Allergen-specific immunotherapy: is it vaccination against toxins after all?

IgG in the control of FcεRI activation: a battle on multiple fronts

The rising global incidence of IgE-mediated allergic reactions poses a significant challenge to the quality of life of affected individuals and to healthcare systems, with current treatments being limited in effectiveness, safety, and disease-modifying capabilities. IgE acts by sensitizing the high-affinity IgE receptor FcεRI expressed by mast cells and basophils, tuning these cells for inflammatory degranulation in response to future allergen encounters. In recent years, IgG has emerged as an essential negative regulator of IgE-dependent allergic inflammation. Mechanistically, studies have proposed different pathways by which IgG can interfere with the activation of IgE-mediated inflammation. Here, we briefly summarize the major proposed mechanisms of action by which IgG controls the IgE-FcεRI inflammatory axis and how those mechanisms are currently applied as therapeutic interventions for IgE-mediated inflammation.

Successful Allergen-Specific Immunotherapy: Induction of Unresponsiveness by 'Vaccination'

The mechanisms of action of allergen-specific immunotherapy (AIT) are often referred to as the induction of 'tolerance'. However, immunological 'tolerance' is defined as an alteration in the function or composition of immune cells. For AIT, this is not always the case, because it can also induce allergen-specific IgG antibodies that block allergic responses. To include all possible mechanisms that may mediate successful AIT, it is advantageous to use the scientific term 'unresponsiveness' instead of 'tolerance'. In praxis, the term 'vaccination' is also appropriate, as AIT medications are specialized vaccines.

The early-phase transcriptome and the clinical efficacy analysis in three modes of subcutaneous immunotherapy for allergic rhinitis

Background

Allergen immunotherapy is the only etiological treatment for allergic rhinitis.

Objective

To analyze the efficacy, safety, and mechanism of subcutaneous immunotherapy (SCIT).

Methods

The efficacy, safety, and serum immunological changes of 3 modes of subcutaneous immunotherapy were compared. Peripheral blood mononuclear cells (PBMC) transcriptome changes were obtained on the Illumina sequencing platforms. We confirmed differentially expressed genes (DEGs) by quantitative real-time polymerase chain reaction (PCR). The DEGs were analyzed by gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and protein-protein interaction (PPI) networks. The correlation between the common DEGs and clinical indicators was analyzed by Origin 2022.

Results

The 3 SCITs were all effective after 1 year. The Combined Symptom and Medication Score (CSMS) and Visual Analog Score (VAS) in rush immunotherapy (RIT) are lowest after 24 and 48 weeks of treatment among the 3 groups. After treatment, the levels of sIgE, sIgE/tIgE, Th2 cytokines, Th17 cytokines, and percentage of peripheral eosinophils (EOS%) decreased significantly (P＜0.05), while the levels of Th1 type cytokines did not change significantly. Transcriptome analysis identified 24, 24, and 91 DEGs at W3 and 42, 52, 175 DEGs at W7 in conventional immunotherapy (CIT), cluster immunotherapy (CLIT), and RIT groups, respectively. The pathways and functions involved in SCIT include secretion of Th1/2 cytokines, immune cell differentiation. Unlike CIT and CLIT, DEGs are also involved in T cell tolerance induction, T cell anergy, and lymphocyte anergy in RIT. CXCR1, CXCR2, and IER3 had a specific effect on reflecting the improvement of symptoms in allergic rhinitis patients with SCIT.

Conclusion

The clinical efficacy of RIT appeared earlier than CIT and CLIT. Clinicians can use the highly conserved gene expression profile to evaluate responses to immunotherapy.

Quality of life in allergic rhinitis patients treated with intralymphatic immunotherapy (ILIT): A 19-year follow-up

Background

In 2002-2005, we conducted a phase I/II clinical trial where a new allergy immunotherapy (AIT) route was introduced: intralymphatic immunotherapy (ILIT). Ultrasound guidance allowed injection of allergen directly into inguinal lymph nodes. Grass pollen-allergic patients received 3 injections with 1-month intervals. The short ILIT was more patient-friendly, required lower dosing, and was comparable with SCIT regarding short-term efficacy, which was used as a reference.

Objective

Nineteen years after ILIT, the same patients were followed up to assess the long-term effect on quality of life and efficacy of the treatment.

Methods

Patients who received ILIT and SCIT in 2002-2005 and an additional group of patients, who completed SCIT in 2015-2018, were recruited. All participants received a trial-specific in-house questionnaire and a standardized Rhinoconjunctivitis Quality of Life Questionnaire. Data were recorded off- (February 2021) and on- (May-June 2021) season. Descriptive statistics were applied.

Results

Of 58 and 54 patients who originally received ILIT or SCIT, 25 (43%) and 29 (54%) patients, respectively, returned the questionnaires for analysis. Four (16%) and 3 (11%) of the ILIT and SCIT patients, respectively, developed complete protection against grass pollen-mediated rhinitis, whereas another 15 (60%) and 20 (69%) expressed satisfaction with the received AIT. In both groups, any persistent symptoms were reported as mild. Medication usage in the ILIT and SCIT groups was comparable. Nineteen (76%) and 23 (79%) patients, respectively, expressed satisfaction with their AIT.

