Identification of aero-allergens from Rhizopus oryzae: an immunoproteomic approach

Screening of potential antigens from whole proteome and development of multi-epitope vaccine against Rhizopus delemar using immunoinformatics approaches

Mucormycosis is a deadly fungal disease mainly caused by Rhizopus oryzae (strain 99-880), also known as Rhizopus delemar. Previously, mucormycosis occurs in immunocompromised patients of diabetes mellitus, cancer, organ transplant, etc. But there was a drastic increase in mucormycosis cases in the ongoing COVID-19 pandemic. Despite several available therapies and antifungal treatments, the mortality rate of mucormycosis is about more than 50%. Currently, there is no vaccine available in the market for mucormycosis that urgently needs to develop a potential vaccine against mucormycosis with high efficacy. In the present study, we have screened 4 genome-derived predicted antigens (GDPA) through sequential filtration of the whole proteome of R. delemar using different benchmarked bioinformatics tools. These 4 GDPA along with 4 randomly selected experimentally reported antigens (ERA) were sourced for prediction of B- and T- cell epitopes and utilized in designing of two potential multi-epitope vaccine candidates which can induce both innate and adaptive immunity against R. delemar. Besides these, comparative immune simulation studies and in silico cloning were performed using L. lactis as an expression system for their possible uses as oral vaccines. This is the first multi-epitope vaccine designed against R. delemar through systematic pipelined reverse vaccinology and immunoinformatic approaches. Although the wet-lab based experimental validation of designed vaccines is required before testing in the preclinical model, the current study will significantly help in reducing the cost of experimentation as well as improving the efficacy of vaccine therapy against mucormycosis and other pathogenic diseases.Communicated by Ramaswamy H. Sarma.

Cloning and immunobiochemical analyses on recombinant chymopapain allergen Cari p 2 showing pollen-fruit cross-reaction

Papaya is reported to trigger food and respiratory allergy. Here, we identified chymopapain Cari p 2 as an allergen that can sensitize atopic individuals through fruit consumption followed by respiratory hazards through pollen exposure. Recombinant Cari p 2 displayed IgE-reactivity with 78% of papaya allergic sera. rCari p 2 also displayed allergenic activity through basophil degranulation. rCari p 2 is correctly folded and showed irreversible denaturation in the melting curve. rCari p 2 displayed IgE-cross-reactivity with homologous cysteine proteases from kiwi and pineapple. Cari p 2 transcript was also detected in papaya pulps. rCari p 2 was resistant to pepsin digestion and retained IgE-reactivity after 60 minutes of pepsin digestion. In mouse model, rCari p 2 was found to elicit inflammatory responses in the lung and gastrointestinal epithelium. Hence, Cari p 2 is a newly characterized allergen with diagnostic and immunotherapeutic potential for managing allergic disorders in papaya sensitized individuals.

Identification and biochemical characterization of Asp t 36, a new fungal allergen from Aspergillus terreus

Aspergillus terreus is an allergenic fungus, in addition to causing infections in both humans and plants. However, the allergens in this fungus are still unknown, limiting the development of diagnostic and therapeutic strategies. We used a proteomic approach to search for allergens, identifying 16 allergens based on two-dimensional immunoblotting with A. terreus susceptible patient sera. We further characterized triose-phosphate isomerase (Asp t 36), one of the dominant IgE (IgE)-reactive proteins. The gene was cloned and expressed in Escherichia coli. Phylogenetic analysis showed Asp t 36 to be highly conserved with close similarity to the triose-phosphate isomerase protein sequence from Dermatophagoides farinae, an allergenic dust mite. We identified four immunodominant epitopes using synthetic peptides, and mapped them on a homology-based model of the tertiary structure of Asp t 36. Among these, two were found to create a continuous surface patch on the 3D structure, rendering it an IgE-binding hotspot. Biophysical analysis indicated that Asp t 36 shows similar secondary structure content and temperature sensitivity with other reported triose-phosphate isomerase allergens. In vivo studies using a murine model displayed that the recombinant Asp t 36 was able to stimulate airway inflammation, as demonstrated by an influx of eosinophils, goblet cell hyperplasia, elevated serum Igs, and induction of Th2 cytokines. Collectively, our results reveal the immunogenic property of Asp t 36, a major allergen from A. terreus, and define a new fungal allergen more broadly. This allergen could serve as a potent candidate for investigating component resolved diagnosis and immunotherapy.

