The TNF cytokine family: one track in a road paved by many.

During the quarter of a century since TNF was isolated, much knowledge has been gained of the identity of other ligands besides TNF in the TNF cytokine family, and of the proximal signaling molecules that these ligands activate. The numerous laboratories contributing to this advance have approached TNF research from various points of view. The research pathway taken in my own laboratory, which is outlined in this article, has been driven by the desire to elucidate mechanisms that regulate cell death.

Apoptosis induced in normal human hepatocytes by tumor necrosis factor-related apoptosis-inducing ligand.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been reported to induce apoptosis in various tumor cells but not in nontransformed, normal cells. Preclinical studies in mice and nonhuman primates have shown that administration of TRAIL can induce apoptosis in human tumors, but that no cytotoxicity to normal organs or tissues is found. The susceptibility of tumor cells to TRAIL and an apparent lack of activity in normal cells has lead to a proposal to use TRAIL in cancer therapy. Here, we assessed the sensitivity of hepatocytes from rat, mouse, rhesus monkey and human livers to TRAIL-induced apoptosis. TRAIL induced apoptosis in normal human hepatocytes in culture but not in hepatocytes isolated from the other species. Human hepatocytes showed characteristic features of apoptosis, including cytoplasmic shrinkage, the activation of caspases and DNA fragmentation. Apoptosis and cell death in human hepatocytes was massive and rapid, occurring in more than 60% of the cells exposed to TRAIL within 10 hours. These results indicate that there are species differences in sensitivity to TRAIL, and that substantial liver toxicity might result if TRAIL were used in human cancer therapy.

Structure of CrmE, a virus-encoded tumour necrosis factor receptor.

Vaccinia virus (VACV), the smallpox vaccine, encodes many proteins that subvert the host immune response. One of these, cytokine response modifier E (CrmE), is secreted by infected cells and protects these cells from apoptotic challenge by tumour necrosis factor alpha (TNFalpha). We have expressed recombinant CrmE from VACV strain Lister in Escherichia coli, shown that the purified protein is monomeric in solution and competent to bind TNFalpha, and solved the structure to 2.0 A resolution. This is the first structure of a virus-encoded tumour necrosis factor receptor (TNFR). CrmE shares significant sequence similarity with mammalian type 2 TNF receptors (TNFSFR1B, p75; TNFR type 2). The structure confirms that CrmE adopts the canonical TNFR fold but only one of the two "ligand-binding" loops of TNFRSF1A is conserved in CrmE, suggesting a mechanism for the higher affinity of poxvirus TNFRs for TNFalpha over lymphotoxin-alpha. The roles of dimerisation and pre-ligand-assembly domains (PLADs) in poxvirus and mammalian TNFR activity are discussed.

Picomole-level mapping of protein disulfides by mass spectrometry following partial reduction and alkylation.

We have deduced the disulfide bond linkage patterns, at very low protein levels (<0.5 nmol), in two cysteine-rich polypeptide domains using a new strategy involving partial reduction/alkylation of the protein, followed by peptide mapping and tanden mass spectrometry (MS/MS) sequencing on a nanoflow liquid chromatography-MS/MS system. The substrates for our work were the cysteine-rich ectodomain of human Fn14, a member of the tumor necrosis factor receptor family, and the IgV domain of murine TIM-1 (T-cell, Ig domain, and mucin domain-1). We have successfully determined the disulfide linkages for Fn14 and independently confirmed those of the IgV domain of TIM-1, whose crystal structure was published recently. The procedures that we describe here can be used to determine the disulfide structures for proteins with complex characteristics. They will also provide a means to obtain important information for structure-function studies and to ensure correct protein folding and batch-to-batch consistency in commercially produced recombinant proteins.

Characterization of a novel TNF-like ligand and recently described TNF ligand and TNF receptor superfamily genes and their constitutive and inducible expression in hematopoietic and non-hematopoietic cells.

