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

Interleukin-23 promotes a distinct CD4 T cell activation state characterized by the production of interleukin-17

Interleukin (IL)-17 is a pro-inflammatory cytokine that is produced by activated T cells. Despite increasing evidence that high levels of IL-17 are associated with several chronic inflammatory diseases including rheumatoid arthritis, psoriasis, and multiple sclerosis, the regulation of its expression is not well characterized. We observe that IL-17 production is increased in response to the recently described cytokine IL-23. We present evidence that murine IL-23, which is produced by activated dendritic cells, acts on memory T cells, resulting in elevated IL-17 secretion. IL-23 also induced expression of the related cytokine IL-17F. IL-23 is a heterodimeric cytokine and shares a subunit, p40, with IL-12. In contrast to IL-23, IL-12 had only marginal effects on IL-17 production. These data suggest that during a secondary immune response, IL-23 can promote an activation state with features distinct from the well characterized Th1 and Th2 profiles.

Viral mimicry of cytokines, chemokines and their receptors

Viruses have evolved elegant mechanisms to evade detection and destruction by the host immune system. One of the evasion strategies that have been adopted by large DNA viruses is to encode homologues of cytokines, chemokines and their receptors--molecules that have a crucial role in control of the immune response. Viruses have captured host genes or evolved genes to target specific immune pathways, and so viral genomes can be regarded as repositories of important information about immune processes, offering us a viral view of the host immune system. The study of viral immunomodulatory proteins might help us to uncover new human genes that control immunity, and their characterization will increase our understanding of not only viral pathogenesis, but also normal immune mechanisms. Moreover, viral proteins indicate strategies of immune modulation that might have therapeutic potential.

Interleukin-17 orchestrates the granulocyte influx into airways after allergen inhalation in a mouse model of allergic asthma

Interleukin (IL)-17 is produced by activated memory CD4(+) cells and induces cytokines and chemokines that stimulate neutrophil generation and recruitment. Here, we investigated the involvement of IL-17 in the bronchial influx of neutrophils in experimental allergic asthma. Inhalation of nebulized ovalbumin (OVA) by sensitized mice with bronchial eosinophilic inflammation resulting from chronic OVA exposure induced early IL-17 mRNA expression in inflamed lung tissue, concomitant with a prominent bronchial neutrophilic influx. Anti-IL-17 monoclonal antibodies (mAb) injected before allergen inhalation strongly reduced bronchial neutrophilic influx, in a manner equally as potent as the anti-inflammatory dexamethasone. Remarkably, anti-IL-17 mAb significantly enhanced IL-5 levels in both BAL fluid and serum, and aggravated allergen-induced bronchial eosinophilia. In another series of experiments, anti-IL-17 mAb were given repeatedly during the inhalatory challenge phase with OVA of sensitized mice. This treatment regimen abated bronchial neutrophilia in parallel with reduction of bone marrow and blood neutrophilia. In addition, anti-IL-17 mAb treatment elevated eosinophil counts in the bone marrow and bronchial IL-5 production, without alteration of allergen-induced bronchial hyperresponsiveness. In summary, our results demonstrate that IL-17 expression in airways is upregulated upon allergen inhalation, and constitutes the link between allergen-induced T cell activation and neutrophilic influx. Because neutrophils may be important in airway remodeling in chronic severe asthma, targeting IL-17 may hold therapeutic potential in human asthma.

A gamma-herpesvirus immune evasion gene allows tumor cells in vivo to escape attack by cytotoxic T cells specific for a tumor epitope

DNA vaccines induce CTL attack on target tumor epitopes, but tumor elimination in vivo also requires sufficient effector CTL to enter the site, guided by inflammatory chemokines. Many herpesviruses contain genes for chemokine and chemokine receptor-like proteins to protect infected cells from immune attack. To assess if this evasion strategy could protect tumor cells, we used a model where CTL specific for a single epitope were the only effectors. Following DNA vaccination, CTL eliminated tumor cells from a subcutaneous site. However, introducing a viral gene encoding a secreted broad-spectrum chemokine-binding protein (M3) into tumor cells completely blocked CTL attack. Transduced tumor cells also protected neighboring non-transduced tumor. These findings confirm the importance of chemokines for migration of CTL to a non-lymphoid site. They may have relevance for escape of human virus-associated malignancies, and raise the question of whether analogous molecules might contribute to the failure of CTL to eliminate tumors.

Interleukin 17: an example for gene therapy as a tool to study cytokine mediated regulation of hematopoiesis

Interleukin 17 (IL-17) is an essential proinflammatory T-cell derived cytokine with various biological actions. IL-17 was found to have a pivotal role in microbial host defense by interconnecting lymphoid and myeloid host defense. It also acts as a stimulatory hematopoietic cytokine by expanding myeloid progenitors and initiating proliferation of mature neutrophils. This article summarizes results to date on IL-17 research and discusses gene therapy based strategies that were employed to determine its biological functions and significance. A comprehensive working model for IL-17 is introduced.

Isolation and characterization of chicken interleukin-17 cDNA

Interleukin-17 (IL-17) is a proinflammatory cytokine produced by activated T cells. A 917-bp cDNA encoding the IL-17 gene was isolated from our EST cDNA library prepared from intestinal intraepithelial lymphocytes (IELs) of Eimeria-infected chickens. It contained a 507-bp open reading frame (ORF) predicted to encode a protein of 169 amino acids (aa) with a molecular mass of 18.9 kDa, a 27-residue NH(2)-terminal signal peptide, a single potential N-linked glycosylation site, and 6 cysteine residues conserved with mammalian IL-17. Chicken IL-17 (chIL-17) shared 37%-46% amino acid sequence identity to the previously described mammalian homologs and also was homologous to the ORF 13 of Herpesvirus saimiri (HVS 13). By Northern blot analysis, IL-17 transcripts were identified in a reticuloendotheliosis virus (REV)-transformed chicken lymphoblast cell line (CU205) and conconavalin A (ConA)-stimulated splenic lymphocytes but not other chicken cell lines or normal tissues. Conditioned medium from COS-7 cells transfected with ChIL-17 cDNA induced IL-6 production by chicken embryonic fibroblasts, suggesting a functional role for the cytokine in avian immunity.

Transgenic overexpression of human IL-17E results in eosinophilia, B-lymphocyte hyperplasia, and altered antibody production

We have identified and cloned a novel human cytokine with homology to cytokines of the interleukin-17 (IL-17) family, which we have termed human IL-17E (hIL-17E). With the identification of several IL-17 family members, it is critical to understand the in vivo function of these molecules. We have generated transgenic mice overexpressing hIL-17E using an apolipoprotein E (ApoE) hepatic promoter. These mice displayed changes in the peripheral blood, particularly, a 3-fold increase in total leukocytes consisting of increases in eosinophils, lymphocytes, and neutrophils. Splenomegaly and lymphoadenopathy were predominant and included marked eosinophil infiltrates and lymphoid hyperplasia. CCR3(+) eosinophils increased in the blood and lymph nodes of the transgenic mice by 50- and 300-fold, respectively. Eosinophils also increased 8- to 18-fold in the bone marrow and spleen, respectively. In the bone marrow, most of the eosinophils had an immature appearance. CD19(+) B cells increased 2- to 5-fold in the peripheral blood, 2-fold in the spleen, and 10-fold in the lymph nodes of transgenic mice, whereas CD4(+) T lymphocytes increased 2-fold in both blood and spleen. High serum levels of the cytokines IL-2, IL-4, IL-5, granulocyte colony-stimulating factor, eotaxin, and interferon gamma were observed. Consistent with B-lymphocyte increases, serum immunoglobulin (Ig) M, IgG, and IgE were significantly elevated. Antigenic challenge of the transgenic mice with keyhole limpet hemocyanin (KLH) resulted in a decrease in anti-KLH IgG accompanied by increases of anti-KLH IgA and IgE. In situ hybridization of transgenic tissues revealed that IL-17Rh1 (IL-17BR/Evi27), a receptor that binds IL-17E, is up-regulated. Taken together, these data indicate that IL-17E regulates hematopoietic and immune functions, stimulating the development of eosinophils and B lymphocytes. The fact that hIL-17E overexpression results in high levels of circulating eosinophils, IL-4, IL-5, eotaxin, and IgE suggests that IL-17E may be a proinflammatory cytokine favoring Th2-type immune responses.

