Allergen-Specific Immunotherapy Alters the Frequency, as well as the FcR and CLR Expression Profiles of Human Dendritic Cell Subsets

Current practices and future trends in cockroach allergen immunotherapy

PURPOSE OF REVIEW

This review evaluates the current modes of allergen-specific immunotherapy for cockroach allergens, in terms of clinical outcomes and explores future trends in the research and development needed for a more targeted cockroach immunotherapy approach with the best efficacy and minimum adverse effects.

SUMMARY

Cockroach allergy is an important risk factor for allergic rhinitis in the tropics, that disproportionately affects children and young adults and those living in poor socio-economic environments. Immunotherapy would provide long-lasting improvement in quality of life, with reduced medication intake. However, the present treatment regime is long and has a risk of adverse effects. In addition, cockroach does not seem to have an immuno-dominant allergen, that has been traditionally used to treat allergies from other sources. Future trends of cockroach immunotherapy involve precision diagnosis, to correctly identify the offending allergen. Next, precision immunotherapy with standardized allergens, which have been processed in a way that maintains an immunological response without allergic reactions. This approach can be coupled with modern adjuvants and delivery systems that promote a Th1/Treg environment, thereby modulating the immune response away from the allergenic response.

Allergic rhinitis behavioral changes after Indonesian house dust mites allergenic extract administration as immunotherapy

Background: Allergy is a hypersensitivity reaction that is generally mediated by Immunoglobulin E (IgE). More than 25% of the world’s population is suspected of having these various diseases, and the prevalence and progression of these diseases have continued to increase significantly in recent years. Among these allergy-related diseases, allergic rhinitis and food allergy are the types of allergies with the highest prevalence. Clinical manifestations of allergic rhinitis include sneezing, rhinorrhea, nasal itching, and nasal congestion. Objective: This study aimed to determine the behavioral changes of allergic rhinitis after Indonesian House Dust Mites (IHDM) allergenic extract administration as an immunotherapy. Methods: Eight male BALB/c mice aged 6-8 weeks in each group were treated for seven groups. The sensitization phase is given intraperitoneal, the desensitization phase is given by subcutaneous, and the challenge phase is given intranasal. The allergic parameters were observed, such as nose rubbing and sneezing. The parameters were observed for 15 minutes after the challenge administration. Results: The results showed that the administration of Indonesian House Dust Mites as immunotherapy decreased the frequency of nose rubbing and sneezing after the administration of immunotherapy compared to the allergic rhinitis model. Conclusions: The administration of the Indonesia House Dust Mites as immunotherapy decreased the allergic rhinitis immune response by altering the behavioral parameter.

Antibody Fc-chimerism and effector functions: When IgG takes advantage of IgA

Recent advances in the development of therapeutic antibodies (Abs) have greatly improved the treatment of otherwise drug-resistant cancers and autoimmune diseases. Antibody activities are mediated by both their Fab and the Fc. However, therapeutic Abs base their protective mechanisms on Fc-mediated effector functions resulting in the activation of innate immune cells by FcRs. Therefore, Fc-bioengineering has been widely used to maximise the efficacy and convenience of therapeutic antibodies. Today, IgG remains the only commercially available therapeutic Abs, at the expense of other isotypes. Indeed, production, sampling, analysis and related in vivo studies are easier to perform with IgG than with IgA due to well-developed tools. However, interest in IgA is growing, despite a shorter serum half-life and a more difficult sampling and purification methods than IgG. Indeed, the paradigm that the effector functions of IgG surpass those of IgA has been experimentally challenged. Firstly, IgA has been shown to bind to its Fc receptor (FcR) on effector cells of innate immunity with greater efficiency than IgG, resulting in more robust IgA-mediated effector functions in vitro and better survival of treated animals. In addition, the two isotypes have been shown to act synergistically. From these results, new therapeutic formats of Abs are currently emerging, in particular chimeric Abs containing two tandemly expressed Fc, one from IgG (Fcγ) and one from IgA (Fcα). By binding both FcγR and FcαR on effector cells, these new chimeras showed improved effector functions in vitro that were translated in vivo. Furthermore, these chimeras retain an IgG-like half-life in the blood, which could improve Ab-based therapies, including in AIDS. This review provides the rationale, based on the biology of IgA and IgG, for the development of Fcγ and Fcα chimeras as therapeutic Abs, offering promising opportunities for HIV-1 infected patients. We will first describe the main features of the IgA- and IgG-specific Fc-mediated signalling pathways and their respective functional differences. We will then summarise the very promising results on Fcγ and Fcα containing chimeras in cancer treatment. Finally, we will discuss the impact of Fcα-Fcγ chimerism in prevention/treatment strategies against infectious diseases such as HIV-1.