A novel (TL1), a recently described (TL2) TNF-like, and three recently described TNF receptor-like (TR1, TR2, TR3) molecules were identified by searching a cDNA database. TL1 and TL2 are type-II membrane proteins. TR2 and TR3 are type-I membrane proteins whereas TR1 appears to be a secreted protein. TL1, TL2, TR2 and TR3 were expressed in hematopoietic cells, whereas TR1 was not. Northern blots hybridized with the cDNA probes revealed multiple forms of RNA as well as inducible expression of TL1, TL2, TR2 and TR3. TL2 and TR3, in particular, were highly induced in activated CD4+ T cells. Radiation hybrid mapping localized TR1 and TL2 to 8q24 and 3q26, respectively, which are not near any known superfamily members. TL1 was mapped to 9q32, near CD30L (9q33) and TR2 and TR3 mapped to the region of chromosome 1 that contains the TNFR-II, 4-1BB, OX40 and CD30 gene cluster at 1p36. Only TR3 in this cluster possesses a death domain. Southern blot analysis revealed the presence of TL and TR genes in different mammalian species. TL2, TR1, TR2 and TR3 were recently described by others as TRAIL/Apo-2L, OPG, HVEM and DR3/WSL-1/Apo-3/TRAMP/LARD, respectively.

TRUNDD, a new member of the TRAIL receptor family that antagonizes TRAIL signalling.

TRAIL/Apo-2L induces rapid apoptosis of a variety of tumor cell lines. A family of tumor necrosis factor receptor-related molecules have been identified as receptors for TRAIL. Herein, we report the identification of another member of the TRAIL receptor family, TRUNDD (TRAIL receptor with a truncated death domain). The TRUNDD transcript was detected in multiple human tissues. TRUNDD is highly homologous to all known TRAIL receptors and has an extracellular TRAIL-binding domain but lacks a functional intracellular death domain and does not induce apoptosis. Consistent with an inhibitory role, ectopic expression of TRUNDD attenuated TRAIL-induced apoptosis in mammalian cells.

Recombinant glucocorticoid induced tumor necrosis factor receptor (rGITR) induces NOS in murine macrophage.

Glucocorticoid induced tumor necrosis factor receptor (GITR) is a new member of the tumor necrosis factor-nerve growth factor receptor superfamily of which the function has not been well studied. The extracellular domain of GITR was produced in Escherichia coli and purified as a single band of predicted M(r) of 18.0 kDa. GITR and GITR ligand were expressed constitutively on the surface of Raw 264.7 macrophage cell line and murine peritoneal macrophages. An extracellular domain of GITR can activate murine macrophages to express inducible nitric oxide synthase and to generate nitric oxide in a dose- and time-dependent manner.

Characterization of human homologue of 4-1BB and its ligand.

The human homologue of 4-1BB (H4-1BB) cDNA was isolated from PMA plus ionomycin-treated human peripheral T-cell cDNA libraries. The amino acid sequence deduced from the nucleotide sequence showed that the protein is composed of 255 amino acids with 2 potential N-linked glycosylation sites. The molecular weight of its protein backbone is calculated to be 27 kDa. The H4-1BB contains features such as signal sequence and transmembrane domain, indicating that it is a receptor protein. This protein showed 60% identity of amino acid sequence to mouse 4-1BB. In the cytoplasmic domain there are 5 regions of amino acid sequences conserved from mouse to human, indicating that these residues might be important in the 4-1BB function. H4-1BB mRNA was detected in unstimulated peripheral blood T cells and was inducible in T-cell lines such as Jurkat and CEM. H4-1BB-AP, a fusion protein between the H4-1BB extracellular domain and alkaline phosphatase, was used to identify the ligand for the H4-1BB. Although the H4-1BB ligand was detected in both T and B cells of human peripheral blood, the ligand was preferentially expressed in primary B cells and B-cell lines. Daudi, a B-cell lymphoma, was one of the B-cell lines that carried a higher number of ligands. Scatchard analysis showed that the Kd = 1.4 x 10(9) M and the number of ligands in Daudi cell was 4.2 x 10(3).

Tumour necrosis factor (TNF) binding proteins (soluble TNF receptor forms) with possible roles in inflammation and malignancy.

Inhibitors of Tumour Necrosis Factor (TNF) may be necessary for protection of the host against harmful systemic manifestations of this cytokine such as in the septic syndrome and inflammatory conditions. TNF-binding proteins (TNF-BP) have been identified and shown to be the soluble extracellular domains of two transmembrane TNF receptors produced by proteolytic cleavage. TNF-BP inactivates TNF by formation of high affinity complexes thereby reducing the binding of TNF to target cell membrane receptors. In addition, TNF is stabilized in complex with TNF-BP, and under certain conditions the complex may act as a slow releaser of biologically active TNF. TNF can induce the release of TNF-BP in vivo which might neutralize the bioactivity of TNF. Cytokine control by natural and recombinant cytokine inhibitors such as TNF-BP could be a promising therapeutic approach in chronic inflammatory disorders to shift the balance between a cytokine-induced response and counteracting "anticytokines". A local production of TNF-BP in some tumour tissues may inactivate TNF for the benefit of the tumour. In some leukemias e.g. B-cell chronic lymphocytic leukemia, where TNF can act as a growth factor for the malignant cells, TNF-BP may be growth inhibitory.

