Anti-interleukin-10 antibodies in patients with chronic active Epstein-Barr virus infection

Functional Implications of Epstein-Barr Virus Lytic Genes in Carcinogenesis

Epstein-Barr virus (EBV) is associated with a diverse range of tumors of both lymphoid and epithelial origin. Similar to other herpesviruses, EBV displays a bipartite life cycle consisting of latent and lytic phases. Current dogma indicates that the latent genes are key drivers in the pathogenesis of EBV-associated cancers, while the lytic genes are primarily responsible for viral transmission. In recent years, evidence has emerged to show that the EBV lytic phase also plays an important role in EBV tumorigenesis, and the expression of EBV lytic genes is frequently detected in tumor tissues and cell lines. The advent of next generation sequencing has allowed the comprehensive profiling of EBV gene expression, and this has revealed the consistent expression of several lytic genes across various types of EBV-associated cancers. In this review, we provide an overview of the functional implications of EBV lytic gene expression to the oncogenic process and discuss possible avenues for future investigations.

Epstein-Barr virus, interleukin-10 and multiple sclerosis: A ménage à trois

Multiple Sclerosis (MS) is an autoimmune disease that is characterized by inflammation and demyelination of nerve cells. There is strong evidence that Epstein-Barr virus (EBV), a human herpesvirus infecting B cells, greatly increases the risk of subsequent MS. Intriguingly, EBV not only induces human interleukin-10 but also encodes a homologue of this molecule, which is a key anti-inflammatory cytokine of the immune system. Although EBV-encoded IL-10 (ebvIL-10) has a high amino acid identity with its cellular counterpart (cIL-10), it shows more restricted and partially weaker functionality. We propose that both EBV-induced cIL-10 and ebvIL-10 act in a temporally and functionally coordinated manner helping the pathogen to establish latency in B cells and, at the same time, to balance the function of antiviral T cells. As a result, the EBV load persisting in the immune system is kept at a constant but individually different level (set point). During this immunological tug of war between virus and host, however, MS can be induced as collateral damage if the set point is too high. Here, we discuss a possible role of ebvIL-10 and EBV-induced cIL-10 in EBV-driven pathogenesis of MS.

Viral IL-10 promotes cell proliferation and cell cycle progression via JAK2/STAT3 signaling pathway in nasopharyngeal carcinoma cells

Epstein-Barr virus (EBV) is positively related to the morbidity of nasopharyngeal carcinoma (NPC) in Asia. After infection, EBV can produce several proteins, including viral interleukin-10 (vIL-10). But the mechanism by which vIL-10 contributes to NPC cell proliferation and cell cycle progression is not well understood. In this study, EBV negative and positive cell lines, and the JAK2/STAT3 signal pathway inhibitor AG490 were used to illustrate the role of vIL-10 in NPC. Cell proliferation and cell cycle were measured by CCK-8 and flow cytometry. The expression levels of related protein were measured by Western blotting. High concentrations of vIL-10 and IL-6 were found in the EBV positive patients. The expression level of IL-6 was positively related to the presence of concentration of vIL-10. vIL-10 can promote cancer cell proliferation and G1 to S phase transmission via upregulating the IL-6 protein level by activating the JAK2/STAT3 signal pathway. Furthermore, EBV can induce the formation of cytotoxic T cells, whereas vIL-10 can block the function of cytotoxic T cells. Taken together, these results suggest that vIL-10 promotes cell proliferation and cell cycle progression via JAK2/STAT3 signaling pathway in NPC.

Autoantibodies against BAFF, APRIL or IL21 - an alternative pathogenesis for antibody-deficiencies?

BACKGROUND

The ability of anti-cytokine antibodies to play a disease-causing role in the pathogenesis of immunodeficiencies is widely accepted. The aim of this study was to investigate whether autoantibodies against BAFF (important B cell survival signal), APRIL (important plasma cell survival signal), or Interleukin-21 (important cytokine for immunoglobulin class switch) present an alternative mechanism for the development of the following primary antibody deficiencies (PADs): common variable immune deficiency (CVID) or selective IgA deficiency (sIgAD).

RESULTS

Two hundred thirty-two sera from patients with PADs were screened for autoantibodies against cytokines by ELISA. Statistical data analysis yielded a significant difference (p < 0.01) between the healthy donor sera and both PAD cohorts. The analysis was deepened by subdividing the patient collective into groups with distinct B cell phenotypes but no significant differences were found. For selected sera with notable high ELISA-read outs functional analysis ensued. Anti-BAFF and anti-APRIL antibodies were further examined by a B cell survival assay, whilst the functional relevance of putative anti-IL-21 autoantibodies was investigated by means of a STAT3 phosphorylation assay. However, the results of these experiments revealed no discernible functional effect.