Contribution of interleukin 17 to human cartilage degradation and synovial inflammation in osteoarthritis

OBJECTIVE

To compare the effect of interleukin (IL)-17, IL-1beta and TNF-alpha on chemokine production by human chondrocytes and synovial fibroblasts isolated from patients with osteoarthritis (OA). The expression of IL-1beta mRNA by OA chondrocytes was also assessed, as well as the presence and expression of IL-17 receptor (IL-17R) in OA chondrocytes and synovial fibroblasts after stimulation with IL-17, IL-1beta and TNF-alpha.

DESIGN

Synovial fibroblasts and chondrocytes isolated from patients with OA were stimulated in vitro with IL-17, IL-1beta or TNF-alpha. Supernatants were collected and immunoassayed for the presence of IL-8, GRO-alpha (CXC chemokines) and MCP-1, RANTES (CC chemokines). The cells were used to detect the presence of IL-17R and the expression of IL-17R mRNA. Stimulated chondrocytes were also used to detect IL-1beta production and mRNA expression.

RESULTS

IL-17 upregulated the release of IL-8 and GRO-alpha both by synovial fibroblasts and chondrocytes, and the release of MCP-1 only by chondrocytes. IL-17 was a weaker stimulator than IL-1beta and TNF-alpha, except for GRO-alpha release which was maximally upregulated by IL-1beta, less by IL-17 and minimally by TNF-alpha. When compared to IL-1beta, IL-17 was more active on chondrocytes than on fibroblasts. In chondrocytes the expression of IL-1beta mRNA was enhanced by IL-17 and TNF-alpha, with a maximum level reached by IL-1beta. IL-17 and TNF-alpha stimulated IL-1beta release in few subjects. Neither IL-17, IL-1beta nor TNF-alpha modulated the presence of IL-17R and the expression of IL-17R mRNA.

CONCLUSIONS

These data suggest that IL-17 could contribute to cartilage breakdown and synovial infiltration in OA by inducing both the release of chemokines by chondrocytes and synovial fibroblasts and, in a less extent, the synthesis of IL-1beta by chondrocytes.

Elevated chemokine responses are maintained in lungs after clearance of viral infection

We observed two patterns of chemokine expression in the lungs of mice infected with murine gammaherpesvirus 68: peaks of chemokine expression correlated with or occurred after the peak of viral gene expression. Chemokine expression remained elevated through 29 days postinfection.

Antigen-specific T cell sensitization is impaired in IL-17-deficient mice, causing suppression of allergic cellular and humoral responses

Interleukin-17 (IL-17) is a proinflammatory cytokine produced by T cells. The involvement of IL-17 in human diseases has been suspected because of its detection in sera from asthmatic patients and synovial fluids from arthritic patients. In this study, we generated IL-17-deficient mice and investigated the role of IL-17 in various disease models. We found that contact, delayed-type, and airway hypersensitivity responses, as well as T-dependent antibody production, were significantly reduced in the mutant mice, while IL-17 deficiency of donor T cells did not affect acute graft-versus-host reaction. The results suggest that impaired responses were caused by the defects of allergen-specific T cell activation. Our findings indicate that IL-17 plays an important role in activating T cells in allergen-specific T cell-mediated immune responses.

Extracellular signal-regulated kinases 1 and 2 participate in interleukin-17 plus tumor necrosis factor-alpha-induced stabilization of interleukin-6 mRNA in human pancreatic myofibroblasts

In human pancreatic myofibroblasts, interleukin (IL)-17 markedly enhances tumor necrosis factor (TNF)-alpha-induced IL-6 secretion through the induction of IL-6 mRNA stabilization. Induced stability of IL-6 mRNA was markedly decreased by the inhibitors of extracellular signal-regulated kinase (ERKs), PD98059 and U0216. This indicates that activation of the ERK pathway is involved in the induction of IL-6 mRNA stabilization by IL-17 plus TNF-alpha.

Addition of interleukin 1 (IL1) and IL17 soluble receptors to a tumour necrosis factor alpha soluble receptor more effectively reduces the production of IL6 and macrophage inhibitory protein-3alpha and increases that of collagen in an in vitro model of rheumatoid synoviocyte activation

OBJECTIVES

To evaluate the usefulness of combination treatment with cytokine inhibitors.

METHODS

A simplified model was set up to evaluate the effect of tumour necrosis factor alpha (TNFalpha) soluble receptors (sTNFR) used alone and in combination with soluble interleukin 1 receptor (sIL1R) and sIL17R on the production of markers of inflammation (IL6), of migration of dendritic cells (macrophage inhibitory protein-3alpha (MIP-3alpha)), and of matrix synthesis (C-propeptide of type 1 collagen (P1CP)). Synoviocytes were stimulated with supernatants of activated peripheral blood mononuclear cells (PBMC) from patients with rheumatoid arthritis (RA). Soluble receptors (sR) were preincubated at 1 gammag/ml alone or in combination with the supernatants before addition to RA synoviocytes. IL6, MIP-3alpha, and P1CP production was measured by enzyme linked immunosorbent assay (ELISA) in 48 hour synoviocyte supernatants.

RESULTS

IL6 production decreased by 16% with sTNFR alone compared with no sTNFR (p<0.001) and by 41% with the combination of the three sR (p<0.001). MIP-3alpha production decreased by 77% with sTNFR alone compared with no sTNFR (p<0.001) and by 98% with the combination of the three sR (p<0.001). In the presence of sTNFR alone, P1CP production increased by 25% compared with no sR (p<0.01). The combination of the three sR increased P1CP production by 48% (p<0.01).

CONCLUSION

The effect of sTNFR on IL6, MIP-3alpha, and P1CP production by RA synoviocytes stimulated by activated PBMC supernatants was further enhanced when combined with sIL1R and sIL17R.

Interleukin 17 modulates the immune response to vaccinia virus infection

Interleukin 17 (IL-17) is a newly identified cytokine that has a homolog in herpesvirus saimiri. We inserted murine IL-17 into vaccinia virus to study the role of IL-17 in viral infection. Vaccinia virus expressing IL-17 (vv-IL17) and its parental control virus (vv-pRB) grew to similar titers in vitro; however, vv-IL17 was more virulent in mice with a threefold lower LD(50) than for vv-pRB, and mean time to death of 2.8 days versus 4.5 days. Mice infected with vv-IL17 had higher titers of virus in the ovaries (P < 0.02) and showed a decrease in NK cell cytotoxicity (P < 0.02) on day 3 after infection. No significant difference was found in CTL activity. In addition, a significant decrease in IgG2a (P < 0.01) and increases in IgG1, IgG3, and IgA (P < 0.03) vaccinia virus-specific antibody titers were observed in mice infected with vv-IL17 versus vv-pRB, suggesting a Th-2-like response to infection. These data indicate that IL-17 modulates the immune response during virus infection.

