Water restriction in cowpea plants [Vigna unguiculata (L.) Walp.]: Metabolic changes and tolerance induction

ABSTRACT Global climate change tends to intensify water unavailability, especially in semi-arid regions, directly impacting agricultural production. Cowpea is one of the crops with great socio-economic importance in the Brazilian semi-arid region, cultivated mainly under rainfed farming and considered moderately tolerant to water restriction. This species has physiological and biochemical mechanisms of adaptation to these stress factors, but there is still no clear vision of how these responses can not only allow survival, but also ensure yield advances in the field. Besides acclimation mechanisms, the exogenous application of abiotic (salicylic acid, silicon, proline, methionine, and potassium nitrate) and biotic (rhizobacteria) elicitors is promising in mitigating the effects of water restriction. The present literature review discusses the acclimation mechanisms of cowpea and some cultivation techniques, especially the application of elicitors, which can contribute to maintaining crop yield under different water scenarios. The application of elicitors is an alternative way to increase the sustainability of production in rainfed farming in semi-arid regions. However, the use of eliciting substances in cowpea still needs to be carefully explored, given the difficulties caused by genotypic and edaphoclimatic variability under field conditions.

Tolerogenic Delivery of a Hybrid Insulin Peptide Markedly Prolongs Islet Graft Survival in the Non-Obese Diabetic (NOD) Mouse

The induction of antigen (Ag)-specific tolerance and replacement of islet β-cells are major ongoing goals for the treatment of Type 1 Diabetes (T1D). Our group previously showed that a hybrid insulin peptide (2.5HIP) is a critical autoantigen for diabetogenic CD4⁺ T cells in the non-obese diabetic (NOD) mouse model. In this study, we investigated whether induction of Ag-specific tolerance using 2.5HIP-coupled tolerogenic nanoparticles (NPs) could protect diabetic NOD mice from disease recurrence upon syngeneic islet transplantation. Islet graft survival was significantly prolonged in mice treated with 2.5HIP NPs, but not NPs containing the insulin B chain peptide 9-23. Protection in 2.5HIP NP-treated mice was attributed both to the simultaneous induction of anergy in 2.5HIP-specific effector T cells and to the expansion of Foxp3+ regulatory T cells specific for the same antigen. Notably, our results indicate that effector function of graft-infiltrating CD4⁺ and CD8⁺ T cells specific for other β-cell epitopes was significantly impaired, suggesting a novel mechanism of therapeutically induced linked suppression. This work establishes that tolerance induction with a hybrid insulin peptide can delay recurrent autoimmunity in NOD mice, which could inform the development of an Ag-specific therapy for T1D.

Tolerogenic Delivery of a Hybrid Insulin Peptide Markedly Prolongs Islet Graft Survival in the Non-Obese Diabetic (NOD) Mouse

The induction of antigen (Ag)-specific tolerance and replacement of islet β-cells are major ongoing goals for the treatment of Type 1 Diabetes (T1D). Our group previously showed that a hybrid insulin peptide (2.5HIP) is a critical autoantigen for diabetogenic CD4⁺ T cells in the non-obese diabetic (NOD) mouse model. In this study, we investigated whether induction of Ag-specific tolerance using 2.5HIP-coupled tolerogenic nanoparticles (NPs) could protect diabetic NOD mice from disease recurrence upon syngeneic islet transplantation. Islet graft survival was significantly prolonged in mice treated with 2.5HIP NPs, but not NPs containing the insulin B chain peptide 9-23. Protection in 2.5HIP NP-treated mice was attributed both to the simultaneous induction of anergy in 2.5HIP-specific effector T cells and to the expansion of Foxp3+ regulatory T cells specific for the same antigen. Notably, our results indicate that effector function of graft-infiltrating CD4⁺ and CD8⁺ T cells specific for other β-cell epitopes was significantly impaired, suggesting a novel mechanism of therapeutically induced linked suppression. This work establishes that tolerance induction with a hybrid insulin peptide can delay recurrent autoimmunity in NOD mice, which could inform the development of an Ag-specific therapy for T1D.