CONCLUSION

Whilst statistical analysis of ELISA results showed significant differences between patients and healthy controls, in our set of patients functional tests yielded no evidence for an involvement of autoantibodies against BAFF, APRIL, or IL-21 in the pathogenesis of CVID or sIgAD.

Mimicry of cytokine pathways by human herpesviruses

ABSTRACT 

Viruses have evolved to subvert host cell pathways to enable their replication and persistence. In particular, virus-encoded gene products target the host's immune system to evade elimination by antiviral immune defenses. Cytokines are soluble, secreted proteins, which regulate many aspects of immune responses, by providing signals through cell surface receptors on target cells. Cytokine pathways are therefore attractive targets for modulation by viruses during their replication cycle. This review deals with modulation of cytokine pathways by the human herpesvirus, a family of viruses that are capable of life-long persistence in the host and cause severe disease particularly in immunocompromised individuals.

Pathogen manipulation of cIL-10 signaling pathways: opportunities for vaccine development?

Interleukin-10 (IL-10) is a tightly regulated, pleiotropic cytokine that has profound effects on all facets of the immune system, eliciting cell-type-specific responses within cells expressing the IL-10 receptor (IL-10R). It is considered a master immune regulator, and imbalances in IL-10 expression, resulting from either inherent or infectious etiologies, have far reaching clinical ramifications. Regarding infectious diseases, there has been accumulating recognition that many pathogens, particularly those that establish lifelong persistence, share a commonality of their natural histories: manipulation of IL-10-mediated signaling pathways. Multiple viral, bacterial, protozoal, and fungal pathogens appear to have evolved mechanisms to co-opt normal immune functions, including those involving IL-10R-mediated signaling, and immune effector pathways away from immune-mediated protection toward environments of immune evasion, suppression, and tolerance. As a result, pathogens can persist for the life of the infected host, many of whom possess otherwise competent immune systems. Because of pathogenic avoidance of immune clearance, persistent infections can exact incalculable physical and financial costs, and represent some of the most vexing challenges for improvements in human health. Enormous benefits could be gained by the development of efficient prevention and/or therapeutic strategies that block primary infection, or clear the infection. There are now precedents that indicate that modalities focusing on pathogen-mediated manipulation of IL-10 signaling may have clinical benefit.

Vaccination against a virus-encoded cytokine significantly restricts viral challenge

Identification of immune correlates of protection for viral vaccines is complicated by multiple factors, but there is general consensus on the importance of antibodies that neutralize viral attachment to susceptible cells. Development of new viral vaccines has mostly followed this neutralizing antibody paradigm, but as a recent clinical trial of human cytomegalovirus (HCMV) vaccination demonstrated, this singular approach can yield limited protective efficacy. Since HCMV devotes >50% of its coding capacity to proteins that modulate host immunity, it is hypothesized that expansion of vaccine targets to include this part of the viral proteome will disrupt viral natural history. HCMV and rhesus cytomegalovirus (RhCMV) each encode an ortholog to the cellular interleukin-10 (cIL-10) cytokine: cmvIL-10 and rhcmvIL10, respectively. Despite extensive sequence divergence from their host's cIL-10, each viral IL-10 retains nearly identical functionality to cIL-10. Uninfected rhesus macaques were immunized with engineered, nonfunctional rhcmvIL-10 variants, which were constructed by site-directed mutagenesis to abolish binding to the cIL-10 receptor. Vaccinees developed antibodies that neutralized rhcmvIL-10 function with no cross-neutralization of cIL-10. Following subcutaneous RhCMV challenge, the vaccinees exhibited both reduced RhCMV replication locally at the inoculation site and systemically and significantly reduced RhCMV shedding in bodily fluids compared to controls. Attenuation of RhCMV infection by rhcmvIL-10 vaccination argues that neutralization of viral immunomodulation may be a new vaccine paradigm for HCMV by expanding potential vaccine targets.