Allergenicity assessment of Delonix regia pollen grain and identification of allergens by immunoproteomic approach

Background

Plantation of road-side avenue trees has become a major part of urbanization programme for megacity beautification and environmental management. Due to evergreen habit and vibrant flower colour, Delonix regia (Gulmohor/Flamboyant) is frequently selected as ornamental tree for plantation programme. However, D. regia pollen is related to IgE mediated allergic reactions and no allergen has been reported so far.

Objective

Measuring the prevalence of D. regia pollen sensitivity among the local atopic individuals and identifying the allergens using immunoproteomic tools.

Methods

Aerobiological study was conducted for a period of two years to record the D. regia pollen concentration in the outdoor ambient air. Clinico-immunological tests were performed on atopic individuals to check the prevalence of sensitivity against D. regia pollen. Allergens were detected in the pollen proteome, fractionated in 1D and 2D gel by IgE serology and finally identified by mass spectrometry.

Result

In the study area D. regia pollen grains were present in ample amount in the air during May to July. About 38% of atopic individuals displayed positive Skin Prick Test (SPT) against D. regia pollen along with elevated level of specific IgE and histamine in the sera. Immunoproteomic analyses revealed the presence of 14 IgE reactive proteins in the 2D pollen proteome, of which 8 IgE reactive proteins were identified by MALDI TOF/TOF using homology driven proteomic approach.

Conclusion

This study demonstrated pollen related allergy symptoms by D. regia and gave significant message regarding the plantation programme to avoid the unnecessary load of allergic pollen. Also, a panel of 8 allergens were identified for the first time from D. regia pollen. Detailed study of these allergens would help to design immunotherapeutic strategies for pollinosis management.

Identifying novel allergens from a common indoor mould Aspergillus ochraceus

The increasing burden of respiratory disease is a rising concern in India. Although chronic colonisation is primarily caused by pathogenic fungi, the common environmental fungi also play an important role in developing sensitisation. This study aims to examine the allergenic potency of mycelial proteins of a common indoor fungus Aspergillus ochraceus to a selected atopic patient cohort as well as to identify the novel IgE-binding proteins through an immunoproteomic approach. 1-D and 2-D IgE specific western blot detected the IgE reactive proteins which were identified through MALDI-TOF/TOF and manual de novo peptide sequencing. The results revealed the detection of 10 cross-reactive IgE-binding proteins. Cluster analysis of 1-D immunoblot with individual patient sera identified NADP(+)-dependent glycerol dehydrogenase (GldB) homologous protein as a major allergen, which was further purified and the allergenicity was assessed. Other IgE-binding proteins showed homology with allergens like short-chain dehydrogenase, NAD-dependent mannitol dehydrogenase, and subtilisin-like serine protease. GldB purified under native conditions showed IgE reactivity amongst the selected patient cohort, which is reported for the first time in this study. The identified IgE-binding proteins can act as candidate molecules for developing hypoallergenic vaccines for designing specific immunotherapeutic techniques to fungal allergy. THE SIGNIFICANCE OF THE STUDY: Exposure to environmental fungal allergens is directly associated with promoting allergic response as well as complicating existing respiratory disease, leading to poor respiratory health. Amongst others, Aspergillus spp. contributes to the majority of the fungal derived atopic diseases. Aspergillus ochraceus is a common indoor mould in India, however, its allergenic potency was not explored till date. In this study, we establish A. ochraceus responsible to cause an allergic response to susceptible individuals and identified 10 IgE-binding proteins using an immunoproteomics approach for the first time. A. ochraceus being unsequenced, a homology-driven proteomics approach was used to identify the IgE-binding proteins which can be extended to identify proteins from other unsequenced species. The information on the IgE-binding proteins could be used as a step towards characterising them by molecular and structural methods to investigate the molecular basis of allergenicity. This will also help to enrich the existing database of allergenic proteins and pave a way towards developing therapeutic avenues.

Biochemical Characteristics and Allergenic Activity of Common Fungus Allergens

Fungi form a large kingdom with more than 1.5 million species. Fungal spores are universal atmospheric components and are generally recognized as important causes of allergic disorders, including allergic rhinitis, allergic rhinosinusitis, asthma, and allergic bronchopulmonary aspergillosis. The 4 genera which have the closest connection with allergic disorder are Cladosporium, Alternaria, Aspergillus and Penicillium. The cDNA sequences of many fungi allergens and the amino acids involved in their immunoglobulin E binding and T-cell activation have already been elucidated. Until now, 111 allergens from 29 fungal genera have been approved by the International Allergen Nomenclature Sub-committee. This review mainly focuses on the biochemical characteristics and allergenic activity of important allergens from common environmental fungi.

