appearance of cells with 52-65 arb. units DNA (blast-transformed atypical mononuclears infected with the virus) which are normally absent.

SH2D1A mutations in Japanese males with severe Epstein-Barr virus--associated illnesses

X-linked lymphoproliferative disease (XLP), a genetic disorder characterized by immunodeficiency to Epstein-Barr virus (EBV) infection, has been linked to mutations in the SH2D1A gene. To search for the occurrence of SH2D1A mutations in Japan, we performed genetic analysis of the SH2D1A gene in 40 males presenting with severe EBV-associated illnesses, including fulminant infectious mononucleosis, EBV-positive lymphoma, and severe chronic active EBV infection. SH2D1A mutations were detected in 10 of these 40 patients. Five of these 10 cases were sporadic. Patients with SH2D1A mutations displayed severe acute infectious mononucleosis with hyperimmunoglobulin M, hypogammaglobulinemia, and B-cell malignant lymphoma. By contrast, chronic active EBV infection was not associated with SH2D1A mutations. XLP survivors exhibited normal levels of circulating EBV-DNA during convalescence, suggesting that SH2D1A protein is not directly responsible for control of EBV replication. Thus, genetic analysis of the SH2D1A gene is particularly useful in the diagnosis of sporadic cases and carriers of XLP. (Blood. 2001;98:1268-1270)

Identification of quantitative trait loci controlling activation of TRBV4 CD8+ T cells during murine gamma-herpesvirus-induced infectious mononucleosis

The murine gamma-herpesvirus, MHV-68, shares important biological and genetic features with the human gamma-herpesvirus, Epstein-Barr virus. Following intranasal infection, mice develop an infectious mononucleosis-like syndrome accompanied by increased numbers of activated CD8+ T cells in the blood. A consistent feature of the CD8+ T-cell activation is a marked increase in the frequency of cells expressing a TRBV4+ T-cell receptor. Previous studies suggested that the magnitude of TRBV4 expansion varied significantly among mouse strains, and was influenced by both MHC and non-MHC genes. Detailed analysis of strains with high (C57BL/6) or low (DBA/2) TRBV4 CD8+ T-cell expansion showed that differences in the degree of expansion were not a consequence of variation in genetic susceptibility to the viral infection. Rather, the magnitude of the TRBV4 CD8+ T-cell expansion correlated with differences in expression of the unidentified stimulatory ligand on activated, latently infected B cells. In the present study, analysis of TRBV4 expansion in C57BL/6, DBA/2, B6D2 F1 mice, BXD recombinant inbred strains, and the progeny of C57BL/6xDBA/2 F1 hybrids backcrossed to C57BL/6 demonstrated strong cumulative dominance of the low DBA/2 trait and moderately high heritability (h2 approximately 0.5). Two quantitative trait loci (QTLs) strongly associated with variance in TRBV4 expansion were identified using simple and composite mapping procedures. The first QTL is located on Chromosome (Chr) 17, near or proximal to H2. The second QTL is located on Chr 6 in a region spanning the Tcrb and Cd8a loci.

Cytogenetic impairments of peripheral blood lymphocytes during infectious mononucleosis

We performed chromosomal analysis and micronucleus test of peripheral blood lymphocytes during infectious mononucleosis. The content of lymphocytes with structural chromosome aberrations and micronuclei increased in patients with pronounced clinical and hematological signs of infectious mononucleosis (acute stage). There were cells with changed number of chromosomes. These cytogenetic abnormalities persisted both during convalescence and in the delayed period after recovery.

The flow cytometric analysis of telomere length in antigen-specific CD8+ T cells during acute Epstein-Barr virus infection

Acute infectious mononucleosis (AIM) induced by Epstein-Barr virus (EBV) infection is characterized by extensive expansion of antigen-specific CD8+ T cells. One potential consequence of this considerable proliferative activity is telomere shortening, which predisposes the EBV-specific cells to replicative senescence. To investigate this, a method was developed that enables the simultaneous identification of EBV specificity of the CD8+ T cells, using major histocompatibility complex (MHC) class I/peptide complexes, together with telomere length, which is determined by fluorescence in situ hybridization. Despite the considerable expansion, CD8+ EBV-specific T cells in patients with AIM maintain their telomere length relative to CD8+ T cells in normal individuals and relative to CD4+ T cells within the patients themselves and this is associated with the induction of the enzyme telomerase. In 4 patients who were studied up to 12 months after resolution of AIM, telomere lengths of EBV-specific CD8+ T cells were unchanged in 3 but shortened in one individual, who was studied only 5 months after initial onset of infection. Substantial telomere shortening in EBV-specific CD8+ T cells was observed in 3 patients who were studied between 15 months and 14 years after recovery from AIM. Thus, although telomerase activation may preserve the replicative potential of EBV-specific cells in AIM and after initial stages of disease resolution, the capacity of these cells to up-regulate this enzyme after restimulation by the persisting virus may dictate the extent of telomere maintenance in the memory CD8+ T-cell pool over time.