Thermosensitive PLGA–PEG–PLGA Hydrogel as Depot Matrix for Allergen-Specific Immunotherapy

Allergen-specific immunotherapy (AIT) is the only currently available curative treatment option for allergic diseases. AIT often includes depot-forming and immunostimulatory adjuvants, to prolong allergen presentation and to improve therapeutic efficacy. The use of aluminium salts in AIT, which are commonly used as depot-forming adjuvants, is controversially discussed, due to health concerns and Th2-promoting activity. Therefore, there is the need for novel delivery systems in AIT with similar therapeutic efficacy compared to classical AIT strategies. In this study, a triblock copolymer (hydrogel) was assessed as a delivery system for AIT in a murine model of allergic asthma. We show that the hydrogel combines the advantages of both depot function and biodegradability at the same time. We further demonstrate the suitability of hydrogel to release different bioactive compounds in vitro and in vivo. AIT delivered with hydrogel reduces key parameters of allergic inflammation, such as inflammatory cell infiltration, mucus hypersecretion, and allergen-specific IgE, in a comparable manner to standard AIT treatment. Additionally, hydrogel-based AIT is superior in inducing allergen-specific IgG antibodies with potentially protective functions. Taken together, hydrogel represents a promising delivery system for AIT that is able to combine therapeutic allergen administration with the prolonged release of immunomodulators at the same time.

Allergic Rhinitis: What Do We Know About Allergen-Specific Immunotherapy?

Allergic rhinitis (AR) is an IgE-mediated disease that is characterized by Th2 joint inflammation. Allergen-specific immunotherapy (AIT) is indicated for AR when symptoms remain uncontrolled despite medication and allergen avoidance. AIT is considered to have been effective if it alleviated allergic symptoms, decreased medication use, improved the quality of life even after treatment cessation, and prevented the progression of AR to asthma and the onset of new sensitization. AIT can be administered subcutaneously or sublingually, and novel routes are still being developed, such as intra-lymphatically and epicutaneously. AIT aims at inducing allergen tolerance through modification of innate and adaptive immunologic responses. The main mechanism of AIT is control of type 2 inflammatory cells through induction of various functional regulatory cells such as regulatory T cells (Tregs), follicular T cells (Tfr), B cells (Bregs), dendritic cells (DCregs), innate lymphoid cells (IL-10⁺ ILCs), and natural killer cells (NKregs). However, AIT has a number of disadvantages: the long treatment period required to achieve greater efficacy, high cost, systemic allergic reactions, and the absence of a biomarker for predicting treatment responders. Currently, adjunctive therapies, vaccine adjuvants, and novel vaccine technologies are being studied to overcome the problems associated with AIT. This review presents an updated overview of AIT, with a special focus on AR.