Tolerogenic Delivery of a Hybrid Insulin Peptide Markedly Prolongs Islet Graft Survival in the Non-Obese Diabetic (NOD) Mouse

The induction of antigen (Ag)-specific tolerance and replacement of islet β-cells are major ongoing goals for the treatment of Type 1 Diabetes (T1D). Our group previously showed that a hybrid insulin peptide (2.5HIP) is a critical autoantigen for diabetogenic CD4+ T cells in the non-obese diabetic (NOD) mouse model. In this study, we investigated whether induction of Ag-specific tolerance using 2.5HIP-coupled tolerogenic nanoparticles (NPs) could protect diabetic NOD mice from disease recurrence upon syngeneic islet transplantation. Islet graft survival was significantly prolonged in mice treated with 2.5HIP NPs, but not NPs containing the insulin B chain peptide 9-23. Protection in 2.5HIP NP-treated mice was attributed both to the simultaneous induction of anergy in 2.5HIP-specific effector T cells and to the expansion of Foxp3+ regulatory T cells specific for the same antigen. Notably, our results indicate that effector function of graft-infiltrating CD4+ and CD8+ T cells specific for other β-cell epitopes was significantly impaired, suggesting a novel mechanism of therapeutically induced linked suppression. This work establishes that tolerance induction with a hybrid insulin peptide can delay recurrent autoimmunity in NOD mice, which could inform the development of an Ag-specific therapy for T1D.

Mechanistic and Biomarker Studies to Demonstrate Immune Tolerance in Multiple Sclerosis

The induction of specific immunological tolerance represents an important therapeutic goal for multiple sclerosis and other autoimmune diseases. Sound knowledge of the target antigens, the underlying pathomechanisms of the disease and the presumed mechanisms of action of the respective tolerance-inducing approach are essential for successful translation. Furthermore, suitable tools and assays to evaluate the induction of immune tolerance are key aspects for the development of such treatments. However, investigation of the mechanisms of action underlying tolerance induction poses several challenges. The optimization of sensitive, robust methods which allow the assessment of low frequency autoreactive T cells and the long-term reduction or change of their responses, the detection of regulatory cell populations and their immune mediators, as well as the validation of specific biomarkers indicating reduction of inflammation and damage, are needed to develop tolerance-inducing approaches successfully to patients. This short review focuses on how to demonstrate mechanistic proof-of-concept in antigen-specific tolerance-inducing therapies in MS.

Chimerism-Based Tolerance to Kidney Allografts in Humans: Novel Insights and Future Perspectives

Chronic rejection and immunosuppression-related toxicity severely affect long-term outcomes of kidney transplantation. The induction of transplantation tolerance – the lack of destructive immune responses to a transplanted organ in the absence of immunosuppression – could potentially overcome these limitations. Immune tolerance to kidney allografts from living donors has been successfully achieved in humans through clinical protocols based on chimerism induction with hematopoietic cell transplantation after non-myeloablative conditioning. Notably, two of these protocols have led to immune tolerance in a significant fraction of HLA-mismatched donor-recipient combinations, which represent the large majority of cases in clinical practice. Studies in mice and large animals have been critical in dissecting tolerance mechanisms and in selecting the most promising approaches for human translation. However, there are several key differences in tolerance induction between these models and humans, including the rate of success and stability of donor chimerism, as well as the relative contribution of different mechanisms in inducing donor-specific unresponsiveness. Kidney allograft tolerance achieved through durable full-donor chimerism may be due to central deletion of graft-reactive donor T cells, even though mechanistic data from patient series are lacking. On the other hand, immune tolerance attained with transient mixed chimerism-based protocols initially relies on Treg-mediated suppression, followed by peripheral deletion of donor-reactive recipient T-cell clones under antigenic pressure from the graft. These conclusions were supported by data deriving from novel high-throughput T-cell receptor sequencing approaches that allowed tracking of alloreactive repertoires over time. In this review, we summarize the most important mechanistic studies on tolerance induction with combined kidney-bone marrow transplantation in humans, discussing open issues that still need to be addressed and focusing on techniques developed in recent years to efficiently monitor the alloresponse in tolerance trials. These cutting-edge methods will be instrumental for the development of immune tolerance protocols with improved efficacy and to identify patients amenable to safe immunosuppression withdrawal.

