Engineered Alt a 13 Fragment of Alternaria alternata Abrogated IgE Binding without Affecting T-cell Stimulation

Mechanisms of Alternaria pathogenesis in animals and plants

Alternaria species are cosmopolitan fungi darkly pigmented by melanin that infect numerous plant species causing economically important agricultural spoilage of various food crops. Alternaria spp. also infect animals, being described as entomopathogenic fungi but also infecting warm-blooded animals, including humans. Their clinical importance in human health, as infection agents, lay in the growing number of immunocompromised patients. Moreover, Alternaria spp. are considered some of the most abundant and potent sources of airborne sensitizer allergens causing allergic respiratory diseases, as severe asthma. Among the numerous strategies deployed by Alternaria spp. to attack their hosts, the production of toxins, carrying critical concerns to public health as food contaminant, and the production of hydrolytic enzymes such as proteases, can be highlighted. Alternaria proteases also trigger allergic symptoms in individuals with fungal sensitization, acting as allergens and facilitating antigen access to the host subepithelium. Here, we review the current knowledge about the mechanisms of Alternaria pathogenesis in plants and animals, the strategies used by Alternaria to cope with the host defenses, and the involvement Alternaria allergens and mechanisms of sensitization.

Changes in the Sensitization Pattern to Alternaria alternata Allergens in Patients Treated with Alt a 1 Immunotherapy

Alternaria alternata is the most important allergenic fungus, with up to 20% of allergic patients affected. The sensitization profile of patients sensitized to A. alternata and how it changes when treated with immunotherapy is not known. Our objective is to determine the allergen recognition pattern of allergic patients to A. alternata and to study its association to the parameters studied in a clinical trial recently published. Sera of 64 patients from the clinical trial of immunotherapy with native major allergen Alt a 1 were analyzed by immunoblotting; 98. 4% of the patients recognized Alt a 1. The percentage of recognition for Alt a 3, Alt a 4, and/or Alt a 6, Alt a 7, Alt a 8, Alt a 10 and/or Alt a 15 was 1.6%, 21.9%, 12.5%, 12.5%, and 12.5% respectively. Of the 64 patients, 45 (70.3%) only recognized Alt a 1 among the allergens present in the A. alternata extract. Immunotherapy with Alt a 1 desensitizes treated patients, reducing their symptoms and medication consumption through the elimination of Alt a 1 sensitization, which is no longer present in the immunoblotting of some patients. There may be gender differences in the pattern of sensitization to A. alternata allergens, among others.

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.

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.

Preclinical safety and immunological efficacy of Alternaria alternata polymerized extracts

Introduction

Alternaria alternata is a widespread fungi whose allergy is a risk factor for asthma development. The use of a polymerized allergen extract (allergoid) may be safer than native extract based treatments while maintaining efficacy. The objective of this study was to characterize biochemically and immunochemically a new Alternaria alternata allergoid.

Methods

Characterization of native and allergoid extracts was performed by determination of protein content, protein and allergenic profile, biological potency, identification of Alternaria allergens, and Alt a 1 quantification. Safety was evaluated in toxicological assays (Ames test, limit test, and fish embryo acute toxicity test in zebrafish, and maximum tolerated dose and Dose‐range finding study in rats). Efficacy was evaluated as the capacity to induce IgG antibodies that block IgE‐binding to the allergen and cytokine induction (IFN‐γ, IL‐4, IL‐6, IL‐10, and TNF‐α) in PBMC from atopic donors.

Results

Protein and antigenic profiles showed significant modification of the depigmented allergoid with respect to the native extract, inducing a lower IgE binding capacity. Alt a 1, Alt a 3, Alt a 6, and Alt a 8 allergen sequences were identified in the polymer. No toxicological nor genotoxicity effects were observed. The polymer induced IgG antibodies that blocked human IgE binding epitopes, and it induced higher IL‐10 levels and similar levels of the other cytokines than native extract in PBMC.

Conclusions

This new A. alternata allergoid could be an effective immunotherapy treatment leading to cytokine stimulation and inducing synthesis of IgG antibodies able to block IgE binding to the allergen. In addition, no toxicological effect was observed, and it may be safer than native extract due to its lower IgE binding capacity and cytokine induction that suggest tolerance induction via T cell shift to Treg (IL‐10).