Compromised anti-tumor-immune features of myeloid cell components in chronic myeloid leukemia patients

Chronic myeloid leukemia (CML) is a form of myeloproliferative neoplasm caused by the oncogenic tyrosine kinase BCR-ABL. Although tyrosine kinase inhibitors have dramatically improved the prognosis of patients with CML, several problems such as resistance and recurrence still exist. Immunological control may contribute to solving these problems, and it is important to understand why CML patients fail to spontaneously develop anti-tumor immunity. Here, we show that differentiation of conventional dendritic cells (cDCs), which are vital for anti-tumor immunity, is restricted from an early stage of hematopoiesis in CML. In addition, we found that monocytes and basophils, which are increased in CML patients, express high levels of PD-L1, an immune checkpoint molecule that inhibits T cell responses. Moreover, RNA-sequencing analysis revealed that basophils express genes related to poor prognosis in CML. Our data suggest that BCR-ABL not only disrupts the “accelerator” (i.e., cDCs) but also applies the “brake” (i.e., monocytes and basophils) of anti-tumor immunity, compromising the defense against CML cells.

Unexplored horizons of cDC1 in immunity and tolerance

Dendritic cells are a specialized subset of hematopoietic cells essential for mounting immunity against tumors and infectious disease as well as inducing tolerance for maintenance of homeostasis. DCs are equipped with number of immunoregulatory or stimulatory molecules that interact with other leukocytes to modulate their functions. Recent advances in DC biology identified a specific role for the conventional dendritic cell type 1 (cDC1) in eliciting cytotoxic CD8+ T cells essential for clearance of tumors and infected cells. The critical role of this subset in eliciting immune responses or inducing tolerance has largely been defined in mice whereas the biology of human cDC1 is poorly characterized owing to their extremely low frequency in tissues. A detailed characterization of the functions of many immunoregulatory and stimulatory molecules expressed by human cDC1 is critical for understanding their biology to exploit this subset for designing novel therapeutic modalities against cancer, infectious disease and autoimmune disorders.

Trained immunity and tolerance in innate lymphoid cells, monocytes, and dendritic cells during allergen-specific immunotherapy

BACKGROUND

Despite the efficacy of allergen-specific immunotherapy (AIT), the role of trained immunity and tolerance in this process has not been elucidated.

OBJECTIVE

Here, we have performed a comprehensive longitudinal analysis of the systemic innate immune cell repertoire during the course of AIT.

METHODS

Patients with allergy received standard preseasonal subcutaneous AIT with allergoids to birch and/or grass. Healthy controls were monitored without any intervention. Flow cytometry of innate lymphoid cell (ILC), natural killer cell, monocyte cell, and dendritic cell (DC) subsets was performed at baseline, 3 months (birch season), 6 months (grass seasons), and 12 months after the therapy in patients or at similar seasonal time points in controls. Additional analyses were performed in the third-year birch and grass season.

RESULTS

We observed a durable decrease in group 2 ILCs and an increase of group 1 ILCs after AIT, with dynamic changes in their composition. We found that an expansion of CD127⁺CD25⁺⁺ clusters caused observed shifts in the heterogeneity of group 1 ILCs. In addition, we observed development of CD127⁺CD25⁺⁺c-Kit⁺ group 3 ILC clusters. Moreover, we found an increase in the number of intermediate monocytes in parallel with a reduction in nonclassical monocytes during the first year after AIT. Classical and intermediate monocytes presented significant heterogeneity in patients with allergy, but AIT reduced the HLA-DR⁺⁺ clusters. Finally, an increase in plasmacytoid DCs and CD141⁺ myeloid DCs was observed in individuals with allergy, whereas the number of CD1c⁺ myeloid DCs was reduced during the first year of AIT.

CONCLUSION

AIT induces changes in the composition and heterogeneity of circulating innate immune cells and brings them to the level observed in healthy individuals. Monitoring of ILCs, monocytes, and DCs during AIT might serve as a novel biomarker strategy.