Identification of differentially glycosylated forms of the soluble p75 tumor necrosis factor (TNF) receptor in human urine.

Human urine is known to contain a 30 kDa soluble form of the p75-TNF receptor (sTNF-R2). In this work we have purified sTNF-R2 from the urine of normal subjects and further characterized its structure and activity. sTNF-R2 was resolved by reducing SDS-PAGE in a major band of 30 kDa, similar in size to the previously described urinary sTNFR2, and in a minor band of 45 kDa. "Western" blotting analysis with anti-TNF-R1 and anti-TNF-R2 antibodies showed that both bands were immunologically related to the membrane TNF-R2. Glycosylation studies indicated that the 30 kDa is N-glycosylated while the 45 kDa form is N- and O-glycosylated, and suggested that both forms contain terminally linked sialic acid that is differentially recognized by lectins. These results indicate that human urine contains, besides the 30 kDa form, a new form of 45 kDa characterized by different glycosylation type and degree.

Expression and characterization of a recombinant soluble form of bovine tumor necrosis factor receptor type I.

A recombinant soluble bovine tumor necrosis factor receptor type I (sboTNF-RI) was expressed in the methylotrophic yeast Pichia pastoris and evaluated for its ability to inhibit bovine tumor necrosis factor alpha (TNF-alpha) cytotoxicity. A cDNA encoding the extracellular domain of bovine TNF-RI was placed under the control of the powerful and tightly regulated alcohol oxidase1 (AOX1) gene promoter of the pPICZa A vector and the resulting construct integrated into the 5' region of the alcohol oxidase genes of GS115 and KM71 strains of Pichia. Soluble bovine TNF-RI was secreted into the medium following induction of the AOX1 gene promoter with methanol, and purified to greater than 95% purity by ion-exchange chromatography. In in vitro assays, the purified recombinant sboTNF-RI will block the cytolytic activity of bovine TNF-alpha on WEHI 164 cells clone 13 by 50% when used at a concentration of 170 microg/ml, and by nearly 90% when used at a concentration of 310 microg/ml. Results of this study suggest that recombinant sboTNF-RI may have therapeutic value as a TNF inhibitor in cattle with coliform mastitis.

Development of a baculovirus expression system for soluble porcine tumor necrosis factor receptor type I and soluble porcine tumor necrosis factor receptor type I-IgG fusion protein.

Tumor necrosis factor-alpha (TNF-alpha) is a key mediator of inflammatory responses and gram-negative bacterial sepsis, but the role that it plays during Salmonella enterica species bacterial infections in swine has not yet been elucidated. To facilitate studies on the role of TNF-alpha on the pathology associated with Salmonella infections in pigs, recombinant soluble porcine TNF receptor type I (rspTNF-RI) and soluble TNF receptor type I fused to the Fc region of porcine IgG1 (rspTNF-RI-IgG) were expressed in insect cells using a baculovirus expression system. The proteins were secreted into the cell culture media and purified by anti-soluble porcine TNF-RI antibody and protein G affinity chromatography, respectively. The yield of protein using this method was approximately 1.5mg rspTNF-RI and 4mg rspTNF-RI-IgG/L of cell culture medium. In in vitro assays, rspTNF-RI-IgG was approximately 10-fold (0.97 vs. 10.00pmol/ml) more effective than rspTNF-RI at completely inhibiting the cytotoxic activity of 500U of recombinant porcine TNF-alpha on 3 x 10(4) WEHI 164 murine fibrosarcoma, clone 13, cells. Compared to previously described methods, this method yields significantly more biologically active rspTNF-RI.

Purification of TNF binding proteins.

The finding that the two tumor necrosis factor receptors (TNFR) exist in soluble form in various body fluids not only has substantiated the paradigm of naturally existing soluble cytokine receptors but also has represented a milestone on the road to the biochemical and biological characterization of the two TNFRs. This chapter gives a simple, basic protocol for the purification of the two soluble TNFRs. The protocols found here may be easily adapted for the purification of various other soluble cytokine receptors. The purified proteins may be used in biological experiments or for the generation of specific research tools such as polyclonal or monoclonal antibodies.

Tumor necrosis factor-alpha binding in porcine primary stromal-vascular cell cultures.

