Jeffrey I. Cohen

Herpesvirus Saimiri encodes a new cytokine, IL-17, which binds to a novel cytokine receptor

Herpesvirus Saimiri gene 13 (HVS13) exhibits 57% identity with the predicted sequence of a T cell-derived molecule termed CTLA8. Recombinant HVS13 and CTLA8 stimulate transcriptional factor NF-kappaB activity and Interleukin-6 (IL-6) secretion in fibroblasts, and costimulate T cell proliferation. An HVS13.Fc fusion protein was used to isolate a cDNA encoding a novel receptor that also binds CTLA8. This receptor is unrelated to previously identified cytokine receptor families. A recombinant soluble receptor inhibited T cell proliferation and IL-2 production induced by PHA, concanavalin A (conA), and anti-TCR MAb. These results define CTLA8 and HVS13 as novel cytokines that bind to a novel cytokine receptor. We propose to call these molecules IL-17, vIL-17, and IL-17R, respectively.

Expression of Epstein–Barr Virus Transformation–Associated Genes in Tissues of Patients with EBV Lymphoproliferative Disease

Epstein-Barr virus (EBV) has been associated with serious or fatal lymphoproliferative disease in immunocompromised patients. EBV nuclear protein 2 and latent membrane protein are characteristically expressed in B lymphocytes proliferating in vitro in response to growth transformation by EBV. These two proteins are thought to be effectors of lymphocyte growth since they increase the expression of B-lymphocyte activation (CD23) and cell-adhesion (LFA 3 and ICAM 1) molecules in vitro. Using monoclonal antibody-immune microscopy, we have demonstrated that these two EBV proteins and their associated B-lymphocyte activation or adhesion molecules are expressed in the infiltrating B lymphocytes in immunocompromised patients with EBV lymphoproliferative disease. These monoclonal antibodies should be useful in the early diagnosis of EBV lymphoproliferative disease and in distinguishing it from other B-lymphocyte cancers associated with EBV, such as Burkitts lymphoma. The finding of EBV nuclear protein 2 and latent membrane protein and their associated activation or adhesion molecules provides a further pathophysiologic link between EBV and the proliferation of B lymphocytes in immunocompromised patients.

