C-type natriuretic peptide induces inotropic and lusitropic effects in human 3D-engineered cardiac tissue: Implications for the regulation of cardiac function in humans

The role of C-type natriuretic peptide (CNP) in the regulation of cardiac function in humans remains to be established as previous investigations have been confined to animal model systems. Here, we used well-characterized engineered cardiac tissues (ECTs) generated from human stem cell-derived cardiomyocytes and fibroblasts to study the acute effects of CNP on contractility. Application of CNP elicited a positive inotropic response as evidenced by increases in maximum twitch amplitude, maximum contraction slope and maximum calcium amplitude. This inotropic response was accompanied by a positive lusitropic response as demonstrated by reductions in time from peak contraction to 90% of relaxation and time from peak calcium transient to 90% of decay that paralleled increases in maximum contraction decay slope and maximum calcium decay slope. To establish translatability, CNP-induced changes in contractility were also assessed in rat ex vivo (isolated heart) and in vivo models. Here, the effects on force kinetics observed in ECTs mirrored those observed in both the ex vivo and in vivo model systems, whereas the increase in maximal force generation with CNP application was only detected in ECTs. In conclusion, CNP induces a positive inotropic and lusitropic response in ECTs, thus supporting an important role for CNP in the regulation of human cardiac function. The high degree of translatability between ECTs, ex vivo and in vivo models further supports a regulatory role for CNP and expands the current understanding of the translational value of human ECTs. NEW FINDINGS: What is the central question of this study? What are the acute responses to C-type natriuretic peptide (CNP) in human-engineered cardiac tissues (ECTs) on cardiac function and how well do they translate to matched concentrations in animal ex vivo and in vivo models? What is the main finding and its importance? Acute stimulation of ECTs with CNP induced positive lusitropic and inotropic effects on cardiac contractility, which closely reflected the changes observed in rat ex vivo and in vivo cardiac models. These findings support an important role for CNP in the regulation of human cardiac function and highlight the translational value of ECTs.

Hepatocyte mARC1 promotes fatty liver disease

Background & Aims

Non-alcoholic fatty liver disease (NAFLD) has a prevalence of ∼25% worldwide, with significant public health consequences yet few effective treatments. Human genetics can help elucidate novel biology and identify targets for new therapeutics. Genetic variants in mitochondrial amidoxime-reducing component 1 (MTARC1) have been associated with NAFLD and liver-related mortality; however, its pathophysiological role and the cell type(s) mediating these effects remain unclear. We aimed to investigate how MTARC1 exerts its effects on NAFLD by integrating human genetics with in vitro and in vivo studies of mARC1 knockdown.

Methods

Analyses including multi-trait colocalisation and Mendelian randomisation were used to assess the genetic associations of MTARC1. In addition, we established an in vitro long-term primary human hepatocyte model with metabolic readouts and used the Gubra Amylin NASH (GAN)-diet non-alcoholic steatohepatitis mouse model treated with hepatocyte-specific N-acetylgalactosamine (GalNAc)-siRNA to understand the in vivo impacts of MTARC1.

Results

We showed that genetic variants within the MTARC1 locus are associated with liver enzymes, liver fat, plasma lipids, and body composition, and these associations are attributable to the same causal variant (p.A165T, rs2642438 G>A), suggesting a shared mechanism. We demonstrated that increased MTARC1 mRNA had an adverse effect on these traits using Mendelian randomisation, implying therapeutic inhibition of mARC1 could be beneficial. In vitro mARC1 knockdown decreased lipid accumulation and increased triglyceride secretion, and in vivo GalNAc-siRNA-mediated knockdown of mARC1 lowered hepatic but increased plasma triglycerides. We found alterations in pathways regulating lipid metabolism and decreased secretion of 3-hydroxybutyrate upon mARC1 knockdown in vitro and in vivo.

Conclusions

Collectively, our findings from human genetics, and in vitro and in vivo hepatocyte-specific mARC1 knockdown support the potential efficacy of hepatocyte-specific targeting of mARC1 for treatment of NAFLD.

Impact and implications

We report that genetically predicted increases in MTARC1 mRNA associate with poor liver health. Furthermore, knockdown of mARC1 reduces hepatic steatosis in primary human hepatocytes and a murine NASH model. Together, these findings further underscore the therapeutic potential of targeting hepatocyte MTARC1 for NAFLD.