The binding characteristics of tumor necrosis factor-alpha receptors (TNFRs) in primary stromal-vascular cultures from fat tissue of 7-d-old pigs were analyzed. Cells were plated and maintained in 10% fetal bovine serum from day 0 to day 3 and then switched to serum-free medium from day 3 to day 6 to induce lipid filling. On days 3 and 6 of culture, some of the cells were lysed for ligand and immunoblotting and the remainder subjected to competitive and inhibitory-binding assays. Media from day 6 of culture were subjected to ligand and immunoblotting. Competitive binding analysis showed one-site bindings, with IC50s in the nanomolar and Kds in the picomolar ranges, that were not significantly different at both time-points of measurement. However, the Bmax decreased significantly with differentiation. Preincubation with antibody against TNF receptor type 1 (TNFR1) or TNF receptor type 2 reduced the specific binding by 95 and 15%, respectively, suggesting a dominating role of TNFR1 in 125I-labeled TNFalpha (125I-TNFalpha) binding. This was further supported by ligand blotting of cell lysates. Ligand and immunoblotting of cell lysates indicated that TNFalpha utilizes both types of surface receptors and their isoforms which were not modified during differentiation. Ligand blotting of media revealed soluble receptors with high Mr implying the formation of multimers. Immunoblotting suggested the presence of both types of TNFRs, but a greater abundance of soluble TNFR1. Also, it indicated the additional formation of smaller oligomers from both types of soluble receptors suggesting higher affinity of larger multimers for 125I-TNFalpha.

Cloning and expression of porcine recombinant soluble tumor necrosis factor receptor 1.

OBJECTIVE: To clone, sequence, and express porcine recombinant soluble tumor necrosis factor receptor 1 (sTNFR1). PROCEDURE: A polymerase chain reaction (PCR)-based library enrichment technique was used to isolate a fragment of porcine TNFR1. The mature extracellular domain of porcine TNFR1 was subcloned into an expression vector and expressed in Escherichia coli as a fusion protein. Protein product was purified by immunoaffinity chromatography, using a commercially available affinity gel specific for the marker peptide of the fusion protein. The bioactivity of the purified protein was tested for its ability to inhibit TNF-mediated cytotoxicity in a PK(15) bioassay. RESULTS: A 927-base pair fragment of porcine TNFR1 encoding the entire extracellular and transmembrane domains, as well as 75 amino acids of the cytoplasmic domain, was isolated from a porcine lung cDNA library. The extracellular domain was expressed as a soluble TNFR1 fusion protein with a yield of 120 to 150 microg/L of culture. Affinity-purified porcine sTNFR1 was able to inhibit TNF-mediated cytotoxicity of porcine PK(15) cells in dose-dependent manner. CONCLUSIONS: Porcine recombinant sTNFR1 inhibits TNF bioactivity in vitro. This recombinant protein will be useful for developing TNFR1 antibodies and studying the roles of TNF and TNFR1 in the pathogenesis of infectious diseases in swine.

Construction and purification of the murine p75-murine IgG1 fusion protein.

Etanercept (Amgen Inc, Thousand Oaks, CA) is a human soluble p75 tumor necrosis factor (TNF) receptor-human-IgG1 (hup75 TNFR-huIgG1) fusion protein used in the treatment of chronic inflammatory diseases in humans, including rheumatoid arthritis, juvenile rheumatoid arthritis, ankylosing spondylitis, psoriatic arthritis, and psoriasis. To be able to study the effects of the soluble receptor fusion protein in mouse models, including those that mimic human granulomatous infections, a murine soluble p75-TNF receptor-murine IgG1 (murine p75-murine IgG1) fusion protein had to be constructed. This article discusses the generation, large-scale production, and purification of this molecule.

Enhanced expressions of endometrial tumour necrosis factor alpha and its receptors during early pregnancy in bonnet monkeys.

Tumour necrosis factor alpha (TNF-alpha), a pro-inflammatory cytokine may play an active role in stimulating inflammatory reactions during pregnancy. However, the expression of endometrial TNF-alpha has not been investigated especially during early pregnancy, a phenomenon invariably accompanied by inflammatory reaction. In the present study, the endometrial expressions of TNF-alpha and its receptors (TNFR1 and TNFR2) during early pregnancy, when the embryo lies free in the zona hatched state in the uterine lumen, were analyzed by immunohistochemistry. The endometrial expressions of TNF-alpha, TNFR1 and TNFR2 were found to be significantly up-regulated (p < 0.05) in the glandular epithelium on day 6 post-ovulation in pregnant animals. The alteration in the expression of these molecules may contribute to the induction of local inflammatory reactions during implantation.