Epstein-Barr virus-associated gastric carcinoma in Mexico: analysis of 135 consecutive gastrectomies in two hospitals

Epstein-Barr virus (EBV) has been implicated in the genesis of gastric carcinoma. The presence of clonal episomal viral forms in the nuclei of neoplastic gastric epithelial cells suggests that viral infection occurs before the development of gastric carcinoma. Mexico is a country at high risk for gastric cancer-it is the second cause of death among patients who die of cancer in that country. A series of 135 consecutive non-selected gastrectomies from two hospitals in Mexico City were analyzed to search for EBV in gastric carcinomas. EBV-encoded small non-polyadenylated RNA (EBER) in situ hybridization was performed on 5-microm paraffin-embedded tissue sections. Age, gender, anatomical site, histological type, and invasiveness of gastric carcinomas were obtained from the records in the corresponding Departments of Pathology. Eleven (8.15%) of the 135 cases were EBER-1-positive gastric carcinomas. Six occurred in males and five in females. In three women, the neoplasia was localized in the antrum. Five of the 11 cases were lymphoepithelioma-like carcinomas and, in two of them, an unusual foreign body-type inflammation was observed. Environmental factors could influence the distinctive pathologic features of EBV-associated gastric carcinoma in the Mexican population.

Redox control of Epstein-Barr virus replication by human thioredoxin/ATL-derived factor: differential regulation of lytic and latent infection

Human thioredoxin (hTRX)/adult T-cell leukemia (ATL)-derived factor (ADF) was originally reported as an interleukin-2 (IL-2) receptor-alpha-inducing factor produced by human T-cell lymphotropic virus-1-positive (HTLV-1+) cell lines. Growing evidence indicates that hTRX/ADF plays important roles in cellular responses against oxidative stress and is involved in a variety of cellular functions. A high level of hTRX/ADF expression is also observed in other human virus-infected cell lines including those of Epstein-Barr virus (EBV) and human papillomavirus. In this report, we analyzed the effect of hTRX/ADF on lytic amplification and persistent replication of EBV as a model for lytic versus latent phase of viral replication in host cells. Addition of hTRX/ADF clearly suppressed lytic replication of EBV in Raji cells and B95-8 cells induced to the lytic phase of 12-O-tetradecanoylphorbol-13-acetate (TPA), and it prevented the death of these cells evoked by the lytic induction. In contrast, hTRX/ADF did not have any effect on persistent replication in the latent phase. These data indicated that hTRX/ADF prevents EBV-transformed cells from proceeding into the lytic phase and regulates cohabitation of EBV and its host cells.

Determination of Epstein-Barr virus (EBV) load by RT-PCR and cellular dilution

Epstein-Barr virus (EBV) is a ubiquitous human herpesvirus which establishes life-long latency in the B-lymphocytes of infected individuals. Epstein-Barr virus is associated with Hodgkin's disease, AIDS-associated lymphoma and post-transplant lymphoproliferative disease (PTLD). In PTLD, the onset of malignancy correlates with a rise in EBV load. The relationship between malignancy and EBV load in other EBV-associated malignancies is not known. Epstein-Bar virus latency is associated with the expression of a limited set of viral transcripts. The most numerous of these are the EBERs (Epstein-Barr early RNAs). The high copy number of the EBERs in each latently infected cell led the author to combine serial dilution of lymphocytes with reverse transcriptase polymerase chain reaction (RT-PCR) for EBER-1 as a means to rapidly quantitate EBV load. The highest viral load was seen in a bone marrow transplant patient, where one in 3906 lymphocytes harboured EBV. Elevated viral load was seen in two solid-organ transplant patients. Viral loads in healthy volunteers ranged from less than one in 1x10(6) to one in 6.25x10(4). Reverse transcriptase polymerase chain reaction for EBER-1 in serial lymphocyte dilutions should allow the relationship of EBV load and malignancy to be examined in a number of disease settings and should also provide a quantitative picture of the impact of anti-viral therapy.