Genetic evidence implicating natriuretic peptide receptor-3 in cardiovascular disease risk: a Mendelian randomization study

BACKGROUND

C-type natriuretic peptide (CNP) is a known target for promoting growth and has been implicated as a therapeutic opportunity for the prevention and treatment of cardiovascular disease (CVD). This study aimed to explore the effect of CNP on CVD risk using the Mendelian randomization (MR) framework.

METHODS

Instrumental variables mimicking the effects of pharmacological intervention on CNP were identified as uncorrelated genetic variants located in the genes coding for its primary receptors, natriuretic peptide receptors-2 and 3 (NPR2 and NPR3), that associated with height. We performed MR and colocalization analyses to investigate the effects of NPR2 signalling and NPR3 function on CVD outcomes and risk factors. MR estimates were compared to those obtained when considering height variants from throughout the genome.

RESULTS

Genetically-proxied reduced NPR3 function was associated with a lower risk of CVD, with odds ratio (OR) 0.74 per standard deviation (SD) higher NPR3-predicted height, and 95% confidence interval (95% CI) 0.64-0.86. This effect was greater in magnitude than observed when considering height variants from throughout the genome. For CVD subtypes, similar MR associations for NPR3-predicted height were observed when considering the outcomes of coronary artery disease (0.75, 95% CI 0.60-0.92), stroke (0.69, 95% CI 0.50-0.95) and heart failure (0.77, 95% CI 0.58-1.02). Consideration of CVD risk factors identified systolic blood pressure (SBP) as a potential mediator of the NPR3-related CVD risk lowering. For stroke, we found that the MR estimate for NPR3 was greater in magnitude than could be explained by a genetically predicted SBP effect alone. Colocalization results largely supported the MR findings, with no evidence of results being driven by effects due to variants in linkage disequilibrium. There was no MR evidence supporting effects of NPR2 on CVD risk, although this null finding could be attributable to fewer genetic variants being identified to instrument this target.

CONCLUSIONS

This genetic analysis supports the cardioprotective effects of pharmacologically inhibiting NPR3 receptor function, which is only partly mediated by an effect on blood pressure. There was unlikely sufficient statistical power to investigate the cardioprotective effects of NPR2 signalling.

Multicomponent Plasmid Protects Mice From Spontaneous Autoimmune Diabetes

Type 1 diabetes is an autoimmune disease in which insulin-secreting β-cells are destroyed, leading to a life-long dependency on exogenous insulin. There are no approved disease-modifying therapies available, and future immunotherapies would need to avoid generalized immune suppression. We developed a novel plasmid expressing preproinsulin2 and a combination of immune-modulatory cytokines (transforming growth factor-beta-1, interleukin [IL] 10 and IL-2) capable of near-complete prevention of autoimmune diabetes in non-obese diabetic mice. Efficacy depended on preproinsulin2, suggesting antigen-specific tolerization, and on the cytokine combination encoded. Diabetes suppression was achieved following either intramuscular or subcutaneous injections. Intramuscular plasmid treatment promoted increased peripheral levels of endogenous IL-10 and modulated myeloid cell types without inducing global immunosuppression. To prepare for first-in-human studies, the plasmid was modified to allow for selection without the use of antibiotic resistance; this modification had no impact on efficacy. This pre-clinical study demonstrates that this multi-component, plasmid-based antigen-specific immunotherapy holds potential for inducing self-tolerance in persons at risk of developing type 1 diabetes. Importantly, the study also informs on relevant cytokine and immune cell biomarkers that may facilitate clinical trials. This therapy is currently being tested for safety and tolerability in a phase 1 trial (ClinicalTrials.gov Identifier: NCT04279613).

Current state of antigen-specific immunotherapy for type 1 diabetes

PURPOSE OF REVIEW

Update on antigen-specific immunotherapy (ASIT) in type 1 diabetes (T1D) with focus on deoxyribonucleic acid (DNA)-induced immunization and the current obstacles to further research and clinical realization.

RECENT FINDINGS

In T1D, immune system imbalances together with malfunctioning islet-specific processes cause autoreactive immune cells to destroy beta cells in the islets. ASIT may restore self-tolerance; however, the approach has yet to fully meet its promise and may require co-administration of antigen (preproinsulin) and suitable immune response modifiers.