Conclusions

Grass pollen ILIT leads to long-term significant improvement in rhinitis-associated quality of life 19 years after treatment, and the ILIT quality-of-life effect was not inferior to that of SCIT.

Bacterial expression systems based on Tymovirus-like particles for the presentation of vaccine antigens

Virus-like particles (VLPs) are virus-derived artificial nanostructures that resemble a native virus-stimulating immune system through highly repetitive surface structures. Improved safety profiles, flexibility in vaccine construction, and the ease of VLP production and purification have highlighted VLPs as attractive candidates for universal vaccine platform generation, although exploration of different types of expression systems for their development is needed. Here, we demonstrate the construction of several simple Escherichia coli expression systems for the generation of eggplant mosaic virus (EMV) VLP-derived vaccines. We used different principles of antigen incorporation, including direct fusion of EMV coat protein (CP) with major cat allergen Feld1, coexpression of antigen containing and unmodified (mosaic) EMV CPs, and two coexpression variants of EMV VLPs and antigen using synthetic zipper pair 18/17 (SYNZIP 18/17), and coiled-coil forming peptides E and K (Ecoil/Kcoil). Recombinant Fel d 1 chemically coupled to EMV VLPs was included as control experiments. All EMV-Feld1 variants were expressed in E. coli, formed Tymovirus-like VLPs, and were used for immunological evaluation in healthy mice. The immunogenicity of these newly developed vaccine candidates demonstrated high titers of Feld1-specific Ab production; however, a comparably high immune response against carrier EMV was also observed. Antibody avidity tests revealed very specific Ab production (more than 50% specificity) for four out of the five vaccine candidates. Native Feld1 recognition and subclass-specific antibody tests suggested that the EMV-SZ18/17-Feld1 complex and chemically coupled EMV-Feld1 vaccines may possess characteristics for further development.

Knowledge mapping of immunotherapy for allergic rhinoconjunctivitis: a bibliometric study (2002-2021)

BACKGROUND

Allergic rhinoconjunctivitis (ARC) is a common chronic inflammatory disease. Numerous studies on the treatment of ARC have been published. By contrast, there are few bibliometric studies on immunotherapy for ARC. The purpose of this article is to describe the current treatments for ARC and to identify the trends in immunotherapy for ARC.

METHODS

Publications were searched from the Web of Science (WOS) Core Collection on April 25, 2022. CiteSpace and Microsoft Excel software were used for further bibliometric analysis.

RESULTS

A total of 969 publications on immunotherapy for ARC in English were retrieved. The number of relevant publications has been continuously increasing over the past 20 years, with many of the publications coming from Germany and the United States of America. In terms of institutions, the ALK Company in Denmark, Imperial College London in United Kingdom, and Charite-Universitatsmedizin Berlin in Germany published the most articles on immunotherapy for ARC. Meanwhile, Allergy and Journal of Allergy and Clinical Immunology published the most number of studies, and Oliver Pfaar from Germany authored the most number of articles. "Subcutaneous immunotherapy," "international consensus," "allergen immunotherapy," and "recommendation" were the most popular subjects. Thus, directions in research can be predicted as studies regarding mechanisms of ARC, clinical trials, and extracts have reported high-quality results.

CONCLUSION

Over the past 20 years, the overall quality of research on immunotherapy for ARC has gradually improved, allowing the introduction of specific and targeted treatment. Currently, the main focus of ARC research is the novel routes of drug delivery and combined treatment with biological agents.

MicroCrystalline Tyrosine-adsorbed immunotherapy

PURPOSE OF REVIEW

The purpose of this article is to provide an overview of the literature pertaining to the use of MicroCrystalline Tyrosine (MCT) in the immunotherapy with an emphasis on recent developments.

RECENT FINDINGS

In addition to significant effectiveness and safety profiles, additional aspects of interest such as booster immunotherapy concepts, sustained clinical effects, long-term efficacy and disease-modifying effects are being focused on in the recently published studies. The depot adjuvant MCT also shows potential in promising disease-challenge models such as for malaria and melanoma.

SUMMARY

MCT-adsorbed immunotherapy products have been shown to provide convincing overall safety, tolerability and efficacy outcomes, as well in vulnerable groups such as children and asthmatic patients.

On the role of allergen-specific IgG subclasses for blocking human basophil activation

Successful treatment of IgE mediated allergies by allergen-specific immunotherapy (AIT) usually correlates with the induction of allergen-specific IgG4. However, it is not clear whether IgG4 prevents the allergic reaction more efficiently than other IgG subclasses. Here we aimed to compare allergen-specific monoclonal IgG1 and IgG4 antibodies in their capacity to inhibit type I allergic reactions by engaging FcγRIIb. We found that IgG1, which is the dominant subclass induced by viruses, binds with a similar affinity to the FcγRIIb as IgG4 and is comparable at blocking human basophil activation from allergic patients; both by neutralizing the allergen as well as engaging the inhibitory receptor FcγRIIb. Hence, the IgG subclass plays a limited role for the protective efficacy of AIT even if IgG4 is considered the best correlate of protection, most likely simply because it is the dominant subclass induced by classical AITs.

