Isolation and immunological characterization of a novel Cladosporium herbarum allergen structurally homologous to the α/β hydrolase fold superfamily

Characterizing the Fungal Microbiome in Date (Phoenix dactylifera) Fruit Pulp and Peel from Early Development to Harvest

Date palm (Phoenix dactylifera) is considered to be a highly important food crop in several African and Middle Eastern countries due to its nutritional value and health-promoting properties. Microbial contamination of dates has been of concern to consumers, but very few works have analyzed in detail the microbial load of the different parts of date fruit. In the present work, we characterized the fungal communities of date fruit using a metagenomic approach, analyzing the data for differences between microbial populations residing in the pulp and peel of “Medjool” dates at the different stages of fruit development. The results revealed that Penicillium, Cladosporium, Aspergillus, and Alternaria were the most abundant genera in both parts of the fruit, however, the distribution of taxa among the time points and tissue types (peel vs. pulp) was very diverse. Penicillium was more abundant in the pulp at the green developmental stage (Kimri), while Aspergillus was more frequent in the peel at the brown developmental stage (Tamer). The highest abundance of Alternaria was detected at the earliest sampled stage of fruit development (Hababauk stage). Cladosporium had a high level of abundance in peel tissues at the Hababauk and yellow (Khalal) stages. Regarding the yeast community, the abundance of Candida remained stable up until the Khalal stage, but exhibited a dramatic increase in abundance at the Tamer stage in peel tissues, while the level of Metschnikowia, a genus containing several species with postharvest biocontrol activity, exhibited no significant differences between the two tissue types or stages of fruit development. This work constitutes a comprehensive metagenomic analysis of the fungal microbiome of date fruits, and has identified changes in the composition of the fungal microbiome in peel and pulp tissues at the different stages of fruit development. Notably, this study has also characterized the endophytic fungal microbiome present in pulp tissues of dates.

Suppressive subtractive hybridization reveals different gene expression between high and low virulence strains of Cladosporium cladosporioides

Cladosporium cladosporioides is a ubiquitous fungus, causing infections in plants, humans, and animals. Suppression subtractive hybridization (SSH) and quantitative real-time PCR (qRT-PCR) were used in this study to identify differences in gene expression between two C. cladosporioides strains, the highly virulent Z20 strain and the lowly virulent Zt strain. A total of 61 unigenes from the forward library and 42 from the reverse library were identified. Gene ontology (GO) analysis showed that these genes were involved in various biological processes, cellular components and molecular functions. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that the unigenes in the forward library corresponded to 5 different pathways and the reverse library unigenes were involved in 3 different pathways. The qRT-PCR results indicated that expressions of APL1, GUD1, CSE1, SPBC3E7.04c and MFS were significantly different between Z20 and Zt strains, while genes encoding the senescence-associated proteins, pse1, nup107, mip1, pex2, icl1 and α/β hydrolase exhibited no significant differences between the two strains. In addition, we found that 5 unigenes encoding mip1, chk1, icl1, α/β hydrolase and β-glucosidase may be associated with pathogenicity. One unigene (MFS) may be related to the resistance to 14 α-demethylase inhibitor fungicides, and 5 unigenes (PEX2, NUP107, PSE1, APL1, and SPBC3E7.04c) may be related to either low spore yield or earlier aging of the Zt strain. Our study may help better understand the molecular mechanism of C. cladosporioides infection, and therefore improve the treatment and prevention of C. cladosporioides induced diseases.

Fungi: the neglected allergenic sources

Allergic diseases are considered the epidemics of the twentieth century estimated to affect more than 30% of the population in industrialized countries with a still increasing incidence. During the past two decades, the application of molecular biology allowed cloning, production and characterization of hundreds of recombinant allergens. In turn, knowledge about molecular, chemical and biologically relevant allergens contributed to increase our understanding of the mechanisms underlying IgE-mediated type I hypersensitivity reactions. It has been largely demonstrated that fungi are potent sources of allergenic molecules covering a vast variety of molecular structures including enzymes, toxins, cell wall components and phylogenetically highly conserved cross-reactive proteins. Despite the large knowledge accumulated and the compelling evidence for an involvement of fungal allergens in the pathophysiology of allergic diseases, fungi as a prominent source of allergens are still largely neglected in basic research as well as in clinical practice. This review aims to highlight the impact of fungal allergens with focus on asthma and atopic dermatitis.

Transaldolases are novel and immunoglobulin E cross-reacting fungal allergens

BACKGROUND

Mould-induced atopic respiratory diseases are a worldwide problem. Characterization of fungal allergens is of major clinical importance.

OBJECTIVE

We identified a novel transaldolase family allergen of Cladosporium and Penicillium species.

METHODS

Fungal allergens were identified by immunoblotting, peptide mass mapping and partial sequencing, cDNA cloning and IgE epitope mapping.

RESULTS

A 36.5 kDa IgE-binding component in a partially purified C. cladosporioides preparation was identified. Mass spectrometric analyses suggest that this novel IgE-reacting allergen is a transaldolase. A corresponding full-length 1246 bp cDNA encoding a polypeptide of 325 residues was isolated. The newly identified transaldolase allergen has been designated as Cla c 14.0101. The cDNA encoding the Pencillium chrysogenum transaldolase was isolated by RT-PCR according to the cDNA sequence encoding a P. chrysogenum Wisconsin 54-1255 hypothetical protein. The purified rCla c 14.0101 protein reacted with IgE antibodies in 10 (38%) of 26 Cladosporium cladosporioides-sensitized asthmatic patients. Nine of the 10 rCla c 14.0101-positive sera have IgE binding against the recombinant Penicillium transaldolase (rPen ch 35.0101). Among the eight fungal transaldolase-positive sera tested, three showed IgE binding against the recombinant human transaldolase. To determine cross-reactivity between the Cladosporium and Penicillium fungi, IgE cross-reactivity was detected between these two fungal transaldolase allergens by inhibition assays. Both the N- and the C-terminal fragments of Cla c 14.0101 were recognized by IgE antibodies. The C-terminal IgE-reacting determinant was narrowed down to a region encompassing Thr257 to Ser278 of Cla c 14.0101. It was mapped onto a loop-like structure of a 3D model constructed for Cla c 14.0101.

CONCLUSION AND CLINICAL RELEVANCE

We identified transaldolase as a novel and IgE cross-reactive allergen family of C. cladosporioides and P. chrysogenum. In addition, an IgE-reacting fragment (Thr257 to Ser278) was pinpointed to a loop-like structure on Cla c 14.0101. Results obtained provide important information in clinical mould allergy.