ACAID as a potential therapeutic approach to modulate inflammation in neurodegenerative diseases

Role of CD4+ T cell-derived cytokines in the pathogenesis of uveitis

Uveitis refers to a diverse group of inflammatory diseases that affecting the uveal tract, comprising the iris, ciliary body, and choroid, with potential repercussions ranging from visual impairment to blindness. The role of autoimmunity in uveitis etiology is complex and still under investigation. CD4+ T cells intricately regulate immune responses in uveitis through their diverse subtypes: Th1, Th2, Th17, Treg (T regulatory), and Tfh (follicular T helper) cells. Each T cell subtype secretes specific cytokines with either pathogenic or protective implications in uveitis. Th1 cells, characterized by IFN-γ secretion and T-bet expression, drive type 1 immune responses against intracellular pathogens. Conversely, Th2 cells, which produce interleukin (IL)-4, IL-5, and IL-13 and express the transcription factor GATA3, mediate type 2 immune responses to larger extracellular threats like helminths. Th17 cells, generating IL-17 and IL-22 and controlled by RORγt, engage in type 3 immune responses against select pathogens. Tfh cells, releasing IL-21 and governed by Bcl6, aid B cell antibody production. Conversely, Tregs, identified by Foxp3, exert regulatory functions in immune homeostasis. This review delves into the roles of CD4+ T cell-derived cytokines in uveitis, emphasizing their intricate involvement in disease progression and resolution. Insight into these mechanisms might guide therapeutic approaches targeting CD4+ T cell responses in uveitis management.

The role of γδ T cells in the immunopathogenesis of inflammatory diseases: from basic biology to therapeutic targeting

The γδ T cells are lymphocytes with an innate-like phenotype that can distribute to different tissues to reside and participate in homeostatic functions such as pathogen defense, tissue modeling, and response to stress. These cells originate during fetal development and migrate to the tissues in a TCR chain-dependent manner. Their unique manner to respond to danger signals facilitates the initiation of cytokine-mediated diseases such as spondyloarthritis and psoriasis, which are immune-mediated diseases with a very strong link with mucosal disturbances, either in the skin or the gut. In spondyloarthritis, γδ T cells are one of the main sources of IL-17 and, therefore, the main drivers of inflammation and probably new bone formation. Remarkably, this population can be the bridge between gut and joint inflammation.

Looking beyond Self-Protection: The Eyes Instruct Systemic Immune Tolerance Early in Life

The eyes provide themselves with immune tolerance. Frequent skin inflammatory diseases in young blind people suggest, nonetheless, that the eyes instruct a systemic immune tolerance that benefits the whole body. We tested this premise by using delayed skin contact hypersensitivity (DSCH) as a tool to compare the inflammatory response developed by sighted (S) and birth-enucleated (BE) mice against oxazolone or dinitrofluorobenzene at the ages of 10, 30 and 60 days of life. Adult mice enucleated (AE) at 60 days of age were also assessed when they reached 120 days of life. BE mice displayed exacerbated DSCH at 60 but not at 10 or 30 days of age. AE mice, in contrast, show no exacerbated DSCH. Skin inflammation in 60-day-old BE mice was hapten exclusive and supported by distinct CD8+ lymphocytes. The number of intraepidermal T lymphocytes and migrating Langerhans cells was, however, similar between S and BE mice by the age of 60 days. Our observations support the idea that the eyes instruct systemic immune tolerance that benefits organs outside the eyes from an early age. The higher prevalence of inflammatory skin disorders reported in young people might then reflect reduced immune tolerance associated with the impaired functional morphology of the eyes.

Retinal Degeneration: A Window to Understand the Origin and Progression of Parkinson’s Disease?

Parkinson’s disease (PD), the second most prevalent neurodegenerative disorder, manifests with motor and non-motor symptoms associated with two main pathological hallmarks, including the deterioration of dopaminergic cells and aggregation of alpha-synuclein. Yet, PD is a neurodegenerative process whose origin is uncertain and progression difficult to monitor and predict. Currently, a possibility is that PD may be secondary to long lasting peripheral affectations. In this regard, it has been shown that retinal degeneration is present in PD patients. Although it is unknown if retinal degeneration precedes PD motor symptoms, the possibility exists since degeneration of peripheral organs (e.g., olfaction, gut) have already been proven to antedate PD motor symptoms. In this paper, we explore this possibility by introducing the anatomical and functional relationship of retina and brain and providing an overview of the physiopathological changes of retinal structure and visual function in PD. On the basis of the current status of visual deficits in individuals with PD, we discuss the modalities and pathological mechanism of visual function or morphological changes in the retina and focus on the correlation between visual impairment and some representative structural features with clinical significance. To consider retinal degeneration as a contributor to PD origin and progress is important because PD evolution may be monitored and predicted by retinal studies through state-of-the-art techniques of the retina. It is significant to integrally understand the role of retinal morphological and functional changes in the neurodegenerative process for the diagnosis and therapeutic strategies of PD.