SUMMARY

A self-tolerant immune system may be regained using ASIT where T effector cells are repressed and/or T regulatory cells are induced. Administration of exogenous antigens has been safe in T1D. Conversely, adequate and lasting beta cell preservation has yet to be tested in sufficiently large clinical trials in suitable patients and may require targeting of multiple parts of the immunopathophysiology using combination therapies. DNA-based induction of native antigen expression to ensure important posttranscriptional modifications and presentation to the immune system together with tolerance-enhancing immune response modifiers (i.e., cytokines) may be more efficacious than exogenous antigens given alone. Progress is limited mainly by the scarcity of validated biomarkers to track the effects of ASIT in T1D.

Anti-interleukin-21 antibody and liraglutide for the preservation of β-cell function in adults with recent-onset type 1 diabetes: a randomised, double-blind, placebo-controlled, phase 2 trial

BACKGROUND

Type 1 diabetes is characterised by progressive loss of functional β-cell mass, necessitating insulin treatment. We aimed to investigate the hypothesis that combining anti-interleukin (IL)-21 antibody (for low-grade and transient immunomodulation) with liraglutide (to improve β-cell function) could enable β-cell survival with a reduced risk of complications compared with traditional immunomodulation.

METHODS

This randomised, parallel-group, placebo-controlled, double-dummy, double-blind, phase 2 trial was done at 94 sites (university hospitals and medical centres) in 17 countries. Eligible participants were adults aged 18-45 years with recently diagnosed type 1 diabetes and residual β-cell function. Individuals with unstable type 1 diabetes (defined by an episode of severe diabetic ketoacidosis within 2 weeks of enrolment) or active or latent chronic infections were excluded. Participants were randomly assigned (1:1:1:1), with stratification by baseline stimulated peak C-peptide concentration (mixed-meal tolerance test [MMTT]), to the combination of anti-IL-21 and liraglutide, anti-IL-21 alone, liraglutide alone, or placebo, all as an adjunct to insulin. Investigators, participants, and funder personnel were masked throughout the treatment period. The primary outcome was the change in MMTT-stimulated C-peptide concentration at week 54 (end of treatment) relative to baseline, measured via the area under the concentration-time curve (AUC) over a 4 h period for the full analysis set (intention-to-treat population consisting of all participants who were randomly assigned). After treatment cessation, participants were followed up for an additional 26-week off-treatment observation period. This trial is registered with ClinicalTrials.gov, NCT02443155.

FINDINGS

Between Nov 10, 2015, and Feb 27, 2019, 553 adults were assessed for eligibility, of whom 308 were randomly assigned to receive either anti-IL-21 plus liraglutide, anti-IL-21, liraglutide, or placebo (77 assigned to each group). Compared with placebo (ratio to baseline 0·61, 39% decrease), the decrease in MMTT-stimulated C-peptide concentration from baseline to week 54 was significantly smaller with combination treatment (0·90, 10% decrease; estimated treatment ratio 1·48, 95% CI 1·16-1·89; p=0·0017), but not with anti-IL-21 alone (1·23, 0·97-1·57; p=0·093) or liraglutide alone (1·12, 0·87-1·42; p=0·38). Despite greater insulin use in the placebo group, the decrease in HbA_1c (a key secondary outcome) at week 54 was greater with all active treatments (-0·50 percentage points) than with placebo (-0·10 percentage points), although the differences versus placebo were not significant. The effects diminished upon treatment cessation. Changes in immune cell subsets across groups were transient and mild (<10% change over time). The most frequently reported adverse events included gastrointestinal disorders, in keeping with the known side-effect profile of liraglutide. The rate of hypoglycaemic events did not differ significantly between active treatment groups and placebo, with an exception of a lower rate in the liraglutide group than in the placebo group during the treatment period. No events of diabetic ketoacidosis were observed. One participant died while on liraglutide (considered unlikely to be related to trial treatment) in connection with three reported adverse events (hypoglycaemic coma, pneumonia, and brain oedema).

INTERPRETATION

The combination of anti-IL-21 and liraglutide could preserve β-cell function in recently diagnosed type 1 diabetes. The efficacy of this combination appears to be similar to that seen in trials of other disease-modifying interventions in type 1 diabetes, but with a seemingly better safety profile. Efficacy and safety should be further evaluated in a phase 3 trial programme.

FUNDING

Novo Nordisk.