Immunotherapies in the treatment of immunoglobulin E‑mediated allergy: Challenges and scope for innovation (Review)

Immunoglobulin E (IgE)‑mediated allergy or hypersensitivity reactions are generally defined as an unwanted severe symptomatic immunological reaction that occurs due to shattered or untrained peripheral tolerance of the immune system. Allergen‑specific immunotherapy (AIT) is the only therapeutic strategy that can provide a longer‑lasting symptomatic and clinical break from medications in IgE‑mediated allergy. Immunotherapies against allergic diseases comprise a successive increasing dose of allergen, which helps in developing the immune tolerance against the allergen. AITs exerttheirspecial effectiveness directly or indirectly by modulating the regulator and effector components of the immune system. The number of success stories of AIT is still limited and it canoccasionallyhave a severe treatment‑associated adverse effect on patients. Therefore, the formulation used for AIT should be appropriate and effective. The present review describes the chronological evolution of AIT, and provides a comparative account of the merits and demerits of different AITs by keeping in focus the critical guiding factors, such as sustained allergen tolerance, duration of AIT, probability of mild to severe allergic reactions and dose of allergen required to effectuate an effective AIT. The mechanisms by which regulatory T cells suppress allergen‑specific effector T cells and how loss of natural tolerance against innocuous proteins induces allergy are reviewed. The present review highlights the major AIT bottlenecks and the importantregulatory requirements for standardized AIT formulations. Furthermore, the present reviewcalls attention to the problem of 'polyallergy', which is still a major challenge for AIT and the emerging concept of 'component‑resolved diagnosis' (CRD) to address the issue. Finally, a prospective strategy for upgrading CRD to the next dimension is provided, and a potential technology for delivering thoroughly standardized AIT with minimal risk is discussed.

Prediction of clinical efficacy of subcutaneous immunotherapy for Artemisia sieversiana pollen allergic rhinitis by serum metabolomics

BACKGROUND/PURPOSE

Specific immunotherapy is the only effective etiological treatment for allergic rhinitis, but subcutaneous immunotherapy has a slow onset and poor compliance. Predicting the clinical efficacy of subcutaneous immunotherapy in advance can reduce unnecessary medical costs and resource waste. This study aimed to identify metabolites that could predict the efficacy of subcutaneous immunotherapy on seasonal allergic rhinitis by serum metabolomics.

METHODS

Patients (n = 43) with Artemisia sieversiana pollen allergic rhinitis were enrolled and treated with subcutaneous immunotherapy for one year. Patients were divided into the ineffective group (n = 10) and effective group (n = 33) according to the therapeutic index. Serum samples were collected before treatment. Metabolomics was determined by liquid chromatography-mass spectrometry combined with gas chromatography-mass spectrometry and analyzed differential compounds and related metabolic pathways.

RESULTS

A total of 129 differential metabolites (P < 0.05) were identified and 4 metabolic pathways, namely taurine and hypotaurine metabolism, pentose and glucuronate interconversions, pentose phosphate pathway, and alanine, aspartate, and glutamate metabolism, were involved.

CONCLUSION

Some metabolites, such as hypotaurine, taurine, and l-alanine, have the potential to become predictive biomarkers for effective subcutaneous immunotherapy.

The Potential of Exosomes in Allergy Immunotherapy

Allergic diseases represent a global health and economic burden of increasing significance. The lack of disease-modifying therapies besides specific allergen immunotherapy (AIT) which is not available for all types of allergies, necessitates the study of novel therapeutic approaches. Exosomes are small endosome-derived vesicles delivering cargo between cells and thus allowing inter-cellular communication. Since immune cells make use of exosomes to boost, deviate, or suppress immune responses, exosomes are intriguing candidates for immunotherapy. Here, we review the role of exosomes in allergic sensitization and inflammation, and we discuss the mechanisms by which exosomes could potentially be used in immunotherapeutic approaches for the treatment of allergic diseases. We propose the following approaches: (a) Mast cell-derived exosomes expressing IgE receptor FcεRI could absorb IgE and down-regulate systemic IgE levels. (b) Tolerogenic exosomes could suppress allergic immune responses via induction of regulatory T cells. (c) Exosomes could promote TH1-like responses towards an allergen. (d) Exosomes could modulate IgE-facilitated antigen presentation.

Advances in allergen-specific immune cell measurements for improved detection of allergic sensitization and immunotherapy responses

Over the past two decades, precision medicine has advanced diagnostics and treatment of allergic diseases. Component-resolved analysis of allergen sensitization facilitates stratification of patients. Furthermore, new formulations of allergen immunotherapy (AIT) products can more effectively deliver the relevant components. Molecular insights from the identification of allergen component sensitization and clinical outcomes of treatment with new AIT formulations can now be utilized for a deeper understanding of the nature of the pathogenic immune response in allergy and how this can be corrected by AIT. Fundamental in these processes are the allergen-specific B and T cells. Within the large B- and T-cell compartments, only those that specifically recognize the allergen with their immunoglobulin (Ig) or T-cell receptor (TCR), respectively, are of clinical relevance. With peripheral blood allergen-specific B- and T-cell frequencies below 1%, bulk cell analysis is typically insufficiently sensitive. We here review the latest technologies to detect allergen-specific B and T cells, as well as new developments in utilizing these tools for diagnostics and therapy monitoring to advance precision medicine for allergic diseases.