Cutting edge: IL-17D, a novel member of the IL-17 family, stimulates cytokine production and inhibits hemopoiesis

A novel cytokine termed IL-17D was cloned using nested RACE PCR. It is a secreted cytokine with homology to the IL-17 family of proteins. IL-17D is preferentially expressed in skeletal muscle, brain, adipose tissue, heart, lung, and pancreas. Treatment of endothelial cells with purified rIL-17D protein stimulated the production of IL-6, IL-8, and GM-CSF. The increased expression of IL-8 was found to be NF-kappa B-dependent. rIL-17D also demonstrated an inhibitory effect on hemopoiesis of myeloid progenitor cells in colony formation assays.

New IL-17 family members promote Th1 or Th2 responses in the lung: in vivo function of the novel cytokine IL-25

We have biologically characterized two new members of the IL-17 cytokine family: IL-17F and IL-25. In contrast to conventional in vitro screening approaches, we have characterized the activity of these new molecules by direct in vivo analysis and have compared their function to that of other IL-17 family members. Intranasal administration of adenovirus expressing IL-17, IL-17C, or IL-17F resulted in bronchoalveolar lavage neutrophilia and inflammatory gene expression in the lung. In contrast, intranasal administration of IL-25-expressing adenovirus or IL-25 protein resulted in the production of IL-4, IL-5, IL-13, and eotaxin mRNA in the lung and marked eosinophilia in the bronchoalveolar lavage and lung tissue. Mice given intranasal IL-25 also developed epithelial cell hyperplasia, increased mucus secretion, and airway hyperreactivity. IL-25 gene expression was detected following Aspergillus and Nippostrongylus infection in the lung and gut, respectively. IL-25-induced eosinophilia required IL-5 and IL-13, but not IL-4 or T cells. Following IL-25 administration, the IL-5(+) staining cells were CD45R/B220(+), Thy-1(+/-), but were NK1.1-, Ly-6G(GR-1)-, CD4-, CD3-, and c-kit-negative. gamma-common knockout mice did not develop eosinophilia in response to IL-25, nor were IL-5(+) cells detected. These findings suggest the existence of a previously unrecognized cell population that may initiate Th2-like responses by responding to IL-25 in vivo. Further, these data demonstrate the heterogeneity of function within the IL-17 cytokine family and suggest that IL-25 may be an important mediator of allergic disease via production of IL-4, IL-5, IL-13, and eotaxin.

Evidence for the early involvement of interleukin 17 in human and experimental renal allograft rejection

Inflammatory processes can stimulate renal epithelial cells to release cytokines, chemoattractants and matrix proteins into the interstitium, thus contributing to interstitial injury during acute allograft rejection. To test the role of interleukin 17 (IL-17) in this process, cultured human renal epithelial cells (hRECs) were first established and treated with or without human IL-17 (hIL-17) for 2, 4, 8 and 10 h in vitro. Significant elevations of IL-6 and IL-8 levels were noted in the supernatants in a dose-dependent and time-dependent manner, as also for IL-6 mRNA expression. Secondly, using a rat acute allograft rejection model, the correlation between IL-17 expression and histopathological changes was serially studied. The results demonstrated that increased expression of IL-17 protein on infiltrating mononuclear cells (MNCs) was detectable on day 2. This corresponds to the borderline change of acute rejection according to the Banff classification, and it increased progressively to day 5. Serial study of IL-6, IL-8 and IL-17 mRNA expression of the renal allograft confirmed IL-17 mRNA expression in the allograft early on post-transplant day 2, whereas IL-6 and IL-8 expression started on day 3. Thirdly, IL-17 expression was observed in human renal allograft and urinary sediment. IL-17 protein expression was found in human subclinical (borderline) rejection renal allograft biopsy tissue and none in biopsy tissue not showing any evidence of rejection. There was also a 100% detectable rate of IL-17 mRNA expression in the MNCs of urinary sediment of patients with subclinical borderline rejection. These results demonstrate that hRECs exposed to IL-17 can produce inflammatory mediators with the potential to stimulate early alloimmune responses, which may also serve to give warning of acute renal allograft rejection.

IL-17 stimulates inflammatory responses via NF-kappaB and MAP kinase pathways in human colonic myofibroblasts

Colonic subepithelial myofibroblasts (SEMFs) may play a role in the modulation of mucosal inflammatory responses. We investigated the effects of interleukin (IL)-17 on IL-6 and chemokine [IL-8 and monocyte chemoattractant protein (MCP)-1] secretion in colonic SEMFs. Cytokine expression was determined by ELISA and Northern blotting. Nuclear factor kappa B (NF-kappaB) DNA-binding activity was evaluated by electrophortetic gel mobility shift assay (EMSA). The activation of mitogen-activated protein kinase (MAPK) was assessed by immunoblotting. IL-6, IL-8, and MCP-1 secretions were rapidly induced by IL-17. IL-17 induced NF-kappaB activation within 45 min after stimulation. A blockade of NF-kappaB activation markedly reduced these responses. MAPK inhibitors (SB-203580, PD-98059, and U-0126) significantly reduced the IL-17-induced IL-6 and chemokine secretion. The combination of either IL-17 + IL-1beta or IL-17 + tumor necrosis factor (TNF)-alpha enhanced cytokine secretion; in particular, the effects of IL-17 + TNF-alpha on IL-6 secretion were much stronger than the other responses. This was dependent on the enhancement of IL-6 mRNA stability. In conclusion, human SEMFs secreted IL-6, IL-8, and MCP-1 in response to IL-17. These responses might play an important role in the pathogenesis of gut inflammation.

Interleukin-17 inhibits tumor cell growth by means of a T-cell-dependent mechanism

Interleukin 17 (IL-17) is a proinflammatory cytokine produced by activated CD4(+) memory T cells. We previously showed that IL-17 increased the growth rate of human cervical tumors transplanted into athymic nude mice. To address the possible role of T cells in the biologic activity of IL-17 for tumor control, we grafted 2 murine hematopoietic immunogenic tumors (P815 and J558L) transfected with a complementary DNA encoding murine IL-17 into syngeneic immunocompetent mice. We found that growth of the 2 IL-17-producing tumors was significantly inhibited compared with that of mock-transfected tumors. In contrast to the antitumor activity of IL-17 observed in immunocompetent mice, we observed no difference in the in vivo growth of IL-17-transfected or mock-transfected P815 cells (P815-IL-17 and P815-Neo, respectively) transplanted into nude mice. We then showed that IL-17 increased generation of specific cytolytic T lymphocytes (CTLs) directed against the immunodominant antigens from P815 called A, B, C, D, and E, since all mice injected with P815-IL-17 developed a P815-specific CTL response, whereas only 6 of 16 mice immunized with P815-Neo had a specific CTL response against the antigens. The induction of CTLs was associated with establishment of a tumor-protective immunity. These experiments suggest that T lymphocytes are involved in the antitumor activity of IL-17. Therefore, IL-17, like other cytokines, appears to be a pleiotropic cytokine with possible protumor or antitumor effects on tumor development, which often depends on the immunogenicity of tumor models.