Costimulatory Molecules and Immune Checkpoints Are Differentially Expressed on Different Subsets of Dendritic Cells

Dendritic cells (DCs) play a crucial role in initiating and shaping immune responses. The effects of DCs on adaptive immune responses depend partly on functional specialization of distinct DC subsets, and partly on the activation state of DCs, which is largely dictated by environmental signals. Fully activated immunostimulatory DCs express high levels of costimulatory molecules, produce pro-inflammatory cytokines, and stimulate T cell proliferation, whereas tolerogenic DCs express low levels of costimulatory molecules, produce immunomodulatory cytokines and impair T cell proliferation. Relevant to the increasing use of immune checkpoint blockade in cancer treatment, signals generated from inhibitory checkpoint molecules on DC surface may also contribute to the inhibitory properties of tolerogenic DCs. Yet, our knowledge on the expression of inhibitory molecules on human DC subsets is fragmentary. Therefore, in this study, we investigated the expression of three immune checkpoints on peripheral blood DC subsets, in basal conditions and upon exposure to pro-inflammatory and anti-inflammatory stimuli, by using a flow cytometric panel that allows a direct comparison of the activatory/inhibitory phenotype of DC-lineage and inflammatory DC subsets. We demonstrated that functionally distinct DC subsets are characterized by differential expression of activatory and inhibitory molecules, and that cDC1s in particular are endowed with a unique immune checkpoint repertoire characterized by high TIM-3 expression, scarce PD-L1 expression and lack of ILT2. Notably, this unique cDC1 repertoire was subverted in a group of patients with myelodysplastic syndromes included in the study. Applied to the characterization of DCs in the tumor microenvironment, this panel has the potential to provide valuable information to be used for investigating the role of DC subsets in cancer, guiding DC-targeting treatments, and possibly identifying predictive biomarkers for clinical response to cancer immunotherapy.

Mechanisms of allergen-specific immunotherapy: Diverse mechanisms of immune tolerance to allergens

OBJECTIVE

The aim of this review is to provide an overview of the current knowledge on the mechanisms of allergen immunotherapy based on the recent publications and clinical trials.

DATA SOURCES

PubMed literature review.

STUDY SELECTIONS

In this review, we focus on diverse mechanisms of AIT and provide an insight into alternative routes of administration. Additionally, we review and discuss the most recent studies investigating potential biomarkers and highlight their role in clinical settings.

RESULTS

Successful allergen-specific immunotherapy (AIT) induces the reinstatement of tolerance toward allergens and represents a disease-modifying treatment. In the last decades, substantial progress in understanding the mechanisms of AIT has been achieved. Establishment of long-term clinical tolerance to allergens engages a complex network of interactions, modulating the functions of basophils, mast cells, allergen-specific regulatory T and B cells, and production of specific antibodies. The reduction of symptoms and clinical improvement is achieved by skewing the immune response away from allergic inflammation.

CONCLUSION

Although the complex nature of AIT mechanisms is becoming more clear, the need to discover reliable biomarkers to define patients likely to respond to the treatment is emerging.

FcεRI expression and IgE binding by dendritic cells and basophils in allergic rhinitis and upon allergen immunotherapy

BACKGROUND

In humans, both basophils and dendritic cells (DCs) express the high-affinity IgE receptor (FcεRI).

OBJECTIVE

To gain more insight into the relation between serum IgE levels and FcεRI expression and IgE binding by DCs and basophils in house dust mite (HDM) allergy and during subcutaneous immunotherapy (SCIT).

METHODS

We measured FcεRI, IgE and HDM allergen on DCs (conventional type 2 DCs, cDC2s; plasmacytoid dendritic cells, pDCs) and basophils by flow cytometry in 22 non-allergic vs 52 allergic subjects and upon HDM SCIT in 28 allergic subjects. IgE levels were measured in serum.