Perspectives on RNA Vaccine Candidates for COVID-19

With the current outbreak caused by SARS-CoV-2, vaccination is acclaimed as a public health care priority. Rapid genetic sequencing of SARS-CoV-2 has triggered the scientific community to search for effective vaccines. Collaborative approaches from research institutes and biotech companies have acknowledged the use of viral proteins as potential vaccine candidates against COVID-19. Nucleic acid (DNA or RNA) vaccines are considered the next generation vaccines as they can be rapidly designed to encode any desirable viral sequence including the highly conserved antigen sequences. RNA vaccines being less prone to host genome integration (cons of DNA vaccines) and anti-vector immunity (a compromising factor of viral vectors) offer great potential as front-runners for universal COVID-19 vaccine. The proof of concept for RNA-based vaccines has already been proven in humans, and the prospects for commercialization are very encouraging as well. With the emergence of COVID-19, mRNA-1273, an mRNA vaccine developed by Moderna, Inc. was the first to enter human trials, with the first volunteer receiving the dose within 10 weeks after SARS-CoV-2 genetic sequencing. The recent interest in mRNA vaccines has been fueled by the state of the art technologies that enhance mRNA stability and improve vaccine delivery. Interestingly, as per the "Draft landscape of COVID-19 candidate vaccines" published by the World Health Organization (WHO) on December 29, 2020, seven potential RNA based COVID-19 vaccines are in different stages of clinical trials; of them, two candidates already received emergency use authorization, and another 22 potential candidates are undergoing pre-clinical investigations. This review will shed light on the rationality of RNA as a platform for vaccine development against COVID-19, highlighting the possible pros and cons, lessons learned from the past, and the future prospects.

Biologics and Allergy Immunotherapy in the Treatment of Allergic Diseases

Allergic diseases represent some of the most chronic and costly chronic conditions. Medical management may require long-term pharmacotherapy, which is often associated with poor adherence. Although medications provide symptomatic control, they do not modify the allergic disease. Patients may prefer disease-modifying treatments that provide lasting benefits after discontinuation. To date, allergy immunotherapy is the only proved disease modification therapy associated with lasting benefits after discontinuation. However, allergy immunotherapy safety and efficacy has only been established in allergic rhinitis, mild to moderate asthma, and some patients with atopic dermatitis.

EAACI Allergen Immunotherapy User's Guide

Allergen immunotherapy is a cornerstone in the treatment of allergic children. The clinical efficiency relies on a well-defined immunologic mechanism promoting regulatory T cells and downplaying the immune response induced by allergens. Clinical indications have been well documented for respiratory allergy in the presence of rhinitis and/or allergic asthma, to pollens and dust mites. Patients who have had an anaphylactic reaction to hymenoptera venom are also good candidates for allergen immunotherapy. Administration of allergen is currently mostly either by subcutaneous injections or by sublingual administration. Both methods have been extensively studied and have pros and cons. Specifically in children, the choice of the method of administration according to the patient's profile is important. Although allergen immunotherapy is widely used, there is a need for improvement. More particularly, biomarkers for prediction of the success of the treatments are needed. The strength and efficiency of the immune response may also be boosted by the use of better adjuvants. Finally, novel formulations might be more efficient and might improve the patient's adherence to the treatment. This user's guide reviews current knowledge and aims to provide clinical guidance to healthcare professionals taking care of children undergoing allergen immunotherapy.

Vaccine against peanut allergy based on engineered virus-like particles displaying single major peanut allergens

BACKGROUND

Peanut allergy is a severe and increasingly frequent disease with high medical, psychosocial, and economic burden for affected patients and wider society. A causal, safe, and effective therapy is not yet available.

OBJECTIVE

We sought to develop an immunogenic, protective, and nonreactogenic vaccine candidate against peanut allergy based on virus-like particles (VLPs) coupled to single peanut allergens.

METHODS

To generate vaccine candidates, extracts of roasted peanut (Ara R) or the single allergens Ara h 1 or Ara h 2 were coupled to immunologically optimized Cucumber Mosaic Virus-derived VLPs (CuMVtt). BALB/c mice were sensitized intraperitoneally with peanut extract absorbed to alum. Immunotherapy consisted of a single subcutaneous injection of CuMVtt coupled to Ara R, Ara h 1, or Ara h 2.

RESULTS

The vaccines CuMVtt-Ara R, CuMVtt-Ara h 1, and CuMVtt-Ara h 2 protected peanut-sensitized mice against anaphylaxis after intravenous challenge with the whole peanut extract. Vaccines did not cause allergic reactions in sensitized mice. CuMVtt-Ara h 1 was able to induce specific IgG antibodies, diminished local reactions after skin prick tests, and reduced the infiltration of the gastrointestinal tract by eosinophils and mast cells after oral challenge with peanut. The ability of CuMVtt-Ara h 1 to protect against challenge with the whole extract was mediated by IgG, as shown via passive IgG transfer. FcγRIIb was required for protection, indicating that immune complexes with single allergens were able to block the allergic response against the whole extract, consisting of a complex allergen mixture.

