Phase Ib evaluation of a self-adjuvanted protamine formulated mRNA-based active cancer immunotherapy, BI1361849 (CV9202), combined with local radiation treatment in patients with stage IV non-small cell lung cancer.

BACKGROUND: Preclinical studies demonstrate synergism between cancer immunotherapy and local radiation, enhancing anti-tumor effects and promoting immune responses. BI1361849 (CV9202) is an active cancer immunotherapeutic comprising protamine-formulated, sequence-optimized mRNA encoding six non-small cell lung cancer (NSCLC)-associated antigens (NY-ESO-1, MAGE-C1, MAGE-C2, survivin, 5T4, and MUC-1), intended to induce targeted immune responses. METHODS: We describe a phase Ib clinical trial evaluating treatment with BI1361849 combined with local radiation in 26 stage IV NSCLC patients with partial response (PR)/stable disease (SD) after standard first-line therapy. Patients were stratified into three strata (1: non-squamous NSCLC, no epidermal growth factor receptor (EGFR) mutation, PR/SD after ≥4 cycles of platinum- and pemetrexed-based treatment [n = 16]; 2: squamous NSCLC, PR/SD after ≥4 cycles of platinum-based and non-platinum compound treatment [n = 8]; 3: non-squamous NSCLC, EGFR mutation, PR/SD after ≥3 and ≤ 6 months EGFR-tyrosine kinase inhibitor (TKI) treatment [n = 2]). Patients received intradermal BI1361849, local radiation (4 × 5 Gy), then BI1361849 until disease progression. Strata 1 and 3 also had maintenance pemetrexed or continued EGFR-TKI therapy, respectively. The primary endpoint was evaluation of safety; secondary objectives included assessment of clinical efficacy (every 6 weeks during treatment) and of immune response (on Days 1 [baseline], 19 and 61). RESULTS: Study treatment was well tolerated; injection site reactions and flu-like symptoms were the most common BI1361849-related adverse events. Three patients had grade 3 BI1361849-related adverse events (fatigue, pyrexia); there was one grade 3 radiation-related event (dysphagia). In comparison to baseline, immunomonitoring revealed increased BI1361849 antigen-specific immune responses in the majority of patients (84%), whereby antigen-specific antibody levels were increased in 80% and functional T cells in 40% of patients, and involvement of multiple antigen specificities was evident in 52% of patients. One patient had a partial response in combination with pemetrexed maintenance, and 46.2% achieved stable disease as best overall response. Best overall response was SD in 57.7% for target lesions. CONCLUSION: The results support further investigation of mRNA-based immunotherapy in NSCLC including combinations with immune checkpoint inhibitors. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT01915524 .

A phase I/IIa study of the mRNA-based cancer immunotherapy CV9201 in patients with stage IIIB/IV non-small cell lung cancer.

CV9201 is an RNActive®-based cancer immunotherapy encoding five non-small cell lung cancer-antigens: New York esophageal squamous cell carcinoma-1, melanoma antigen family C1/C2, survivin, and trophoblast glycoprotein. In a phase I/IIa dose-escalation trial, 46 patients with locally advanced (n = 7) or metastatic (n = 39) NSCLC and at least stable disease after first-line treatment received five intradermal CV9201 injections (400-1600 µg of mRNA). The primary objective of the trial was to assess safety. Secondary objectives included assessment of antibody and ex vivo T cell responses against the five antigens, and changes in immune cell populations. All CV9201 dose levels were well-tolerated and the recommended dose for phase IIa was 1600 µg. Most AEs were mild-to-moderate injection site reactions and flu-like symptoms. Three (7%) patients had grade 3 related AEs. No related grade 4/5 or related serious AEs occurred. In phase IIa, antigen-specific immune responses against ≥ 1 antigen were detected in 63% of evaluable patients after treatment. The frequency of activated IgD+CD38hi B cells increased > twofold in 18/30 (60%) evaluable patients. 9/29 (31%) evaluable patients in phase IIa had stable disease and 20/29 (69%) had progressive disease. Median progression-free and overall survival were 5.0 months (95% CI 1.8-6.3) and 10.8 months (8.1-16.7) from first administration, respectively. Two- and 3-year survival rates were 26.7% and 20.7%, respectively. CV9201 was well-tolerated and immune responses could be detected after treatment supporting further clinical investigation.

