The ecology and pathology of Epstein-Barr virus

EBV-microRNAs as Potential Biomarkers in EBV-related Fever: A Narrative Review

At present, timely and accurate diagnosis and effective treatment of Epstein- Barr Virus (EBV) infection-associated fever remain a difficult challenge. EBV encodes 44 mature microRNAs (miRNAs) that inhibit viral lysis, adjust inflammatory response, regulate cellular apoptosis, promote tumor genesis and metastasis, and regulate tumor cell metabolism. Herein, we have collected the specific expression data of EBV-miRNAs in EBV-related fevers, including infectious mononucleosis (IM), EBVassociated hemophagocytic lymphohistiocytosis (EBV-HLH), chronic active EBV infection (CAEBV), and EBV-related tumors, and proposed the potential value of EBVmiRNAs as biomarkers to assist in the identification, diagnosis, and prognosis of EBVrelated fever, as well as therapeutic targets for drug development.

Butyric Acid in Saliva of Chronic Periodontitis Patients Induces Transcription of the EBV Lytic Switch Activator BZLF1: A Pilot Study

BACKGROUND/AIM

Epstein-Barr virus (EBV) associates with human chronic periodontitis (CP) progression. We previously demonstrated that butyric acid (BA), produced by periodontopathic bacteria, induced EBV lytic switch activator BZLF1 expression. We investigated whether short chain fatty acids (SCFAs) in CP patients' saliva enabled EBV reactivation.

MATERIALS AND METHODS

Saliva was collected from seven CP patients and five periodontally healthy individuals. SCFAs were quantified using HPLC. BZLF1 mRNA and its pertinent protein ZEBRA were determined with Real-time PCR and western blotting. Histone H3 acetylation (AcH3) was further examined.

RESULTS

BZLF1 mRNA expression and transcriptional activity in EBV-infected Daudi cells were induced only when treated with the CP saliva. Among SCFAs, BA alone correlated significantly with the BZLF1 transcription (r=0.88; p<0.02). As expected, CP patients' saliva induced AcH3.

CONCLUSION

BA in saliva may play a role in EBV reactivation and hence contribute to EBV-related disease progression in CP patients.

EBV LMP1 in Gingival Epithelium Potentially Contributes to Human Chronic Periodontitis via Inducible IL8 Production

BACKGROUND/AIM

Human chronic periodontitis is a major health problem. Although some oral bacteria have been reported to be putative pathogens, Epstein-Barr virus (EBV) is reported to be associated with the progression of periodontitis. However, the role of EBV in the aetiology of periodontitis is unknown. Therefore, we investigated periodontal pathogenesis of EBV to confirm whether EBV-encoded latent membrane protein 1 (LMP1) induces Interleukin-8 (IL8) production in human gingival cells.

MATERIALS AND METHODS

Real-time polymerase chain reaction, luciferase assay, enzyme-linked immunosorbent assay (ELISA), and western blotting were performed for determining IL8 mRNA expression, nuclear factor kappa B (NF-ĸB) transcription, IL8 production, and the phosphorylation of NF-ĸB p65 and Inhibitor of kappa B alpha (IĸBα), respectively, in Ca9-22 human gingival epithelial cells. Two LMP1 mutants lacking C-terminal activating region (CATR) domains responsible for activating NF-ĸB were used.

RESULTS

Extremely high IL8 production was induced by LMP1 in time- and dose-dependent manner, where simultaneous phosphorylation of NF-κB p65 and IĸBα and transcription of NF-ĸB were observed. On the contrary, IL8 production and NF-ĸB transcription were drastically inhibited by dominant negative mutant of IĸBα. Moreover, the LMP1 mutants failed to induce IL8 production.

CONCLUSION

Our findings suggest that due to CATR domains, LMP1 contributes to the progression of periodontitis via IL8 production attributable to NF-ĸB activation.

