Disruptive anti-IgE inhibitors prevent mast cell-dependent early airway response in viable atopic lung tissue

Generation of a virus-like particles based vaccine against IgE

BACKGROUND

Anti-IgE immunotherapy with monoclonal antibodies represents a breakthrough in treatment of severe allergic diseases. However, drawbacks such as short half-life and high price are not negligible. Our objective is to develop an anti-IgE vaccine based on virus-like particles (VLPs) which can induce long-lasting neutralizing IgG anti-IgE antibodies reducing allergic responses without causing intrinsic mast cell activation due to IgE cross-linking.

METHODS

The vaccines were made by chemically coupling three synthetic mouse IgE-Fc fragments to plant-derived immunologically optimized CuMVTT VLPs. The immunogenicity of the vaccines was tested by immunizing naive or allergic mice either with the coupled vaccines or the VLP control followed by systemic or local allergen challenge.

RESULTS

Mice immunized with the vaccines exhibited high titers of anti-IgE antibodies in the sera and high levels of anti-IgE secreting plasma cells in lymphoid organs. Moreover, free IgE in serum were reduced by the induced anti-IgE antibodies; therefore, less IgE was bound to FcεRI on the surface of basophils. In line with these reduced IgE levels on effector cells after vaccination, immunized mice were protected from challenge with allergens. Importantly, despite presence of anti-IgE antibodies, no signs of acute or chronic allergic response were seen in immunized allergic mice.

CONCLUSION

The generated vaccines can effectively induce anti-IgE antibodies that did not cause allergic responses in sensitized mice but were able to decrease the level of free and cell bound IgE and protected sensitized animals from allergic responses upon allergen challenge.

Research Advances in Mast Cell Biology and Their Translation Into Novel Therapies for Anaphylaxis

Anaphylaxis is an acute, potentially life-threatening systemic allergic reaction for which there are no known reliable preventative therapies. Its primary cell mediator, the mast cell, has several pathophysiologic roles and functions in IgE-mediated reactions that continue to be poorly understood. Recent advances in the understanding of allergic mechanisms have identified novel targets for inhibiting mast cell function and activation. The prevention of anaphylaxis is within reach with new drugs that could modulate immune tolerance, mast cell proliferation and differentiation, and IgE regulation and production. Several US Food and Drug Administration-approved drugs for chronic urticaria, mastocytosis, and cancer are also being repurposed to prevent anaphylaxis. New therapeutics have not only shown promise in potential efficacy for preventing IgE-mediated reactions, but in some cases, they are able to inform us about mast cell mechanisms in vivo. This review summarizes the most recent advances in the treatment of anaphylaxis that have arisen from new pharmacologic tools and our current understanding of mast cell biology.

Precision cut intestinal slices, a novel model of acute food allergic reactions

BACKGROUND

Food allergy affects up to 10% of the pediatric population. Despite ongoing efforts, treatment options remain limited. Novel models of food allergy are needed to study response patterns downstream of IgE-crosslinking and evaluate drugs modifying acute events. Here, we report a novel human ex vivo model that displays acute, allergen-specific, IgE-mediated smooth muscle contractions using precision cut intestinal slices (PCIS).

METHODS

PCIS were generated using gut tissue samples from children who underwent clinically indicated surgery. Viability and metabolic activity were assessed from 0 to 24 h. Distribution of relevant cell subsets was confirmed using single nucleus RNA sequencing. PCIS were passively sensitized using plasma from peanut allergic donors or peanut-sensitized non-allergic donors, and exposed to various stimuli including serotonin, histamine, FcɛRI-crosslinker, and food allergens. Smooth muscle contractions and mediator release functioned as readouts. A novel program designed to measure contractions was developed to quantify responses. The ability to demonstrate the impact of antihistamines and immunomodulation from peanut oral immunotherapy (OIT) was assessed.

RESULTS

PCIS viability was maintained for 24 h. Cellular distribution confirmed the presence of key cell subsets including mast cells. The video analysis tool reliably quantified responses to different stimulatory conditions. Smooth muscle contractions were allergen-specific and reflected the clinical phenotype of the plasma donor. Tryptase measurement confirmed IgE-dependent mast cell-derived mediator release. Antihistamines suppressed histamine-induced contraction and plasma from successful peanut OIT suppressed peanut-specific PCIS contraction.

CONCLUSION

PCIS represent a novel human tissue-based model to study acute, IgE-mediated food allergy and pharmaceutical impacts on allergic responses in the gut.

Antibacterial intraosseous implant surface coating that responds to changes in the bacterial microenvironment

Bone implant-associated infection is one of the most challenging problems encountered by orthopedic surgeons. There is considerable interest in the development of drug-loaded antibacterial coatings for the surfaces of metal implants. However, it is difficult to achieve the stable local release of an effective drug dose for many antibacterial coatings. In the present study, analyses of the thickness and water contact angle of multiple layers confirmed the successful assembly of multilamellar membrane structures. Measurement of the zone of bacterial inhibition indicated gradual degradation of the (montmorillonite [MMT]/hyaluronic acid [HA])₁₀ multilamellar film structure with concentration-dependent degradation during incubation with hyaluronidase solution and Staphylococcus aureus. In vivo results resembled the in vitro results. Overall, the findings confirm that the (MMT/HA-rifampicin)₁₀ multilamellar film structure exhibits good antibacterial properties and excellent biocompatibility. Further studies of the clinical potential of the antibacterial coating prepared in this experiment are warranted.