Peripheral T-cell lymphoma in herpesvirus saimiri-infected tamarins: tumor cell lines reveal subgroup-specific differences

Efficiency of lymphoma induction by herpesvirus saimiri (HVS) isolates correlates with the genetically defined viral subgroups A, B, and C. To compare subgroup-specific effects, highly susceptible tamarins were infected with HVS strain A-11, B-SMHI, or C-488. All animals developed T-cell lymphomas indistinguishable with respect to clinical, pathological, and virological parameters. Ex vivo T-cell lines were established readily from the HVS C-488 animal, less efficiently in the presence of HVS A-11, and from only a single HVS B-SMHI sample. These cultivated cells revealed strain-specific biochemical characteristics. HVS A-11 strongly induced the expression of tyrosine kinase Lyn. HVS C-488 led to the activation of STAT3, which is most likely linked to the association of virus-encoded Tip with tyrosine kinase Lck. The lack of these activities in HVS B-SMHI-transformed cells may correlate with the reduced oncogenic phenotype of this virus in species other than tamarins.

Expression, modulation and signalling of IL-17 receptor in fibroblast-like synoviocytes of patients with rheumatoid arthritis

Interleukin-17 (IL-17) has been characterized as a proinflammatory cytokine produced by CD4+ CD45RO+ memory T cells. Overproduction of IL-17 was detected in the synovium of patients with rheumatoid arthritis (RA) compared to patients with osteoarthritis. In contrast to the restricted expression of IL-17, the IL-17 receptor (IL-17R/CDw217) is expressed ubiquitously. Using a real-time RT-PCR assay, we detected similar absolute levels of IL-17R mRNA expression in fibroblast-like synoviocytes (SFC) from patients with RA (mean 9 pg/microg total RNA; ranged from 0.1 pg to 96 pg IL-17R mRNA/microg total RNA) compared to synoviocytes of non-RA patients. Analysis of the IL-17R surface expression confirmed the results obtained for IL-17R mRNA expression. Exposure of SFC to IL-17 led to a mRNA induction of CXC chemokines IL-8, GRO-alpha and GRO-beta. An anti-IL-17 antibody blocked these effects of IL-17. The MAPK p38 appears necessary for the regulation of IL-8, GRO-alpha and GRO-beta expression as shown by inhibition with SB203580. The inhibitors genistein (tyrosine kinase inhibitor) and calphostin C (inhibitor of protein kinase C) reduced significantly the IL-17-stimulated mRNA expression of IL-8, GRO-alpha and GRO-beta in SFC, whereas PD98059 (inhibitor of MEK-1/2) was without effect. Pharmacological drugs used in therapy of RA, such as cyclosporin and methotrexate, induced a fourfold increase of IL-17R mRNA expression and augmented the IL-17-stimulated IL-8 expression. Our results support the hypothesis that IL-17/IL-17R may play a significant role in the pathogenesis of RA contributing to an unbalanced production of cytokines as well as participating in connective tissue remodelling.

Expression of IL-17B in neurons and evaluation of its possible role in the chromosome 5q-linked form of Charcot-Marie-Tooth disease

IL-17B is a recently identified homolog of IL-17. Northern analysis revealed that IL-17B mRNA is expressed at very high levels in spinal cord and at much lower and more variable levels in trachea, prostate, lung, small intestine, testes, adrenal, and pancreas. In developing mouse embryos IL-17B expression was first detected at day 11 and appeared to peak at day 15. In situ analysis of mouse spinal cord, dorsal root ganglia, and brain demonstrated that IL-17B mRNA is primarily expressed by the neurons. Immunohistochemical analysis of human spinal cord, dorsal root ganglia, cerebral cortex, cerebellum, and hippocampus demonstrated that IL-17B protein is primarily localized to the neuronal cell bodies and axons. Radiation hybrid mapping localized the IL-17B gene to a region on human chromosome 5q that is associated with a rare autosomal recessive form of Charcot-Marie-Tooth demyelinating disease. However, no changes were found in the coding regions, splice junctions, intron 1, or the 5' and 3' untranslated regions of IL-17B genes of patients affected with this disease.

Sef is a feedback-induced antagonist of Ras/MAPK-mediated FGF signalling

Fibroblast growth factors (FGFs) are pleiotrophic growth factors that control cell proliferation, migration, differentiation and embryonic patterning. During early zebrafish embryonic development, FGFs regulate dorsoventral patterning by controlling ventral bone morphogenetic protein (BMP) expression. FGFs function by binding and activating high-affinity tyrosine kinase receptors. FGF activity is negatively regulated by members of the Sprouty family, which antagonize Ras signalling induced by receptor tyrosine kinases. On the basis of similarities in their expression patterns during embryonic development, we have identified five genes that define a synexpression group -- fgf8, fgf3, sprouty2, sprouty4, as well as a novel gene, sef (similar expression to fgf genes). Sef encodes a conserved putative transmembrane protein that shares sequence similarities with the intracellular domain of the interleukin 17 receptor. Here we show that in zebrafish, Sef functions as a feedback-induced antagonist of Ras/Raf/MEK/MAPK-mediated FGF signalling.

IL-17 expression as a possible predictive parameter for subclinical renal allograft rejection

In the present study we have tried to establish the role of IL-17 in subclinical renal allograft rejection. In this animal model, renal grafts from BN (RT1n) were transplanted heterotopically into LEW (RT1l) rats. As controls, LEW grafts were transplanted into LEW rats. The histopathological examination demonstrated that the changes in the allograft kidney on day 2 were similar to those ranked as borderline changes according to the Banff classification scale. On day 2, the serum level of blood urea nitrogen (BUN) and creatinine were the same as on day 1. The examination of allograft cytokines mRNA showed that IL-17 mRNA expressed earlier on the second postoperative day, peaked at day 5, and then declined, becoming almost undetectable at day 9, when most rats died. IL-17 antigen was also proven, by histochemical staining, to be expressed early, however we could not find the same early appearance on other Th1/Th2 cytokines. In human renal biopsy samples, the IL-17 antigen could be found scattered around in the borderline changed rejected renal allografts without evidence of a serum creatinine increase, but was undetectable both in normal controls and in renal transplant tissue without signs of rejection. IL-17 mRNA was detected in the mononuclear cells of the urinary sediment of patients suffering from borderline subclinical rejection. From the above results we can hypothesize that IL-17 could serve as a predictive parameter for borderline subclinical renal allograft rejection in the future.