Oral Tolerance Induction by Bothrops jararaca Venom in a Murine Model and Cross-Reactivity with Toxins of Other Snake Venoms

Oral tolerance is defined as a specific suppression of cellular and humoral immune responses to a particular antigen through prior oral administration of an antigen. It has unique immunological importance since it is a natural and continuous event driven by external antigens. It is characterized by low levels of IgG in the serum of animals after immunization with the antigen. There is no report of induction of oral tolerance to Bothrops jararaca venom. Here, we induced oral tolerance to B. jararaca venom in BALB/c mice and evaluated the specific tolerance and cross-reactivity with the toxins of other Bothrops species after immunization with the snake venoms adsorbed to/encapsulated in nanostructured SBA-15 silica. Animals that received a high dose of B. jararaca venom (1.8 mg) orally responded by showing antibody titers similar to those of immunized animals. On the other hand, mice tolerized orally with three doses of 1 µg of B. jararaca venom showed low antibody titers. In animals that received a low dose of B. jararaca venom and were immunized with B. atrox or B. jararacussu venom, tolerance was null or only partial. Immunoblot analysis against the venom of different Bothrops species provided details about the main tolerogenic epitopes and clearly showed a difference compared to antiserum of immunized animals.

FcεRI Cluster Size Determines Effective Mast Cell Desensitization without Effector Responses in vitro

<b><i>Background:</i></b> Allergen-specific desensitization of mast cell (MC) IgE receptors (FcεRI) is an important mechanism of allergen-specific immunotherapy that enables tolerance induction via systemic desensitization. Experimental in vitro IgE-mediated MC desensitization is a potential tool to understand the molecular mechanisms underlying this therapy. Desensitized MCs exhibit internalized IgE and its FcεRI receptors in response to suboptimal doses of allergen without provoking activation. The ovalbumin (OVA) allergen exhibits altered allergenicity upon heat treatment. MC reactions are fundamentally regulated by allergen features (i.e., allergenicity); however, the effects of allergenicity on desensitization remain unclear. <b><i>Objectives:</i></b> This study aimed to examine the impact of allergenicity on the establishment of in vitro MC desensitization using naive OVA (nOVA) and heated OVA (hOVA), which could induce varying MC effector responses. <b><i>Method:</i></b> Bone marrow-derived MCs (BMMCs) were sensitized with OVA-specific IgE, desensitized with sequentially increasing doses of nOVA or hOVA at 10-min intervals, and challenged with nOVA. To evaluate desensitization, the cell surface expression level and subcellular localization of FcεRI-bound IgE were analyzed before and after the final nOVA challenge. MC activation was determined by measuring the release of β-hexosaminidase into supernatants. <b><i>Results:</i></b> Desensitized cells exhibited impaired activation following OVA challenge. Both nOVA and hOVA induced BMMC desensitization under different conditions. Formation of small IgE-FcεRI cluster BMMCs, which adequately represent the desensitized state, was significant. The size of the internalized IgE-FcεRI clusters might be correlated with the desensitized state of MCs. <b><i>Conclusions:</i></b> We demonstrate that the optimal size of IgE-FcεRI clusters for in vitro BMMC desensitization differed significantly depending on allergenicity, and the efficacy of desensitization was reflected by IgE-FcεRI cluster formation. Our study provides information on the characteristics of IgE-FcεRI internalization for successful desensitization in vitro.