Epstein-Barr virus-associated T-/natural killer cell lymphoproliferative diseases

Epstein-Barr virus (EBV) is a ubiquitous virus that infects the majority of the world population by adulthood. The major target for infection is the B lymphocyte, and acute infection causes vigorous EBV-specific killer T-cell responses exemplified clinically by acute infectious mononucleosis (IM). EBV infection usually persists latently life-long without eliciting any clinical symptoms. Rarely, active EBV infection is prolonged, with abnormal expansions of EBV-infected T or NK cells, conditions collectively defined here as EBV-associated T/NK lymphoproliferative diseases. Hemophagocytic lymphohistiocytosis (HLH), chronic active EBV infection (CAEBV), NK lymphoma/leukemia, and T-cell lymphoma are entities included in this category. Hypersensitivity to mosquito bite (HMB) represents a unique syndrome characterized by expansion of EBV-infected NK cells in the peripheral circulation and within the inflammatory skin lesions induced by mosquito bites. Target cell specificity, defects in host immune responses, and strain differences of EBV may account for ectopic EBV infections and for the unique clinical presentations characteristic of each illness.     

Persistent epstein-barr virus infection mimicking juvenile chronic myelogenous leukemia: immunologic and hematologic studies

Epstein-Barr virus (EBV) infections may induce a diverse clinical picture, ranging from the well characterized infectious mononucleosis (IM) syndrome to the rare X-linked lymphoproliferative syndrome. We describe two unrelated children, a 21-mo-old white boy and a 15-mo-old black girl, who presented with the clinical and laboratory findings characteristically seen in juvenile chronic myelogenous leukemia (JCML). Results of periodic serodiagnostic tests indicated that they likely have persistent infection with EBV. Both had elevated IgG antibody to viral capsid antigen (greater than or equal to 1:320) and antibody to early antigen (1:20-1:40) that have persisted for 3 yr of more. Both patients had EBV-specific suppressor cell activity, decreased natural killer cell activity, and diminished antibody- dependent cell-mediated cytotoxicity (ADCC) activity. These changes suggest an underlying defect in the immunoregulatory network controlling EBV infection. The patients have shown clinical improvement without treatment. It appears that EBV infections are capable of inducing symptoms similar to those seen in JCML. Careful evaluation for evidence of EBV infection in patients presenting with symptoms compatible with JCML seems warranted.     

A boy with fatal infectious mononucleosis suspected as the first Japanese case of X-linked lymphoproliferative syndrome

We report a case of a 10-month-old boy who died of severe hepatic failure after a prolonged course of infectious mononucleosis. He also presented interstitial pneumonitis, meningoencephalitis and aplastic anaemia. Epstein-Barr virus (EBV)-specific cytotoxic T lymphocyte (CTL) activity had not been detected in his peripheral blood during the course of the illness. Studies of his mother revealed a severe reactivation pattern of anti-EBV antibodies and decreased EBV-specific CTL activity. An X-linked familial susceptibility to EBV infection such as X-linked lymphoproliferative syndrome (XLP) might be associated with his fatal EBV infection.     

Quantitative analysis of Epstein-Barr virus (EBV)-specific CD8+ T cells in patients with chronic active EBV infection

To clarify the pathogenesis of chronic active Epstein-Barr virus (EBV) infection, EBV-specific CD8+ T cells were enumerated, by use of human leukocyte antigen (HLA)-A*2402-restricted tetramers, in 8 patients with chronic active EBV infection, 10 patients with infectious mononucleosis, and 16 EBV-seropositive healthy control subjects. In most of the patients with chronic active EBV infection, EBV-specific CD8+ T cells were not detected. Of note, latent membrane protein 2-specific CD8+ T cells were not detectable in any patients with chronic active EBV infection. In contrast, EBV-specific CD8+ T cells were detected in patients with infectious mononucleosis and in healthy control subjects. Low frequencies of EBV-specific CD8+ T cells may be one of the immunological features of chronic active EBV infection.     