Allergenicity assessment of fungal species using immunoclinical and proteomic techniques: a study on Fusarium lateritium

Airborne fungal spores are extensively reported as the elicitors of respiratory allergies in human. Fusarium lateritium is one such fungal species reported for eliciting significant skin prick results from India. The present study aims to analyze the allergenic potential of F. lateritium followed by the identification of allergens. The total protein of F. lateritium was subjected to 1dimensional (1D) and 2D gel electrophoresis followed by corresponding IgE-specific immunoblots. We found 8 immunoreactive bands/zones in (1D) immunoblot using 11 F. lateritium-sensitised patient sera. In 1D immunoblot, a 34 kDa band was detected in >80% of the patients and hence considered as a potential allergen of F. lateritium. Corresponding 34 kDa spot in 2D-immunoblot was analyzed by mass spectrometric analysis and identified as Glyceraldehyde 3-phosphate dehydrogenase. The identified F. lateritium allergen holds the potential to instigate vaccine development for immunotherapy of F. lateritium sensitized patients.

Immunoproteomic Approach of Extracellular Antigens From Paracoccidioides Species Reveals Exclusive B-Cell Epitopes

Fungi of the Paracoccidioides genus are the etiological agents of paracoccidioidomycosis (PCM), a systemic mycosis restricted to the countries of Latin America. Currently, the Paracoccidioides complex is represented by Paracoccidioides lutzii, Paracoccidioides americana, Paracoccidioides brasiliensis, Paracoccidioides restrepiensis, and Paracoccidioides venezuelensis. Even with advances in techniques used for diagnosing fungal diseases, high rates of false-positive results for PCM are still presented. Additionally, there is no efficient antigen that can be used to follow up the efficiency of patient treatment. The immunoproteomic is considered a powerful tool for the identification of antigens. In addition, antigens are molecules recognized by the immune system, which make them excellent targets for diagnostic testing of diseases caused by microorganisms. In this vein, we investigated which antigens are secreted by species representing Paracoccidioides complex to increase the spectrum of molecules that could be used for future diagnostic tests, patient follow-up, or PCM therapy. To identify the profile of antigens secreted by Paracoccidioides spp., immunoproteomic approaches were used combining immunoprecipitation, followed by antigen identification by nanoUPLC-MS^E-based proteomics. Consequently, it was possible to verify differences in the exoantigen profiles present among the studied species. Through a mass spectrometry approach, it was possible to identify 79 exoantigens in Paracoccidioides species. Using bioinformatics tools, two unique exoantigens in P. lutzii species were identified, as well as 44 epitopes exclusive to the Paracoccidioides complex and 12 unique antigenic sequences that can differentiate between Paracoccidioides species. Therefore, these results demonstrate that Paracoccidioides species have a range of B-cell epitopes exclusive to the complex as well as specific to each Paracoccidioides species. In addition, these analyses allowed us the identification of excellent biomarker candidates for epidemiology screening, diagnosis, patient follow-up, as well as new candidates for PCM therapy.

Molecular characterization of a fungal cyclophilin allergen Rhi o 2 and elucidation of antigenic determinants responsible for IgE-cross-reactivity

Cyclophilins are structurally conserved pan-allergens showing extensive cross-reactivity. So far, no precise information on cross-reactive IgE-epitopes of cyclophilins is available. Here, an 18-kDa IgE-reactive cyclophilin (Rhi o 2) was purified from Rhizopus oryzae, an indoor mold causing allergic sensitization. Based on LC-MS/MS-derived sequences of natural Rhi o 2, the full-length cDNA was cloned, and expressed as recombinant (r) allergen. Purified rRhi o 2 displayed IgE-reactivity and basophil degranulation with sera from all cyclophilin-positive patients. The melting curve of properly folded rRhi o 2 showed partial refolding after heat denaturation. The allergen displayed monomeric functional peptidyl-prolyl cis-trans isomerase (PPIase) activity. In IgE-inhibition assays, rRhi o 2 exhibited extensive cross-reactivity with various other cyclophilins reported as allergens from diverse sources including its homologous human autoantigen. By generating a series of deletion mutants, a conserved 69-residue (Asn⁸¹-Asn¹⁴⁹) fragment at C terminus of Rhi o 2 was identified as crucial for IgE-recognition and cross-reactivity. Grafting of the Asn⁸¹-Asn¹⁴⁹ fragment within the primary structure of yeast cyclophilin CPR1 by replacing its homologous sequence resulted in a hybrid molecule with structural folds similar to Rhi o 2. The IgE-reactivity and allergenic activity of the hybrid cyclophilin were greater than that of CPR1. Therefore, the Asn⁸¹-Asn¹⁴⁹ fragment can be considered as the site of IgE recognition of Rhi o 2. Hence, Rhi o 2 serves as a candidate antigen for the molecular diagnosis of mold allergy, and determination of a major cross-reactive IgE-epitope has clinical potential for the design of next-generation immunotherapeutics against cyclophilin-induced allergies.