Characterization of specific antibodies against cytomegalovirus (CMV)-encoded interleukin 10 produced by 28% of CMV-seropositive blood donors

Cytomegalovirus (CMV) has evolved multiple immunological evasion strategies, including the encoding of viral interleukin (IL)-10 homologues (cmvIL-10). In this study, cmvIL-10 bound avidly to the same receptors on blood mononuclear cells and was as bio-potent as native human IL-10. Seventeen percent of plasma samples from 3200 Danish blood donors (corresponding to 28 % of the anti-CMV IgG-positive donors) contained substantial levels of anti-cmvIL-10 IgG antibodies, as measured by a radioimmunoassay for human anti-cmvIL-10 antibodies. The antibodies neither cross-reacted with native human IL-10 nor with Epstein-Barr virus-encoded IL-10. Anti-cmvIL-10 antibodies potently inhibited the binding of cmvIL-10 to cellular receptors, and they specifically inhibited cmvIL-10-induced JAK-STAT signalling. Ultimately, anti-cmvIL-10 antibodies blocked the inhibitory effect of cmvIL-10 on lipopolysaccharide-induced tumour necrosis factor alpha and IL-1β from blood mononuclear cells. Taken together, our data signify that cmvIL-10 has been produced during CMV infection, and that anti-cmvIL-10 IgG antibodies represent an effective immunological counter reaction against cmvIL-10.

Acquired predisposition to mycobacterial disease due to autoantibodies to IFN-gamma

Genetic defects in the IFN-gamma response pathway cause unique susceptibility to intracellular pathogens, particularly mycobacteria, but are rare and do not explain mycobacterial disease in the majority of affected patients. We postulated that acquired defects in macrophage activation by IFN-gamma may cause a similar immunological phenotype and thus explain the occurrence of disseminated intracellular infections in some patients without identifiable immune deficiency. Macrophage activation in response to IFN-gamma and IFN-gamma production were studied in whole blood and PBMCs of 3 patients with severe, unexplained nontuberculous mycobacterial infection. In all 3 patients, IFN-gamma was undetectable following mitogen stimulation of whole blood, but significant quantities were detectable in the supernatants of PBMCs when stimulated in the absence of the patients' own plasma. The patients' plasma inhibited the ability of IFN-gamma to increase production of TNF-alpha by both autologous and normal donor PBMCs, and recovery of exogenous IFN-gamma from the patients' plasma was greatly reduced. Using affinity chromatography, surface-enhanced laser desorption/ionization mass spectrometry, and sequencing, we isolated an IFN-gamma-neutralizing factor from the patients' plasma and showed it to be an autoantibody against IFN-gamma. The purified anti-IFN-gamma antibody was shown to be functional first in blocking the upregulation of TNF-alpha production in response to endotoxin; second in blocking induction of IFN-gamma-inducible genes (according to results of high-density cDNA microarrays); and third in inhibiting upregulation of HLA class II expression on PBMCs. Acquired defects in the IFN-gamma pathway may explain unusual susceptibility to intracellular pathogens in other patients without underlying, genetically determined immunological defects.

Stress-associated changes in the steady-state expression of latent Epstein-Barr virus: implications for chronic fatigue syndrome and cancer

Antibodies to several Epstein-Barr virus (EBV)-encoded enzymes are observed in patients with different EBV-associated diseases. The reason for these antibody patterns and the role these proteins might play in the pathophysiology of disease, separate from their role in virus replication, is unknown. In this series of studies, we found that purified EBV deoxyuridine triphosphate nucleotidohydrolase (dUTPase) can inhibit the replication of human peripheral blood mononuclear cells in vitro and upregulate the production of TNF-alpha, IL-1beta, IL-6, IL-8, and IL-10. It also enhanced the ability of natural killer cells to lyse target cells. The EBV dUTPase also significantly inhibited the replication of mitogen-stimulated lymphocytes and the synthesis of IFN-gamma by cells isolated from lymph nodes and spleens obtained from mice inoculated with the protein. It also produced sickness behaviors known to be induced by some of the cytokines that were studied in the in vitro experiments. These symptoms include an increase in body temperature, a decrease in body mass and in physical activity. The data provide a new perspective on how an early nonstructural EBV-encoded protein can cause immune dysregulation and produce clinical symptoms observed in patients with chronic fatigue syndrome (CFS) separate from its role in virus replication and may serve as a new approach to help identify one of the etiological agents for CFS. The data also provide additional insight into the pathophysiology of EBV infection, inflammation, and cancer.