Suppression of diabetes by accumulation of non-islet-specific CD8+ effector T cells in pancreatic islets

The inflammatory lesion at the pancreatic islet in type 1 diabetes (T1D) contains a heterogeneous infiltrate of T cells. In human and mouse studies, a large majority (98 to 99%) of the cytotoxic CD8⁺ T cells (CTLs) within islets are not specific to any islet antigen and are thought to passively add to tissue damage. We show by intravital confocal microscopy the opposite, immune-regulatory function of this cohort of CTLs. Diabetes did not develop in mice with islets showing high levels of infiltration of non-islet-specific CTLs not recognizing local antigens. Accumulation of such CTLs resulted in lower activation and proliferation of islet-specific CTLs, leading them to enter a state of unresponsiveness due to limited access to antigens at the inflammatory lesion. This nonspecific suppression by nonautoreactive CTLs was recapitulated in a model of viral meningitis, may explain viral interference in autoimmunity, and provides insight into the regulation of organ-specific autoimmune responses.

The Development of Immunotherapy Strategies for the Treatment of Type 1 Diabetes

Optimized insulin therapies, increased use of continuous glucose monitoring/insulin pumps and most importantly the arrival of reliable closed loop systems will undeniably lead to a reduction in the burden of complications that arise from type 1 diabetes. However, insulin therapy will only ever treat the symptoms of the disease and will not alter the underlying pathology. The aim of immunotherapy treatment is to modulate the immune system, a strategy that has been successful in autoimmune conditions such as multiple sclerosis, rheumatoid arthritis and lupus. However, the success rate of immunotherapy treatment in type 1 diabetes has been low. There are several distinct stages of T1D development. In this review, we summarize the most important immunotherapeutic approaches tested thus far and focus on the characteristic features and unmet need within the different stages of the disease.

Act1 is a negative regulator in T and B cells via direct inhibition of STAT3

Although Act1 (adaptor for IL-17 receptors) is necessary for IL-17-mediated inflammatory responses, Act1- (but not Il17ra-, Il17rc-, or Il17rb-) deficient mice develop spontaneous SLE- and Sjögren's-like diseases. Here, we show that Act1 functions as a negative regulator in T and B cells via direct inhibition of STAT3. Mass spectrometry analysis detected an Act1-STAT3 complex, deficiency of Act1 (but not Il17ra-, Il17rc-, or Il17rb) results in hyper IL-23- and IL-21-induced STAT3 activation in T and B cells, respectively. IL-23R deletion or blockade of IL-21 ameliorates SLE- and Sjögren's-like diseases in Act1-/- mice. Act1 deficiency results in hyperactivated follicular Th17 cells with elevated IL-21 expression, which promotes T-B cell interaction for B cell expansion and antibody production. Moreover, anti-IL-21 ameliorates the SLE- and Sjögren's-like diseases in Act1-deficient mice. Thus, IL-21 blocking antibody might be an effective therapy for treating SLE- and Sjögren's-like syndrome in patients containing Act1 mutation.

Antigen-Specific Peptide Immunotherapy for Type 1 Diabetes: Proof of Safety, Hope for Efficacy

Antigen-specific immunotherapy has long been hailed as the ideal disease-modifying approach for type 1 diabetes, both for disease prevention and reversal. A small phase 1 trial now demonstrates safety of a peptide-based treatment in recently diagnosed adults.

Immunohistochemical assessment of glucagon-like peptide 1 receptor (GLP-1R) expression in the pancreas of patients with type 2 diabetes

AIMS

Glucagon-like peptide-1 (GLP-1) is an incretin hormone which stimulates insulin release and inhibits glucagon secretion from the pancreas in a glucose-dependent manner. Incretin-based therapies, consisting of GLP-1 receptor (GLP-1R) agonists and dipeptidyl peptidase-4 (DPP-4) inhibitors, are used for the treatment of type 2 diabetes (T2D). Immunohistochemical studies for GLP-1R expression have been hampered previously by the use of unspecific polyclonal antibodies. This study aimed to assess the expression levels of GLP-1R in a set of T2D donor samples obtained via nPOD.

METHODS

This study used a new monoclonal antibody to assess GLP-1R expression in pancreatic tissue from 23 patients with T2D, including 7 with a DPP-4 inhibitor and 1 with a history of GLP-1R agonist treatment. A software-based automated image analysis algorithm was used for quantitating intensities and area fractions of GLP-1R positive compartments.