Condiciones para el análisis de proteínas del micelio de Lentinula edodes obtenido por fermentación en estado líquido

Lentinula edodes es una seta comestible con potencial para el desarrollo de nutraceúticos. Sin embargo, son incipientes los trabajos enfocados en su producción biotecnológica y el desarrollo de herramientas analíticas que permitan profundizar en su composición. En esta investigación se estudió la producción de biomasa del hongo en el tiempo mediante fermentación en estado líquido y se seleccionaron las condiciones que permiten la obtención de extractos para la aplicación de herramientas para análisis proteómicos. Los métodos de extracción de proteínas, ácido tricloroacético (TCA)-Acetona y TCA-Acetona-Fenol, fueron comparados en términos del rendimiento de extracción y los perfiles de separación usando electroforesis en 1D (SDS-PAGE) y 2D (IEF-SDS PAGE). Se determinó que a los 10 días de crecimiento se obtiene la mayor producción de biomasa y proteína total. La extracción con TCA-Acetona-Fenol presentó un mayor rendimiento, mayor resolución y número de bandas en la electroforesis 1D. En 2DE los dos métodos permitieron la extracción de proteínas con puntos isoeléctricos en el rango de pH 3-10, pero el método TCA-Acetona-Fenol conllevó a una extracción diferencial, favoreciendo el rango de 33 a 113 kDa. Estos resultados se constituyen en una primera aplicación de técnicas de separación electroforética para futuros estudios proteómicos

Identification of airborne pollen allergens from two avenue trees of India

An attempt has been made to detect airborne pollen of Lagerstroemia speciosa (LS) and Spathodea campanulata (SC) - two common avenue trees of India as potential sources of aeroallergens and also to identify the major IgE-reactive components present in them. The airborne pollen concentration was assessed using a Burkard sampler. A detailed questionnaire on clinical data of 1490 patients was recorded based on hospital data. We assessed the allergenicity of pollen by in vivo and in vitro tests. The correlation among meteorological factors, pollen seasons and allergenic potency of patients was assessed by multiple regression analysis. The sensitivity of patients to pollen antigens was highly correlated with pollen seasons. In SDS-PAGE, 15 protein bands were detected from LS pollen, while 14 bands from SC. The IgE-specific immunoblotting with patients' sera allergic to LS displayed five major allergens, while four major allergens were detected from SC. This would be the first report from India to prove the allergenic potentiality of airborne pollen of these two common avenue trees of India.

Spectrum of Allergens and Allergen Biology in India

The growing prevalence of allergy and asthma in India has become a major health concern with symptoms ranging from mild rhinitis to severe asthma and even life-threatening anaphylaxis. The "allergen repertoire" of this subcontinent is highly diverse due to the varied climate, flora, and food habits. The proper identification, purification, and molecular characterization of allergy-eliciting molecules are essential in order to facilitate an accurate diagnosis and to design immunotherapeutic vaccines. Although several reports on prevalent allergens are available, most of these studies were based on preliminary detection and identification of the allergens. Only a few of these allergen molecules have been characterized by recombinant technology and structural biology. The present review first describes the composition, distribution pattern, and natural sources of the predominant allergens in India along with the prevalence of sensitization to these allergens across the country. We go on to present a comprehensive report on the biochemical, immunological, and molecular information on the allergens reported so far from India. The review also covers the studies on allergy- related biosafety assessment of transgenic plants. Finally, we discuss the allergen-specific immunotherapy trials performed in India.

Cari p 1, a Novel Polygalacturonase Allergen From Papaya Acting as Respiratory and Food Sensitizer