Epstein-Barr Virus Infections: Biology, Pathogenesis, and Management

Dr. Stephen E. Straus (Medical Virology Section, Laboratory of Clinical Investigation, National Institute of Allergy and Infectious Diseases [NIAID], National Institutes of Health [NIH], Bethesda, Maryland): Epstein-Barr virus (EBV) is a ubiquitous pathogen that has evolved an effective strategy for infection, persistence, and spread; EBV infection occurs in more than 90% of the population, most often without evident consequences [1, 2]. The clinical outcome of infection rests on the compromise struck between the virus and the hosta fragile interplay of competing forces. Epstein-Barr virus, for its part, unswervingly pursues a genetic mission to infect B lymphocytes, to endow them with an endless potential to pass the virus on to their progeny, and to do so while evading immune clearance. The host response is less predictable and determines whether an EBV infection becomes symptomatic. An ineffectual response, which occurs in persons with congenital or acquired immunodeficiency, permits the unbridled proliferation of virus-infected B cells. In contrast, the curious predilection of adolescents and adults to experience symptomatic infection and the features of the mononucleosis syndrome that ensues suggests that an excessive host response to EBV can also lead to illness. The biology of EBV, the diseases it provokes, the nature of the virus-host interaction and how it is controlled or subverted, and the limited means available to manage EBV infections are the subjects of this conference. Epidemiology The paradigmatic disease associated with EBV is infectious mononucleosis. The description and epidemiology of infectious mononucleosis predated by decades the recognition of EBV as its dominant cause; cytomegalovirus, human immunodeficiency virus (HIV), and Toxoplasma gondii are infrequent causes of mononucleosis-like illness [3, 4]. Infectious mononucleosis occurs at all ages, but most cases occur during adolescence and early adulthood [5]. It is now understood that the restricted age distribution of infectious mononucleosis is delimited at the lower end by the greater capacity of children to resolve a primary EBV infection with few or no symptoms. Although adults do not handle EBV as well as children, by the age of 25 years most are already seropositive and not susceptible to reinfection. In developing countries, EBV infection occurs early in life. Nearly the entire population of a developing country becomes infected before adolescence. Thus, symptomatic infectious mononucleosis is uncommon in such countries. In areas with high standards of hygiene, such as the United States and western Europe, where EBV infection may be delayed until adulthood, infectious mononucleosis is more prevalent. The increase in the incidence of infectious mononucleosis with improved sanitary conditions may explain why this disease was not described until the latter half of the nineteenth century [3]. Mononucleosis-like infections may occur more than once, but such episodes are generally not caused by a resurgence of viral activity. Reactivation disease appears exclusively in transplant recipients and similarly impaired persons [6]; there has never been a confirmed case of symptomatic reactivation EBV disease in a healthy person. Most serial mononucleosis-like episodes are caused by sequential infections with different pathogens. Thus, EBV infection stands in stark contrast to other herpesvirus infections, which have a definite proclivity toward recurrences. Salivary tissues are the recognized repositories of EBV, and periodic shedding from such tissue is a necessary feature of this viruss biology. Shedding is sustained for months after infection and then falls gradually; in 15% to 20% of all attempts, the virus can be recovered from saliva [7]. Immune compromise in transplant recipients and patients with the acquired immunodeficiency syndrome (AIDS) leads to higher rates of shedding (average, 50% to 80%) [8]. Evidence of the viruss presence in cervical epithelium and semen has emerged, but sexual transmission has not been proved [9]. Exchange of saliva would appear sufficient to explain EBV transfer to partners and the corresponding difficulty of transmitting this virus in the home, in the hospital, or in other confined quarters where the issue has been carefully examined [5, 10]. The virus can be transmitted to susceptible recipients by blood transfusion or bone marrow transplantation [11, 12], but such transmission is rare. Studies of natural or experimental transmission of infectious mononucleosis documented an incubation period of 3 to 7 weeks [13]. Clinical Spectrum Infectious Mononucleosis The classic syndrome of mononucleosis is defined as a clinical triad of fever, pharyngitis, and adenopathy [14], although many other symptoms and signs also occur (Table 1). The diagnosis of acute EBV infectious mononucleosis is based on clinical presentation and supportive laboratory findings, including an absolute lymphocytosis in which more than 10% of cells are atypical, as well as heterophile antibody titers of at least 1:56 by the traditional Paul-Bunnell-Davidsohn test or positive rapid slide assays such as the Mono-Latex test (Wampole Laboratories, Cranbury, New Jersey) [15]. About 93% of patients who fulfill the above criteria have primary EBV infection; if the criteria are relaxed, the proportion decreases [16]. Table 1. The Most Common Symptoms and Signs of Infectious Mononucleosis* The fortuitous discovery in 1967 that EBV causes infectious mononucleosis led quickly to the development of virus-specific antibody tests that, despite broad misunderstanding and overinterpretation, remain useful serologic tools, primarily for the diagnosis of primary illness but also as adjuncts in the evaluation of chronic or malignant sequelae of EBV infection (Table 2) [4, 17]. Table 2. Serologic Responses of Patients with Epstein-Barr Virus-associated Diseases Immunoglobulin M antibodies to the EBV viral capsid antigen (anti-VCA) evolve quickly with infection, persist for weeks to months, and do not reappear. Thus, their detection is presumptive evidence of recent primary infection. Analysis of paired acute and convalescent sera shows a rise, a subsequent fall, and a lifelong persistence of IgG anti-VCA, usually in titers ranging from 1:40 to 1:2560. Measurement of IgA anti-VCA is not useful except in the diagnosis and management of nasopharyngeal carcinoma. Antibodies to viral early (pre-DNA synthesis) antigens (anti-EA) of the diffuse or restricted types develop in most primary infections, peak in titers of less than 1:640, and wane with time. They persist frequently enough, though, that their presence in low titers is of no diagnostic significance [18]. Antibodies to EBV nuclear antigen (anti-EBNA) are detected in traditional assays relatively late after the onset of symptoms in infectious mononucleosis, so that their absence in a previously well person who develops acute illness suggests an ongoing EBV infection. The EBV-specific serologic tests were all originally done by immunofluorescence microscopy. The titers discussed above apply only to those assays. Newer tests involving enzyme-linked techniques, Western blots, or other immunoassays yield results that are not directly comparable to these standard methods. Moreover, even for a given assay, performance standards differ considerably from laboratory to laboratory, making the scrutiny of results acquired at different times in different places a fruitless exercise. Infectious mononucleosis is, with rare exceptions, a self-limited disease. Adenopathy or splenomegaly can persist for weeks and provoke some anxiety about their cause, but unless symptoms or signs progress well beyond the period of the acute illness, further workup is not warranted. Primary EBV infections, with or without the features of infectious mononucleosis, have many recognized complications (Table 3) that fall into various categories mostly dependent on immunopathologic responses to the virus. Ominous complications such as severe autoimmune hemolysis, airway obstruction from grossly enlarged tonsils, splenic rupture, and encephalitis, among others, are seen in otherwise healthy patients. Agranulocytosis, aplastic anemia, and other rare but grave features of acute, progressive EBV infection can arise in healthy patients but may indicate a demonstrable deficiency of cellular immunity [19]. Table 3. Complications of Infectious Mononucleosis Lymphoproliferative Disorders Many EBV-associated lymphoproliferative lesions are recognized in persons with congenital or acquired cellular immune deficiency [20]. X-linked lymphoproliferative disease is a rare disorder of young boys who develop fulminant mononucleosis after EBV infection. The disease is characterized by B- and T-cell infiltration of organs with displacement of bone marrow elements [21]. Over two thirds of affected patients die of hemorrhage or infection within weeks, and 100% die by 40 years of age. Survivors of the acute infection experience aplastic anemia, hypo-or hypergammaglobulinemia, opportunistic infections, or lymphomas. Epstein-Barr virus-associated lymphoproliferative disease also occurs in 1% to 3% of bone marrow, kidney, or liver transplant recipients. About 5% to 10% of heart or heart-lung transplants have developed EBV-associated B-cell tumors [20]. The marked degree of immunosuppression in these patients may allow outgrowth of EBV-infected B cells, resulting in lymphoproliferative lesions. The reversal of some of these lesions after a reduction in immunosuppressive therapy emphasizes the role of the immune system in controlling EBV infection in the normal host. In transplant recipients, as well as in patients with AIDS, EBV-associated B-cell tumors may have either polyclonal, monoclonal, or mixed phenotypes. Death from progressive expansion of tumors, immunodeficiency, and opportunistic infections is frequent. Chronic infectious mononucleosis is a rare, heter