A New RNA-Based Adjuvant Enhances Virus-Specific Vaccine Responses by Locally Triggering TLR- and RLH-Dependent Effects.

Among innovative adjuvants conferring a Th1-shift, RNAdjuvant is a promising candidate. This adjuvant consists of a 547-nt uncapped noncoding ssRNA containing polyU repeats that is stabilized by a cationic carrier peptide. Whereas vaccination of mice with an influenza subunit vaccine induced moderate virus-specific IgG1, vaccination together with RNAdjuvant significantly enhanced this IgG1 and additionally promoted the formation of IgG2b/c, which is indicative of Th1 responses. Furthermore, such sera neutralized influenza virus, whereas this effect was not detected upon vaccination with the subunit vaccine alone. Similarly, upon vaccination with virus-like particles displaying vesicular stomatitis virus G protein, RNAdjuvant promoted the formation of virus-specific IgG2b/c and enhanced neutralizing IgG responses to an extent that mice were protected against lethal virus infection. RNAdjuvant induced dendritic cells to upregulate activation markers and produce IFN-I. Although these effects were strictly TLR7 dependent, RNAdjuvant-mediated augmentation of vaccine responses needed concurrent TLR and RIG-I-like helicase signaling. This was indicated by the absence of the adjuvant effect in vaccinated MyD88-/-Cardif-/- mice, which are devoid of TLR (with the exception of TLR3) and RIG-I-like helicase signaling, whereas in vaccinated MyD88-/- mice the adjuvant effect was reduced. Notably, i.m. RNAdjuvant injection induced local IFN-I responses and did not induce systemic effects, implying good tolerability and a favorable safety profile for RNAdjuvant.

Distinct transcriptional changes in non-small cell lung cancer patients associated with multi-antigenic RNActive® CV9201 immunotherapy.

We recently completed a phase I/IIa trial of RNActive® CV9201, a novel mRNA-based therapeutic vaccine targeting five tumor-associated antigens in non-small cell lung cancer (NSCLC) patients. The aim of the study presented here was to comprehensively analyze changes in peripheral blood during the vaccination period and to generate hypotheses facilitating the identification of potential biomarkers correlating with differential clinical outcomes post RNActive® immunotherapy. We performed whole-genome expression profiling in a subgroup of 22 stage IV NSCLC patients before and after initiation of treatment with CV9201. Utilizing an analytic approach based on blood transcriptional modules (BTMs), a previously described, sensitive tool for blood transcriptome data analysis, patients segregated into two major clusters based on transcriptional changes post RNActive® treatment. The first group of patients was characterized by the upregulation of an expression signature associated with myeloid cells and inflammation, whereas the other group exhibited an expression signature associated with T and NK cells. Patients with an enrichment of T and NK cell modules after treatment compared to baseline exhibited significantly longer progression-free and overall survival compared to patients with an upregulation of myeloid cell and inflammatory modules. Notably, these gene expression signatures were mutually exclusive and inversely correlated. Furthermore, our findings correlated with phenotypic data derived by flow cytometry as well as the neutrophil-to-lymphocyte ratio. Our study thus demonstrates non-overlapping, distinct transcriptional profiles correlating with survival warranting further validation for the development of biomarker candidates for mRNA-based immunotherapy.

Self-adjuvanted mRNA vaccination in advanced prostate cancer patients: a first-in-man phase I/IIa study.