CONCLUSIONS

Our data suggest that vaccination using single peanut allergens displayed on CuMVtt may represent a novel therapy against peanut allergy with a favorable safety profile.

Clinical Efficacy Evaluation of 1-Year Subcutaneous Immunotherapy for Artemisia sieversiana Pollen Allergic Rhinitis by Serum Metabolomics

Subcutaneous immunotherapy is the only treatment that improves the natural progression of allergic rhinitis and maintains long-term outcomes after discontinuation of the drug. Metabolomics is increasingly applied in the study of allergic diseases, including allergic rhinitis. However, little is known about the discovery of metabolites that can evaluate clinical efficacy and possible mechanisms of Artemisia sieversiana pollen subcutaneous immunotherapy. Thirty-three patients with Artemisia sieversiana pollen allergic rhinitis significantly improved after 1-year subcutaneous immunotherapy treatment, while ten patients were ineffective. Pre- and post-treatment serum samples from these patients were analyzed by metabolomics based on the combined detection of liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry. As a result, L-Tyrosine can be a potential biomarker because of its opposite trend in effective patients and ineffective patients. And mechanism of immunotherapy may be closely related to NO and nitric oxide synthase. The discovery of potential biomarkers and metabolic pathways has contributed to the in-depth study of mechanisms of subcutaneous immunotherapy treatment of Artemisia sieversiana pollen allergic rhinitis.

Vaccination against Allergy: A Paradigm Shift?

Since the discovery that IgE antibodies mediate allergy, decades of research have unraveled complex mechanisms associated with conventional immunotherapy and the vital protagonists that shape 'immune tolerance' to allergens. Debate exists on what should constitute the dominant effector mechanism in driving rational drug designs for next-generation immunotherapies. As vaccine technology continues to advance, the development of novel vaccines in this area of continued medical need might stand on a threshold of breakthrough inspired by experiments by Dunbar on the passive vaccination of allergic animals more than 100 years ago. In this opinion article, we discuss both novel insights into IgG antibodies as the principle effector modality induced by specific immunotherapy and advances in antigen-carrier design that may catapult allergy treatment into our modern world.

Recent developments and highlights in immune monitoring of allergen immunotherapy

Allergic diseases are the most common chronic immune-mediated disorders and can manifest with an enormous diversity in clinical severity and symptoms. Underlying mechanisms for the adverse immune response to allergens and its downregulation by treatment are still being revealed. As a result, there have been, and still are, major challenges in diagnosis, prediction of disease progression/evolution and treatment. Currently, the only corrective treatment available is allergen immunotherapy (AIT). AIT modifies the immune response through long-term repeated exposure to defined doses of allergen. However, as the treatment usually needs to be continued for several years to be effective, and can be accompanied by adverse reactions, many patients face difficulties completing their schedule. Long-term therapy also potentially incurs high costs. Therefore, there is a great need for objective markers to predict or to monitor individual patient's beneficial changes in immune response during therapy so that efficacy can be identified as early as possible. In this review, we specifically address recent technical developments that have generated new insights into allergic disease pathogenesis, and how these could potentially be translated into routine laboratory assays for disease monitoring during AIT that are relatively inexpensive, robust and scalable.

Transcriptome analysis and safety profile of the early-phase clinical response to an adjuvanted grass allergoid immunotherapy

Background

Specific immunotherapy is the only type of disease-modifying treatment, which induces rapid desensitization and long-term sustained unresponsiveness in patients with seasonal allergic rhinoconjunctivitis. The safety and tolerability of a new cumulative dose regimen of 35600 SU Grass MATA MPL for subcutaneous immunotherapy were assessed in pre-seasonal, single-blind, placebo controlled Phase I clinical study. Underlying immunological mechanisms were explored using transcriptome analysis of peripheral blood mononuclear cells.

Methods

Study subjects with a history of moderate to severe seasonal allergic rhinitis and/or conjunctivitis (SAR) due to grass (Pooideae) pollen exposure were randomized on a 1:1 ratio to receive either six 1.0 mL injections of cumulative dose regimen 35600 SU of Grass MATA MPL or placebo. The study consisted of three periods: screening, randomization and treatment and End of Study period. Blood samples were taken for clinical safety laboratory assessments and for the assessment of gene expression analysis during screening visit and End of Study visit. The safety statistics was calculated using Fisher's exact test. Delta Delta Ct method analysis of RT² Profiler PCR Array gene expression results was used to calculate changes in gene expression level. Genes with the absolute value of log₂ fold change greater than ±1.1 and p-value less than 0.05 were identified as differentially expressed and underwent IPA data analysis.

Results

The results of the study indicated that the higher cumulative dose regimen of the immunotherapy was well-tolerated. Changes in gene expression profile were associated with early immune responses implicating innate and adaptive immune mechanisms. Pathways and mechanistic network analysis via IPA mapped differentially expressed genes onto canonical pathways related to T cell differentiation, cytokine signalling and Th1/Th2 activation pathways. The transcriptome findings of the study could be further verified in large-scale field studies in order to explore their potential as predictive markers of successful immunotherapy.

Conclusions

The higher dose cumulative regime 35600 SU of Grass MATA MPL vaccine was well tolerated and safe. Molecular markers IL-27, IL-10, IL-4, TNF, IFNγ, TGFβ and TLR4 were the main predicted molecular drivers of the observed gene expression changes following early stages of SIT with Grass MATA MPL immunotherapy.