Immune responses to retinal gene therapy using adeno-associated viral vectors - Implications for treatment success and safety

Recombinant adeno-associated virus (AAV) is the leading vector for gene therapy in the retina. As non-pathogenic, non-integrating, replication deficient vector, the recombinant virus efficiently transduces all key retinal cell populations. Successful testing of AAV vectors in clinical trials of inherited retinal diseases led to the recent approval of voretigene neparvovec (Luxturna) for the treatment of RPE65 mutation-associated retinal dystrophies. However, studies applying AAV-mediated retinal gene therapy independently reported intraocular inflammation and/or loss of efficacy after initial functional improvements. Both observations might be explained by targeted removal of transduced cells via anti-viral defence mechanisms. AAV has been shown to activate innate pattern recognition receptors (PRRs) such as toll-like receptor (TLR)-2 and TLR-9 resulting in the release of inflammatory cytokines and type I interferons. The vector can also induce capsid-specific and transgene-specific T cell responses and neutralizing anti-AAV antibodies which both limit the therapeutic effect. However, the target organ of retinal gene therapy, the eye, is known as an immune-privileged site. It is characterized by suppression of inflammation and promotion of immune tolerance which might prevent AAV-induced immune responses. This review evaluates AAV-related immune responses, toxicity and inflammation in studies of retinal gene therapy, identifies influencing variables of these responses and discusses potential strategies to modulate immune reactions to AAV vectors to increase the safety and efficacy of ocular gene therapy.

Anterior chamber associated immune deviation used as a neuroprotective strategy in rats with spinal cord injury

The inflammatory response is probably one of the main destructive events occurring after spinal cord injury (SCI). Its progression depends mostly on the autoimmune response developed against neural constituents. Therefore, modulation or inhibition of this self-reactive reaction could help to reduce tissue destruction. Anterior chamber associated immune deviation (ACAID) is a phenomenon that induces immune-tolerance to antigens injected into the eye´s anterior chamber, provoking the reduction of such immune response. In the light of this notion, induction of ACAID to neural constituents could be used as a potential prophylactic therapy to promote neuroprotection. In order to evaluate this approach, three experiments were performed. In the first one, the capability to induce ACAID of the spinal cord extract (SCE) and the myelin basic protein (MBP) was evaluated. Using the delayed type hypersensibility assay (DTH) we demonstrated that both, SCE and MBP were capable of inducing ACAID. In the second experiment we evaluated the effect of SCE-induced ACAID on neurological and morphological recovery after SCI. In the results, there was a significant improvement of motor recovery, nociceptive hypersensitivity and motoneuron survival in rats with SCE-induced ACAID. Moreover, ACAID also up-regulated the expression of genes encoding for anti-inflammatory cytokines and FoxP3 but down-regulated those for pro-inflamatory cytokines. Finally, in the third experiment, the effect of a more simple and practical strategy was evaluated: MBP-induced ACAID, we also found significant neurological and morphological outcomes. In the present study we demonstrate that the induction of ACAID against neural antigens in rats, promotes neuroprotection after SCI.

Cellular and Molecular Mechanisms of Anterior Chamber-Associated Immune Deviation (ACAID): What We Have Learned from Knockout Mice

Anterior chamber-associated immune deviation (ACAID) is a well-known phenomenon that can occur after an antigen is introduced without any danger signal into the anterior chamber of a murine eye. It is reported to lead to an antigen-specific immune deviation throughout the body. Despite the relatively little evidence of this phenomenon in humans, it has been suggested as a potential prophylactic strategy in allograft rejections and in several autoimmune diseases. Cellular and molecular mechanisms of ACAID have been explored in different murine models mainly as proofs of concept, first by direct analyses of immune components in normal immunocompetent settings and by cell transfer experiments. Later, use of knockout (KO) mice has helped considerably to decipher ACAID mechanisms. However, several factors raise questions about the reliability and validity of studies using KO murine models. This mini-review summarizes results obtained with KO mice and discusses their advantages, their potential weaknesses, and their potential methods for further progress.