RESULTS

Serum IgE correlated differentially with FcεRI expression and IgE binding depending on cell type and allergic status. In non-allergic subjects, FcεRI/IgE surface densities increased with serum IgE to a significantly stronger degree on basophils compared to cDC2s. By contrast, in allergic subjects FcεRI/IgE surface densities increased with serum IgE to a slightly stronger degree on cDC2s compared to basophils. In addition, the data set suggests sequential loading of IgE onto FcεRI expressed by these cells (basophils>cDC2s>pDCs). Finally, HDM SCIT induced a temporary increase in serum IgE, which was paralleled by a peak in FcεRI and IgE on DCs, but not on basophils.

CONCLUSIONS & CLINICAL RELEVANCE

This study provides a comprehensive insight into the relation between serum IgE and FcεRI/IgE on basophils and DC subsets. The novel finding that HDM SCIT induces a temporary increase in FcεRI expression on DCs, but not on basophils, can be an incentive for future research on the potential tolerogenic role of IgE/FcεRI signalling in DCs in the setting of allergen immunotherapy.

CLEC10A Is a Specific Marker for Human CD1c+ Dendritic Cells and Enhances Their Toll-Like Receptor 7/8-Induced Cytokine Secretion

Dendritic cells (DCs) are major players for the induction of immune responses. Apart from plasmacytoid DCs (pDCs), human DCs can be categorized into two types of conventional DCs: CD141⁺ DCs (cDC1) and CD1c⁺ DCs (cDC2). Defining uniquely expressed surface markers on human immune cells is not only important for the identification of DC subpopulations but also a prerequisite for harnessing the DC subset-specific potential in immunomodulatory approaches, such as antibody-mediated antigen targeting. Although others identified CLEC9A as a specific endocytic receptor for CD141⁺ DCs, such a receptor for CD1c⁺ DCs has not been discovered, yet. By performing transcriptomic and flow cytometric analyses on human DC subpopulations from different lymphohematopoietic tissues, we identified CLEC10A (CD301, macrophage galactose-type C-type lectin) as a specific marker for human CD1c⁺ DCs. We further demonstrate that CLEC10A rapidly internalizes into human CD1c⁺ DCs upon binding of a monoclonal antibody directed against CLEC10A. The binding of a CLEC10A-specific bivalent ligand (the MUC-1 peptide glycosylated with N-acetylgalactosamine) is limited to CD1c⁺ DCs and enhances the cytokine secretion (namely TNFα, IL-8, and IL-10) induced by TLR 7/8 stimulation. Thus, CLEC10A represents not only a candidate to better define CD1c⁺ DCs—due to its high endocytic potential—CLEC10A also exhibits an interesting candidate receptor for future antigen-targeting approaches.

A review of clinical efficacy, safety, new developments and adherence to allergen-specific immunotherapy in patients with allergic rhinitis caused by allergy to ragweed pollen (Ambrosia artemisiifolia)

Allergic rhinitis is a common health problem in both children and adults. The number of patients allergic to ragweed (Ambrosia artemisiifolia) is on the rise throughout Europe, having a significant negative impact on the patients' and their family's quality of life. Allergen-specific immunotherapy (AIT) has disease-modifying effects and can induce immune tolerance to allergens. Both subcutaneous immunotherapy and sublingual immunotherapy with ragweed extracts/preparations have clear positive clinical efficacy, especially over pharmacological treatment, even years after the treatment has ended. AIT also has very good safety profiles with extremely rare side effects, and the extracts/preparations used in AIT are commonly well tolerated by patients. However, patient adherence to treatment with AIT seems to be quite low, mostly due to the fact that treatment with AIT is relatively time-demanding and, moreover, due to patients not receiving adequate information and education about the treatment before it starts. AIT is undergoing innovations and improvements in clinical efficacy, safety and patient adherence, especially with new approaches using new adjuvants, recombinant or modified allergens, synthetic peptides, novel routes of administration (epidermal or intralymphatic), and new protocols, which might make AIT more acceptable for a wider range of patients and novel indications. Patient education and support (eg, recall systems) is one of the most important goals for AIT in the future, to further enhance treatment success.