Immunological aspects of Epstein-Barr virus infection

Epstein-Barr virus (EBV) is a member of ubiquitous gamma herpes viruses, which primarily induces acute infectious mononucleosis (IM) or subclinical infection in susceptible subjects. The host reactions account for the clinical manifestation of IM. This virus also contributes to the development of lymphoid or epithelial malignancies. The outgrowth of EBV-infected B-cells is first controlled by interferon (IFN)-gamma and natural killer (NK) cells, and later by EBV-specific cytotoxic T-lymphocytes (CTL). To overcome the host responses and establish the persistent infection, EBV conducts the protean strategies of immune evasion. Several EBV genes modulate apoptotic signals and cytokine balances to persist B-cell infection without insulting the host. Uncontrolled lymphoproliferation occurs as EBV(+) B-cell lymphoproliferative disease (LPD)/lymphoma in AIDS, posttransplant, or primary immunodeficiency diseases (PID). On the other hand, EBV(+) T/NK cells are involved in EBV-associated hemophagocytic lymphohistiocytosis (EBV-HLH) or chronic active EBV infection (CAEBV) in children having no underlying immunodeficiencies, and at times lead to the clonal evolution of T/NK-cell LPD/lymphomas. Recent advance in molecular techniques has enabled us to analyze the clonality of EBV-infected lymphocytes and to quantify the gene expression of EBV and cytokines. Dominant autocrine loop of T helper (Th) 2 and Th1 may exert in EBV(+) B-LPD and T-LPD, respectively. Intensive studies on the immunological interface between effector components and EBV(+) target cells will provide more information on clarifying the pathogenesis of EBV-associated lymphoid malignancies, as well as on exploiting the therapeutic and preventive strategies for the formidable EBV-associated disease in childhood.     

Progressive telomere shortening of Epstein-Barr virus-specific memory T cells during HIV infection: contributor to exhaustion?

Individuals infected with human immunodeficiency virus (HIV) have low numbers of functional Epstein-Barr virus (EBV)-specific CD8+ T cells in the face of a high EBV load, suggesting that these cells have become exhausted. We investigated whether the observed chronic EBV loads during HIV infection could cause exhaustion of EBV-specific T cells by using flow-FISH (flow cytometry in combination with fluorescence in situ hybridization) to analyze the telomere length of EBV-specific CD8+ T cells. Enhanced telomere shortening of EBV-specific T cells was observed during HIV infection, compared with the decline in telomere length observed in the CD8+ T cells of healthy subjects. Thus, chronic exposure to high antigen levels may lead to the progressive shortening of telomeres of antigen-specific T cells, which may impair viral control.     

EBV-associated mononucleosis leads to long-term global deficit in T-cell responsiveness to IL-15

In mice, interleukin-7 (IL-7) and IL-15 are involved in T-cell homeostasis and the maintenance of immunologic memory. Here, we follow virus-induced responses in infectious mononucleosis (IM) patients from primary Epstein-Barr virus (EBV) infection into long-term virus carriage, monitoring IL-7 and IL-15 receptor (IL-R) expression by antibody staining and cytokine responsiveness by STAT5 phosphorylation and in vitro proliferation. Expression of IL-7Ralpha was lost from all CD8+ T cells, including EBV epitope-specific populations, during acute IM. Thereafter, expression recovered quickly on total CD8+ cells but slowly and incompletely on EBV-specific memory cells. Expression of IL-15Ralpha was also lost in acute IM and remained undetectable thereafter not just on EBV-specific CD8+ populations but on the whole peripheral T- and natural killer (NK)-cell pool. This deficit, correlating with defective IL-15 responsiveness in vitro, was consistently observed in patients up to 14 years after IM but not in patients after cytomegalovirus (CMV)-associated mononucleosis, or in healthy EBV carriers with no history of IM, or in EBV-naive individuals. By permanently scarring the immune system, symptomatic primary EBV infection provides a unique cohort of patients through which to study the effects of impaired IL-15 signaling on human lymphocyte functions in vitro and in vivo.     

Epstein-Barr virus infections in families: the role of children with infectious mononucleosis

We performed a prospective evaluation of Epstein-Barr virus (EBV) infections in 78 families with a childhood index case of EBV-infectious mononucleosis (EBV-IM). During the acute index episode, adult family (household) contacts, compared with control adults, had a greater rate of oropharyngeal EBV excretion and high serum antibody responses, which suggested a recent antecedent reactivation of an old EBV infection. The increased prevalence of oropharyngeal EBV and acute serological responses found in sibling family contacts during the early surveillance period suggested that these contacts had experienced an increased rate of primary-type EBV infections shortly before or concurrent with the index case. Although nonimmune sibling contacts seroconverted at a slow rate, five of nine manifested IM with their eventual documented primary EBV infection. This study noted significant intrafamilial EBV activity surrounding an episode of childhood EBV-IM. Reactivation of an old EBV infection in adults may be an important source of virus for susceptible children within these families. Siblings of a childhood case of EBV-IM appear to be at increased risk for manifesting IM with their primary EBV infection.     