RESULTS

The highest intensity GLP-1R immunostaining was seen in beta-cells in islets (average signal intensity, 76.1 [±8.1]). GLP-1R/insulin double-labelled single cells or small clusters of cells were also frequently located within or in close vicinity of ductal epithelium in all samples and with the same GLP-1R immunostaining intensity as found in beta-cells in islets. In the exocrine pancreas a large proportion of acinar cells expressed GLP-1R with a 3-fold lower intensity of immunoreactivity as compared to beta-cells (average signal intensity 25.5 [±3,3]). Our studies did not unequivocally demonstrate GLP-1R immunoreactivity on normal-appearing ductal epithelium. Pancreatic intraepithelial neoplasia (PanINs; a form of non-invasive pancreatic ductular neoplasia) was seen in most samples, and a minority of these expressed low levels of GLP-1R.

CONCLUSION

These data confirm the ubiquity of early stage PanIN lesions in patients with T2D and do not support the hypothesis that incretin-based therapies are associated with progression towards the more advanced stage PanIN lesions.

Blockade but not overexpression of the junctional adhesion molecule C influences virus-induced type 1 diabetes in mice

Type 1 diabetes (T1D) results from the autoimmune destruction of insulin-producing beta-cells in the pancreas. Recruitment of inflammatory cells is prerequisite to beta-cell-injury. The junctional adhesion molecule (JAM) family proteins JAM-B and JAM–C are involved in polarized leukocyte transendothelial migration and are expressed by vascular endothelial cells of peripheral tissue and high endothelial venules in lympoid organs. Blocking of JAM-C efficiently attenuated cerulean-induced pancreatitis, rheumatoid arthritis or inflammation induced by ischemia and reperfusion in mice. In order to investigate the influence of JAM-C on trafficking and transmigration of antigen-specific, autoaggressive T-cells, we used transgenic mice that express a protein of the lymphocytic choriomeningitis virus (LCMV) as a target autoantigen in the β-cells of the islets of Langerhans under the rat insulin promoter (RIP). Such RIP-LCMV mice turn diabetic after infection with LCMV. We found that upon LCMV-infection JAM-C protein was upregulated around the islets in RIP-LCMV mice. JAM-C expression correlated with islet infiltration and functional beta-cell impairment. Blockade with a neutralizing anti-JAM-C antibody reduced the T1D incidence. However, JAM-C overexpression on endothelial cells did not accelerate diabetes in the RIP-LCMV model. In summary, our data suggest that JAM-C might be involved in the final steps of trafficking and transmigration of antigen-specific autoaggressive T-cells to the islets of Langerhans.

The microbiology of human hygiene and its impact on type 1 diabetes

The incidence of type 1 diabetes (T1D), as with several other autoimmune diseases and conditions, began to notably rise in the latter half of the last century. Most cases of T1D are not solely attributable to genetics and therefore, environmental influences are proposed to account for the difference. Humans live today in general under much more hygienic conditions than their ancestors. Although human enteroviruses (HEV) have been strongly implicated as causative environmental agents of T1D, recent work has shown that the bacterial genera in the gut of diabetics compared with non-diabetics, can vary significantly. Here, we consider these data in light of our non-hygienic human past in order to discuss a possible relationship between the resident bacterial biome and acute infectious events by HEV, suggesting how this may have influenced T1D incidences in the past and the risk for developing T1D today.

Intravital imaging of CTLs killing islet cells in diabetic mice

Type 1 diabetes (T1D) is caused by autoimmune destruction of the insulin-producing β cells in the pancreatic islets, which are essentially mini-organs embedded in exocrine tissue. CTLs are considered to have a predominant role in the autoimmune destruction underlying T1D. Visualization of CTL-mediated killing of β cells would provide new insight into the pathogenesis of T1D, but has been technically challenging to achieve. Here, we report our use of intravital 2-photon imaging in mice to visualize the dynamic behavior of a virally expanded, diabetogenic CTL population in the pancreas at cellular resolution. Following vascular arrest and extravasation, CTLs adopted a random motility pattern throughout the compact exocrine tissue and displayed unimpeded yet nonlinear migration between anatomically nearby islets. Upon antigen encounter within islets, a confined motility pattern was acquired that allowed the CTLs to scan the target cell surface. A minority of infiltrating CTLs subsequently arrested at the β cell junction, while duration of stable CTL-target cell contact was on the order of hours. Slow-rate killing occurred in the sustained local presence of substantial numbers of effector cells. Collectively, these data portray the kinetics of CTL homing to and between antigenic target sites as a stochastic process at the sub-organ level and argue against a dominant influence of chemotactic gradients.