X linked lymphoproliferative disease in a United Kingdom family

X linked lymphoproliferative disease (XLP; Duncan's disease) is a rare disorder affecting boys and characterised by a defective immune response to Epstein-Barr virus caused by a mutation in a gene located at chromosome Xq25. Three siblings with XLP in a single UK family are reported and the variation in phenotypic expression of the disease in these siblings described. One of the siblings with life threatening fulminant infectious mononucleosis was successfully treated by chemotherapy, followed by bone marrow transplantation using an unaffected brother as the donor. A healthy baby boy recently born into the family was identified as carrying the defective maternal X chromosome using molecular genetic linkage analysis. This family illustrates the extent of present understanding of this often fatal condition.

The implications of Epstein-Barr virus in multiple sclerosis--a review

The objective of this article is to bring together knowledge about Epstein-Barr virus (EBV) in relation to multiple sclerosis (MS) in order to evaluate its implications in this disease. All MS patients are EBV seropositive, but EBV is not normally detected in the brain. EBV can explain many of the epidemiological dogmas known in MS. In addition, other studies point towards the involvement of EBV in MS. Despite this, other co-actors seem also to be involved. We still need to know whether EBV may be an initiating factor in MS or whether it is a factor in the pathogenesis. Possible ways of EBV involvement are discussed: direct involvement, an autoimmune inducing factor or a transactivating factor. A current treatment study of MS patients with a specific herpes antiviral drug may add further information to the etiology and pathogenesis of MS.

Atypical clonal T-cell proliferation in infectious mononucleosis

An atypical case of infectious mononucleosis characterized by fever, acute tonsillitis, and bilateral cervical adenopathy is reported in a previously healthy young man. Although serology was positive for the Epstein-Barr virus, the patient did not display peripheral blood lymphocytosis or atypical, reactive lymphocytes. The patient's tonsilar tissue revealed an expanded T-zone of diffuse, monomorphous lymphocytes suggestive of lymphoma. Immunophenotypic analysis of the tonsilar tissue demonstrated more than 90% expression of pan-T markers, while pan-B markers were positive in 5-10% of the interfollicular T-zone cells and in 90% of germinal centre cells. In situ hybridization with a probe specific for EBER1 demonstrated positive staining in approximately 1% of the interfollicular tonsilar lymphocytes. Finally, Southern blot analysis of tonsilar tissue demonstrated a clonal rearrangement of the T-cell receptor gene. The patient recovered from his infection and remains in good health years after presenting with his illness. This case illustrates that T-cell clonality must be evaluated with caution in the setting of a viral infection and can occur in association with benign, self-limited infectious mononucleosis.

Pathogenesis of chronic Epstein-Barr virus infection: detection of a virus strain with a high rate of lytic replication

In rare cases Epstein-Barr virus (EBV) leads to chronic active infection (CAEBV) which is characterized by persistant symptoms of infectious mononucleosis. Previously we described a case of persisting polyclonal B-cell lymphocytosis (PPBL) that was associated with CAEBV. Using reverse transcription and polymerase chain reaction we showed that in late passages of a spontaneous cell line, SM, latent EB viral genes such as EBNA1, EBNA2, EBNA3A/3B/ 3C, LMP1 and LMP2A were active. The master gene of the lytic cycle, BZLF1, was silent. This indicated that there was no general defect in immortalization and establishing latency by this CAEBV isolate SM. We obtained virus from the standard immortalizing strain B95-8 and the CAEBV strain SM from latently infected LCL quantified the number of virus particles by competitive PCR and demonstrated that the impaired capacity to immortalize umbilical cord blood lymphocytes was a virus strain-specific property, and was not due to an incapability to infect purified CD19+ B lymphocytes. Transcription of latency- and immortalization-associated genes such as EBNA1, EBNA2 and LMP2A was reduced, in contrast to a strongly enhanced activity of the master gene of the lytic cycle, BZLF1. A scenario for an antagonistic regulation of lytic and latent cycle genes is presented and a role for the pathogenesis of CAEBV is discussed.