Differences in EBV-specific antibody patterns at onset of infectious mononucleosis

The EBV-specific antibody patterns of infectious mononucleosis (IM) patients were analyzed in relation to the onset of symptoms and clinical parameters during the acute phase of the disease. The antibody patterns varied considerably on admission. Three groups of patients were identified: one had not yet attained peak antibody titers, the second was at the peak and the third had passed the peak pattern. Patients with a "peak" current pattern had significantly higher lymphocyte counts, ASAT, ALAT, serum IgG and serum IgA concentrations than patients of the third group. Unexpectedly, there was no difference between the groups with regard to duration of sore throat and general malaise before admission. It thus seems that the lymphocyte proliferation during IM closely parallels the course of the EBV-specific antibody responses, whereas the onset of IM does not closely correlate to a specific stage of the antibody pattern.     

Exposure to holoendemic malaria results in suppression of Epstein-Barr virus-specific T cell immunosurveillance in Kenyan children

BACKGROUND: Malaria and Epstein-Barr virus (EBV) infection are cofactors in the pathogenesis of endemic Burkitt lymphoma (eBL). The mechanisms by which these pathogens predispose to eBL are not known. METHODS: Healthy Kenyan children with divergent malaria exposure were measured for responses to EBV latent and lytic antigens by interferon (IFN)- gamma enzyme-linked immunospot (ELISPOT) assay and interleukin (IL)-10 ELISA. Phytohemagglutinin (PHA), purified protein derivative (PPD), and T cell epitope peptides derived from merozoite surface protein (MSP)-1, a malaria blood-stage antigen, were also evaluated. RESULTS: Children 5-9 years old living in an area holoendemic for malaria had significantly fewer EBV-specific IFN- gamma responses than did children of the same age living in an area with unstable malaria transmission. This effect was not observed for children <5 years old or those >9 years old. In contrast, IFN- gamma responses to PHA, PPD, and Plasmodium falciparum MSP-1 peptides did not significantly differ by age. IL-10 responses to EBV lytic antigens, PPD, and PHA correlated inversely with malaria exposure regardless of age. CONCLUSIONS: Children living in malaria-holoendemic areas have diminished EBV-specific T cell immunosurveillance between the ages of 5 and 9 years, which coincides with the peak age incidence of eBL.     

IgA antibodies to Epstein-Barr virus in infectious mononucleosis

The IgA anti-EBV (Epstein-Barr virus) response during the course of IM (infectious mononucleosis) was investigated. The IgA anti-VCA (viral capsid antigen) response was found not to be restricted to the early acute phase of the EBV infection as is the IgM anti-VCA response. Some patients with normal total serum IgA levels did not respond with measurable EBV specific IgA. These patients and those with low titers of IgA anti-VCA had shorter duration of sore throat than responders with high titers indicative of a strong correlation between the IgA anti-VCA titers and the duration of sore throat. In this way the EBV specific IgA response is unique since recent observations show that local oropharyngeal symptoms during IM appear poorly synchronized with the IgM and the IgG antibody responses. As EB virus is excreted into the oropharynx during IM, antigens are available for local EBV immunization. The results of the present study imply a possible local immunization process as a positive correlation was found between serum IgA anti-VCA and total salivary IgA.     

Human infant respiratory syncytial virus (RSV)-specific type 1 and 2 cytokine responses ex vivo during primary RSV infection

BACKGROUND: Respiratory syncytial virus (RSV) infection is the most common respiratory viral infection resulting in hospitalizations in infants worldwide. Illness severity is likely multifactorial; however, unlike other viral infections, both type 1 and type 2 cytokine responses have been implicated in severe disease. METHODS: We measured RSV-specific cytokine responses ex vivo during primary RSV infection in the blood of 18 infants with polymerase chain reaction-confirmed RSV infection. To focus on primary RSV infection, subjects were all<9 months old. RSV-specific cytokine responses were measured at 3 time points during acute primary RSV infection and at 1 memory time point 3-6 months later. RESULTS: RSV-specific interferon (IFN)- gamma responses were detected in 10 of 18 of infants. Infants with mild disease had higher RSV-specific IFN- gamma memory responses than did those with moderate or severe disease. No consistent correlations between RSV-specific IFN- gamma responses and corticosteroid administration were observed. RSV-specific interleukin (IL)-4 or IL-5 responses to primary RSV infection were detectable in 5 of 18 and 8 of 15 infants, respectively. CONCLUSIONS: During primary RSV infection, many infants demonstrated RSV-specific IFN- gamma responses. The strongest IL-4 and IL-5 responses were detected in 3 infants with severe disease, suggesting that type 2 responses may contribute to the pathogenesis of severe disease.     

