Future therapeutics for the induction of peripheral immune tolerance in autoimmune disease and organ transplantation

Juvenile Idiopathic Arthritis Associated Uveitis. Current Status: Epidemiology, Pathogenesis, and Clinical Issues

Uveitis is the most common extraarticular manifestation of juvenile idiopathic arthritis (JIA) and with no adequate management results in serious eye complications such as cataracts, secondary glaucoma, retinal detachment, and linear corneal dystrophy. This pathology reduces patients’ quality of life and can lead to significant social and economic losses, both due to direct health costs and due to disability (total loss of sight). Childhood uveitis accounts for approximately 5–10% of all uveitis in global population, however their prevalence has been increasing in recent years. The etiology and pathogenesis of JIA-associated uveitis remains poorly studied despite the well-known correlation of uveitis with JIA. Uveitis in children is difficult to diagnose in routine pediatric practice, both due to its course (asymptomatic/mild), and due to challenging verbal communication and examination (young children), which poses significant clinical problem. This article presents current data on the epidemiology, pathogenesis, clinical manifestations, and terminology of JIA-associated uveitis.

Sodium Sulfite Exacerbates Allograft Vasculopathy and Affects Tryptophan Breakdown in Murine Heterotopic Aortic Transplantation

Graft vasculopathy is the main feature of chronic rejection in organ transplantation, with oxidative stress being a major trigger. Inflammation-associated prooxidant processes may be controlled by antioxidants; however, interference with redox-regulated mechanisms is a complex endeavor. An essential feature of the cellular immune response is the acceleration of tryptophan (Trp) breakdown, leading to the formation of several bioactive catabolites. Long-term activation of this immunobiochemical pathway contributes to the establishment of a tolerogenic environment, thereby supporting allograft survival. Herein, the impact of the antioxidant sodium sulfite on the development of graft vasculopathy was assessed in murine aortic transplantation. Allogeneic (BALB/c to C57BL/6) heterotopic murine aortic transplantations were performed. Animals were left untreated or were treated with 10 μl of 0.1 M, of 0.01 M sodium sulfite, or of 0.1 M sodium sulfate, intraperitoneally once/day, until postoperative day (POD) 100. Grafts were assessed by histology, immunohistochemistry, and adhesion molecule gene expression. Serum concentrations of tryptophan and its catabolite kynurenine (Kyn) were measured. On day 100, graft vasculopathy was significantly increased upon treatment with 0.1 M sodium sulfite, compared to allogeneic untreated controls (p = 0.004), which correlated with a significant increase of α-smooth-muscle-actin, Vcam-1, and P-selectin. Serum Kyn concentrations increased in the allogeneic control group over time (p < 0.05, POD ≥ 50), while low-dose sodium sulfite treatment (0.01 M) treatment resulted in a decrease in Kyn levels over time (p < 0.05, POD ≥ 10), compared to the respective baselines (p < 0.05). Longitudinal analysis of serum metabolite concentrations in the different treatment groups further identified an overall effect of sodium sulfite on Kyn concentrations. Antioxidative treatment may result in ambivalent consequences. Our data reveal that an excess of antioxidants like sodium sulfite can aggravate allograft vasculopathy, which further highlights the challenges associated with interventions that interfere with the complex interplay of redox-regulated inflammatory processes.

Substituted arylsulphonamides as inhibitors of perforin-mediated lysis

The structure-activity relationships for a series of arylsulphonamide-based inhibitors of the pore-forming protein perforin have been explored. Perforin is a key component of the human immune response, however inappropriate activity has also been implicated in certain auto-immune and therapy-induced conditions such as allograft rejection and graft versus host disease. Since perforin is expressed exclusively by cells of the immune system, inhibition of this protein would be a highly selective strategy for the immunosuppressive treatment of these disorders. Compounds from this series were demonstrated to be potent inhibitors of the lytic action of both isolated recombinant perforin and perforin secreted by natural killer cells in vitro. Several potent and soluble examples were assessed for in vivo pharmacokinetic properties and found to be suitable for progression to an in vivo model of transplant rejection.

EpCAM-dependent extracellular vesicles from intestinal epithelial cells maintain intestinal tract immune balance

How the intestinal tract develops a tolerance to foreign antigens is still largely unknown. Here we report that extracellular vesicles (EVs) with TGF-β1-dependent immunosuppressive activity are produced by intestinal epithelial cells (IECs) under physiological conditions. Transfer of these EVs into inflammatory bowel disease (IBD) mice induced by dextran sulfate sodium salt decreases IBD severity by inducing regulatory T cells and immunosuppressive dendritic cells. In contrast, decreased endogenous EV production promotes IBD development. IECs produce EVs with increased levels of TGF-β1 upon IBD development in an ERK-dependent manner. Furthermore, these EVs tend to localize in the intestinal tract associated with epithelial cell adhesion molecule (EpCAM). Knockdown of EpCAM in vivo increases the severity of murine IBD, and the protective effect of EVs from IECs with decreased EpCAM on murine IBD is blunted. Therefore, our study indicates that EVs from IECs participate in maintaining the intestinal tract immune balance.

Dendritic cell-based vaccines: barriers and opportunities

Dendritic cells (DCs) have several characteristics that make them an ideal vehicle for tumor vaccines, and with the first US FDA-approved DC-based vaccine in use for the treatment of prostate cancer, this technology has become a promising new therapeutic option. However, DC-based vaccines face several barriers that have limited their effectiveness in clinical trials. A major barrier includes the activation state of the DC. Both DC lineage and maturation signals must be selected to optimize the antitumor response and overcome immunosuppressive effects of the tumor microenvironment. Another barrier to successful vaccination is the selection of target antigens that will activate both CD8(+) and CD4(+) T cells in a potent, immune-specific manner. Finally, tumor progression and immune dysfunction limit vaccine efficacy in advanced stages, which may make DC-based vaccines more efficacious in treating early-stage disease. This review underscores the scientific basis and advances in the development of DC-based vaccines, focuses on current barriers to success and highlights new research opportunities to address these obstacles.

Good news-bad news: the Yin and Yang of immune privilege in the eye

The eye and the brain are prototypical tissues manifesting immune privilege (IP) in which immune responses to foreign antigens, particularly alloantigens are suppressed, and even completely inhibited. Explanations for this phenomenon are numerous and mostly reflect our evolving understanding of the molecular and cellular processes underpinning immunological responses generally. IP is now viewed as a property of many tissues and the level of expression of IP varies not only with the tissue but with the nature of the foreign antigen and changes in the limited conditions under which privilege can operate as a mechanism of immunological tolerance. As a result, IP functions normally as a homeostatic mechanism preserving normal function in tissues, particularly those with highly specialized function and limited capacity for renewal such as the eye and brain. However, IP is relatively easily bypassed in the face of a sufficiently strong immunological response, and the privileged tissues may be at greater risk of collateral damage because its natural defenses are more easily breached than in a fully immunocompetent tissue which rapidly rejects foreign antigen and restores integrity. This two-edged sword cuts its swathe through the eye: under most circumstances, IP mechanisms such as blood-ocular barriers, intraocular immune modulators, induction of T regulatory cells, lack of lymphatics, and other properties maintain tissue integrity; however, when these are breached, various degrees of tissue damage occur from severe tissue destruction in retinal viral infections and other forms of uveoretinal inflammation, to less severe inflammatory responses in conditions such as macular degeneration. Conversely, ocular IP and tumor-related IP can combine to permit extensive tumor growth and increased risk of metastasis thus threatening the survival of the host.