BACKGROUND: CV9103 is a prostate-cancer vaccine containing self-adjuvanted mRNA (RNActive®) encoding the antigens PSA, PSCA, PSMA, and STEAP1. This phase I/IIa study evaluated safety and immunogenicity of CV9103 in patients with advanced castration-resistant prostate-cancer. METHODS: 44 Patients received up to 5 intra-dermal vaccinations. Three dose levels of total mRNA were tested in Phase I in cohorts of 3-6 patients to determine a recommended dose. In phase II, 32 additional patients were treated at the recommended dose. The primary endpoint was safety and tolerability, the secondary endpoint was induction of antigen specific immune responses monitored at baseline and at weeks 5, 9 and 17. RESULTS: The most frequent adverse events were grade 1/2 injection site erythema, injection site reactions, fatigue, pyrexia, chills and influenza-like illness. Possibly treatment related urinary retention occurred in 3 patients. The recommended dose was 1280 µg. A total of 26/33 evaluable patients treated at 1280 µg developed an immune response, directed against multiple antigens in 15 out of 33 patients. One patient showed a confirmed PSA response. In the subgroup of 36 metastatic patients, the Kaplan-Meier estimate of median overall survival was 31.4 months [95 % CI: 21.2; n.a]. CONCLUSIONS: The self-adjuvanted RNActive® vaccine CV9103 was well tolerated and immunogenic. The technology is a versatile, fast and cost-effective platform allowing for creation of vaccines. The follow-up vaccine CV9104 including the additional antigens prostatic acid phosphatase (PAP) and Muc1 is currently being tested in a randomized phase IIb trial to assess the clinical benefit induced by this new vaccination approach. TRIAL REGISTRATION: EU Clinical Trials Register: EudraCT number 2008-003967-37, registered 27 Jan 2009.

A novel RNA-based adjuvant combines strong immunostimulatory capacities with a favorable safety profile.

Protein- and peptide-based tumor vaccines depend on strong adjuvants to induce potent immune responses. Here, we demonstrated that a recently developed novel adjuvant based on a non-coding, long-chain RNA molecule, termed RNAdjuvant(®) , profoundly increased immunogenicity of both antigen formats. RNAdjuvant(®) induced balanced, long-lasting immune responses that resulted in a strong anti-tumor activity. A direct comparison to Poly(I:C) showed superior efficacy of our adjuvant to enhance antigen-specific multifunctional CD8(+) T-cell responses and mediate anti-tumor responses induced by peptide derived from HPV-16 E7 protein in the syngeneic TC-1 tumor, a murine model of human HPV-induced cervical cancer. Moreover, the adjuvant was able to induce functional memory responses that mediated complete tumor remission. Despite its remarkable immunostimulatory activity, our RNA-based adjuvant exhibited an excellent pre-clinical safety profile. It acted only locally at the injection site where it elicited a transient but strong up-regulation of pro-inflammatory and anti-viral cytokines as well as cytoplasmic RNA sensors without systemic cytokine release. This was followed by the activation of immune cells in the draining lymph nodes. Our data indicate that our RNA-based adjuvant is a safe and potent immunostimulator that may profoundly improve the efficacy of a variety of cancer vaccines.

Phase Ib study evaluating a self-adjuvanted mRNA cancer vaccine (RNActive®) combined with local radiation as consolidation and maintenance treatment for patients with stage IV non-small cell lung cancer.