Persistently high Epstein-Barr virus (EBV) loads in peripheral blood lymphocytes from patients with chronic active EBV infection

Chronic active Epstein-Barr virus infection (CAEBV) is a severe illness with unusual EBV activation that persists for years, and its pathogenesis is largely unknown. After the creation of an accurate and reproducible polymerase chain reaction system to quantify EBV DNA, virus loads in peripheral blood lymphocytes (PBL) were determined in 54 children: 15 with CAEBV, 16 with infectious mononucleosis (IM), and 23 healthy children. Children with CAEBV and those with IM had high virus loads. Lower loads were detected in 47% of seropositive healthy donors. There were two distinct differences between children with CAEBV and those with IM: The former had greater viral replication (10(3)-10(7) copies/2.5x10(5) PBL) than those with IM, and viral replication declined in children with IM whereas active replication persisted for years in subjects with CAEBV. Persisting high virus loads are a possible diagnostic criterion for CAEBV. EBV loads may enable classification and prognosis of EBV infections.     

Antibody responses to Epstein-Barr virus-determined nuclear antigen (EBNA)-1 and EBNA-2 in acute and chronic Epstein-Barr virus infection.

Five distinct Epstein-Barr virus (EBV)-determined nuclear antigens (EBNA-1 to EBNA-5) were recently identified. Antibody responses to these antigens could conceivably differ, and thus prove of serodiagnostic value, in EBV-associated disease processes. As a first step, murine or human cell lines transfected with appropriate EBV DNA fragments and stably expressing either EBNA-1 or EBNA-2 were used to determine the frequency and time of emergence of antibodies to these two antigens in the course of acute and chronic infectious mononucleosis (IM) and to assess their titers in so-called chronic active EBV infections. Following IM, antibodies to EBNA-2 arose first and, after reaching peak titers, declined again in time to lower persistent or even nondetectable levels. Antibodies to EBNA-1 emerged several weeks or months after anti-EBNA-2 and gradually attained the titers at which they persisted indefinitely. The ratios between the anti-EBNA-1 and anti-EBNA-2 titers therefore were generally well below 1.0 during the first 6-12 months after IM and turned to well above 1.0 during the second year. In clear cases of chronic IM, the inversion of this ratio was delayed or prevented. In the less well-defined chronic EBV infections, low ratios were observed in only some of the patients. Because many of these illnesses were not ushered in by a proven IM and often showed EBV-specific antibody profiles within the normally expected range, a causal role of the virus in these cases remains doubtful.     

Dysfunctional Epstein-Barr virus (EBV)-specific CD8(+) T lymphocytes and increased EBV load in HIV-1 infected individuals progressing to AIDS-related non-Hodgkin lymphoma.

Acquired immunodeficiency syndrome-related non-Hodgkin lymphomas (AIDS-NHL) are thought to arise because of loss of Epstein-Barr Virus (EBV)-specific cellular immunity. Here, an investigation was done to determine whether cellular immunity to EBV is lost because of physical loss or dysfunction of EBV-specific cytotoxic T cells. Data on EBV-specific cellular immunity were correlated with EBV load. For comparison, individuals who progressed to AIDS with opportunistic infections (AIDS-OI) and long-term asymptomatics (LTAs) were studied. The number of virus-specific T cells was detected using tetrameric HLA-EBV-peptide complexes; function of these EBV-specific T cells was determined using the interferon-gamma (IFN-gamma) Elispot assay. It was observed that EBV-specific CD8(+) T cells were present in normal numbers in human immunodeficiency virus (HIV)-infected individuals. However, their functional capacity was decreased compared with HIV(-) individuals. In AIDS-NHL patients, EBV-specific T cells were not physically lost in the course of HIV-1 infection but showed progressive loss of their capability to produce IFN-gamma in response to EBV peptides. This loss of function correlated with lower CD4(+) T-cell numbers and was accompanied by increasing EBV load. In HIV-1-infected LTA individuals, in whom CD4(+) T-cell numbers were maintained, and progressors to AIDS-OI, IFN-gamma-producing EBV-specific T cells were stable and EBV load remained stable or decreased in the course of HIV infection, suggestive of immune control. Our data indicate that functional loss of EBV-specific CD8(+) T cells with a concomitant increase in EBV load may play a role in the pathogenesis of AIDS-NHL.     