Immunization of cats to induce neutralizing antibodies against Fel d 1, the major feline allergen in human subjects

BACKGROUND

Cat allergy in human subjects is usually caused by the major cat allergen Fel d 1 and is found in approximately 10% of the Western population. Currently, there is no efficient and safe therapy for cat allergy available. Allergic patients usually try to avoid cats or treat their allergy symptoms.

OBJECTIVE

We developed a new strategy to treat Fel d 1-induced allergy in human subjects by immunizing cats against their own major allergen, Fel d 1.

METHODS

A conjugate vaccine consisting of recombinant Fel d 1 and a virus-like particle derived from the cucumber mosaic virus containing the tetanus toxin-derived universal T-cell epitope tt830-843 (CuMVTT) was used to immunize cats. A first tolerability and immunogenicity study, including a boost injection, was conducted by using the Fel-CuMVTT vaccine alone or in combination with an adjuvant.

RESULTS

The vaccine was well tolerated and had no overt toxic effect. All cats induced a strong and sustained specific IgG antibody response. The induced anti-Fel d 1 antibodies were of high affinity and exhibited a strong neutralization ability tested both in vitro and in vivo. A reduction in the endogenous allergen level and a reduced allergenicity of tear samples, were observed.

CONCLUSION

Vaccination of cats with Fel-CuMVTT induces neutralizing antibodies and might result in reduced symptoms of allergic cat owners. Both human subjects and animals could profit from this treatment because allergic cat owners would reduce their risk of developing chronic diseases, such as asthma, and become more tolerant of their cats, which therefore could stay in the households and not need to be relinquished to animal shelters.

Structural Analysis of Recent Allergen-Antibody Complexes and Future Directions

PURPOSE OF REVIEW

Allergen-antibody complexes are extremely valuable in describing the detailed molecular features of epitopes. This review summarizes insights gained from recently published co-structures and what obstacles impede the acquisition of further data.

RECENT FINDINGS

Structural epitope data helped define the epitopes of two anti-Fel d 1 antibodies undergoing phase I clinical trials, providing a greater level of detail than was possible through hydrogen-deuterium exchange protection studies. Separately, a human camelid-like antibody structure with lysozyme described several unique features in a long variable loop that interacted with the active site cleft of Gal d 4. Finally, a co-structure conclusively demonstrated that Phl p 7 could function as a superantigen and that an antibody could simultaneously recognize two epitopes. These remarkable assertions would not have been possible without visualization of the complex. Only three new complexes have appeared in the last few years, suggesting that there are major impediments to traditional production and crystallization. The structural data was extremely valuable in describing epitopes. New techniques like cryo-EM may provide an alternative to crystallography.

Analysis of Leukocyte Behaviors on Microfluidic Chips

The orchestration of massive leukocytes in the immune system protects humans from invading pathogens and abnormal cells in the body. So far, researches focusing on leukocyte behaviors are performed based on both in vivo and in vitro models. The in vivo animal models are usually less controllable due to their extreme complexity and nonignorable species issue. Therefore, many researchers turn to in vitro models. With the advances in micro/nanofabrication, the microfluidic chip has emerged as a novel platform for model construction in multiple biomedical research fields. Specifically, the microfluidic chip is used to study leukocyte behaviors, due to its incomparable advantages in high throughput, precise control, and flexible integration. Moreover, the small size of the microstructures on the microfluidic chip can better mimic the native microenvironment of leukocytes, which contributes to a more reliable recapitulation. Herein are reviewed the recent advances in microfluidic chip-based leukocyte behavior analysis to provide an overview of this field. Detailed discussions are specifically focused on host defense against pathogens, immunodiagnosis, and immunotherapy studies on microfluidic chips. Finally, the current technical challenges are discussed, as well as possible innovations in this field to improve the related applications.

Newly designed hemagglutinin-Der p 2 chimera is a potential candidate for allergen specific immunotherapy

Aim To investigate the immunomodulatory potential of a chimera composed of the receptor-binding domain of hemagglutinin 1 (H1s) from Influenza virus and Der p 2 (D2) allergen for allergen-specific immunotherapy of house-dust mite allergy (HDM).

MAIN METHODS

H1sD2 chimera and D2 allergen were produced by genetic engineering in E. coli. Recombinant antigens were extracted from inclusion bodies by urea, then refolded and purified by immobilized- metal affinity chromatography (IMAC). Purity was verified by 2D-PAGE and secondary structures were assessed by CD spectroscopy. IgE reactivity of H1sD2 and D2 was tested in western blot with sera from 8 persons with clinical history of HDM allergy. Immunogenicity of H1sD2 and D2 were analyzed in Balb/c mice. Cytokine profile was analyzed by ELISA after stimulation of mouse spleen cells with H1sD2 and D2. Leukocyte population abundance of cells isolated from spleen and lymph node was assessed by flow cytometry.