BACKGROUND: Advanced non-small cell lung cancer (NSCLC) represents a significant unmet medical need. Despite advances with targeted therapies in a small subset of patients, fewer than 20% of patients survive for more than two years after diagnosis. Cancer vaccines are a promising therapeutic approach that offers the potential for durable responses through the engagement of the patient's own immune system. CV9202 is a self-adjuvanting mRNA vaccine that targets six antigens commonly expressed in NSCLC (NY-ESO-1, MAGEC1, MAGEC2, 5 T4, survivin, and MUC1). METHODS/DESIGN: The trial will assess the safety and tolerability of CV9202 vaccination combined with local radiation designed to enhance immune responses and will include patients with stage IV NSCLC and a response or stable disease after first-line chemotherapy or therapy with an EGFR tyrosine kinase inhibitor. Three histological and molecular subtypes of NSCLC will be investigated (squamous and non-squamous cell with/without EGFR mutations). All patients will receive two initial vaccinations with CV9202 prior to local radiotherapy (5 GY per day for four successive days) followed by further vaccinations until disease progression. The primary endpoint of the study is the number of patients experiencing Grade >3 treatment-related adverse events. Pharmacodynamic analyses include the assessment of immune responses to the antigens encoded by CV9202 and others not included in the panel (antigen spreading) and standard efficacy assessments. DISCUSSION: RNActive self-adjuvanted mRNA vaccines offer the potential for simultaneously inducing immune responses to a wide panel of antigens commonly expressed in tumors. This trial will assess the feasibility of this approach in combination with local radiotherapy in NSCLC patients. TRIAL REGISTRATION: Clinicaltrials.gov: NCT01915524/EudraCT No.: 2012-004230-41.

mRNA-based vaccines synergize with radiation therapy to eradicate established tumors.

BACKGROUND: The eradication of large, established tumors by active immunotherapy is a major challenge because of the numerous cancer evasion mechanisms that exist. This study aimed to establish a novel combination therapy consisting of messenger RNA (mRNA)-based cancer vaccines and radiation, which would facilitate the effective treatment of established tumors with aggressive growth kinetics. METHODS: The combination of a tumor-specific mRNA-based vaccination with radiation was tested in two syngeneic tumor models, a highly immunogenic E.G7-OVA and a low immunogenic Lewis lung cancer (LLC). The molecular mechanism induced by the combination therapy was evaluated via gene expression arrays as well as flow cytometry analyses of tumor infiltrating cells. RESULTS: In both tumor models we demonstrated that a combination of mRNA-based immunotherapy with radiation results in a strong synergistic anti-tumor effect. This was manifested as either complete tumor eradication or delay in tumor growth. Gene expression analysis of mouse tumors revealed a variety of substantial changes at the tumor site following radiation. Genes associated with antigen presentation, infiltration of immune cells, adhesion, and activation of the innate immune system were upregulated. A combination of radiation and immunotherapy induced significant downregulation of tumor associated factors and upregulation of tumor suppressors. Moreover, combination therapy significantly increased CD4+, CD8+ and NKT cell infiltration of mouse tumors. CONCLUSION: Our data provide a scientific rationale for combining immunotherapy with radiation and provide a basis for the development of more potent anti-cancer therapies.

A development that may evolve into a revolution in medicine: mRNA as the basis for novel, nucleotide-based vaccines and drugs.

Recent advances strongly suggest that mRNA rather than DNA will be the nucleotide basis for a new class of vaccines and drugs. Therapeutic cancer vaccines against a variety of targets have been developed on this basis and initial clinical experience suggests that preclinical activity can be successfully translated to human application. Likewise, prophylactic vaccines against viral pathogens and allergens have demonstrated their activity in animal models. These successes could be extended preclinically to mRNA protein and gene replacement therapy as well as the induction of pluripotent stem cells by mRNA encoded transcription factors. The production of mRNA-based vaccines and drugs is highly flexible, scalable and cost competitive, and eliminates the requirement of a cold chain. mRNA-based drugs and vaccines offer all the advantages of a nucleotide-based approach at reduced costs and represent a truly disruptive technology that may start a revolution in medicine.

A novel, disruptive vaccination technology: self-adjuvanted RNActive(®) vaccines.