Papaya has been reported to elicit IgE-mediated hypersensitivity via pollen inhalation and fruit consumption. Certain papaya sensitive patients with food allergy were found to experience recurrent respiratory distresses even after quitting the consumption of fruits. This observation prompted us to investigate the allergens commonly present in fruits and pollen grains of papaya. A discovery approach consisting of immunoproteomic detection followed by molecular characterization led to the identification of a novel papaya allergen designated as Cari p 1. This allergen was detected as a 56 kDa IgE-reactive protein from pollen as well as fruit proteome through serological analysis. The protein was identified as an endopolygalacturonase by tandem mass spectrometry. Full length Cari p 1 cDNA was isolated from papaya pollen, cloned in expression vector, and purified as recombinant allergen. The recombinant protein was monomeric and displayed pectinolytic activity. Recombinant Cari p 1 reacted with IgE-antibodies of all the papaya sensitized patient sera. In addition to IgE-reactivity, rCari p 1 displayed allergenic activity by stimulating histamine release from IgE-sensitized granulocytes. CD-spectroscopy of rCari p 1 revealed the presence of predominantly β-sheet characters. The melting curve of the allergen showed partial refolding from a fully denatured state indicating the possible presence of conformational IgE-epitopes characteristic of inhalant allergens in addition to the linear IgE-epitopes of food allergens. The expression of this allergen in papaya fruits was detected by immunoblot with anti-Cari p 1 rabbit IgG and reconfirmed by PCR. In an in vivo mouse model, rCari p 1 exhibited a comparable level of inflammatory responses in the lung and duodenum tissues explaining the dual role of Cari p 1 allergen in respiratory sensitization via pollen inhalation and sensitization of gut mucosa via fruit consumption. Purified rCari p 1 can be used a marker allergen for component-resolved molecular diagnosis. Further immunological studies on Cari p 1 are warranted to design immunotherapeutic vaccine for the clinical management of papaya allergy.

Fungal Contaminants in Drinking Water Regulation? A Tale of Ecology, Exposure, Purification and Clinical Relevance

Microbiological drinking water safety is traditionally monitored mainly by bacterial parameters that indicate faecal contamination. These parameters correlate with gastro-intestinal illness, despite the fact that viral agents, resulting from faecal contamination, are usually the cause. This leaves behind microbes that can cause illness other than gastro-intestinal and several emerging pathogens, disregarding non-endemic microbial contaminants and those with recent pathogenic activity reported. This white paper focuses on one group of contaminants known to cause allergies, opportunistic infections and intoxications: Fungi. It presents a review on their occurrence, ecology and physiology. Additionally, factors contributing to their presence in water distribution systems, as well as their effect on water quality are discussed. Presence of opportunistic and pathogenic fungi in drinking water can pose a health risk to consumers due to daily contact with water, via several exposure points, such as drinking and showering. The clinical relevance and influence on human health of the most common fungal contaminants in drinking water is discussed. Our goal with this paper is to place fungal contaminants on the roadmap of evidence based and emerging threats for drinking water quality safety regulations.

Proteomics in India: the clinical aspect

Proteomics has emerged as a highly promising bioanalytical technique in various aspects of applied biological research. In Indian academia, proteomics research has grown remarkably over the last decade. It is being extensively used for both basic as well as translation research in the areas of infectious and immune disorders, reproductive disorders, cardiovascular diseases, diabetes, eye disorders, human cancers and hematological disorders. Recently, some seminal works on clinical proteomics have been reported from several laboratories across India. This review aims to shed light on the increasing use of proteomics in India in a variety of biological conditions. It also highlights that India has the expertise and infrastructure needed for pursuing proteomics research in the country and to participate in global initiatives. Research in clinical proteomics is gradually picking up pace in India and its future seems very bright.

Clinical and immuno-proteomic approach on Lantana camara pollen allergy-a major health hazard

BACKGROUND

The incidence of allergic diseases is increasing gradually and is a global burden affecting the socio-economic quality of life. Identification of allergens is the first step towards paving the way for therapeutic interventions against atopic diseases. Our previous investigation figured out that total pollen load correlated significantly with the rise of respiratory allergy in a subtropical city in India. The most dominant pollen responsible for IgE sensitivity in most patients emerged to be from Lantana camara (LC) an obnoxious weed growing in and around suburban areas of West Bengal. In this study, we identified allergenic components from this shrub using an immunoproteomic approach.

METHODS

Determination of dominant pollen species was done using aerobiological sampling during two consecutive years and correlated with hospitalization and skin prick test. Serum was collected from LC positive patients and checked for in vitro allergenicity using ELISA and Histamine assay. Total proteome was profiled in SDS-PAGE, 2D PAGE and immunoblotted to detect IgE binding proteins which were further identified using mass spectrometry.

RESULTS

Lantana camara pollen emerged as a significant contributor from the correlation study with hospital admission of the respiratory allergy sufferers and its extract demonstrated an elevated IgE response in ELISA and histamine release assay tests. Five IgE reactive bands/zones were observed in 1D blot which resolved to 12 allergo-reactive spots in the 2D blot. Mass spectrometric analysis identified nine spots that grouped into four diverse proteins. Pathogenesis-related Thaumatin-like protein was found to be one of the major allergens in Lantana camara.