Expression level of a pancreatic neo-antigen in beta cells determines degree of diabetes pathogenesis

It is not fully understood how the expression level of autoantigens in beta cells impacts autoimmune diabetes (T1D) development. Earlier studies using ovalbumin and also insulin had shown that secreted antigens could enhance diabetes development through facilitated presentation by antigen presenting cells. Here we sought to determine how the expression level of a membrane bound, non-secreted or cross-presented neo-antigen, the glycoprotein (GP) of lymphocytic choriomeningitis virus (LCMV), would influence T1D. We found that an RIP-LCMV transgenic mouse line exhibiting higher levels of beta cell GP expression developed more severe diabetes after LCMV infection or transfer of high numbers of activated autoreactive T cells. Importantly, all beta cells were lost and a significant increase in morbidity and mortality from T1D was noted. Insulitis and accumulation of autoaggressive CD8 cells was more profound in the RIP-LCMV-GP high-expressor line. Interestingly, the additional introduction of neo-antigen-specific CD4(+) helper or regulatory T cells was able to influence diabetogenesis positively or negatively. We conclude that a higher degree of autoantigen expression results in increased diabetes susceptibility. Therefore, autoantigens such as insulin that are expressed at higher levels in beta cells might have a more profound impact on diabetes pathogenesis.

Polymorphic variants of LIGHT (TNF superfamily-14) alter receptor avidity and bioavailability

The TNF superfamily member homologous to lymphotoxins, exhibits inducible expression, and competes with HSV glycoprotein D for herpesvirus entry mediator (HVEM), a receptor expressed by T lymphocytes (LIGHT) [TNF superfamily (SF)-14], is a key cytokine that activates T cells and dendritic cells and is implicated as a mediator of inflammatory, metabolic, and malignant diseases. LIGHT engages the lymphotoxin-beta receptor (LTbetaR) and HVEM (TNFRSF14), but is competitively limited in activating these receptors by soluble decoy receptor-3 (DcR3; TNFRSF6B). Two variants in the human LIGHT alter the protein at E214K (rs344560) in the receptor-binding domain and S32L (rs2291667) in the cytosolic domain; however, the functional impact of these polymorphisms is unknown. A neutralizing Ab failed to bind the LIGHT-214K variant, indicating this position as a part of the receptor-binding region. Relative to the predominant reference variant S32/E214, the other variants showed altered avidity with LTbetaR and less with HVEM. Heterotrimers of the LIGHT variants decreased binding avidity to DcR3 and minimized the inhibitory effect of DcR3 toward LTbetaR-induced activation of NF-kappaB. In patients with immune-mediated inflammatory diseases, such as rheumatoid arthritis, DcR3 protein levels were significantly elevated. Immunohistochemistry revealed synoviocytes as a significant source of DcR3 production, and DcR3 hyperexpression is controlled by posttranscriptional mechanisms. The increased potential for LTbetaR signaling, coupled with increased bioavailability due to lower DcR3 avidity, provides a mechanism of how polymorphic variants in LIGHT could contribute to the pathogenesis of inflammatory diseases.

Dimorphic histopathology of long-standing childhood-onset diabetes

AIMS/HYPOTHESIS

Childhood diabetes is thought to usually result from autoimmune beta cell destruction (type 1A) with eventual total loss of beta cells. Analysis of C-peptide in children characterised at diabetes onset for autoantibodies shows heterogeneous preservation of insulin secretion in long-standing diabetes. The aim of this study was to characterise the pancreases of childhood-onset diabetes in order to define the pathological basis of this heterogeneity.

METHODS

We evaluated 20 cadaveric organ donor pancreases of childhood-onset long-term patients for disease heterogeneity and obtained corresponding C-peptide measurements.

RESULTS

Pancreases from the majority of cadaveric donors contained only insulin-deficient islets (14 of 20). The remaining six patients (30%) had numerous insulin-positive cells within at least some islets, with two different histological patterns. Pattern A (which we would associate with type 1A diabetes) had lobular retention of areas with 'abnormal' beta cells producing the apoptosis inhibitor survivin and HLA class I. In pattern B, 100% of all islets contained normal-appearing but quantitatively reduced beta cells without survivin or HLA class I.