Specific missense mutations in NEMO result in hyper-IgM syndrome with hypohydrotic ectodermal dysplasia

The gene that encodes nuclear factor κ (NF-κB) essential modulator (or NEMO, also known as IKKγ) is required for activation of the transcription factor NF-κB. We describe mutations in the puta-tive zinc-finger domain of NEMO that result in an X-linked primary immunodeficiency characterized by hyper-IgM syndrome and hypohydrotic ectodermal dysplasia (XHM-ED). These mutations prevent CD40 ligand (CD40L)-mediated degradation of inhibitor of NF-κB α (IκB-α) and account for the following observations: B cells from XHM-ED patients are unable to undergo immunoglobulin class-switch recombination and antigen-presenting cells (APCs) are unable to synthesize the NF-κB–regulated cytokines interleukin 12 (IL-12) or tumor necrosis factor α (TNF-α) when stimulated with CD40L. Nevertheless, innate immunity is preserved in XHM-ED patients because APCs retain the capacity to respond to stimulation by lipopolysaccharide or Staphylococcus aureus Cowans antigen (SAC). Overall, the phenotype observed in XHM-ED patients shows that the putative zinc-finger domain of NEMO has a regulatory function and demonstrates the definite requirement of CD40-mediated NF-κB activation for B cell immunoglobulin class-switching.

Second messenger role for Mg2+ revealed by human T-cell immunodeficiency

The magnesium ion, Mg2+, is essential for all life as a cofactor for ATP, polyphosphates such as DNA and RNA, and metabolic enzymes, but whether it plays a part in intracellular signalling (as Ca2+ does) is unknown. Here we identify mutations in the magnesium transporter gene, MAGT1, in a novel X-linked human immunodeficiency characterized by CD4 lymphopenia, severe chronic viral infections, and defective T-lymphocyte activation. We demonstrate that a rapid transient Mg2+ influx is induced by antigen receptor stimulation in normal T cells and by growth factor stimulation in non-lymphoid cells. MAGT1 deficiency abrogates the Mg2+ influx, leading to impaired responses to antigen receptor engagement, including defective activation of phospholipase Cγ1 and a markedly impaired Ca2+ influx in T cells but not B cells. These observations reveal a role for Mg2+ as an intracellular second messenger coupling cell-surface receptor activation to intracellular effectors and identify MAGT1 as a possible target for novel therapeutics.Summary The magnesium ion, Mg2+, is essential for all life as a cofactor for ATP, polyphosphates such as DNA and RNA, and metabolic enzymes, but whether it plays a role in intracellular signaling similar to Ca2+ is unknown. In this study, we identify mutations in the magnesium transporter gene, MAGT1, in a novel X-linked human immunodeficiency characterized by CD4 lymphopenia, severe chronic viral infections, and defective T lymphocyte activation. We demonstrate that a rapid transient Mg2+ influx is induced by antigen receptor stimulation in T cells or growth factor stimulation in non-lymphoid cells. MagT1 deficiency abrogates the Mg2+ influx leading to impaired responses to antigen receptor engagement including defective activation of phospholipase Cγ and a markedly impaired Ca2+ influx in T cells but not B cells. These observations reveal a role for Mg2+ as an intracellular second messenger and identify MagT1 as a possible target for novel therapeutics.