IL-6 secretion by human pancreatic periacinar myofibroblasts in response to inflammatory mediators

There is increasing evidence that IL-6 plays an important role in the pathophysiology of acute pancreatitis via its broad proinflammatory actions. To identify the local biosynthetic site for IL-6 in human pancreas, we investigated IL-6 secretion in human pancreatic periacinar myofibroblasts. IL-6 secretion was determined by ELISA and Northern blotting. The activation of NF-kappaB was assessed by EMSA. The activation of mitogen-activated protein kinase (MAPK) was assessed by immunoblotting. IL-6 secretion was rapidly induced by IL-17, IL-1beta, and TNF-alpha. EMSAs demonstrated that IL-17, IL-1beta, and TNF-alpha induced NF-kappaB activation within 1.5 h after stimulation, and a blockade of NF-kappaB activation by the pyrrolidine derivative of dithiocarbamate and tosyl-phe-chloromethylketone markedly reduced the IL-17-, IL-1beta-, or TNF-alpha-induced IL-6 gene expression. Furthermore, IL-17, IL-1beta, and TNF-alpha induced a rapid activation of extracellular signal-related kinase p42/44 and p38 MAPKs, and specific MAPK inhibitors (SB203580, PD98059, and U0216) significantly reduced IL-17-, IL-1beta-, or TNF-alpha-induced IL-6 secretion, indicating the role of MAPKs in the induction of IL-6. The combination of either IL-17 plus IL-1beta or IL-17 plus TNF-alpha enhanced IL-6 secretion and IL-6 mRNA expression; in particular, the effects of IL-17 plus TNF-alpha were much stronger than those induced by IL-17 plus IL-1beta. TNF-alpha-induced IL-6 mRNA degraded rapidly at any concentrations, and the combination of IL-17 and TNF-alpha markedly enhanced IL-6 mRNA stability. This indicates that the effects of IL-17 plus TNF-alpha were regulated at the post-transcriptional level. In conclusion, pancreatic periacinar myofibroblasts secreted a large amount of IL-6 in response to proinflammatory cytokines. These cells might play an important role in the pathogenesis of acute pancreatitis via IL-6 secretion.

Increased granulopoiesis through interleukin-17 and granulocyte colony-stimulating factor in leukocyte adhesion molecule-deficient mice

Many mutant mice deficient in leukocyte adhesion molecules display altered hematopoiesis and neutrophilia. This study investigated whether peripheral blood neutrophil concentrations in these mice are elevated as a result of accumulation of neutrophils in the circulation or altered hematopoiesis mediated by a disrupted regulatory feedback loop. Chimeric mice were generated by transplanting various ratios of CD18(+/+) and CD18(-/-) unfractionated bone marrow cells into lethally irradiated wild-type mice, resulting in approximately 0%, 10%, 50%, 90%, or 100% CD18 null neutrophils in the blood. The presence of only 10% CD18(+/+) neutrophils was sufficient to prevent the severe neutrophilia seen in mice reconstituted with CD18(-/-) bone marrow cells. These data show that the neutrophilia in CD18(-/-) mice is not caused by enhanced neutrophil survival or the inability of neutrophils to leave the vascular compartment. In CD18(-/-), CD18(-/-)E(-/-), CD18(-/-)P(-/-), EP(-/-), and EPI(-/-) mice, levels of granulocyte colony-stimulating factor (G-CSF) and interleukin-17 (IL-17) were elevated in proportion to the neutrophilia seen in these mice, regardless of the underlying mutation. Antibiotic treatment or the propensity to develop skin lesions did not correlate with neutrophil counts. Blocking IL-17 or G-CSF function in vivo significantly reduced neutrophil counts in severely neutrophilic mice by approximately 50% (P <.05) or 70% (P <.01), respectively. These data show that peripheral blood neutrophil numbers are regulated by a feedback loop involving G-CSF and IL-17 and that this feedback loop is disrupted when neutrophils cannot migrate into peripheral tissues.

Forced expression of murine IL-17E induces growth retardation, jaundice, a Th2-biased response, and multiorgan inflammation in mice

IL-17 is a proinflammatory cytokine, and its in vivo expression induces neutrophilia in mice. IL-17E is a recently described member of an emerging family of IL-17-related cytokines. IL-17E has been shown to bind IL-17Rh1, a protein distantly related to the IL-17R, suggesting that IL-17E probably possesses unique biological functions. In this study, we have identified the murine ortholog of IL-17E and developed transgenic mice to characterize its actions in vivo. Biological consequences of overexpression of murine (m)IL-17E, both unique to IL-17E and similar to IL-17, were revealed. Exposure to mIL-17E resulted in a Th2-biased response, characterized by eosinophilia, increased serum IgE and IgG1, and a Th2 cytokine profile including elevated serum levels of IL-13 and IL-5 and elevated gene expression of IL-4, IL-5, IL-10, and IL-13 was observed in many tissues. Increased gene expression of IFN-gamma in several tissues and elevated serum TNF-alpha were also noted. In addition, IL-17E induces G-CSF production in vitro and mIL-17E-transgenic mice had increased serum G-CSF and exhibit neutrophilia, a property shared by IL-17. Moreover, exposure to mIL-17E elicited pathological changes in multiple tissues, particularly liver, heart, and lungs, characterized by mixed inflammatory cell infiltration, epithelial hyperplasia, and hypertrophy. Taken together, these findings suggest that IL-17E is a unique pleiotropic cytokine and may be an important mediator of inflammatory and immune responses.

Enhancing effect of IL-1, IL-17, and TNF-alpha on macrophage inflammatory protein-3alpha production in rheumatoid arthritis: regulation by soluble receptors and Th2 cytokines

Macrophage inflammatory protein (MIP)-3alpha is a chemokine involved in the migration of T cells and immature dendritic cells. To study the contribution of proinflammatory cytokines and chemokines to the recruitment of these cells in rheumatoid arthritis (RA) synovium, we looked at the effects of the monocyte-derived cytokines IL-1beta and TNF-alpha and the T cell-derived cytokine IL-17 on MIP-3alpha production by RA synoviocytes. Addition of IL-1beta, IL-17, and TNF-alpha induced MIP-3alpha production in a dose-dependent manner. At optimal concentrations, IL-1beta (100 pg/ml) was much more potent than IL-17 (100 ng/ml) and TNF-alpha (100 ng/ml). When combined at lower concentrations, a synergistic effect was observed. Conversely, the anti-inflammatory cytokines IL-4 and IL-13 inhibited MIP-3alpha production by activated synoviocytes, but IL-10 had no effect. Synovium explants produced higher levels of MIP-3alpha in RA than osteoarthritis synovium. MIP-3alpha-producing cells were located in the lining layer and perivascular infiltrates in close association with CD1a immature dendritic cells. Addition of exogenous IL-17 or IL-1beta to synovium explants increased MIP-3alpha production. Conversely, specific soluble receptors for IL-1beta, IL-17, and TNF-alpha inhibited MIP-3alpha production to various degrees, but 95% inhibition was obtained only when the three receptors were combined. Similar optimal inhibition was also obtained with IL-4, but IL-13 and IL-10 were less active. These findings indicate that interactions between monocyte and Th1 cell-derived cytokines contribute to the recruitment of T cells and dendritic cells by enhancing the production of MIP-3alpha by synoviocytes. The inhibitory effect observed with cytokine-specific inhibitors and Th2 cytokines may have therapeutic applications.

Cutting edge: IL-17F, a novel cytokine selectively expressed in activated T cells and monocytes, regulates angiogenesis and endothelial cell cytokine production

A novel secreted cytokine, termed IL-17F, was cloned using nested RACE PCR. This cytokine bears homology to IL-17. IL-17F was expressed only in activated CD4(+) T cells and activated monocytes. Recombinant human IL-17F did not stimulate the proliferation of hematopoietic progenitors or the migration of mature leukocytes. However, it markedly inhibited the angiogenesis of human endothelial cells and induced endothelial cells to produce IL-2, TGF-beta, and monocyte chemoattractant protein-1.