Nucleotide based vaccines represent an enticing, novel approach to vaccination. We have developed a novel immunization technology, RNActive(®) vaccines, that have two important characteristics: mRNA molecules are used whose protein expression capacity has been enhanced by 4 to 5 orders of magnitude by modifications of the nucleotide sequence with the naturally occurring nucleotides A (adenosine), G (guanosine), C (cytosine), U (uridine) that do not affect the primary amino acid sequence. Second, they are complexed with protamine and thus activate the immune system by involvement of toll-like receptor (TLR) 7. Essentially, this bestows self-adjuvant activity on RNActive(®) vaccines. RNActive(®) vaccines induce strong, balanced immune responses comprising humoral and cellular responses, effector and memory responses as well as activation of important subpopulations of immune cells, such as Th1 and Th2 cells. Pre-germinal center and germinal center B cells were detected in human patients upon vaccination. RNActive(®) vaccines successfully protect against lethal challenges with a variety of different influenza strains in preclinical models. Anti-tumor activity was observed preclinically under therapeutic as well as prophylactic conditions. Initial clinical experiences suggest that the preclinical immunogenicity of RNActive(®) could be successfully translated to humans.

Protective efficacy of in vitro synthesized, specific mRNA vaccines against influenza A virus infection.

Despite substantial improvements, influenza vaccine production-and availability-remain suboptimal. Influenza vaccines based on mRNA may offer a solution as sequence-matched, clinical-grade material could be produced reliably and rapidly in a scalable process, allowing quick response to the emergence of pandemic strains. Here we show that mRNA vaccines induce balanced, long-lived and protective immunity to influenza A virus infections in even very young and very old mice and that the vaccine remains protective upon thermal stress. This vaccine format elicits B and T cell-dependent protection and targets multiple antigens, including the highly conserved viral nucleoprotein, indicating its usefulness as a cross-protective vaccine. In ferrets and pigs, mRNA vaccines induce immunological correlates of protection and protective effects similar to those of a licensed influenza vaccine in pigs. Thus, mRNA vaccines could address substantial medical need in the area of influenza prophylaxis and the broader realm of anti-infective vaccinology.

Developing mRNA-vaccine technologies.

mRNA vaccines combine desirable immunological properties with an outstanding safety profile and the unmet flexibility of genetic vaccines. Based on in situ protein expression, mRNA vaccines are capable of inducing a balanced immune response comprising both cellular and humoral immunity while not subject to MHC haplotype restriction. In addition, mRNA is an intrinsically safe vector as it is a minimal and only transient carrier of information that does not interact with the genome. Because any protein can be expressed from mRNA without the need to adjust the production process, mRNA vaccines also offer maximum flexibility with respect to development. Taken together, mRNA presents a promising vector that may well become the basis of a game-changing vaccine technology platform. Here, we outline the current knowledge regarding different aspects that should be considered when developing an mRNA-based vaccine technology.

Highly potent mRNA based cancer vaccines represent an attractive platform for combination therapies supporting an improved therapeutic effect.

Direct vaccination with mRNA encoding tumor antigens is a novel and promising approach in cancer immunotherapy. CureVac's mRNA vaccines contain free and protamine-complexed mRNA. Such two-component mRNA vaccines support both antigen expression and immune stimulation. These self-adjuvanting RNA vaccines, administered intradermally without any additional adjuvant, induce a comprehensive balanced immune response, comprising antigen specific CD4+ T cells, CD8+ T cells and B cells. The balanced immune response results in a strong anti-tumor effect and complete protection against antigen positive tumor cells. This tumor inhibition elicited by mRNA vaccines is a result of the concerted action of different players. After just two intradermal vaccinations, we observe multiple changes at the tumor site, including the up-regulation of many genes connected to T and natural killer cell activation, as well as genes responsible for improved infiltration of immune cells into the tumor via chemotaxis. The two-component mRNA vaccines induce a very fast and boostable immune response. Therefore, the vaccination schedules can be adjusted to suit the clinical situation. Moreover, by combining the mRNA vaccines with therapies in clinical use (chemotherapy or anti-CTLA-4 antibody therapy), an even more effective anti-tumor response can be elicited. The first clinical data obtained from two separate Phase I/IIa trials conducted in PCA (prostate cancer) and NSCLC (non-small cell lung carcinoma) patients have shown that the two-component mRNA vaccines are safe, well tolerated and highly immunogenic in humans.