A Poxvirus-Encoded Semaphorin Induces Cytokine Production from Monocytes and Binds to a Novel Cellular Semaphorin Receptor, VESPR

The vaccinia virus A39R protein is a member of the semaphorin family. A39R.Fc protein was used to affinity purify an A39R receptor from a human B cell line. Tandem mass spectrometry of receptor peptides yielded partial amino acid sequences that allowed the identification of corresponding cDNA clones. Sequence analysis of this receptor indicated that it is a novel member of the plexin family and identified a semaphorin-like domain within this family, thus suggesting an evolutionary relationship between receptor and ligand. A39R up-regulated ICAM-1 on, and induced cytokine production from, human monocytes. These data, then, describe a receptor for an immunologically active semaphorin and suggest that it may serve as a prototype for other plexin-semaphorin binding pairs.

Priming of protective T cell responses against virus-induced tumors in mice with human immune system components

Many pathogens that cause human disease infect only humans. To identify the mechanisms of immune protection against these pathogens and also to evaluate promising vaccine candidates, a small animal model would be desirable. We demonstrate that primary T cell responses in mice with reconstituted human immune system components control infection with the oncogenic and persistent Epstein-Barr virus (EBV). These cytotoxic and interferon-γ–producing T cell responses were human leukocyte antigen (HLA) restricted and specific for EBV-derived peptides. In HLA-A2 transgenic animals and similar to human EBV carriers, T cell responses against lytic EBV antigens dominated over recognition of latent EBV antigens. T cell depletion resulted in elevated viral loads and emergence of EBV-associated lymphoproliferative disease. Both loss of CD4+ and CD8+ T cells abolished immune control. Therefore, this mouse model recapitulates features of symptomatic primary EBV infection and generates T cell–mediated immune control that resists oncogenic transformation.

Epstein–Barr virus-associated lymphoproliferative disease in non-immunocompromised hosts: a status report and summary of an international meeting, 8–9 September 2008

BACKGROUND Recently novel Epstein-Barr virus (EBV) lymphoproliferative diseases (LPDs) have been identified in non-immunocompromised hosts, both in Asia and Western countries. These include aggressive T-cell and NK-cell LPDs often subsumed under the heading of chronic active Epstein-Barr virus (CAEBV) infection and EBV-driven B-cell LPDs mainly affecting the elderly. DESIGN To better define the pathogenesis, classification, and treatment of these disorders, participants from Asia, The Americas, Europe, and Australia presented clinical and experimental data at an international meeting. RESULTS The term systemic EBV-positive T-cell LPD, as adopted by the WHO classification, is preferred as a pathological classification over CAEBV (the favored clinical term) for those cases that are clonal. The disease has an aggressive clinical course, but may arise in the background of CAEBV. Hydroa vacciniforme (HV) and HV-like lymphoma represent a spectrum of clonal EBV-positive T-cell LPDs, which have a more protracted clinical course; spontaneous regression may occur in adult life. Severe mosquito bite allergy is a related syndrome usually of NK cell origin. Immune senescence in the elderly is associated with both reactive and neoplastic EBV-driven LPDs, including EBV-positive diffuse large B-cell lymphomas. CONCLUSION The participants proposed an international consortium to facilitate further clinical and biological studies of novel EBV-driven LPDs.

Patients with X-linked lymphoproliferative disease have a defect in 2B4 receptor-mediated NK cell cytotoxicity.

Patients with the X‐linked lymphoproliferative disorder (XLPD) are unable to control Epstein‐Barr virus (EBV)‐induced infections and lymphoproliferation. This disease is caused by a deficit of SAP, an adapter protein involved in the signal transduction of several cell surface receptors of the CD2 superfamily. One of these receptors, called 2B4, is expressed on NK cells, cytotoxic T cells and myeloid cells and activates NK cell cytotoxicity. Here we show that XLPD patients have a defect of 2B4 receptor‐mediated NK cell cytotoxicity. This defect may contribute to the pathogenesis of XLPD by reducing NK cell lysis of EBV‐infected B cells.

Recent Advances in Varicella-Zoster Virus Infection

This conference paper focuses on recent developments in the biology, clinical presentation, treatment, and prevention of varicella-zoster virus infections.