KEY FINDINGS

Purified recombinant proteins H1sD2 (42 kDa) and D2 (15 kDa) revealed well defined secondary structures, and preserved IgE reactive epitopes. Analysis of supernatants of mouse spleen cells after stimulation with H1sD2 and D2, revealed a qualitatively different cytokine profile from H1sD2 immunized mouse cells (increase in IL10). CD8+ cells were decreased in the lymph node of D2 immunized mice, whereas H1sD2 immunization led to an increase of CD8+ cells in both the lymph node and the spleen.

SIGNIFICANCE

H1sD2 chimera attenuates Der p 2-inherent Th2 response and directs the immune response toward Th1 and Treg phenotype.

Identification of specifically reduced Th2 cell subsets in allergic rhinitis patients after sublingual immunotherapy

BACKGROUND

Although Th2 cells are well known to play important roles in allergic diseases including allergic rhinitis (AR), the factors that induce and sustain the pathogenesis of AR remain unclear. The recent development of sublingual immunotherapy (SLIT) is expected to allow changes to the underlying pathogenesis of AR. However, which Th2 cell subsets are important in house dust mite-induced AR (HDM-AR), the influence of SLIT on the pathogenic Th2 cells, and the association of Th2 cell subsets with SLIT efficacy have not been clarified.

METHODS

The cytokine production and frequency of HDM-reactive T-cell subsets in peripheral blood mononuclear cells (PBMCs) were evaluated using flow cytometry in 89 HDM-AR patients (placebo [n = 43] and HDM 300 IR [n = 46]) who participated in a placebo-controlled study of SLIT with HDM tablets. All patients provided samples both before treatment as a baseline and at the end of the 52-week study. The PBMCs were stained with CellTrace™ Violet (CTV) before culture with HDM extract, and HDM-reactive T cells were detected as the proliferated cells with diminished CTV.

RESULTS

HDM-reactive IL-5⁺ IL-13⁺ CD27^- CD161⁺ CD4⁺ cells and ST2⁺ CD45RO⁺ CD4⁺ cells were observed in the peripheral blood from each patient with HDM-AR; these cells significantly decreased after SLIT in the group treated with active tablets. HDM-reactive ST2⁺ CD45RO⁺ CD4⁺ cells were significantly lower in active-responders.

CONCLUSION

Allergen-reactive ST2⁺ CD45RO⁺ CD4⁺ cells or those combined with IL-5⁺ IL-13⁺ CD27^- CD161⁺ CD4⁺ cells may be useful as markers indicating the successful treatment of SLIT. These cells may play a crucial role in the pathogenesis of AR as pathogenic memory Th2 cells.

Virus-like particles (VLP) in prophylaxis and immunotherapy of allergic diseases

BACKGROUND

Apart from active allergen avoidance, immunotherapy is regarded as the most effective form of treatment available for type I allergies. Such treatments involve the administration of allergen preparations in various forms and by various routes. Virus-like particles (VLPs) offer a very effective platform for immunization with the allergen and are characterized by high immunogenicity, low allergenicity and high clinical efficacy. Formulations that include Toll-like receptor ligands, T cell stimulatory epitopes and/or depot-forming adjuvants appear to enhance activation of the relevant immune cells. Short nucleotide sequences including CpG motifs have also been intensively explored as potent stimulators of dendritic cells and B cells.

METHODS

The present paper is based on a systematic literature search in PubMed and MEDLINE, and focuses on the pertinent immunological processes and on clinical data relating to use of VLPs and CpG motifs for the treatment of allergic rhinitis (AR).

RESULTS

Many published studies have reported positive clinical results following administration of VLPs, either alone or in combination with CpG motifs and, in some cases, even in the absence of the allergen-specific allergen.

CONCLUSIONS

These results indicate that VLPs modulate immune responses in ways which underline their exceptional promise as a platform for the immunotherapy of allergic disorders. However, clinical evaluations remain limited, and further large-scale and longer-term studies will be necessary to substantiate the efficacy and safety of these novel therapies.

Homology modeling and epitope prediction of Der f 33

Dermatophagoides farinae (Der f), one of the main species of house dust mites, produces more than 30 allergens. A recently identified allergen belonging to the alpha-tubulin protein family, Der f 33, has not been characterized in detail. In this study, we used bioinformatics tools to construct the secondary and tertiary structures and predict the B and T cell epitopes of Der f 33. First, protein attribution, protein patterns, and physicochemical properties were predicted. Then, a reasonable tertiary structure was constructed by homology modeling. In addition, six B cell epitopes (amino acid positions 34–45, 63–67, 103–108, 224–230, 308–316, and 365–377) and four T cell epitopes (positions 178–186, 241–249, 335–343, and 402–410) were predicted. These results established a theoretical basis for further studies and eventual epitope-based vaccine design against Der f 33.