Herpes Simplex Virus Type 1 and Other Pathogens are Key Causative Factors in Sporadic Alzheimer's Disease

This review focuses on research in epidemiology, neuropathology, molecular biology, and genetics regarding the hypothesis that pathogens interact with susceptibility genes and are causative in sporadic Alzheimer's disease (AD). Sporadic AD is a complex multifactorial neurodegenerative disease with evidence indicating coexisting multi-pathogen and inflammatory etiologies. There are significant associations between AD and various pathogens, including Herpes simplex virus type 1 (HSV-1), Cytomegalovirus, and other Herpesviridae, Chlamydophila pneumoniae, spirochetes, Helicobacter pylori, and various periodontal pathogens. These pathogens are able to evade destruction by the host immune system, leading to persistent infection. Bacterial and viral DNA and RNA and bacterial ligands increase the expression of pro-inflammatory molecules and activate the innate and adaptive immune systems. Evidence demonstrates that pathogens directly and indirectly induce AD pathology, including amyloid-β (Aβ) accumulation, phosphorylation of tau protein, neuronal injury, and apoptosis. Chronic brain infection with HSV-1, Chlamydophila pneumoniae, and spirochetes results in complex processes that interact to cause a vicious cycle of uncontrolled neuroinflammation and neurodegeneration. Infections such as Cytomegalovirus, Helicobacter pylori, and periodontal pathogens induce production of systemic pro-inflammatory cytokines that may cross the blood-brain barrier to promote neurodegeneration. Pathogen-induced inflammation and central nervous system accumulation of Aβ damages the blood-brain barrier, which contributes to the pathophysiology of AD. Apolipoprotein E4 (ApoE4) enhances brain infiltration by pathogens including HSV-1 and Chlamydophila pneumoniae. ApoE4 is also associated with an increased pro-inflammatory response by the immune system. Potential antimicrobial treatments for AD are discussed, including the rationale for antiviral and antibiotic clinical trials.

Anatomical mapping of human herpesvirus reservoirs of infection

Following primary infection, all eight human herpesviruses persist lifelong in the human host. However, a mapping of all anatomic sites of human herpesvirus persistence is lacking. Fresh tissue specimens representing approximately 40 major anatomic sites from eight autopsies were screened using a recently developed real-time PCR method for detection of all eight human herpesviruses. Patients with evidence of active herpesvirus infection (herpes simplex 1 (HSV-1), herpes simplex 2 (HSV-2), varicella-zoster virus (VZV), Epstein-Barr virus (EBV), cytomegalovirus (CMV), herpesvirus 6 (HHV-6), herpesvirus 7 (HHV-7), and herpesvirus 8 (HHV-8)) at the time of death were excluded to avoid detection of widely disseminated infection. Despite this precaution, widespread HSV-1 positivity (with blood positivity) was detected in one case-an elderly male who died of cardiac arrest. In a middle-aged male with HIV-AIDS, HSV-1 was found in neural and pharyngeal tissues, skin, cartilage, bone, and urinary bladder, whereas in two other cases, HSV-1 was restricted to neural tissues. HSV-2 was detected in a single site, the anus, in the male with HIV-AIDS. VZV was detected only twice, once in the adrenal gland and once in the small intestine. CMV was detected in three cases, most commonly in nasal mucosa, trachea, thyroid, intestine, and liver. EBV was detected in all eight cases, especially in nasal mucosa, tonsil, spleen, lymph node, tongue, and intestine, but in only two of six whole-blood specimens. HHV-6, like EBV, was detected in all eight cases, most commonly in salivary glands, thyroid, stomach, intestines, liver, and pancreas. HHV-7, like EBV and HHV-6, was detected in all eight cases, most commonly in salivary glands, tonsil, lymph nodes, and bone marrow. HHV-8 was detected in only two sites (both lymph nodes) from two cases. Herpesviruses were detected in three of six whole-blood specimens, including HSV-1, EBV, HHV-6, and HHV-7. These results represent the most comprehensive mapping of herpesvirus tissue distribution in humans reported to date.

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.

Antifungal and antiviral chemotherapy

Fungal and viral infections are difficult to treat, since fungal infections commonly rebound after suppression by the antifungal agent and current antiviral drugs are only virustatic, allowing the virus to reassert its pathogenicity if not eliminated by the host defenses. In addition, fungal infections commonly are associated with significant biofilms, retarding drug penetration, and the fluid nature of the oral cavity does not promote drug-fungus contact for long periods of time. Both mycotic and viral pathogens are developing sophisticated methods to elude the toxic effects of drugs intended to eliminate their existence. The drug therapy of oral fungal and viral infections is therefore limited but occasionally successful (more with fungal than viral infections) and is often relegated to palliative care. The specter of drug resistance and its promotion by prolonged, repetitive and frivolous use must always be foremost in the clinician's mind.

