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Dilated cardiomyopathy (DCM) is typically defined by left ventricular dilation and systolic dysfunction in the absence of a clear precipitant. Idiopathic disease is common; up to 50% of patients with DCM have no cause found despite imaging, genetic and biopsy assessments. Treatment remains focused on managing symptoms, reducing the risk of sudden cardiac death and ameliorating the structural and electrical complications of disease progression. In the absence of aetiology-specific treatments, the condition remains associated with a poor prognosis; mortality is approximately 40% at 10 years. The role of immune-mediated inflammatory injury in the development and progression of DCM was first proposed over 30 years ago. Despite the subsequent failures of three large clinical trials of immunosuppressive treatment (ATTACH, RENEWAL and the Myocarditis Treatment Trial), evidence for an abnormal adaptive immune response in DCM remains significant. In this review, we summarise and discuss available evidence supporting immune dysfunction in DCM, with a specific focus on cellular immunity. We also highlight current clinical and experimental treatments. We propose that the success of future immunosuppressive treatment trials in DCM will be dependent on the deep immunophenotyping of patients, to identify those with active inflammation and/or an abnormal immune response who are most likely to respond to therapy.

Aims Chronic heart failure (CHF) is a systemic syndrome with a poor prognosis and a need for novel therapies. We investigated whether whole blood transcriptomic profiling can provide new mechanistic insights into cardiovascular (CV) mortality in CHF. Methods and results Transcriptome profiles were generated at baseline from 944 CHF patients from the BIOSTAT-CHF study, of whom 626 survived and 318 died from a CV cause during a follow-up of 21 months. Multivariable analysis, including adjustment for cell count, identified 1153 genes (6.5%) that were differentially expressed between those that survived or died and strongly related to a validated clinical risk score for adverse prognosis. The differentially expressed genes mainly belonged to five non-redundant pathways: adaptive immune response, proteasome-mediated ubiquitin-dependent protein catabolic process, T-cell co-stimulation, positive regulation of T-cell proliferation, and erythrocyte development. These five pathways were selectively related (RV coefficients >0.20) with seven circulating protein biomarkers of CV mortality (fibroblast growth factor 23, soluble ST2, adrenomedullin, hepcidin, pentraxin-3, WAP 4-disulfide core domain 2, and interleukin-6) revealing an intricate relationship between immune and iron homeostasis. The pattern of survival-associated gene expression matched with 29 perturbagen-induced transcriptome signatures in the iLINCS drug-repurposing database, identifying drugs, approved for other clinical indications, that were able to reverse in vitro the molecular changes associated with adverse prognosis in CHF. Conclusion Systematic modelling of the whole blood protein-coding transcriptome defined molecular pathways that provide a link between clinical risk factors and adverse CV prognosis in CHF, identifying both established and new potential therapeutic targets.

A potential immunotherapeutic role for AZD1656 (a glucokinase activator) in the treatment of COVID-19 was hypothesized. The ARCADIA trial investigated the safety and efficacy of AZD1656 in diabetic patients admitted to hospital with COVID-19.The ARCADIA trial was a Phase II randomised, double-blind, placebo-controlled clinical trial. Adult diabetic patients, admitted with COVID-19, were recruited at 28 hospitals in the UK, Romania and Czech Republic and randomly assigned (1:1) to receive AZD1656 tablets (100mg twice a day), or matched placebo, for up to 21 days, in addition to usual care. All involved were masked to treatment allocation. The primary endpoint was clinical improvement measured at Day 14. The Full Analysis Set (FAS) included all patients who received at least one dose of assigned treatment. ARCADIA is complete and registered with ClinicalTrials.gov (NCT04516759).Between 29 September 2020 to 16 April 2021, 170 patients were screened and 156 patients were randomised, three of whom did not commence treatment. Of the remaining 153, 80 were assigned to AZD1656 and 73 were assigned to placebo and included in the Full Analysis Set (FAS). The primary analysis showed no statistically significant difference between groups (AZD1656: 76·3%; Placebo: 69·9%,Although the trial did not achieve its primary endpoint, AZD1656 was associated with a decrease in deaths and a reduction in the duration of hospitalisation, as compared to Placebo. Immunophenotyping and immunochemistry indicated an immunomodulatory effect of AZD1656. The trial suggests a beneficial therapeutic effect of AZD1656 and identifies a new therapeutic concept: small molecule activation of endogenous homeostatic immune cells which themselves become the therapeutic agent within the body. Phase 2 trials of this size carry the risk of false positive results and confirmation of these results in a larger clinical trial is now required.UK Research and Innovation (UKRI) 'Innovate UK' programme and Excalibur Medicines Ltd.

Heart failure with preserved ejection fraction (HFpEF) is increasing in prevalence worldwide, already accounting for at least half of all heart failure (HF). As most patients with HFpEF are obese with metabolic syndrome, metabolic stress has been implicated in syndrome pathogenesis. Recently, compelling evidence for bidirectional crosstalk between metabolic stress and chronic inflammation has emerged, and alterations in systemic and cardiac immune responses are held to participate in HFpEF pathophysiology. Indeed, based on both preclinical and clinical evidence, comorbidity-driven systemic inflammation, coupled with metabolic stress, have been implicated together in HFpEF pathogenesis. As metabolic alterations impact immune function(s) in HFpEF, major changes in immune cell metabolism are also recognized in HFpEF and in HFpEF-predisposing conditions. Both arms of immunity - innate and adaptive - are implicated in the cardiomyocyte response in HFpEF. Indeed, we submit that crosstalk among adipose tissue, the immune system, and the heart represents a critical component of HFpEF pathobiology. Here, we review recent evidence in support of immunometabolic mechanisms as drivers of HFpEF pathogenesis, discuss pivotal biological mechanisms underlying the syndrome, and highlight questions requiring additional inquiry.