Advances in Mast Cell Biology

Mast cells (MCs) contribute prominently to all allergic diseases, yet are still poorly understood owing to their exclusive residence in tissues. Recently, the use of RNA-sequencing, proteomics, and other technological advances have accelerated the acquisition of new knowledge. This includes an expanded definition of MC heterogeneity and developmental origins, previously unrecognized functions for MCs, discoveries of genetic causes of MC-related disorders, the introduction of new therapies for clonal MC disease, and the identification of new potential target for treatments. This issue of Advances addresses key studies from 2020 to 2021.

Regulation of Trafficking and Signaling of the High Affinity IgE Receptor by FcεRIβ and the Potential Impact of FcεRIβ Splicing in Allergic Inflammation

Mast cells are tissue-resident immune cells that function in both innate and adaptive immunity through the release of both preformed granule-stored mediators, and newly generated proinflammatory mediators that contribute to the generation of both the early and late phases of the allergic inflammatory response. Although mast cells can be activated by a vast array of mediators to contribute to homeostasis and pathophysiology in diverse settings and contexts, in this review, we will focus on the canonical setting of IgE-mediated activation and allergic inflammation. IgE-dependent activation of mast cells occurs through the high affinity IgE receptor, FcεRI, which is a multimeric receptor complex that, once crosslinked by antigen, triggers a cascade of signaling to generate a robust response in mast cells. Here, we discuss FcεRI structure and function, and describe established and emerging roles of the β subunit of FcεRI (FcεRIβ) in regulating mast cell function and FcεRI trafficking and signaling. We discuss current approaches to target IgE and FcεRI signaling and emerging approaches that could target FcεRIβ specifically. We examine how alternative splicing of FcεRIβ alters protein function and how manipulation of splicing could be employed as a therapeutic approach. Targeting FcεRI directly and/or IgE binding to FcεRI are promising approaches to therapeutics for allergic inflammation. The characteristic role of FcεRIβ in both trafficking and signaling of the FcεRI receptor complex, the specificity to IgE-mediated activation pathways, and the preferential expression in mast cells and basophils, makes FcεRIβ an excellent, but challenging, candidate for therapeutic strategies in allergy and asthma, if targeting can be realized.

Novel Approaches in the Inhibition of IgE-Induced Mast Cell Reactivity in Food Allergy

Allergy is an IgE-dependent type-I hypersensitivity reaction that can lead to life-threatening systemic symptoms such as anaphylaxis. In the pathogenesis of the allergic response, the common upstream event is the binding of allergens to specific IgE, inducing cross-linking of the high-affinity FcεRI on mast cells, triggering cellular degranulation and the release of histamine, proteases, lipids mediators, cytokines and chemokines with inflammatory activity. A number of novel therapeutic options to curb mast cell activation are in the pipeline for the treatment of severe allergies. In addition to anti-IgE therapy and allergen-specific immunotherapy, monoclonal antibodies targeted against several key Th2/alarmin cytokines (i.e. IL-4Rα, IL-33, TSLP), active modification of allergen-specific IgE (i.e. inhibitory compounds, monoclonal antibodies, de-sialylation), engagement of inhibitory receptors on mast cells and allergen-specific adjuvant vaccines, are new promising options to inhibit the uncontrolled release of mast cell mediators upon allergen exposure. In this review, we critically discuss the novel approaches targeting mast cells limiting allergic responses and the immunological mechanisms involved, with special interest on food allergy treatment.

A modified protocol for successful miRNA profiling in human precision-cut lung slices (PCLS)

Objective

Human precision cut lung slices (PCLS) are widely used as an ex vivo model system for drug discovery and development of new therapies. PCLS reflect the functional heterogeneity of lung tissue and possess relevant lung cell types. We thus determined the use of PCLS in studying non-coding RNAs notably miRNAs, which are important gene regulatory molecules. Since miRNAs play key role as mediators of respiratory diseases, they can serve as valuable prognostic or diagnostic biomarkers, and in therapeutic interventions, of lung diseases. A technical limitation though is the vast amount of agarose in PCLS which impedes (mi)RNA extraction by standard procedures. Here we modified our recently published protocol for RNA isolation from PCLS to enable miRNA readouts.

Results

The modified method relies on the separation of lysis and precipitation steps, and a clean-up procedure with specific magnetic beads. We obtained successfully quality miRNA amenable for downstream applications such as RTqPCR and whole transcriptome miRNA analysis. Comparison of miRNA profiles in PCLS with published data from human lung, identified all important miRNAs regulated in IPF, COPD, asthma or lung cancer. Therefore, this shows suitability of the method for analyzing miRNA targets and biomarkers in the valuable human PCLS model.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13104-021-05674-w.

Past, present, and future of anti-IgE biologics

About 20 years after the identification of immunoglobulin E (IgE) and its key role in allergic hypersensitivity reactions against normally harmless substances, scientists have started inventing strategies to block its pathophysiological activity in 1986. The initial concept of specific IgE targeting through the use of anti-IgE antibodies has gained a lot of momentum and within a few years independent research groups have reported successful generation of first murine monoclonal anti-IgE antibodies. Subsequent generation of optimized chimeric and humanized versions of these antibodies has paved the way for the development of therapeutic anti-IgE biologicals as we know them today. With omalizumab, there is currently still only one therapeutic anti-IgE antibody approved for the treatment of allergic conditions. Since its application is limited to the treatment of moderate-to-severe persistent asthma and chronic spontaneous urticaria, major efforts have been undertaken to develop alternative anti-IgE biologicals that could potentially be used in a broader spectrum of allergic diseases. Several new drug candidates have been generated and are currently assessed in pre-clinical studies or clinical trials. In this review, we highlight the molecular properties of past and present anti-IgE biologicals and suggest concepts that might improve treatment efficacy of future drug candidates.