CONCLUSIONS/INTERPRETATION

Our data demonstrate that C-peptide secretion in long-standing diabetic patients can be explained by two different patterns of beta cell survival,possibly reflecting different subsets of type 1 diabetes.

No significant CTL cross-priming by dendritic cell-derived exosomes during murine lymphocytic choriomeningitis virus infection

Exosomes are small membrane vesicles of endocytic origin that are secreted by most cells in culture, but are also present in serum. They contain a wide array of protein ligands on their surface, which has led to the hypothesis that they might mediate intercellular communication. Indeed, data support that exosomes can transfer Ags to dendritic cells (DC), and, interestingly, that these DC can subsequently induce T cell priming or tolerance. We have investigated whether this concept can be expanded to antiviral immunity. We isolated exosomes from supernatant of cultured bone marrow-derived DC (BMDC) that were infected with lymphocytic choriomeningitis virus (LCMV) or loaded with an immunodominant LCMV peptide, and characterized them by flow cytometry upon binding to beads. We then incubated the exosome preparations with BMDC and looked at their potential to activate LCMV gp33-specific naive and memory CD8 T cells. We found that exosomes do not significantly contribute to CD8 T cell cross-priming in vitro. Additionally, exosomes derived from in vitro-infected BMDC did not exhibit significant in vivo priming activity, as evidenced by the lack of protection following exosome vaccination. Thus, DC-derived exosomes do not appear to contribute significantly to CTL priming during acute LCMV infection.

Reversible changes in serum immunoglobulin galactosylation during the immune response and treatment of inflammatory autoimmune arthritis

OBJECTIVES

Improved DNA sequencer-aided fluorophore-assisted carbohydrate electrophoresis (DSA-FACE) technology was used to monitor the changes in the galactosylation status of serum immunoglobulins during the immune response and therapy of autoimmune arthritis.

METHODS

Collagen-induced arthritis (CIA) was induced in susceptible DBA/1 mice and the undergalactosylation status (UGS) of serum immunoglobulins was determined using the improved DSA-FACE technology. Prophylactic intravenous tolerisation with type II collagen as well as semitherapeutic treatment with dexamethasone (DEX) were performed and UGS was analysed. Next, the serum immunoglobulin glycosylation profiles of patients with rheumatoid arthritis (RA) and spondyloarthropathy (SpA) were studied and changes in the UGS scores during anti-tumour necrosis factor (TNF)alpha therapy followed.

RESULTS

In the longitudinal CIA study, the undergalactosylation state of immunoglobulins was found to be significantly correlated with the clinical arthritis scores. Upon collagen-specific tolerisation as well as glucocorticoid semitherapeutic treatment, improvement of the clinical arthritis scores correlated with decreased levels of UGS. It was also demonstrated that withdrawal of DEX was associated with an increased UGS score. Interestingly, reversibility in the UGS was also shown during treatment of patients with RA and SpA with anti-TNFalpha.

CONCLUSIONS

These findings demonstrate that the UGS of serum immunoglobulins changes during the disease course of CIA and that this UGS is inhibited by antigen-specific and antigen-independent treatment procedures. The observation that Ig galactosylation is a reversible process is also documented during treatment of patients with RA and SpA with anti-TNFalpha.

The intimate relationship between gut and joint in spondyloarthropathies

PURPOSE OF REVIEW

The aim of this article is to highlight recent progress in the combined joint and gut disease in spondyloarthropathies.

RECENT FINDINGS

A set of genes has been identified that are differentially expressed in the colon of spondyloarthropathy and Crohn's disease patients. Reduction of human leukocyte antigen B27 (HLA B27) misfolding by additional beta2-microglobulin in HLA B27 transgenic rats unexpectedly increased disease severity, with more similarities to spondyloarthropathies. By contrast, colitis disappeared.

SUMMARY

Human genomic studies combined with animal model research provide new clues concerning the common pathogenesis of spondyloarthropathy and Crohn's disease, further substantiating the unique relationship between gut and joint inflammation.