Hodgkin disease in adult and juvenile groups from two different geographic regions in Brazil: characterization of clinicopathologic aspects and relationship with Epstein-Barr virus infection

We analyzed clinicopathologic data, immunophenotype, and Epstein-Barr virus (EBV) status in 96 cases of Hodgkin disease (HD) in juveniles (younger than 20 years) and adults (20 years or older) from 2 distinctive states in Brazil. We studied 34 juvenile (group 1) and 16 adult (group 2) cases from Ceara and 31 juvenile (group 3) and 15 adult (group 4) cases from São Paulo. Ceara has a socioeconomic profile similar to a developing country; São Paulo is in better economic condition. Mixed cellularity (MC) was the major histologic subtype among groups 1 (22 [65%]), 3 (21 [68%]), and 4 (7 [47%]); nodular sclerosis (NS) was more frequent in group 2 (8 [50%]). EBV infection was observed in 61 cases (64%), including the following (among others): group 1, MC, 22 (65%) and NS, 4 (12%); group 2, NS, 3 (19%) and MC, 2 (12%); group 3, MC, 16 (52%) and NS, 1 (3%); and group 4, MC, 7 (47%). There was predominance of EBV+ HD cases in group 1 compared with group 3. HD in Brazilian patients is highly associated with EBV infection, but geographic differences reflect histologic subtypes and age distribution.

The immunology of Epstein-Barr virus infection

Epstein-Barr virus is a classic example of a persistent human virus that has caught the imagination of immunologists, virologists and oncologists because of the juxtaposition of a number of important properties. First, the ability of the virus to immortalize B lymphocytes in vitro has provided an antigen presenting cell in which all the latent antigens of the virus are displayed and are available for systematic study. Second, the virus presents an ideal system for studying the immune parameters that maintain latency and the consequences of disturbing this cell-virus relationship. Third, this wealth of immunological background has provided a platform for elucidating the role of the immune system in protection from viral-associated malignancies of B cell and epithelial cell origin. Finally, attention is now being directed towards the development of vaccine formulations which might have broad application in the control of human malignancies.

Infectious mononucleosis

Infectious mononucleosis in its classical presentation consists of the clinical triad of fever, pharyngitis, and cervical lymphadenopathy. The majority of cases are caused by primary infection with the Epstein-Barr virus (EBV). There is, however, a wide clinical spectrum of disease manifestations, including pulmonary, hematologic, and neurologic findings and a series of associated laboratory abnormalities, such as lymphocytosis, heterophile antibodies, and anti-EBV antibodies. The disease is typically self-limited and treated with supportive therapy only. Rarely, serious complications such as airway obstruction, severe thrombocytopenia, or severe hemolytic anemia can occur. Infectious mononucleosis does not cause congenital anomalies, and pregnant women are not at increased risk of serious complications resulting from the disorder.

Role of cytotoxic T lymphocytes in Epstein-Barr virus-associated diseases

Adaptation of persistent infection within the cells of the immune system is a unique characteristic of gamma herpes viruses. A classic example of this is Epstein-Barr virus (EBV), which may have co-evolved with Homo sapiens over millions of years, thus achieving a balance between viral persistence and immune control. In this review, we present an overview of virus and the host immune system interactions that regulate the life-long host-virus relationship in healthy virus carriers and EBV-associated diseases. Extensive analysis of cytotoxic T lymphocyte-mediated immune responses in healthy virus carriers has revealed unique mechanisms used by EBV to maintain a benign persistent state in vivo. On the other hand, this relationship in EBV-associated diseases favors the escape of the virus from the hostile effects of the immune response. This escape is achieved by either down-regulating the expression of highly immunogenic antigens of the virus or by direct modulation of the host cytotoxic T lymphocyte response by virus-encoded proteins.

Epstein-Barr virus infectious mononucleosis

The Epstein-Barr virus (EBV) is the aetiological agent of classical infectious mononucleosis. This review article describes the antigenicity of the virus, the specific antibody response and the stimulated polyclonal heterophile antibody production in the host. The diagnostic tests for EBV infection are discussed, with particular attention drawn to the pitfalls of the Monospot test. Complications are listed and management strategies are outlined. The uses and complications of steroids are discussed. The importance of avoidance of contact sport and the association with splenic rupture is described.