Estimación de la prevalencia de infección tuberculosa latente en pacientes con psoriasis en placas moderada a grave en España. Estudio Latent / Estimation of the prevalence of latent tuberculosis infection in patients with moderate to severe plaque psoriasis in Spain: The Latent study

INTRODUCCIÓN Y OBJETIVO: Los agentes biológicos anti-TNF usados para el tratamiento de la psoriasis moderada y grave pueden incrementar el riesgo de desarrollar tuberculosis activa en pacientes con infección tuberculosa latente. El objetivo principal de este estudio fue estimar la prevalencia de infección tuberculosa latente en pacientes con psoriasis en placas moderada y grave en consultas de dermatología en España. MATERIAL Y MÉTODO: Estudio epidemiológico, no intervencionista, de corte transversal y ámbito nacional, realizado en España en 2011-2012. Se incluyeron pacientes con psoriasis en placas moderada y grave, a los que se les había realizado en los 2 años previos a su inclusión en el estudio al menos una prueba de tuberculina y/o una prueba de liberación de IFN-γ mediante la técnica de ELISA QuantiFERON®-TB gold In Tube. RESULTADOS: Se incluyeron 440 pacientes evaluables. Se había realizado una prueba de tuberculina al 97,7% de los pacientes, resultando positiva en el 23%. En 238 pacientes con una primera prueba negativa se realizó un booster, que fue positivo en el 5%. Se realizó la determinación del QuantiFERON®-TB al 16,8% de los pacientes, resultando positivo en el 20,5%; en 2 de estos pacientes la prueba de la tuberculina había sido negativa. En el total de la muestra, la prevalencia de infección tuberculosa latente fue del 26,6%. El grado de concordancia entre la prueba de tuberculina y el QuantiFERON®-TB fue medio (índice kappa = 0,516; p < 0,001). CONCLUSIONES: La prevalencia de infección tuberculosa latente estimada en este estudio fue similar a la comunicada previamente en España

BACKGROUND AND OBJECTIVE: Anti-tumor necrosis factor therapy for moderate to severe psoriasis can increase the risk of active tuberculosis in patients who have latent tuberculosis infection (LTBI). The main objective of this study was to estimate the prevalence of LTBI in patients with moderate to severe plaque psoriasis being treated in dermatology clinics in Spain. MATERIAL AND METHOD: Non-interventional, cross-sectional, national epidemiological study conducted in Spain in 2011-2012. Patients with moderate to severe plaque psoriasis were included if they had undergone at least one tuberculin skin test (TST) and/or been evaluated with an interferon-γ release assay (IGRA) based on enzyme-linked immunosorbent assay (QuantiFERON® TB Gold In-Tube) in the 2 years preceding the study. RESULTS: Data for 440 patients were valid for analysis. In total, 97.7% of the patients had undergone a TST, with a positive result in 23%. Of the 238 patients in whom the initial result was negative, 5% converted to positive on re-testing for a booster effect. IGRA results were available for 16.8%, 20.5% of them positive. Two of the patients with positive IGRA results had a negative TST. The prevalence of LTBI in the whole sample was 26.6%. The degree of concordance between the TST and the IGRA was moderate (Kappa=0.516; P<.001). CONCLUSIONS: The prevalence of LTBI in this study was similar to previous estimates for Spain

[Increased plasma level of Type I (p55) and Type II (p75) TNF-receptors following trauma]. / Erhöhte Plasmaspiegel der löslichen TNF-Rezeptoren (sTNFRs) Typ I (p55) und Typ II (p75) nach Trauma.

Excessive synthesis and release of proinflammatory cytokines following trauma have been correlated with poor outcome of injured patients. TNF-alpha seems to play a pivotal role as trigger for the induction of systemic inflammation. Recently, two naturally occurring inhibitors of TNF-alpha, soluble TNF-receptors (sTNFRs) p55 and p75, have been characterized. The present study was undertaken to determine whether severe trauma increases circulating sTNFRs dependent on severity of injury. Injured patients (n = 190) revealed significantly increased plasma levels of both sTNFRs throughout the observation period of 21 days compared to healthy volunteers (n = 125). Patients with severe injury (ISS > 16 pts; n = 130) revealed higher (p < 0.0001) levels of sTNFRs on day of admission than patients with minor trauma (< or = 16 pts; n = 60). Thus, anti-inflammatory mechanisms are activated during the posttraumatic course dependent on severity of injury.