[X-chromosome recessive lymphoproliferative disease (XLP): molecular genetic studies]

X-linked lymphoproliferative disease (XLP) is a rare worldwide occurring inherited immunodeficiency which is triggered by Epstein-Barr virus infection. Clinical phenotypes in 21 affected males from 5 German families with XLP ranged from severe and fatal infectious mononucleosis (57%) to acquired hypogammaglobulinaemia (28%), malignant lymphoma (28%), aplastic anaemia (19%) and hypergammaglobulinaemia M (19%). Molecular genetic studies with various polymorphic X-chromosomal DNA markers in 14 XLP families mapped the XLP gene locus to Xq25-q26. Haplotype analysis enables detection of XLP-positive and XLP-negative males already before EBV-infection as well as diagnosis of healthy female carriers within XLP families.

Treatment of EBV-induced lymphoproliferative disorder with epipodophyllotoxin VP16-213

A case of haemophagocytic lymphohistiocytosis consistent with X-linked lymphoproliferative disorder is described. Remission was observed after administration of VP-213, a cytotoxic drug generally used to treat histiocytosis. The child is currently in good clinical health.

[X-chromosomal recessively inherited lymphoproliferative syndrome. An analysis of EBV-induced immune deficiency]

In recent years an increasing number of reports have described Epstein-Barr virus (EBV)-induced lymphoproliferative disease, or portrayed EBV as a cofactor in lymphoproliferative diseases (e.g. Hodgkin's disease, Burkitt's lymphoma and nasopharyngeal carcinoma), in the presence of congenital or acquired immune defects. Improved molecular biological and immunological techniques now permit detailed investigation of EBV itself and of the immune system's reaction to EBV infection. Our analysis of X-chromosome-transmitted lymphoproliferative syndrome (XLP), an immune defect that occurs after EBV infection, depicts the whole spectrum of symptoms of EBV-associated diseases, explains various theories regarding pathogenesis, and discusses diagnostic and therapeutic measures.

Primary Epstein-Barr virus infection with clonal T-cell lymphoproliferation

A case of fatal Epstein-Barr virus infection in a previously healthy girl who was first found to have severe infectious mononucleosis with spontaneous recovery is reported. Because an abnormal immune response to the virus persisted, the disease relapsed, manifesting in cutaneous and pulmonary lesions associated with hemophagocytic syndrome responsible for death. Pathologic findings were characterized by polymorphous atypical lymphoid infiltrate, prominent necrosis, and histiocytic hyperplasia. Lymphoid cells displayed CD8 phenotype and clonal T-cell receptor gene rearrangement. Viral genome was detected in lesions by Southern blot and located in nuclei of lymphoid cells by in situ hybridization. Pathologic findings suggested fatal infectious mononucleosis; however, phenotype and genotype favored a malignant diagnosis. Clonality was demonstrated to have arisen during primary infection. Virologic examination indicated that Epstein-Barr virus was a causative agent. Such a process belongs to the recently recognized spectrum of Epstein-Barr virus-related T-cell lymphoproliferative disorders that might overlap fatal infectious mononucleosis in patients who are especially vulnerable to the virus.

Infectious mononucleosis. Diagnosis by in situ hybridization in two cases with atypical features

Two cases of infectious mononucleosis are reported in which in situ hybridization studies were of use to distinguish this disorder from non-Hodgkin's lymphoma. One patient was an 80-year-old man with a tonsillar mass that histologically resembled non-Hodgkin's lymphoma and, on fixed tissue immunohistochemistry, appeared to contain a population of cells anomalously coexpressing the B-cell marker L26 and the T-cell marker Leu-22, suggesting diffuse large-cell non-Hodgkin's lymphoma. The second patient was a 43-year-old woman with inguinal lymphadenopathy that, on histologic examination, also mimicked diffuse large-cell lymphoma. In situ hybridization studies for Epstein-Barr virus revealed both cases to possess EBV DNA in a pattern characteristic of infectious mononucleosis. In addition, in situ hybridization studies for immunoglobulin light-chain mRNA demonstrated a polyclonal pattern of kappa and lambda mRNA expression. This report demonstrates the utility of the in situ hybridization technique as an adjunct to routine diagnosis.