A Single Early Activation of Invariant NK T Cells Confers Long-Term Protection against Collagen-Induced Arthritis in a Ligand-Specific Manner

The glycosphingolipid alpha-galactosylceramide (alpha-GalCer) has been shown to be a potent activator of invariant NKT (iNKT) cells, rapidly inducing large amounts of both Th1 and Th2 cytokines upon injection in mice. The C-glycoside analog of alpha-GalCer (alpha-C-GalCer), by contrast, results in an enhanced Th1-type response upon activation of iNKT cells. We administered a single dose of these Ags to DBA/1 mice during the early induction phase of collagen-induced arthritis and demonstrated therapeutic efficacy of alpha-GalCer when administered early rather than late during the disease. Surprisingly, the Th1-polarizing analog alpha-C-GalCer also conferred protection. Furthermore, a biphasic role of IFN-gamma in the effect of iNKT cell stimulation was observed. Whereas in vivo neutralization of IFN-gamma release induced by either alpha-GalCer or alpha-C-GalCer early during the course of disease resulted in partial improvement of clinical arthritis symptoms, blockade of IFN-gamma release later on resulted in a more rapid onset of arthritis. Although no phenotypic changes in conventional T cells, macrophages, or APCs could be detected, important functional differences in T cell cytokine production in serum were observed upon polyclonal T cell activation, 2 wk after onset of arthritis. Whereas alpha-GalCer-treated mice produced significantly higher amounts of IL-10 upon systemic anti-CD3 stimulation compared with PBS controls, T cells from alpha-C-GalCer-treated mice, by contrast, produced substantially lower levels of cytokines, suggesting the involvement of different protective mechanisms. In conclusion, these findings suggest long-term, ligand-specific, time-dependent, and partially IFN-gamma-dependent immunomodulatory effects of iNKT cells in collagen-induced arthritis.

NKT cells: manipulable managers of joint inflammation

The importance of T cell participation in the aetiology and pathogenesis of rheumatoid arthritis (RA) is now widely appreciated. The disease is mediated by activated pro-inflammatory, self-reactive T helper cells, instigating the chronic autoimmune response characteristic of rheumatoid inflammation. Natural killer T (NKT) cells are a distinctive population of T cells thought to protect self-tissues from damaging inflammatory immune responses, and are often recognized as a regulatory T cell subtype, regulating the magnitude or class of the immune response. Recently, a number of studies have provided insight concerning the role of NKT cells in different models of autoimmune joint inflammation, suggesting the involvement of this specialized T cell subset in controlling initiation and perpetuation of arthritic disease. The aim of this review is to provide rheumatologists with an introduction of the principal features of NKT cells, to give an overview of the data obtained in animal models of arthritis and to discuss the hypothesized mechanisms. Finally, we will speculate on future prospects with regard to NKT cell-targeted treatment of arthritic disease by use of glycolipids.

Formatted anti-tumor necrosis factor alpha VHH proteins derived from camelids show superior potency and targeting to inflamed joints in a murine model of collagen-induced arthritis

OBJECTIVE

The advent of tumor necrosis factor (TNF)-blocking drugs has provided rheumatologists with an effective, but highly expensive, treatment for the management of established rheumatoid arthritis (RA). Our aim was to explore preclinically the application of camelid anti-TNF VHH proteins, which are single-domain antigen binding (VHH) proteins homologous to human immunoglobulin V(H) domains, as TNF antagonists in a mouse model of RA.

METHODS

Llamas were immunized with human and mouse TNF, and antagonistic anti-TNF VHH proteins were isolated and cloned for bacterial production. The resulting anti-TNF VHH proteins were recombinantly linked to yield bivalent mouse and human TNF-specific molecules. To increase the serum half-life and targeting properties, an anti-serum albumin anti-TNF VHH domain was incorporated into the bivalent molecules. The TNF-neutralizing potential was analyzed in vitro. Mouse TNF-specific molecules were tested in a therapeutic protocol in murine collagen-induced arthritis (CIA). Disease progression was evaluated by clinical scoring and histologic evaluation. Targeting properties were evaluated by 99mTc labeling and gamma camera imaging.

RESULTS

The bivalent molecules were up to 500 times more potent than the monovalent molecules. The antagonistic potency of the anti-human TNF VHH proteins exceeded even that of the anti-TNF antibodies infliximab and adalimumab that are used clinically in RA. Incorporation of binding affinity for albumin into the anti-TNF VHH protein significantly prolonged its serum half-life and promoted its targeting to inflamed joints in the murine CIA model of RA. This might explain the excellent therapeutic efficacy observed in vivo.

CONCLUSION

These data suggest that because of the flexibility of their format, camelid anti-TNF VHH proteins can be converted into potent therapeutic agents that can be produced and purified cost-effectively.