Alternaria alternata allergens: Markers of exposure, phylogeny and risk of fungi-induced respiratory allergy

Alternaria alternata spores are considered a well-known biological contaminant and a very common potent aeroallergen source that is found in environmental samples. The most intense exposure to A. alternata allergens is likely to occur outdoors; however, Alternaria and other allergenic fungi can colonize in indoor environments and thereby increase the fungal aeroallergen exposure levels. A consequence of human exposure to fungal aeroallergens, sensitization to A. alternata, has been unequivocally associated with increased asthma severity. Among allergenic proteins described in this fungal specie, the major allergen, Alt a 1, has been reported as the main elicitor of airborne allergies in patients affected by a mold allergy and considered a marker of primary sensitization to A. alternata. Moreover, A. alternata sensitization seems to be a triggering factor in the development of poly-sensitization, most likely because of the capability of A. alternata to produce, in addition to Alt a 1, a broad and complex array of cross-reactive allergens that present homologs in several other allergenic sources. The study and understanding of A. alternata allergen information may be the key to explaining why sensitization to A. alternata is a risk factor for asthma and also why the severity of asthma is associated to this mold. Compared to other common environmental allergenic sources, such as pollens and dust mites, fungi are reported to be neglected and underestimated. The rise of the A. alternata allergy has enabled more research into the role of this fungal specie and its allergenic components in the induction of IgE-mediated respiratory diseases. Indeed, recent research on the identification and characterization of A. alternata allergens has allowed for the consideration of new perspectives in the categorization of allergenic molds, assessment of exposure and diagnosis of fungi-induced allergies.

Alternaria alternata and its allergens: a comprehensive review

Alternaria alternata is mainly an outdoor fungus whose spores disseminate in warm, dry air, so in temperate climates, their count peaks in the summers. Alternaria may also be found in damp, insufficiently ventilated houses, where its allergenic properties cocreate the sick building syndrome. Mold-induced respiratory allergies and research on Alternaria both have a lengthy history: the first was described as early as 1698 and the second dates back to 1817. However, the two were only linked in 1930 when Alternaria spores were found to cause allergic asthma. The allergenic extracts from Alternaria hyphae and spores still remain in use but are variable and insufficiently standardized as they are often a random mixture of allergenic ingredients and coincidental impurities. In contrast, contemporary biochemistry and molecular biology make it possible to obtain pure allergen molecules. To date, 16 allergens of A. alternata have been isolated, many of which are enzymes: Alt a 4 (disulfide isomerase), Alt a 6 (enolase), Alt a 8 (mannitol dehydrogenase), Alt a 10 (alcohol dehydrogenase), Alt a 13 (glutathione-S-transferase), and Alt a MnSOD (Mn superoxide dismutase). Others have structural and regulatory functions: Alt a 5 and Alt a 12 comprise the structure of large ribosomal subunits and mediate translation, Alt a 3 is a molecular chaperone, Alt a 7 regulates transcription, Alt a NTF2 facilitates protein import into the nucleus, and Alt a TCTP acts like a cytokine. The function of four allergenic proteins, Alt a 1, Alt a 2, Alt a 9, and Alt a 70 kDa, remains unknown.

Mold allergens in respiratory allergy: from structure to therapy

Allergic reactions to fungi were described 300 years ago, but the importance of allergy to fungi has been underestimated for a long time. Allergens from fungi mainly cause respiratory and skin symptoms in sensitized patients. In this review, we will focus on fungi and fungal allergens involved in respiratory forms of allergy, such as allergic rhinitis and asthma. Fungi can act as indoor and outdoor respiratory allergen sources, and depending on climate conditions, the rates of sensitization in individuals attending allergy clinics range from 5% to 20%. Due to the poor quality of natural fungal allergen extracts, diagnosis of fungal allergy is hampered, and allergen-specific immunotherapy is rarely given. Several factors are responsible for the poor quality of natural fungal extracts, among which the influence of culture conditions on allergen contents. However, molecular cloning techniques have allowed us to isolate DNAs coding for fungal allergens and to produce a continuously growing panel of recombinant allergens for the diagnosis of fungal allergy. Moreover, technologies are now available for the preparation of recombinant and synthetic fungal allergen derivatives which can be used to develop safe vaccines for the treatment of fungal allergy.