Oligoclonal T cell receptor gene rearrangements in blood lymphocytes of patients with acute Epstein-Barr virus-induced infectious mononucleosis

Gene rearrangement studies were performed on blood lymphocytes from eight patients with acute Epstein-Barr virus-induced infectious mononucleosis. The diagnosis in each case was based on characteristic clinical, hematologic, and serologic findings. The blood lymphocytes in each patient consisted predominantly of CD8+ T cells. EBV DNA was detected in seven patients by Southern blot analysis (EBV Bam HI W probe, Bam HI). A germline configuration was found for the immunoglobulin heavy and light chain genes (JH probe, Bam HI and Eco RI; C kappa probe, Bam HI; and C lambda probe, Eco RI). T cell receptor gene rearrangements were detected with J gamma and J beta 1 + 2 probes. Using a J gamma probe with two different restriction enzymes (Bgl II and Eco RI), the blood from each patient showed several bands corresponding to the polyclonal pattern previously described in the blood of normal individuals. Using J beta 1 + 2 probes with two different restriction enzymes (Bgl II and Bam HI), each case showed from 3 to about 12 extragermline bands of varying intensity and in different locations from case to case. In addition, each case showed relative deletion of the J beta 1 germline band. This oligoclonal pattern of T cell receptor gene rearrangements has not been previously reported in benign or malignant T cell populations.

Detection of Epstein-Barr virus genomes in archival tissues by polymerase chain reaction

We used oligonucleotide primers designed from DNA sequences unique to the long internal direct repeated region of Epstein-Barr virus (EBV) to enzymatically amplify this segment of the EBV genome in formalin-fixed, paraffin-embedded tissues. The products amplified from EBV templates were detected by hybridization with a labeled probe specific for this highly conserved, reiterated region. Epstein-Barr virus-related sequences were detected in the spleen of a patient with infectious mononucleosis, in lung and lymph node specimens from a patient with pulmonary manifestations of infectious mononucleosis, in various tissues from seven immunosuppressed organ transplant recipients with immunoproliferative disorders, and in small biopsy specimens from a patient with nasopharyngeal carcinoma. No viral sequences were detected in 20 histologically normal spleens or 10 lymph nodes. Polymerase chain reaction technology provides an effective means for documenting EBV infection in archival tissues. This approach should facilitate the diagnosis of posttransplant lymphoproliferative disorders and difficult cases of infectious mononucleosis and nasopharyngeal carcinoma.

Identification of Epstein-Barr virus-infected cells in tonsils of acute infectious mononucleosis by in situ hybridization

In situ hybridization with 35S-labeled Epstein-Barr virus (EBV) probes was applied to paraffin sections of tonsils from seven patients with clinical, serologic, and morphologic evidence of acute infectious mononucleosis. EBV genomes were demonstrated in activated lymphoid B blasts in the interfollicular and perifollicular zones in all these cases. However, in no case could EBV be identified in epithelial cells. These results are at variance with the current concept which attributes a central role to the tonsillar epithelium in primary EBV infection.

In situ demonstration of Epstein-Barr viral genomes in viral-associated B cell lymphoproliferations

Thirteen cases of benign and malignant Epstein-Barr viral (EBV)-associated B cell lymphoproliferations were examined by in situ hybridization studies performed on formalin-fixed, paraffin-embedded tissue sections. EBV nucleic acids were identified in a minority of lymphoid cells in five of six cases of benign infectious mononucleosis studied in tonsil or lymph node specimens. No evidence of EBV was found in two splenectomy specimens from patients with infectious mononucleosis. EBV nucleic acids were identified in one case of fatal, infectious, mononucleosislike immunoblastic proliferation, and were especially concentrated in areas where there were sheets of immunoblasts associated with necrosis. EBV nucleic acids were identified in all four cases of EBV-associated post-transplant lymphoproliferations, including three cases of non-Hodgkin's lymphoma in which a majority of the neoplastic cells contained EBV nucleic acids.

The analysis of EBV proteins which are antigenic in vivo

We have used small random EBV B95-8 DNA fragments to generate a large genomic bank in a plasmid expression vector. This bank was screened with a pool of sera from individuals with IM thus allowing any EBV antigen which evoked an immune response in man to be identified. The characterization of four immunopositive clones obtained in this way is presented in this study. Three of these clones express viral ORF DNA sequences which are parts of larger ORFs in the BamH1 N(het), V and X regions of the B95-8 viral genome. cDNA cloning has been used to confirm that the cloned sequences from BamH1 N and V are expressed in cell culture and to identify the transcription units involved. The fourth clone expresses an ORF sequence located in the viral BamH1 F fragment in a region not previously recognized as having protein coding potential. The experimental design used here must reflect the situation in vivo and consequently these sequences must be expressed and be antigenic during IM.