Messenger RNA-based vaccines with dual activity induce balanced TLR-7 dependent adaptive immune responses and provide antitumor activity.

Direct vaccination with messenger RNA (mRNA) molecules encoding tumor-associated antigens is a novel and promising approach in cancer immunotherapy. The main advantage of using mRNA for vaccination is that the same molecule not only provides an antigen source for adaptive immunity, but can simultaneously bind to pattern recognition receptors, thus stimulating innate immunity. However, achieving both features remains challenging, as the complexation of mRNA required for immune-stimulating activity may inhibit its translatability. In this study, we present a new and more effective vaccine design: a two-component mRNA-based tumor vaccine that supports both: antigen expression and immune stimulation, mediated by Toll like receptor 7 (TLR7). The two-component mRNA vaccines, containing free and protamine-complexed mRNA, induce balanced adaptive immune responses providing humoral as well as T cell mediated immunity. This balanced immune response is based on the induction of antigen-specific CD4(+) T helper cells and cytotoxic CD8(+) T cells. Once activated, these CD4(+) and CD8(+) T cells secrete a wide set of cytokines, which drive a TH1 response. Immunization with the two-component vaccines induces sustained memory responses, mediated by antigen-specific memory T cells. Moreover, treatment of mice with the two-component mRNA vaccine mediates a strong antitumor response against OVA-expressing tumor cells, not only in a prophylactic but also in a therapeutic setting. In conclusion, two-component mRNA vaccines with self-adjuvanting activity induce balanced adaptive immune responses and mediate sustained antitumor activity.

Inhibition of interleukin-6-transsignaling via gp130-Fc in hemorrhagic shock and sepsis.

BACKGROUND: Immune function after hemorrhagic shock and subsequent sepsis is characterized by an early proinflammatory burst of IL-6, and high IL-6 levels have been linked to high mortality after trauma and in sepsis. Trans-signaling is defined as the activation of cells that do not express the membrane bound IL-6 receptor by the complex of IL-6 and the soluble IL-6 receptor (sIL-6R). Gp130-Fc is able to bind the IL-6/sIL-6R complex, and beneficial effects of IL-6 blockade in chronic inflammatory diseases have been shown. The first aim of this study was to investigate the potential effect of a gp130 blockade via the gp130-Fc antibody causing impairment of IL-6 signaling. The second aim was to find out what role the IL-6/sIL-6R complex can play in the context of hemorrhagic shock and subsequent sepsis as an acute inflammatory disease. MATERIAL AND METHODS: Male CBA/J mice were subjected to hemorrhagic shock (35+/-5 mmHg for 90min and fluid resuscitation) or sham operation. At resuscitation each animal received either 0.5mg gp130-Fc or placebo (PL) i.p. At 48 h after resuscitation, both splenocytes and peritoneal macrophages (pMphi) were harvested or polymicrobial sepsis was induced by cecal ligation and puncture. Survival over 10 d was determined. Release of IL-6, TNF-alpha, and IL-10 of pMphi and release of IL-2, IL-10, and IFN-gamma of splenocytes was assessed by ELISA. Proliferation of splenocytes and their morphologic damage were determined. RESULTS: Binding of the IL-6/sIL-6R complex by gp130-Fc led to significant lower IL-6 levels compared with placebo treated animals. Placebo treated males showed depressed proinflammatory immune response (IL-2, IL-6) after hemorrhagic shock. While splenocyte proliferation was significantly reduced directly after hemorrhagic shock and restored after 48 h by gp130-Fc, pMphi cytokine release was not influenced. Finally, survival appeared to be unaffected. CONCLUSION: Transsignaling does not seem to play a pivotal role in the development of the immune dysfunction and mortality in our model of hemorrhage and subsequent sepsis.

IL-6 transsignalling modulates the early effector phase of EAE and targets the blood-brain barrier.