Clinical effects of infusing anti-Epstein-Barr virus (EBV)-specific cytotoxic T-lymphocytes into patients with severe chronic active EBV infection

Immune cell therapy with autologous Epstein-Barr virus (EBV)-specific cytotoxic T-lymphocytes (CTLs) or lymphokine-activated killer (LAK) cells was performed in 2 adults with severe chronic active EBV infection (SCAEBV). The patient in case 1, who had complications of pancytopenia, high fever, and massive splenomegaly, was treated with 13 doses of LAK cell infusion followed by 4 doses of autologous CTL infusion. The patient in case 2, who had liver dysfunction due to natural killer cell-type infection, was treated with 4 doses of autologous CTL infusion. In case 1, the LAK cell infusions were effective in lowering the viral load and improving several biochemical parameters (lactate dehydrogenase, soluble interleukin 2 receptor) and resulted in complete amelioration of the high fever. Subsequent infusions of autologous CTLs reduced the viral load only temporarily and were accompanied by an increase in frequency of EBV-specific T-cells in the blood. However, the patient's main problem of pancytopenia was not resolved. In case 2, infusion of autologous CTLs did not improve the patient's hepatic dysfunction or viral load but caused a significant increase in autoantibody levels. Thus the effect of auto-CTL treatment was limited or deteriorative in SCAEBV patients.     

Chronic Epstein-Barr virus-related hepatitis in immunocompetent patients

INTRODUCTION Epstein-Barr virus (EBV) infects more than 90% of humans by the time of adulthood and persists as a life- long latency, suggesting sophisticated mechanisms for effective immune evasion. Primary EBV infection is usually asymptomatic or results…     

Primary infection with Epstein-Barr virus in a 77-year-old patient with B symptoms and hepatitis -- a case report

Epstein-Barr virus (EBV) infection has a prevalence of 90 % and is - depending on the immune status of the host - associated with a broad spectrum of clinical manifestations. By presenting a case report we would like to demonstrate an unusual clinical course of a primary infection with EBV in an elderly patient. A 77-year-old patient was admitted to hospital in reduced health condition because of a persisting bronchopulmonary infection with B symptoms. The patient had already been treated with antibiotics. Because of elevated liver enzymes, a liver biopsy was performed. Histopathology revealed moderate acute hepatitis with cholangitis und endothelialitis, pointing to an EBV-induced hepatitis. Serological examinations confirmed the diagnosis, revealing a primary infection with positive EBV VCA IgM and IgG. EBV PCR of the liver tissue was positive, viral genome could be demonstrated within lymphocytes. A short period later the patient was discharged to reconvalescence. This case report demonstrates an unusual primary infection with EBV at the age of 77 with atypical clinical symptoms and hepatitis. The relevance of EBV in the differential diagnosis of atypical infectious diseases with hepatitis of unknown aetiology is strengthened on taking data reports from the literature into consideration.     

The immune response to primary EBV infection: a role for natural killer cells

The role of antigen-specific CD3(+)CD8(+) cytotoxic T cells in the control of primary Epstein-Barr Virus (EBV) infection is well established. However, time is required for the antigen-specific immune response to develop and expand. In contrast, innate immune responses, such as natural killer (NK) cells, are considered vital early in the infection process. We analysed the scale, phenotype and function of the NK cell response during symptomatic primary EBV infection, infectious mononucleosis (IM) and showed that NK cell numbers were significantly elevated both at diagnosis of IM and in the first month following diagnosis. There were also significant changes in cell phenotype and function, an increase in the proportion of CD56(bright) cells at diagnosis, and freshly isolated cells showing an enhanced ability to kill EBV-infected cell lines. Moreover, in our cohort of IM patients higher NK cell counts were associated with significantly lower viral load in peripheral blood. Our results suggest NK cells have an important role in the control of primary EBV infection by eliminating infected B cells and augmenting the antigen-specific T cell response via release of immunomodulatory cytokines. The magnitude of the NK cell response may ultimately determine whether primary EBV infection has a clinical outcome.     

A case of severe chronic active infection with Epstein-Barr virus: immunologic deficiencies associated with a lytic virus strain.

Infectious mononucleosis (IM) is a self-limiting, lymphoproliferative disease induced by primary infection with the Epstein-Barr virus (EBV). Infection with EBV leads in general to lifelong asymptomatic persistence of the virus. We report the case of a woman who acquired IM at the age of 15 years and then suffered from recurrent high fever, fatigue, and signs of immunologic disorder for more than 12 years until she died of liver failure. In an attempt to describe and to define the course of chronic active infection with EBV, we performed immunologic and molecular assays that demonstrated lytic replication of EBV in the B and T cells of the peripheral blood. In addition to signs of humoral and cellular immune deficiency, we detected an EBV strain with an impaired capability to immortalize B cells and a tendency to lytic replication, thus contributing to the pathogenesis of this chronic active infection.