Vaccine strategies against Epstein-Barr virus-associated diseases: lessons from studies on cytotoxic T-cell-mediated immune regulation

Development of a vaccine against Epstein-Barr virus (EBV) is constrained by the latency phenotypes adopted by different EBV-associated diseases. Over the last few years an immense body of information on the pattern of viral gene expression in EBV-associated diseases and the role of cytotoxic T cells in the control of these diseases has accumulated. It would seem reasonable to suggest that emerging technologies are at a level where vaccine trials aimed at controlling infectious mononucleosis, post-transplant lymphoproliferative disease, nasopharyngeal carcinoma and Hodgkin's disease are justified. On the other hand, a more cautious approach may be required for the development of vaccines or immunotherapeutic strategies against Burkitt's lymphoma.

Detection and Titration of Human Herpesvirus-8–Specific Antibodies in Sera From Blood Donors, Acquired Immunodeficiency Syndrome Patients, and Kaposi's Sarcoma Patients Using a Whole Virus Enzyme-Linked Immunosorbent Assay

A human herpesvirus-8 (HHV-8) enzyme-linked immunosorbent assay (ELISA) with a whole virus lysate as antigen was developed and used to measure the seroprevalence rate and levels of IgG antibodies to HHV-8 in sera/plasma of various patient groups and blood donors. The virus antigen was prepared from the KS-1 cell line, which produces lytic virus, and therefore contains a broad array of viral proteins. Seroprevalence studies using this ELISA showed the following: 10 of 91 blood donors (11%) had an average HHV-8 antibody titer of 118; 67 of 72 (93%) classic Kaposi's sarcoma (KS) patients were positive with an average titer of 14,111; and 57 of 62 (92%) KS/human immunodeficiency virus (HIV) patients were positive with an average titer of 4,000. A study on a very limited number of serial serum samples from patients before and after diagnosis with KS showed highly elevated antibody titers to HHV-8 virus after KS lesions developed. Preliminary data show that 50% of the sera from HIV-1+ homosexual patients contain IgG antibodies to HHV-8 suggesting that this population is at high risk for developing KS. Antibody results correlated well with the confirmatory immunofluorescent assays (IFA) using KS-1 cells as the substrate. This HHV-8 IgG antibody detection ELISA is sensitive and specific and does not cross-react with Epstein-Barr virus (EBV) or other human herpesviruses. The results of this HHV-8 antibody survey suggest that this rapid ELISA assay can be used to screen large numbers of sera to find those at risk for developing KS.

Targeting a polyepitope protein incorporating multiple class II-restricted viral epitopes to the secretory/endocytic pathway facilitates immune recognition by CD4+ cytotoxic T lymphocytes: a novel approach to vaccine design

The role of CD4+ and CD8+ cells in the generation of an effective immune response against viral infections is well established. Moreover, there is an increasing realization that subunit vaccines which include both CD4+- and CD8+-T-cell epitopes are highly effective in controlling viral infections, as opposed to those which are designed to activate a CD8+- or CD4+-T-cell response alone. One of the major limitations of epitope-based vaccines designed to stimulate virus-specific CD4+ T cells is that endogenously expressed class II-restricted minimal cytotoxic-T-lymphocyte (CTL) epitopes are poorly recognized by CD4+ CTLs. In the present study we attempted to enhance the efficiency of class II-restricted endogenous presentation of minimal class II-restricted CTL epitopes by specifically targeting a polyepitope protein to class II processing compartments through the endosomal and/or lysosomal pathway. A significantly enhanced stimulation of virus-specific CD4+-T-cell clones by antigen-presenting cells (APC) expressing the recombinant polyepitope protein targeted to the endocytic/secretory pathway was readily demonstrated in cytotoxicity assays. In addition, in vitro activation of Epstein-Barr virus- and influenza virus-specific CD4+ memory CTLs by the recombinant constructs encoding the polyepitope protein, specifically targeted to the lysosomal compartment, was also demonstrated. The enhanced stimulatory capacity of APC expressing a lysosome-targeted polyepitope protein has important implications for vaccine design.