Dominant expression of interleukin-10 and transforming growth factor-beta genes in activated T-cells of chronic active Epstein-Barr virus infection

Chronic active Epstein-Barr virus (EBV) infection is a chronic mononucleosis syndrome associated with clonal proliferation of EBV-carrying T-/natural killer (NK)-cells. High levels of circulating EBV and activated T-cells are sustained during the prolonged disease course, whereas it is not clear how ectopic EBV infection in T-/NK-cells has been established and maintained. To assess the biological role of activated T-cells in chronic active EBV infection (CAEBV), EBV DNA and cellular gene expressions in peripheral T-cells were quantified in CAEBV and infectious mononucleosis (IM) patients. In CAEBV, HLA-DR(+) T-cells had higher viral load and larger amounts of IFN gamma, IL-10, transforming growth factor-beta (TGF beta), and cytotoxic T lymphocyte antigen-4 (CTLA4) mRNA than HLA-DR(-)T-cells. HLA-DR(+) T cells of IM patients transcribed more IFN gamma and IL-10 than their HLA-DR(-)T cells. Expression levels of IFN gamma and forkhead box p3 (Foxp3) in CAEBV HLA-DR(+) T-cells were higher than in IM HLA-DR(+) T-cells. The effective variables to discriminate the positivity of HLA-DR were IL-10, IFN gamma, CTLA4, TGF beta, and IL-2 in the order of statistical weight. EBV load in CAEBV T-cells correlated with the expression levels of only IL-10 and TGF beta. These results suggest that CAEBV T-cells are activated to transcribe IFN gamma, IL-10, and TGF beta excessively, and the latter two genes are expressed preferentially in the EBV-infected subsets. The dominant expression of regulatory cytokines in T-cells may imply a viral evasion mechanism in the disease.

Natural killer cell proliferation and circulating cytokines in patients with bilateral basal ganglia calcification

Ten adult patients with symmetrical calcifications in the bilateral basal ganglia (diagnosed as physiological calcifications) were analyzed for lymphocyte subsets and cytokines. Increased number of natural killer (NK) cells were identified in the peripheral blood of seven patients by lymphocyte subset analysis. Tumor necrosis factor-alpha was detected in the sera of five patients and interferon-gamma was detected in one patient. In summary, NK cell propagation and circulating cytokines, particularly tumor necrosis factor-alpha, may be involved in the etiology of basal ganglia calcification.

Cytokine profiles in parotid saliva from HIV-1-infected individuals: changes associated with opportunistic infections in the oral cavity

The purpose of this study was to quantitate levels of cytokines in parotid saliva of subjects infected with human immunodeficiency virus-1 (HIV-1) and to determine if the cytokine profiles differ in subjects with an oral opportunistic infection, i.e., candidiasis or oral hairy leukoplakia. Parotid saliva samples were obtained from HIV-infected individuals with or without candidiasis or oral hairy leukoplakia and from healthy controls and were assessed by ELISA for levels of interleukin (IL)-1, IL-2, IL-4, IL-5, IL-10, transforming growth factor-beta, tumor necrosis factor-alpha and interferon (IFN)-gamma. Saliva from HIV-infected subjects with oral candidiasis had significantly higher levels of IFN-gamma than that seen in HIV-infected individuals with no oral disease and significantly higher levels of IL-2, IL-5 and IFN-gamma than saliva of healthy controls. No significant difference was seen in cytokine levels in saliva from HIV-infected subjects with no oral infections and healthy controls. The HIV-infected subjects with oral hairy leukoplakia displayed significantly higher levels of both IL-1 alpha and IFN-gamma compared with the HIV and no oral disease group and a higher level of IFN-gamma than seen in saliva from the healthy control group. In comparing cytokine levels from both HIV and oral disease groups, significant differences were detected in levels of IL-5 and IL-10. These results indicate that the profile of salivary cytokines is altered as a result of the oral opportunistic infection candidiasis or oral hairy leukoplakia and also by concurrent HIV infection.

Chronic, active Epstein-Barr virus infection

Chronic active Epstein-Barr virus (EBV) infection is an uncommon outcome of EBV infection and may present as a waxing and waning or fulminant syndrome. Unlike acute infectious mononucleosis, wherein EBV establishes lifelong infection and survives by maintaining a delicate balance with the host as a latent infection, in chronic active EBV infection the host-virus balance is disturbed. The mechanisms by which this balance becomes perturbed are likely to be heterogenous and may involve host immune factors, viral factors, or both. A number of subtle immunologic defects have been reported in patients with chronic active EBV infection. Enhanced expression of viral genes has also been noted in some cases. Treatment of chronic active EBV infection has proven difficult, but new modalities including etoposide-based regimens and adoptive transfer of EBV-specific cytotoxic T lymphocytes have shown promise.