Peptide and Recombinant Allergen Vaccines for Food Allergy

Mutation of Disulfide Bond Sites Reduces the Immunoreactivity of Cra a 4 by Changing the Structural Characteristics

Sarcoplasmic calcium-binding protein (Cra a 4) from Crassostrea angulata belongs to the EF-hand superfamily, and understanding of its structure-allergenicity relationship is still insufficient. In this study, chemical denaturants were used to destroy the structure of Cra a 4, showing that disruption of the structure reduced its IgG-/IgE-binding activity. To explore which critical amino acid site affects the allergenicity of Cra a 4, the mutants were obtained by site-directed mutations in the disulfide bonds site (C97), conformational epitopes (I105, D114), or Ca2+-binding region (D106, D110) and their IgG-/IgE-binding activity was reduced significantly using serological tests. Notably, C97A had the lowest immunoreactivity. In addition, two conformational epitopes of Cra 4 were verified. Meanwhile, the increase of the α-helical content, surface hydrophobicity, and surface electrostatic potential of C97A affected its allergenicity. Overall, the understanding of the structure-allergenicity relationship of Cra a 4 allowed the development of a hypoallergenic mutant.

Virtual Screening for SARS-CoV-2 Main Protease Inhibitory Peptides from the Putative Hydrolyzed Peptidome of Rice Bran

The Coronavirus Disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has led to the loss of life and has affected the life quality, economy, and lifestyle. The SARS-CoV-2 main protease (Mpro), which hydrolyzes the polyprotein, is an interesting antiviral target to inhibit the spreading mechanism of COVID-19. Through predictive digestion, the peptidomes of the four major proteins in rice bran, albumin, glutelin, globulin, and prolamin, with three protease enzymes (pepsin, trypsin, and chymotrypsin), the putative hydrolyzed peptidome was established and used as the input dataset. Then, the prediction of the antiviral peptides (AVPs) was performed by online bioinformatics tools, i.e., AVPpred, Meta-iAVP, AMPfun, and ENNAVIA programs. The amino acid composition and cytotoxicity of candidate AVPs were analyzed by COPid and ToxinPred, respectively. The ten top-ranked antiviral peptides were selected and docked to the SARS-CoV-2 main protease using GalaxyPepDock. Only the top docking scored candidate (AVP4) was further analyzed by molecular dynamics simulation for one nanosecond. According to the bioinformatic analysis results, the candidate SARS-CoV-2 main protease inhibitory peptides were 7–33 amino acid residues and formed hydrogen bonds at Thr22–24, Glu154, and Thr178 in domain 2 with short bonding distances. In addition, these top-ten candidate bioactive peptides contain hydrophilic amino acid residues and have a positive net charge. We hope that this study will provide a potential starting point for peptide-based therapeutic agents against COVID-19.

Proteomics for Development of Food Allergy Vaccines

Food allergy is a hypersensitivity reaction to food products initiated by immunologic mechanisms, which represents one of the major concerns in food safety. New therapies for food allergies including oral and epicutaneous allergen-specific immunotherapy are required, and B cell epitope-based allergy vaccines are a good promise to improve this field. In this chapter, we describe a workflow for the design of food allergy vaccines using proteomic tools. The strategy is defined based on the characterization of B cell epitopes for a particular food allergen. For that, the workflow comprises five consecutive steps: (1) shotgun proteomics analysis of different protein isoforms for a particular food allergen, (2) downloading all protein sequences for the specific allergen included in UniProtKB database, (3) analysis by protein-based bioinformatics of B cell epitopes, (4) synthesizing of the selected B cell peptide epitopes, and (5) performing of immunoassays using sera from healthy and allergic patients. The results from this method provide a rationale repository of B cell epitopes for the design of new specific immunotherapies for a particular food allergen. The strategy was optimized for all the beta-parvalbumins (β-PRVBs), which are considered as the main fish allergens. Using this workflow, a total of 35 peptides were identified as B cell epitopes, among them the top 4 B cell peptide epitopes that may induce protective immune response were selected as potential peptide vaccine candidates for fish allergy.

Diagnosis and Management of Food Allergy

Food allergy is an immune-mediated disease and must be differentiated from other adverse effects related to food that are non-immune mediated. Symptoms of immunoglobulin (Ig) E-mediated allergy can range from mild to severe, and life-threatening anaphylaxis may occur. Current recommended strategies for diagnosis include the use of skin prick tests, allergen-specific serum IgE, and/or oral food challenges. Management entails allergen avoidance and appropriate treatment of allergic reactions should accidental ingestions occur. Treatment approaches under investigation include immunotherapy as well as biologics and novel vaccines. Attention has also recently focused on implementing strategies for prevention of food allergy.

One Hundred Ten Years of Allergen Immunotherapy: A Broad Look Into the Future

Allergen immunotherapy (AIT) is the only disease-modifying treatment option for patients with type 1-mediated allergic diseases such as allergic rhinitis/rhinoconjunctivitis with/without allergic asthma. Although many innovations have been developed since the first clinical report of Noon et al in 1911, the improvement of clinical efficacy and tolerability of this treatment is still an important unmet need. Hence, much progress has been made in the characterization of the cell types, cytokines, and intracellular signaling events involved in the development, maintenance, and regulation of allergic reactions, and also in the understanding of the mechanisms of tolerance induction in AIT. This comprehensive review aims to summarize the current innovative approaches in AIT, but also gives an outlook on promising candidates of the future. On the basis of an extensive literature review, integrating a clinical point of view, this article focuses on recent and future innovations regarding biologicals, allergen-derived peptides, recombinant allergens, "Toll"-like receptor agonists and other adjuvants, and novel application routes being developed for future AIT.