Interleukin-6 (IL-6) plays a crucial role in the pathogenesis of experimental autoimmune encephalomyelitis (EAE). It exerts its cellular effects by a membrane-bound IL-6 receptor (IL-6R), or, alternatively, by forming a complex with the soluble IL-6R (sIL-6R), a process named IL-6 transsignalling. Here we investigate the role of IL-6 transsignalling in myelin basic protein (MBP)-induced EAE in the Lewis rat. In vivo blockade of IL-6 transsignalling by the injection of a specifically designed gp130-Fc fusion protein significantly delayed the onset of adoptively transferred EAE in comparison to control rats injected with PBS or isotype IgG. Histological evaluation on day 3 after immunization revealed reduced numbers of T cells and macrophages in the lumbar spinal cord of gp130-Fc treated rats. At the same time, blockade of IL-6 transsignalling resulted in a reduced expression of vascular cell adhesion molecule-1 on spinal cord microvessels while experiments in cell culture failed to show a direct effect on the regulation of endothelial adhesion molecules. In experiments including active EAE and T cell culture, inhibition of IL-6 transsignalling mildly increased T cell proliferation, but did not change severity of active MBP-EAE or regulate Th1/Th17 responses. We conclude that IL-6 transsignalling may play a role in autoimmune inflammation of the CNS mainly by regulating early expression of adhesion molecules, possibly via cellular networks at the blood-brain barrier.

gp130 dimerization in the absence of ligand: preformed cytokine receptor complexes.

It is established that cytokine receptors signal after ligand binding as homo- or hetero-dimers in heteromeric complexes, but it is unclear, when dimerization occurs. To investigate gp130 dimerization, we performed co-precipitation experiments with the endogenous cytokine receptors gp130 and leukemia inhibitory factor receptor (LIF-R) and with gp130 variants carrying two different C-terminal peptide tags. Furthermore, fluorescence resonance energy transfer (FRET) was employed to detect dimerization of two fluorescent-tagged gp130 variants. Confocal laser scanning microscopy was used for FRET detection in live cells. gp130 and LIF-R could be coprecipitated in the absence of ligand. The interaction, however, was intensified by the addition of LIF. Similar results were obtained with the gp130 variants and confirmed by FRET analysis in live cells. The present study clearly demonstrates the existence of preformed but inactive gp130/LIF-R hetero- and gp130/gp130 homo-dimers. The addition of ligand enhanced the respective dimer formation and was required for signal transduction.

Murine liver antigen presenting cells control suppressor activity of CD4+CD25+ regulatory T cells.

CD4(+)CD25(+) regulatory T cells (Treg) are important mediators of peripheral immune tolerance; however, whether Treg participate also in hepatic immune tolerance is not clear. Therefore, we tested the potential of Treg to suppress stimulation of CD4(+) T cells by liver sinusoidal endothelial cells (LSEC), Kupffer cells (KC), or hepatocytes. In the absence of Treg, all 3 types of liver cells could stimulate CD4(+) T cell proliferation; in the presence of Treg, however, CD4(+) T cell proliferation was suppressed. Interaction with KC even stimulated the expansion of the Treg population; LSEC or hepatocytes, in contrast, could not induce proliferation of Treg. Because liver inflammation can be induced by infection, we tested the potential of liver cells to modify Treg suppressor activity in the presence of microbial signals. In the presence of immune-stimulatory CpG-oligonucleotides, LSEC, KC, and hepatocytes could indeed overcome Treg-mediated suppression; in the presence of lipopolysaccharide (LPS), however, only KC and hepatocytes, but not LSEC, could overcome Treg suppressor activity. Hepatocytes from mice with deficient toll-like receptor-4 signaling failed to abrogate Treg suppression in response to LPS, indicating that overcoming Treg suppressor activity was indeed a response of the liver cell and not of the Treg. In conclusion, Treg can suppress CD4(+) T cell stimulation by liver cells. However, in response to microbial signals, the liver cells can overcome the suppressive activity of Treg. Thus, liver cells may facilitate the transition from hepatic immune tolerance to hepatic inflammation by controlling Treg suppressor activity.