Conformational IgE Epitope Mapping of Der p 2 and the Evaluations of Two Candidate Hypoallergens for Immunotherapy

Epitope mapping of Der p 2, a clinically important dust-mite allergen is the first step in designing immunotherapy hypoallergen vaccine candidates. Twenty-one single alanine mutants of Der p 2 were generated and their secondary structure was analysed using circular dichroism spectra. Only one mutant, K96A resulted in a misfolded protein. All mutants were tested for serum IgE reactivity using serum from dust mite allergic individuals by immuno dot-blots. Mutations to five residues, N10, E25, K77, K96 and E102 consistently showed reduced IgE reactions compared to wild-type Der p 2, and therefore these residues constitute the major IgE epitopes of Der p 2. Two mutants with consistent low IgE binding, K96A and E102A, were subsequently evaluated as hypoallergen candidates. IgG antibodies raised in mice against both mutants could inhibit human IgE-binding to WT Der p 2. Both mutants had intact T-cell epitopes as they were able to stimulate peripheral blood mononuclear cell proliferation similar to WT Der p 2. However, a switch in Th1:Th2 cytokine profile was not observed. In summary, we have identified the major conformational epitopes of Der p 2, and evaluated two Der p 2 hypoallergen vaccine candidates for immunotherapy.

Allergens displayed on virus-like particles are highly immunogenic but fail to activate human mast cells

BACKGROUND

The goal of allergen-specific immunotherapy is the induction of protective immune responses in the absence of anaphylactic reactions. We have previously shown that Fel d 1, the major cat allergen, displayed in a repetitive fashion on virus-like particles (VLPs) may fulfill these criteria. Specifically, Fel d 1 on VLPs induced strongly increased protective IgG responses compared to free allergen in mice while anaphylactic reactions were essentially abolished. Here we extend these findings to human mast cells and offer a mechanistic explanation for the reduced anaphylactic activity.

METHODS

We differentiated human mast cells in vitro from blood-derived stem cell progenitors and sensitized the cells with a monoclonal Fel d 1-specific IgE. We compared the capability of Fel d 1 to induce mast cell activation in its free form versus displayed on VLPs and we performed allergen binding studies by surface plasmon resonance as well as flow cytometry.

RESULTS

We show that free Fel d 1 induces degranulation of IgE-sensitized mast cells whereas Fel d 1 displayed on VLPs fails to induce mast cell activation. We demonstrate that this inability to activate mast cells is based on a biophysical as well as a biochemical mechanism. Firstly, Fel d 1 on VLPs showed a strongly impaired ability to bind to surface-bound IgE. Secondly, despite residual binding, repetitively displayed allergen on VLPs failed to cause mast cell activation.

CONCLUSION

These findings indicate that repetitively displaying allergens on VLPs increases their immunogenicity while reducing their potential to cause anaphylactic reactions by essentially eliminating IgE-mediated activation of mast cells.

Assessing asthma in the otolaryngologist's office

PURPOSE OF REVIEW

To familiarize otolaryngologists and other practitioners with basic diagnosis and treatment of asthma in adults and children based on current literature.

RECENT FINDINGS

Increased fractional excretion of nitrous oxide and sputum eosinophils have been identified in asthmatic patients being evaluated for chronic cough and appear to be more sensitive in diagnosis than traditional spirometry. Both sublingual and subcutaneous immunotherapy modalities are effective in decreasing symptoms and medication use in patients with allergic rhinitis and allergic asthma.

SUMMARY

Undiagnosed comorbid asthma is prevalent among patients with chronic rhinosinusitis and allergic rhinitis and control of all diseases processes greatly improves quality of life. Office spirometry is a helpful tool in the evaluation and management of asthma. Otolaryngologists should be able to recognize undiagnosed or poorly controlled asthma, initiate and improve medical therapy, and treat rhinosinusitis to improve asthma control.

New opportunities and challenges in the assessment of drugs for atopic diseases

Atopic conditions (atopic dermatitis, rhinitis, and asthma) belong to the most common noncommunicable diseases and are driven by chronic inflammatory reactions. They have a strong impact on the quality of life and represent a substantial and growing socio-economic burden. Interestingly, there is an increasing interest in the development of new therapeutic options with a number of biologics and small molecules targeting potential key mechanisms in atopic conditions. However, besides the safety issue, most of the new active substances are still evaluated according to the traditional efficacy paradigm focusing on the success in treating exacerbations and flares. Instead, the future approaches in drug development and assessment should rather concentrate on the long-term control of these diseases and consider their potential as disease-modifying strategies in the era of precision medicine. To reach this goal, a number of unsolved issues have to be addressed and consensually accepted by the stakeholders in this field. Thus, a successful and rapid development of new treatments requests a paradigm shift and a new way of thinking in the mind of physicians, pharmaceutical industry, regulators, and HTAs. This seems mandatory in order to optimize drug development and to facilitate the accessibility of new therapies to the growing population of patients suffering from atopic conditions on a global level.

IgE-associated allergic disorders: recent advances in etiology, diagnosis, and treatment

IgE-associated allergic diseases belong to the most common inflammatory conditions. Their clinical manifestation ranges from mild symptoms to life-threatening episodes. Often patients experience a reduction in physical and psychologic well-being and suffer from a decreased quality of life due to disease activity. The continuously rising number of people that are affected by an allergic condition indicates an urgent need for better diagnostics and more efficient treatment options. Recent progress in the understanding of pathophysiologic mechanisms underlying IgE-associated allergic disorders has led to the identification of novel therapeutic targets and the development of drug candidates that are currently under evaluation. In this review, we highlight studies and clinical trials, which have helped to gain further insight in the etiology of IgE-associated allergic conditions as well as advances in the development of diagnostic tools and therapeutic approaches recently published in Allergy (European Journal of Allergy and Clinical Immunology).