IL-17s adopt a cystine knot fold: structure and activity of a novel cytokine, IL-17F, and implications for receptor binding

The proinflammatory cytokine interleukin 17 (IL-17) is the founding member of a family of secreted proteins that elicit potent cellular responses. We report a novel human IL-17 homolog, IL-17F, and show that it is expressed by activated T cells, can stimulate production of other cytokines such as IL-6, IL-8 and granulocyte colony-stimulating factor, and can regulate cartilage matrix turnover. Unexpectedly, the crystal structure of IL-17F reveals that IL-17 family members adopt a monomer fold typical of cystine knot growth factors, despite lacking the disulfide responsible for defining the canonical "knot" structure. IL-17F dimerizes in a parallel manner like neurotrophins, and features an unusually large cavity on its surface. Remarkably, this cavity is located in precisely the same position where nerve growth factor binds its high affinity receptor, TrkA, suggesting further parallels between IL-17s and neurotrophins with respect to receptor recognition.

Interleukin-17 and lung host defense against Klebsiella pneumoniae infection

Bacterial pneumonia remains an important cause of morbidity and mortality worldwide, especially in immune-compromised patients. Cytokines and chemokines are critical molecules expressed in response to invading pathogens and are necessary for normal lung bacterial host defenses. Here we show that interleukin (IL)-17, a novel cytokine produced largely by CD4+ T cells, is produced in a compartmentalized fashion in the lung after challenge with Klebsiella pneumoniae. Moreover, overexpression of IL-17 in the pulmonary compartment using a recombinant adenovirus encoding murine IL-17 (AdIL-17) resulted in the local induction of tumor necrosis factor-alpha, IL-1beta, macrophage inflammatory protein-2, and granulocyte colony-stimulating factor (G-CSF); augmented polymorphonuclear leukocyte recruitment; and enhanced bacterial clearance and survival after challenge with K. pneumoniae. However, simultaneous treatment with AdIL-17 provided no survival benefit after intranasal K. pneumoniae challenge. These data show that IL-17 may have a role in priming for enhanced chemokine and G-CSF production in the context of lung infection and that optimally timed gene therapy with IL-17 may augment host defense against bacterial pneumonia.

IL-17 is increased in asthmatic airways and induces human bronchial fibroblasts to produce cytokines

BACKGROUND

IL-17 is a cytokine that has been reported to be produced by T lymphocytes. In vitro, IL-17 activates fibro-blasts and macrophages for the secretion of GM-CSF, TNF-alpha, IL-1beta, and IL-6. A number of these cytokines are involved in the airway remodeling that is observed within the lungs of asthmatic individuals.

OBJECTIVE

In this study, we investigated the expression of IL-17 in sputum and bronchoalveolar lavage specimens obtained from asthmatic subjects and from nonasthmatic control subjects.

METHODS

IL-17 was detected through use of immunocytochemistry, in situ hybridization, and Western blot. Bronchial fibroblasts were stimulated with IL-17, and cytokine production and chemokine production were detected through use of ELISA and RT-PCR.

RESULTS

Using immunocytochemistry, we demonstrated that the numbers of cells positive for IL-17 are significantly increased in sputum and bronchoalveolar lavage fluids of subjects with asthma in comparison with control subjects (P <.001 and P <.005, respectively). We demonstrated that in addition to T cells, eosinophils in sputum and bronchoalveolar lavage fluids expressed IL-17. Peripheral blood eosinophils were also positive for IL-17, and the level of IL-17 in eosinophils purified from peripheral blood was significantly higher in subjects with asthma than in controls (P <.01). To further investigate the mechanism of action of IL-17 in vivo, we examined the effect of this cytokine on fibroblasts isolated from bronchial biopsies of asthmatic and nonasthmatic subjects. IL-17 did enhance the production of pro-fibrotic cytokines (IL-6 and IL-11) by fibroblasts, and this was inhibited by dexamethasone. Similarly, IL-17 increased the level of other fibroblast-derived inflammatory mediators, such as the alpha-chemokines, IL-8, and growth-related oncogene-alpha.

CONCLUSION

Our results, which demonstrate for the first time that eosinophils are a potential source of IL-17 within asthmatic airways, suggest that IL-17 might have the potential to amplify inflammatory responses through the release of proinflammatory mediators such as alpha-chemokines.

Requirement of interleukin 17 receptor signaling for lung CXC chemokine and granulocyte colony-stimulating factor expression, neutrophil recruitment, and host defense

Bacterial pneumonia is an increasing complication of HIV infection and inversely correlates with the CD4(+) lymphocyte count. Interleukin (IL)-17 is a cytokine produced principally by CD4(+) T cells, which induces granulopoiesis via granulocyte colony-stimulating factor (G-CSF) production and induces CXC chemokines. We hypothesized that IL-17 receptor (IL-17R) signaling is critical for G-CSF and CXC chemokine production and lung host defenses. To test this, we used a model of Klebsiella pneumoniae lung infection in mice genetically deficient in IL-17R or in mice overexpressing a soluble IL-17R. IL-17R-deficient mice were exquisitely sensitive to intranasal K. pneumoniae with 100% mortality after 48 h compared with only 40% mortality in controls. IL-17R knockout (KO) mice displayed a significant delay in neutrophil recruitment into the alveolar space, and had greater dissemination of K. pneumoniae compared with control mice. This defect was associated with a significant reduction in steady-state levels of G-CSF and macrophage inflammatory protein (MIP)-2 mRNA and protein in the lung in response to the K. pneumoniae challenge in IL-17R KO mice. Thus, IL-17R signaling is critical for optimal production of G-CSF and MIP-2 and local control of pulmonary K. pneumoniae infection. These data support impaired IL-17R signaling as a potential mechanism by which deficiency of CD4 lymphocytes predisposes to bacterial pneumonia.

Il-17 mobilizes peripheral blood stem cells with short- and long-term repopulating ability in mice

Autologous and allogeneic bone marrow transplantations have evolved as important cancer therapy modalities. For both indications, peripheral blood has been shown to have distinct advantages over bone marrow as the stem cell source. Cytokine combinations for mobilization have enhanced stem cell yield and accelerated engraftment. However, novel mobilizing agents and strategies are needed to further improve clinical outcomes. Within the donor graft, the dynamic equilibrium between T cells and stem cells critically influences engraftment and transplantation results. IL-17 is a cytokine produced almost exclusively from activated T cells. IL-17 was expressed in vivo with adenovirus technology. Here, proof-of-principle studies demonstrate that IL-17 effectively mobilizes hemopoietic precursor cells (CFU-granulocyte-erythrocyte-macrophage-monocyte, CFU-high proliferative potential) and primitive hemopoietic stem cells (Lin(-/low)c-kit(+)Sca1(+)). Moreover, mouse IL-17 adenovirus-mobilized peripheral blood stem cells rescued lethally irradiated mice. Bone marrow was found to be 45-75% of donor origin at 1 year. In secondary recipients, donor-derived bone marrow cells ranged from 45 to 95%. These data show that IL-17 mobilizes stem cells in mice with short- and long-term reconstituting capacity. Additional comparative studies are needed as well as studies in tumor models to refine distinct potential clinical applications for IL-17-mobilized peripheral blood stem cells.