Mounting evidence has linked the metabolic disease to neurovascular disorders and cognitive decline. Using a murine model of a high-fat high-sugar diet mimicking obesity-induced type 2 diabetes mellitus (T2DM) in humans, we show that pro-inflammatory mediators and altered immune responses damage the blood-brain barrier (BBB) structure, triggering a proinflammatory metabolic phenotype. We find that disruption to tight junctions and basal lamina due to loss of control in the production of matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) causes BBB impairment. Together the disruption to the structural and functional integrity of the BBB results in enhanced transmigration of leukocytes across the BBB that could contribute to an initiation of a neuroinflammatory response through activation of microglia. Using a humanized in vitro model of the BBB and T2DM patient post-mortem brains, we show the translatable applicability of our results. We find a leaky BBB phenotype in T2DM patients can be attributed to a loss of junctional proteins through changes in inflammatory mediators and MMP/TIMP levels, resulting in increased leukocyte extravasation into the brain parenchyma. We further investigated therapeutic avenues to reduce and restore the BBB damage caused by HFHS-feeding. Pharmacological treatment with recombinant annexin A1 (hrANXA1) or reversion from a high-fat high-sugar diet to a control chow diet (dietary intervention), attenuated T2DM development, reduced inflammation, and restored BBB integrity in the animals. Given the rising incidence of diabetes worldwide, understanding metabolic-disease-associated brain microvessel damage is vital and the proposed therapeutic avenues could help alleviate the burden of these diseases.

Visceral adipose tissue (VAT) has multiple roles in orchestrating whole-body energy homeostasis. In addition, VAT is now considered an immune site harboring an array of innate and adaptive immune cells with a direct role in immune surveillance and host defense. We report that conventional dendritic cells (cDCs) in VAT acquire a tolerogenic phenotype through upregulation of pathways involved in adipocyte differentiation. While activation of the Wnt/β-catenin pathway in cDC1 DCs induces IL-10 production, upregulation of the PPARγ pathway in cDC2 DCs directly suppresses their activation. Combined, they promote an anti-inflammatory milieu in vivo delaying the onset of obesity-induced chronic inflammation and insulin resistance. Under long-term over-nutrition, changes in adipocyte biology curtail β-catenin and PPARγ activation, contributing to VAT inflammation.

Effective immunity requires appropriate recirculation of naïve T cells through secondary lymphoid organs and migration of antigen-specific T cells to sites of inflammation. Leukocyte migration is a highly regulated process requiring specific interactions between leukocytes and endothelial cells (EC) termed collectively as the leukocyte adhesion cascade. Recruitment and retention of activated T cells to antigen-rich sites of inflammation is a key event in the immune response, which relies in part on local antigen presentation particularly by EC of inflamed vessels. Here we describe methods to assess the contributions of different molecules on antigen-dependent T cell migration, by utilizing IFN-γ to upregulate MHC molecules on EC and local antigen presentation, both in vitro and in vivo.

There are many routes to exploiting tolerance processes to ensure long–term graft survival. Complete tolerance although attractive as a goal, may not be the most practical in the clinic. Instead simple and low–impact procedures that harness tolerance processes used in conjunction with low doses of immunosuppressive drugs may prove the most reliable and user–friendly of approaches.

Interferon-γ-treated renal tubular epithelial cells induce allospecific tolerance. Following organ transplantation, tissue parenchymal cells commonly express major histocompatibility complex (MHC) class II molecules as a result of local cytokine release, and thus acquire the capacity to present donor MHC alloantigens to alloreactive CD4 + T cells. The consequences of such a presentation are likely to be relevant in the induction of tolerance to the transplanted tissues, and this has been reported in animal models of transplantation and in humans. In this study, the consequences of antigen presentation by interferon-γ (IFN-γ)-treated human renal tubular epithelial cells (RTEC) to resting and activated CD4 + T cells were investigated. Allogeneic RTEC were unable to stimulate proliferation by peripheral blood CD45 RA + or RO + CD4 + T cells from three HLA-mismatched responders. The response to RTEC was partially reconstituted by the addition of murine L cell transfectants expressing human B7.1 (DAP.3-B7), suggesting that the failure of RTEC to stimulate a primary alloresponse was due, at least in part, to a lack of costimulation. T cell clones dependent on B7-mediated co-stimulation also did not respond to peptide presented by RTEC. Most importantly, this lack of reactivity was accompanied by the induction of nonresponsiveness. Incubation with allogeneic, DR-expressing RTEC induced allospecific hyporesponsiveness in both CD45RA + and RO + T cells. Similarly, overnight incubation with antigen-pulsed RTEC induced nonresponsiveness in the B7-dependent T cell clones. These results suggest that MHC class II expression on RTEC may contribute to the induction of an allospecific nonresponsiveness following organ transplantation.