Site-Directed Mutations of Calcium-Binding Sites Contribute to Reducing the Immunoreactivity of the EF-Hand Sarcoplasmic Calcium-Binding Protein in Scylla paramamosain

In order to reduce the immunoreactivity of sarcoplasmic calcium-binding protein (SCP), site-directed mutations were used to replace key amino acids in the conformational epitopes and calcium-binding sites. The mutant SCPs (mSCPs) were expressed in Escherichia coli, and their immunoreactivities were analyzed using iELISA and basophil activation assays. Furthermore, the structural changes of mSCPs were determined from the circular dichroism spectra. The iELISA results showed that mSCPs could effectively inhibit the binding of wild-type SCP (wtSCP) to sensitive serum, with inhibition rates that reached 90%. Moreover, mSCPs could downregulate the expression levels of CD63 and CD203c on the basophil surface. Compared with wtSCP, the peak values were significantly changed, and the calcium binding ability was impaired, which explained the decline in immunoreactivities of the mSCPs. All of the data confirmed that this approach was effective in reducing the immunoreactivity of SCP and could be applied to other shellfish allergens.

Advances in Management of Food Allergy in Children

Food allergy is a potentially life-threatening medical condition and a significant public health concern worldwide. The current management consists of strict avoidance of the culprit food and treating any adverse reactions from unintended food ingestion. The increasing prevalence of food allergy encouraged research and clinical trials in the field of specific allergen immunotherapy (AIT) which represents an appealing approach, especially in pediatric age. AIT consists of the gradual administration of growing amounts of the offending allergen in order to induce food desensitization, which is an increase in the threshold for reactivity while continuing on regular exposure to the allergen. AIT can be administered through oral, sublingual, epicutaneous, and subcutaneous routes. Reports on oral immunotherapy (OIT) thus far have been more extensive. The desirable goal is to achieve "post desensitization effectiveness", that is the ability to introduce food without reaction even after a period of discontinuation of the offending food. Other therapeutic approaches are being studied alongside immunotherapy such as modified proteins, probiotics, Chinese herbal supplements, biologic therapies, and DNA vaccines.

Future research trends in understanding the mechanisms underlying allergic diseases for improved patient care

The specialties of allergy and clinical immunology have entered the era of precision medicine with the stratification of diseases into distinct disease subsets, specific diagnoses, and targeted treatment options, including biologicals and small molecules. This article reviews recent developments in research and patient care and future trends in the discipline. The section on basic mechanisms of allergic diseases summarizes the current status and defines research needs in structural biology, type 2 inflammation, immune tolerance, neuroimmune mechanisms, role of the microbiome and diet, environmental factors, and respiratory viral infections. In the section on diagnostic challenges, clinical trials, precision medicine and immune monitoring of allergic diseases, asthma, allergic and nonallergic rhinitis, and new approaches to the diagnosis and treatment of drug hypersensitivity reactions are discussed in further detail. In the third section, unmet needs and future research areas for the treatment of allergic diseases are highlighted with topics on food allergy, biologics, small molecules, and novel therapeutic concepts in allergen‐specific immunotherapy for airway disease. Unknowns and future research needs are discussed at the end of each subsection.

Diagnosis and Management of Food Allergy

Food allergy is an immune-mediated disease and must be differentiated from other adverse effects related to food that are non-immune mediated. Symptoms of immunoglobulin (Ig) E-mediated allergy can range from mild to severe, and life-threatening anaphylaxis may occur. Current recommended strategies for diagnosis include the use of skin prick tests, allergen-specific serum IgE, and/or oral food challenges. Management entails allergen avoidance and appropriate treatment of allergic reactions should accidental ingestions occur. Treatment approaches under investigation include immunotherapy as well as biologics and novel vaccines. Attention has also recently focused on implementing strategies for prevention of food allergy.

Progress in the Analysis of Food Allergens through Molecular Biology Approaches

Food allergies associated with class E immunoglobulins (IgE) are a serious health problem that affects between 1% and 10% of the population of developing countries, with a variability that depends on the geographical area and age range considered. These allergies are caused by a cross-link reaction between a specific food protein (the allergen) and the host IgE. Allergic reactions can range from mild itching to anaphylactic shock and there are no clues to predict the effects of an allergen. Strict avoidance of allergenic food is the only way to avoid possible serious allergic reactions. In the last 30 years a growing number of molecular studies have been conducted to obtain information on the diffusion of food allergens and to establish the structural basis of their allergenicity. At the same time, these studies have also allowed the development of molecular tools (mainly based on synthetic peptides and recombinant allergens) that can be of great help for diagnostic and therapeutic approaches of food allergies. Accordingly, this review focuses on advances in the study of food allergens made possible by molecular technologies and how results and technologies can be integrated for the development of a systematic food molecular allergology. The review may be of interest both to scientists approaching this field of investigation and to physicians who wish to have an update on the progress of research in diagnosis and therapy of food allergies.

Novel vaccines: Technology and development

The development and widespread use of vaccines, which are defined by the World Health Organization as "biological preparations that improve immunity to a particular disease," represents one of the most significant strides in medicine. Vaccination was first applied to reduce mortality and morbidity from infectious diseases. The World Health Organization estimates that vaccines prevent 2 to 3 million human deaths annually, and these numbers would increase by at least 6 million if all children received the recommended vaccination schedule. However, the origins of allergen immunotherapy share the same intellectual paradigm, and subsequent innovations in vaccine technology have been applied beyond the prevention of infection, including in the treatment of cancer and allergic diseases. This review will focus on how new and more rational approaches to vaccine development use novel biotechnology, target new mechanisms, and shape the immune system response, with an emphasis on discoveries that have direct translational relevance to the treatment of allergic diseases.