IL-1-independent role of IL-17 in synovial inflammation and joint destruction during collagen-induced arthritis

T cell IL-17 displays proinflammatory properties and is expressed in the synovium of patients with rheumatoid arthritis. Its contribution to the arthritic process has not been identified. Here, we show that blocking of endogenous IL-17 in the autoimmune collagen-induced arthritis model results in suppression of arthritis. Also, joint damage was significantly reduced. In contrast, overexpression of IL-17 enhanced collagen arthritis. Moreover, adenoviral IL-17 injected in the knee joint of type II collagen-immunized mice accelerated the onset and aggravated the synovial inflammation at the site. Radiographic and histologic analysis showed markedly increased joint destruction. Elevated levels of IL-1beta protein were found in synovial tissue. Intriguingly, blocking of IL-1alphabeta with neutralizing Abs had no effect on the IL-17-induced inflammation and joint damage in the knee joint, implying an IL-1 independent pathway. This direct potency of IL-17 was underscored in the unabated IL-17-induced exaggeration of bacterial cell wall-induced arthritis in IL-1beta(-/-) mice. In conclusion, this data shows that IL-17 contributes to joint destruction and identifies an IL-1-independent role of IL-17. These findings suggest IL-17 to be a novel target for the treatment of destructive arthritis and may have implications for tissue destruction in other autoimmune diseases.

Cooperation of interleukin-17 and interferon-gamma on chemokine secretion in human fetal intestinal epithelial cells

Interleukin (IL)-17 is a newly identified T cell-derived cytokine that can regulate the functions of a variety of cell types. In this study, we investigated the effects of IL-17 and interferon (IFN)-gamma on chemokine secretion in human fetal intestinal epithelial cells. IL-8 and monocyte chemoattractant protein (MCP)-1 secretion by the human fetal intestinal epithelial cell line, intestine-407, was evaluated by ELISA and Northern blot. The expression of IL-17 receptor (R) was analysed by a binding assay using [(125)I]-labelled IL-17. The activation of nuclear factor-kappa B (NF-kappa B), NF-IL6 and AP-1 was assessed by an electrophoretic gel mobility shift assay (EMSA). IL-17 induced a dose-dependent increase in IL-8 and MCP-1 secretion. The inducing effects of IL-17 on IL-8 and MCP-1 mRNA abundance reached a maximum as early as 3 h, and then gradually decreased. IL-17 and IFN-gamma synergistically increased IL-8 and MCP-1 secretion and mRNA abundance. IFN-gamma induced a weak increase in IL-17 R mRNA abundance, and incubation with IFN-gamma for 24 h enhanced [(125)I]-labelled IL-17-binding by 2.4-fold. IL-17 rapidly induced the phosphorylation and degradation of I kappa B alpha molecules, and the combination of IL-17 and IFN-gamma induced a marked increase in NF-kappa B DNA-binding activity as early as 1.5 h after the stimulation. Furthermore, this combination induced an increase in NF-IL-6 and AP-1 DNA-binding activity. In conclusion, it becomes clear that IL-17 is an inducer of IL-8 and MCP-1 secretion by human fetal intestinal epithelial cells. The combination of IL-17 with IFN-gamma synergistically enhanced chemokine secretion. These effects of IL-17 and IFN-gamma might play an important role in the inflammatory responses in the intestinal mucosa.

High in vivo expression of interleukin-17 receptor in synovial endothelial cells and chondrocytes from arthritis patients

OBJECTIVE

To evaluate the presence of interleukin-17 (IL-17) and the expression of IL-17 receptor (IL-17R) in joint tissues from subjects with different arthritides.

METHODS

Immunohistochemistry was used on frozen synovial and cartilage biopsies to identify cells expressing IL-17 and IL-17R.

RESULTS

IL-17 staining was present only in synovial biopsies of rheumatoid arthritis (RA) (seven out of nine cases). IL-17R was expressed by all synovial biopsies evaluated except for three cases of post-traumatic arthritis (PTA). Vascular endothelial cells mainly expressed IL-17R. The percentage of IL-17R(+) vessels was the highest in RA synovium and the lowest in PTA. Chondrocytes from all types of arthritides were negative for IL-17 staining, but expressed IL-17R; the highest percentage of positive chondrocytes was found in seronegative spondylarthritis and the lowest in RA.

CONCLUSIONS

IL-17-positive cells are found exclusively in RA. On the other hand, synovial endothelial cells and chondrocytes expressing IL-17R are found in the majority of patients with different types of arthritis. This finding suggests a role for a second ligand for IL-17R, which could be either a different cytokine or a different isoform of IL-17.

Subversion and piracy: DNA viruses and immune evasion

During the co-evolution of viruses with their vertebrate hosts, the DNA viruses have acquired an impressive array of immunomodulatory genes to combat host immune responses and their hosts have developed a sophisticated immune system to contain virus infections. In order to replicate, the viruses have evolved mechanisms to inhibit key host anti-virus responses that include apoptosis, interferon production, chemokine production, inflammatory cytokine production, and the activity of cytotoxic T-cells, natural killer cells and antibody. In addition, some of the viruses encode cytokine or chemokine homologues that recruit or expand cell numbers for infection or that subvert the host cellular response from a protective response to a benign one. The specificity of the viral immunomodulatory molecules reflects the life cycle and the pathogenesis of the viruses. Herpesviruses achieve latency in host cells by inducing cell survival and protecting infected cells from immune recognition. This involves interference with cell signal transduction pathways. Many of the viral immunomodulatory proteins are homologues of host proteins that appear to have been pirated from the host and reassorted in the virus genomes. Some of these have unique functions and indicate novel or important aspects of both viral pathogenesis and host immunity to viruses. The specific example of orf virus infection of sheep is described.

The combination of tumor necrosis factor alpha blockade with interleukin-1 and interleukin-17 blockade is more effective for controlling synovial inflammation and bone resorption in an ex vivo model

OBJECTIVE

Anti-tumor necrosis factor a (anti-TNFalpha) therapy has shown efficacy in the treatment of rheumatoid arthritis (RA). Since interleukin-1 (IL-1), TNFalpha, and IL-17 have many additive and/or synergistic effects in vitro, we tested whether their combined inhibition by soluble receptors would lead to an enhanced effect on ex vivo models of synovial inflammation and bone destruction.

METHODS

RA synovium and bone explants were cultured for 7 days in the presence of 1 microg/ml soluble TNFalpha receptor (STNFR; as in current therapy), type II soluble IL-1 receptor (sIL-1RII), or sIL-17R either alone or in combination. Their effects on the production of IL-6 and the release of C-telopeptide of type I collagen (CTX), a marker of type I collagen destruction, were measured by enzyme-linked immunosorbent assay.

RESULTS

In synovium, each soluble receptor alone decreased IL-6 production and CTX release by approximately 35% and approximately 55%, respectively. The combination of all 3 receptors was more effective, inhibiting IL-6 production and collagen degradation by up to 70%. Neither sIL-17R, sIL-1RII, or sTNFR alone had no effect (or an effect of <20% inhibition) on IL-6 production in 18%, 33%, and 22%, respectively, of the samples. In bone, sIL-17R, sIL-1RII, and sTNFR decreased IL-6 production by 23%, 50%, and 37%, respectively, while the combination decreased IL-6 production by 75%. A 50% inhibition of CTX release was obtained with sIL-1RII for 63% of the samples versus 38% of the samples with either sTNFR or sIL-17R. However, the combination of all 3 receptors was not more potent than sIL-1RII alone.

CONCLUSION

The inhibitory effect of sTNFR on IL-6 production and collagen degradation in RA synovium and bone was increased in combination with sIL-17R and sIL-1RII. These results support the concept of combination therapy, which may increase the percentage of responding patients as well as the degree of individual patient response.