Characterization of recombinant per a 10 from Periplaneta americana

Cockroach allergen is a major risk factor for IgE-mediated allergic response and asthma in sensitized individuals. Serine proteases have been identified from various sources and characterized as major allergens. The present study was aimed to express and characterize recombinant allergen Per a 10 (rPer a 10) from Periplaneta americana. rPer a 10 was expressed in Escherichia coli and purified in soluble form, yielding 0.75 mg/liter of culture. Homology of the Per a 10 protein sequence exhibited 27 to 38% similarity to the mite serine protease and 41 to 52% similarity to other insect trypsins. The purified rPer a 10 protein resolved at 28 kDa on SDS-PAGE and was recognized by cockroach-hypersensitive patients' sera by immunoblotting and enzyme-linked immunosorbent assay (ELISA). In competitive ELISA, rPer a 10 required 96 ng of purified protein for 50% inhibition of IgE binding, whereas 34 ng of native protein (nPer a 10) was required for the same inhibition. rPer a 10 and nPer a 10 induced basophil histamine release in the range of 47 to 64% and 60 to 85%, respectively, when sensitized with cockroach-hypersensitive patients' sera. In conclusion, Per a 10 was subcloned, and the protein was purified to homogeneity. rPer a 10 showed reduced IgE binding and histamine release and showed no proteolytic activity. These data suggest that rPer a 10 has potential for immunotherapy.

A rare case of allergic bronchopulmonary mycosis caused by Alternaria alternata

A rare case of allergic bronchopulmonary mycosis (ABPM), caused by Alternaria alternata, is reported in an immunocompetent resident of Delhi. Her complaints included a generalized, urticarial skin rash and occasional pain in the right lower chest. Her differential count showed eosinophils, 22%; absolute eosinophil count (AEC), 2400 cells/μl; and total IgE, 4007 IU/ml. The computerised tomogram (CT) scan of her thorax showed an enhancing lesion with surrounding ground glass haziness in the right lower lobe. Histopathologic examination of the resected lung revealed a necrotizing granulomatous inflammation, parenchymal infiltration by eosinophils, lymphocytes, neutrophils, plasma cells and some exudative bronchiolitis suggestive of ABPM. Observation of KOH wet mounts of repeat sputum and BAL samples demonstrated the presence of septate, brownish hyphae and cultures of these specimens yielded A. alternata (identified by sequencing of the ITS region). Her serum showed a three-fold higher specific IgE to A. alternata antigens than control levels, and the type I cutaneous hypersensitivity response to antigens of A. alternata was strongly positive. She was treated successfully with oral glucocorticoids and itraconazole. To our knowledge, ABPM due to Alternaria alternata has not been reported previously.

Schizophyllum commune as an emerging fungal pathogen: a review and report of two cases

We report Schizophyllum commune as the aetiological agent of one case each of allergic broncho-pulmonary mycosis (ABPM) and pulmonary fungal ball, and present a literature review. The fungus was characterised by clamp connections, hyphal spicules, and formation of basidiocarps with basidiospores. The phenotypic identification was confirmed by sequencing of the ITS region. To-date, ABPM and pulmonary fungal ball to S. commune have been reported exclusively from Japan and North America respectively. Of the 71 globally reported cases due to S. commune, 45 (63%) were bronchopulmonary, 22 (31%) sinusitis and 4 extrapulmonary. Taken together, cases of bronchopulmonary disease and sinusitis numbered 67 (94%), indicating the respiratory tract as the primary target of disease. Concerning the country-wise distribution, Japan topped the list with 33 cases (46%), followed by Iran - 7 cases (10%), U.S.A. - 6 cases (9%), and a lower prevalence of 1.4-6% for the remaining 12 countries. The preponderance of the disease in Japan may be attributed to its greater awareness vis-à-vis that in other countries rather than to any geographical/climatic factors. We believe that the burden of S. commune-incited disease is currently underestimated, warranting comprehensive prospective studies to determine its prevalence.

Mutated glutathione-S-transferase reduced airway inflammation by limiting oxidative stress and Th2 response

Oxidative stress is an important factor in the pathogenesis of asthma. Furthermore, antioxidants like GST are reduced in asthma patients. In the present study, the therapeutic effects of exogenous GST and mGST were evaluated in a mice model. GST mutated at residues 21/27 has reduced IgE binding with similar enzyme activity as that of GST. To evaluate the therapeutic effects of GST, BALB/c mice were immunized and challenged with ovalbumin. Mice were given GST, mGST, and alpha-lipoic acid by inhalation and sacrificed on Day 31 to evaluate inflammation and oxidative stress. Mice treated with mGST showed significantly reduced total cell count (P<0.01) and eosinophils (P<0.01) in BALF compared to GST- or PBS-treated groups. The lung inflammation score was lowest for the mGST-treated group along with reduced IL-4 (P<0.01) and OVA-specific IgE than other groups. Oxidative stress as per the lipid peroxidation level in BALF of mGST-treated mice was reduced significantly in comparison to PBS- or GST-treated mice. In conclusion, inhalation of mGST reduced airway inflammation in mice. Mutated GST with reduced allergenicity has better therapeutic potential and can be explored as an adjunct therapy in asthma.