CONCLUSIONS

This is to our knowledge the first attempt to identify allergens from Lantana camara using a proteomic approach. The allergens identified thereof can be used to prepare hypoallergenic vaccine candidates and design immunotherapy trials against LC pollen and other aeroallergen carriers which are cross-reactive and harbor similar proteins.

Epitope Mapping of Rhi o 1 and Generation of a Hypoallergenic Variant: A CANDIDATE MOLECULE FOR FUNGAL ALLERGY VACCINES

Efficacy of allergen-specific immunotherapy is often severely impaired by detrimental IgE-mediated side effects of native allergen during vaccination. Here, we present the molecular determinants for IgE recognition of Rhi o 1 and eventually converting the allergen into a hypoallergenic immunogen to restrain health hazards during desensitization. Rhi o 1 is a respiratory fungal allergen. Despite having cross-reactivity with cockroach allergen, we observed that non-cross-reactive epitope predominantly determined IgE binding to Rhi o 1. Denaturation and refolding behavior of the allergen confirmed that its IgE reactivity was not essentially conformation-dependent. A combinatorial approach consisting of computational prediction and a peptide-based immunoassay identified two peptides ((44)TGEYLTQKYFNSQRNN and (311)GAEKNWAGQYVVDCNK) of Rhi o 1 that frequently reacted with IgE antibodies of sensitized patients. Interestingly, these peptides did not represent purely linear IgE epitopes but were presented in a conformational manner by forming a spatially clustered surface-exposed epitope conferring optimal IgE-binding capacity to the folded allergen. Site-directed alanine substitution identified four residues of the IgE epitope that were crucial for antibody binding. A multiple mutant (T49A/Y52A/K314A/W316A) showing 100-fold lower IgE binding and reduced allergenic activity was generated. The TYKW mutant retained T-cell epitopes, as evident from its lymphoproliferative capacity but down-regulated pro-allergic IL-5 secretion. The TYKW mutant induced enhanced focusing of blocking IgG antibodies specifically toward the IgE epitope of the allergen. Anti-TYKW mutant polyclonal IgG antibodies competitively inhibited binding of IgE antibodies to Rhi o 1 up to 70% and suppressed allergen-mediated histamine release by 10-fold. In conclusion, this is a simple yet rational strategy based on epitope mapping data to develop a genetically modified hypoallergenic variant showing protective antibody response for immunotherapeutic applications.

Data on mass spectrometry based identification of allergens from sunflower (Helianthus annuus L.) pollen proteome

Allergy is a type of abnormal immune reactions, which is triggered by environmental antigens or allergens and mediated by IgE antibodies. Now-a-days mass spectrometry is the method of choice for allergen identification based on homology searching. Here, we provide the mass spectrometry dataset associated with our previously published research article on identification of sunflower pollen allergens (Ghosh et al., 2015 [1]). In this study allergenicity of sunflower (Helianthus annuus) pollen grains were primarily investigated by clinical studies followed by detailed immunobiochemical and immunoproteomic analyses. The mass spectrometry data for the identification of allergens were deposited to ProteomeXchange Consortium via PRIDE partner repository with the dataset identifier PXD002397.

Taxonomy of Allergenic Fungi

The Kingdom Fungi contains diverse eukaryotic organisms including yeasts, molds, mushrooms, bracket fungi, plant rusts, smuts, and puffballs. Fungi have a complex metabolism that differs from animals and plants. They secrete enzymes into their surroundings and absorb the breakdown products of enzyme action. Some of these enzymes are well-known allergens. The phylogenetic relationships among fungi were unclear until recently because classification was based on the sexual state morphology. Fungi lacking an obvious sexual stage were assigned to the artificial, now-obsolete category, "Deuteromycetes" or "Fungi Imperfecti." During the last 20 years, DNA sequencing has resolved 8 fungal phyla, 3 of which contain most genera associated with important aeroallergens: Zygomycota, Ascomycota, and Basidiomycota. Advances in fungal classification have required name changes for some familiar taxa. Because of regulatory constraints, many fungal allergen extracts retain obsolete names. A major benefit from this reorganization is that specific immunoglobulin E (IgE) levels in individuals sensitized to fungi appear to closely match fungal phylogenetic relationships. This close relationship between molecular fungal systematics and IgE sensitization provides an opportunity to systematically look at cross-reactivity and permits representatives from each taxon to serve as a proxy for IgE to the group.

Purification, Cloning and Immuno-Biochemical Characterization of a Fungal Aspartic Protease Allergen Rhi o 1 from the Airborne Mold Rhizopus oryzae

BACKGROUND

Fungal allergy is considered as serious health problem worldwide and is increasing at an alarming rate in the industrialized areas. Rhizopus oyzae is a ubiquitously present airborne pathogenic mold and an important source of inhalant allergens for the atopic population of India. Here, we report the biochemical and immunological features of its 44 kDa sero-reactive aspartic protease allergen, which is given the official designation 'Rhi o 1'.