Binding of recombinant feline immunodeficiency virus surface glycoprotein to feline cells: role of CXCR4, cell-surface heparans, and an unidentified non-CXCR4 receptor

To address the role of CXCR4 in the cell-surface attachment of the feline immunodeficency virus (FIV), a soluble fusion protein, gp95-Fc, consisting of the surface glycoprotein (SU, gp95) of either a primary (PPR) or cell line-adapted (34TF10) FIV strain was fused in frame with the Fc domain of human immunoglobulin G1. The recombinant SU-immunoadhesins were used as probes to investigate the cellular binding of FIV SU. In agreement with the host cell range properties of both viruses, binding of 34TF10 gp95-Fc was observed for all cell lines tested, whereas PPR gp95-Fc bound only to primary feline T cells. 34TF10 gp95-Fc also bound to Jurkat and HeLa cells, consistent with the ability of FIV to use human CXCR4 as a fusion receptor. As expected, 34TF10 gp95-Fc binding to Jurkat cells was blocked by addition of stromal cell-derived factor 1alpha (SDF-1alpha), as was binding to the 3201 feline lymphoma cell line. However, SDF-1alpha, RANTES, macrophage inflammatory protein 1beta, and heparin all failed to inhibit the binding of either gp95-Fc to primary T cells, suggesting that a non-CXCR4 receptor is involved in the binding of FIV SU. In this regard, an unidentified 40-kDa protein species from the surface of primary T cells but not Jurkat and 3201 cells specifically coprecipitated with both gp95-Fc. Yet another type of binding of 34TF10 gp95-Fc to adherent kidney cells was noted. SDF-1alpha failed to block the binding of 34TF10 gp95-Fc to either HeLa, Crandel feline leukemia, or G355-5 cells. However, binding was severely impaired in the presence of soluble heparin, as well as after enzymatic removal of surface heparans or on cells deficient in heparan expression. These overall findings suggest that in addition to CXCR4, a non-CXCR4 receptor and cell-surface heparans also play an important role in FIV gp95 cell surface interactions on specific target cells.

Herpesvirus saimiri

Herpesvirus saimiri (saimiriine herpesvirus 2) is the classical prototype of the gamma(2)-herpesviruses or rhadinoviruses, which also contains a human member, the Kaposi's sarcoma-associated herpesvirus. The T-lymphotropic Herpesvirus saimiri establishes specific replicative and persistent conditions in different primate host species. Virtually all squirrel monkeys (Saimiri sciureus) are persistently infected with this virus. In its natural host, the virus does not cause disease, whereas it induces fatal acute T-cell lymphoma in other monkey species after experimental infection. The virus can be isolated by cocultivation of permissive epithelial cells with peripheral blood cells from naturally infected squirrel monkeys and from susceptible New World monkeys during the virus-induced disease. Tumour-derived and in vitro-transformed T-cell lines from New World monkeys release virus particles. Herpesvirus ateles is a closely related virus of spider monkeys (Ateles spp.) and has similar pathogenic properties to Herpesvirus saimiri in other New World primate species. Similar to other rhadinoviruses, the genome of Herpesvirus saimiri harbours a series of virus genes with pronounced homology to cellular counterparts including a D-type cyclin, a G-protein-coupled receptor, an interleukin-17, a superantigen homologue, and several inhibitors of the complement cascade and of different apoptosis pathways. Preserved function has been demonstrated for most of the homologues of cellular proteins. These viral functions are mostly dispensable for the transforming and pathogenic capability of the virus. However, they are considered relevant for the apathogenic persistence of Herpesvirus saimiri in its natural host. A terminal region of the non-repetitive coding part of the virus genome is essential for pathogenicity and T-cell transformation. Based on the pathogenic phenotypes and the different alleles of this variable region, the virus strains have been assigned to three subgroups, termed A, B and C. In the highly oncogenic subgroup C strains, the two virus genes stpC and tip are transcribed from one bicistronic mRNA and are essential for transformation and leukaemia induction. stpC fulfils the typical criteria of an oncogene; its product interacts with Ras and tumour necrosis factor-associated factors and induces mitogen-activated protein kinase and nuclear factor kappa B activation. Tip interacts with the RNA transport factor Tap, with signal transduction and activation of transcription factors, and with the T-cellular tyrosine kinase Lck, which is activated by this interaction and phosphorylates Tip as a substrate. It is of particular interest that certain subgroup C virus strains such as C488 are capable of transforming human T lymphocytes to stable growth in culture. The transformed human T cells harbour multiple copies of the viral genome in the form of stable, non-integrated episomes. The cells express only a few virus genes and do not produce virus particles. The transformed cells maintain the antigen specificity and many other essential functions of their parental T-cell clones. Based on the preserved functional phenotype of the transformed T cells, Herpesvirus saimiri provides useful tools for T-cell immunology, for gene transfer and possibly also for experimental adoptive immunotherapy.

Comparative analysis of the transforming mechanisms of Epstein-Barr virus, Kaposi's sarcoma-associated herpesvirus, and Herpesvirus saimiri

Members of the gamma herpesvirus family include the lymphocryptoviruses (gamma-1 herpesviruses) and the rhadinoviruses (gamma-2 herpesviruses). Gammaherpesvirinae uniformly establish long-term, latent, reactivatable infection of lymphocytes, and several members of the gamma herpesviruses are associated with lymphoproliferative diseases. Epstein-Barr virus is a lymphocryptovirus, whereas Kaposi sarcoma-associated herpesvirus and Herpesvirus saimiri are members of the rhadinovirus family. Genes encoded by these viruses are involved in a diverse array of cellular signaling pathways. This review attempts to cover our understanding of how viral proteins deregulate cellular signaling pathways that ultimately contribute to the conversion of normal cells to cancerous cells.

ULBPs, novel MHC class I-related molecules, bind to CMV glycoprotein UL16 and stimulate NK cytotoxicity through the NKG2D receptor

The human cytomegalovirus glycoprotein, UL16, binds to two members of a novel family of molecules, the ULBPs, and to the MHC class I homolog, MICB. The ULBPs are GPI-linked glycoproteins belonging to the extended MHC class I family but are only distantly related to MICB. The ULBP and MICB molecules are ligands for the activating receptor, NKG2D/DAP10, and this interaction is blocked by a soluble form of UL16. The ULBPs stimulate cytokine and chemokine production from NK cells, and expression of ULBPs in NK cell-resistant target cells confers susceptibility to NK cell cytotoxicity. Masking of NK cell recognition of ULBP or MIC antigens by UL16 provides a potential mechanism by which human cytomegalovirus-infected cells might evade attack by the immune system.

IL-17E, a novel proinflammatory ligand for the IL-17 receptor homolog IL-17Rh1

We report identification of interleukin (IL)-17E, a novel member of the IL-17 family of cytokines. IL-17E is a ligand for the recently identified protein termed EVI27/IL-17BR, which we term IL-17 receptor homolog 1 (IL-17Rh1) in light of the multiple reported ligand-receptor relationships. Murine EVI27 was identified through its location at a common site of retroviral integration in BXH2 murine myeloid leukemias. IL-17Rh1 shows highest level expression in kidney with moderate expression in multiple other organs, whereas IL-17E mRNA was detected at very low levels in several peripheral tissues. IL-17E induces activation of NF-kappaB and stimulates production of the proinflammatory chemokine IL-8.