METHOD

The natural Rhi o 1 was purified by sequential column chromatography and its amino acid sequence was determined by mass spectrometry and N-terminal sequencing. Based on its amino acid sequence, the cDNA sequence was identified, cloned and expressed to produce recombinant Rhi o 1. The allergenic activity of rRhi o 1 was assessed by means of its IgE reactivity and histamine release ability. The biochemical property of Rhi o 1 was studied by enzyme assay. IgE-inhibition experiments were performed to identify its cross-reactivity with the German cockroach aspartic protease allergen Bla g 2. For precise characterization of the cross-reactive epitope, we used anti-Bla g 2 monoclonal antibodies for their antigenic specificity towards Rhi o 1. A homology based model of Rhi o 1 was built and mapping of the cross-reactive conformational epitope was done using certain in silico structural studies.

RESULTS

The purified natural nRhi o 1 was identified as an endopeptidase. The full length allergen cDNA was expressed and purified as recombinant rRhi o 1. Purified rRhi o 1 displayed complete allergenicity similar to the native nRhi o 1. It was recognized by the serum IgE of the selected mold allergy patients and efficiently induced histamine release from the sensitized PBMC cells. This allergen was identified as an active aspartic protease functional in low pH. The Rhi o 1 showed cross reactivity with the cockroach allergen Bla g 2, as it can inhibit IgE binding to rBla g 2 up to certain level. The rBla g 2 was also found to cross-stimulate histamine release from the effector cells sensitized with anti-Rhi o 1 serum IgE. This cross-reactivity was found to be mediated by a common mAb4C3 recognizable conformational epitope. Bioinformatic studies revealed high degree of structural resemblances between the 4C3 binding sites of both the allergens.

CONCLUSION/SIGNIFICANCE

The present study reports for the first time anew fungal aspartic protease allergen designated as Rhi o 1, which triggers IgE-mediated sensitization leading to various allergic diseases. Here we have characterized the recombinant Rhi o 1 and its immunological features including cross-reactive epitope information that will facilitate the component-resolved diagnosis of mold allergy.

Mining Novel Allergens from Coconut Pollen Employing Manual De Novo Sequencing and Homology-Driven Proteomics

Coconut pollen, one of the major palm pollen grains is an important constituent among vectors of inhalant allergens in India and a major sensitizer for respiratory allergy in susceptible patients. To gain insight into its allergenic components, pollen proteins were analyzed by two-dimensional electrophoresis, immunoblotted with coconut pollen sensitive patient sera, followed by mass spectrometry of IgE reactive proteins. Coconut being largely unsequenced, a proteomic workflow has been devised that combines the conventional database-dependent analysis of tandem mass spectral data and manual de novo sequencing followed by a homology-based search for identifying the allergenic proteins. N-terminal acetylation helped to distinguish "b" ions from others, facilitating reliable sequencing. This led to the identification of 12 allergenic proteins. Cluster analysis with individual patient sera recognized vicilin-like protein as a major allergen, which was purified to assess its in vitro allergenicity and then partially sequenced. Other IgE-sensitive spots showed significant homology with well-known allergenic proteins such as 11S globulin, enolase, and isoflavone reductase along with a few which are reported as novel allergens. The allergens identified can be used as potential candidates to develop hypoallergenic vaccines, to design specific immunotherapy trials, and to enrich the repertoire of existing IgE reactive proteins.

Search for Allergens from the Pollen Proteome of Sunflower (Helianthus annuus L.): A Major Sensitizer for Respiratory Allergy Patients

BACKGROUND

Respiratory allergy triggered by pollen allergens is increasing at an alarming rate worldwide. Sunflower pollen is thought to be an important source of inhalant allergens. Present study aims to identify the prevalence of sunflower pollinosis among the Indian allergic population and characterizes the pollen allergens using immuno-proteomic tools.

METHODOLOGY

Clinico-immunological tests were performed to understand the prevalence of sensitivity towards sunflower pollen among the atopic population. Sera from selected sunflower positive patients were used as probe to detect the IgE-reactive proteins from the one and two dimensional electrophoretic separated proteome of sunflower pollen. The antigenic nature of the sugar moiety of the glycoallergens was studied by meta-periodate modification of IgE-immunoblot. Finally, these allergens were identified by mass-spectrometry.

RESULTS

Prevalence of sunflower pollen sensitization was observed among 21% of the pollen allergic population and associated with elevated level of specific IgE and histamine in the sera of these patients. Immunoscreening of sunflower pollen proteome with patient sera detected seven IgE-reactive proteins with varying molecular weight and pI. Hierarchical clustering of 2D-immunoblot data highlighted three allergens characterized by a more frequent immuno-reactivity and increased levels of IgE antibodies in the sera of susceptible patients. These allergens were considered as the major allergens of sunflower pollen and were found to have their glycan moiety critical for inducing IgE response. Homology driven search of MS/MS data of these IgE-reactive proteins identified seven previously unreported allergens from sunflower pollen. Three major allergenic proteins were identified as two pectate lyases and a cysteine protease.

CONCLUSION

Novelty of the present report is the identification of a panel of seven sunflower pollen allergens for the first time at immuno-biochemical and proteomic level, which substantiated the clinical evidence of sunflower allergy. Further purification and recombinant expression of these allergens will improve component-resolved diagnosis and therapy of pollen allergy.

Proteomic analysis and candidate allergenic proteins in Populus deltoides CL. "2KEN8" mature pollen

Proteomic analysis was used to generate a map of Populus deltoides CL. "2KEN8" mature pollen proteins. By applying 2-D electrophoresis, we resolved 403 protein spots from mature pollen. Using the matrix-assisted laser desorption/ionization time time-of-flight/time-of-flight tandem mass spectrometry method, we identified 178 distinct proteins from 218 protein spots expressed in mature pollen. Moreover, out of these, 28 proteins were identified as putative allergens. The expression patterns of these putative allergen genes indicate that several of these genes are highly expressed in pollen. In addition, the members of profilin allergen family were analyzed and their expression patterns were compared with their homologous genes in Arabidopsis and rice. Knowledge of these identified allergens has the potential to improve specific diagnosis and allergen immunotherapy treatment for patients with poplar pollen allergy.

Immunoproteomic analysis reveals a convergent humoral response signature in the Sporothrix schenckii complex

Sporotrichosis is a polymorphic disease that affects both humans and animals worldwide. The fungus gains entry into a warm-blooded host through minor trauma to the skin, typically by contaminated vegetation or by scratches and bites from a diseased cat. Cellular and humoral responses triggered upon pathogen introduction play important roles in the development and severity of the disease. We investigated molecules expressed during the host-parasite interplay that elicit the humoral response in human sporotrichosis. For antigenic profiling, Sporothrix yeast cell extracts were separated by two-dimensional (2D) gel electrophoresis and probed with pooled sera from individuals with fixed cutaneous and lymphocutaneous sporotrichosis. Thirty-five IgG-seroreactive spots were identified as eight specific proteins by MALDI-ToF/MS. Remarkable cross-reactivity among Sporothrix brasiliensis, Sporothrix schenckii, and Sporothrix globosa was noted and antibodies strongly reacted with the 70-kDa protein (gp70), irrespective of clinical manifestation. Gp70 was successfully identified in multiple spots as 3-carboxymuconate cyclase. In addition, 2D-DIGE characterization suggested that the major antigen of sporotrichosis undergoes post-translational modifications involving glycosylation and amino acid substitution, resulting in at least six isoforms and glycoforms that were present in the pathogenic species but absent in the ancestral non-virulent Sporothrix mexicana. Although a primary environmental function related to the benzoate degradation pathway of aromatic polymers has been attributed to orthologs of this molecule, our findings support the hypothesis that gp70 is important for pathogenesis and invasion in human sporotrichosis. We propose a diverse panel of new putative candidate molecules for diagnostic tests and vaccine development.

BIOLOGICAL SIGNIFICANCE

Outbreaks due to Sporothrix spp. have emerged over time, affecting thousands of patients worldwide. A sophisticated host-pathogen interplay drives the manifestation and severity of infection, involving immune responses elicited upon traumatic exposure of the skin barrier to the pathogen followed by immune evasion. Using an immunoproteomic approach we characterized proteins of potential significance in pathogenesis and invasion that trigger the humoral response during human sporotrichosis. We found gp70 to be a cross-immunogenic protein shared among pathogenic Sporothrix spp. but absent in the ancestral environmental S. mexicana, supporting the hypothesis that gp70 plays key roles in pathogenicity. For the first time, we demonstrate with 2D-DIGE that post-translational modifications putatively involve glycosylation and amino acid substitution, resulting in at least six isoforms and glycoforms, all of them IgG-reactive. These findings of a convergent humoral response highlight gp70 as an important target serological diagnosis and for vaccine development among phylogenetically related agents of sporotrichosis.