Malassezia sympodialis differently affects the expression of LL-37 in dendritic cells from atopic eczema patients and healthy individuals

BACKGROUND

Atopic eczema (AE) is a multifactorial disease, which has increased in prevalence. The skin-colonizing yeast Malasezzia sympodialis can induce IgE- and T-cell reactivity in patients with AE. LL-37 is an endogenous peptide antibiotic belonging to the cathelicidin family. The aim of this study was to examine whether exposure to M. sympodialis would affect the expression of LL-37 in dendritic cells.

METHODS

The presence of LL-37 was analyzed in monocyte-derived dendritic cells (MDDCs) generated from healthy individuals and patients with AE by Western blotting and the corresponding cDNA by real-time quantitative RT-PCR. Antibacterial activity was measured with an inhibition zone assay in fractions after reverse phase chromatography.

RESULTS

For the first time we here present data, showing that LL-37 is produced by MDDCs. Notably, the secretion of LL-37 was substantially enhanced in M. sympodialis-exposed MDDCs generated from patients with a high degree of eczema, as measured by SCORAD, compared to healthy controls and patients with a low SCORAD. The relative expression of LL-37 transcript in MDDCs generated from patients was up-regulated after 1 h of exposure to M. sympodialis and declined gradually at the time points analyzed, whereas the transcription was unaffected in the MDDCs of healthy controls.

CONCLUSIONS

Our results suggest that M. sympodialis can trigger the innate immune response differently in patients with AE and healthy individuals. The enhanced LL-37 secretion from the MDDCs in the patients with AE may reflect the severity of their inflammatory response to M. sympodialis.

Serum IgE reactivity to Malassezia furfur extract and recombinant M. furfur allergens in patients with atopic dermatitis

IgE reactivity to the opportunistic yeast Malassezia furfur can be found in patients with atopic dermatitis (AD). We have previously cloned and expressed 6 recombinant allergens (rMal f 1, rMal f 5-9) from M. furfur. In the present study, we used ImmunoCAP to investigate whether these rMal f allergens can be useful in the diagnosis of M. furfur-associated AD compared with the M. furfur extract. A total of 156 adult patients with a clinical diagnosis of AD participated in the study. Sixty-four percent had increased total serum IgE levels, 79% had specific IgE antibodies to common inhalant allergens and 47% had IgE antibodies to M. furfur extract. IgE antibodies to any of the rMal f allergens were detected among 86 (55%) of the patients, 14 (16%) of whom did not react to the M. furfur extract. Any individual rMal f allergen detected between 32% and 89% of the patients ImmunoCAP-positive to the M. furfur extract, with the highest sensitivity for rMal f 9. Therefore, a couple of individual rMal f allergens can improve the diagnosis of M. furfur-associated IgE allergies in patients with AD.

Cloning, characterization and expression of complete coding sequences of three IgE binding Malassezia furfur allergens, Mal f 7, Mal f 8 and Mal f 9

Malassezia furfur, formerly known as Pityrosporum orbiculare or P. ovale, is a yeast that colonizes human skin. Normally, this yeast is nonpathogenic but under the influence of predisposing factors it may induce IgE reactivity in patients with atopic dermatitis. Approximately 40-65% of atopic dermatitis patients have IgE antibodies and/or skin reactivity against M. furfur and a higher T-cell response against this yeast is found in atopic dermatitis patients than in healthy individuals. By making a cDNA library displayed on a phage surface, we previously cloned five different IgE-binding proteins, Mal f 5, Mal f 6, MF 7, MF 8 and MF 9, from this yeast. The cDNAs encoding these allergens were sequenced and expressed in Escherichia coli. The sequences of MF 7, MF 8 and MF 9 were not full length (missing their 5'-ends) giving only partial gene products. To obtain complete cDNA sequences, we performed RACE-PCR to amplify the 5'-ends of each cDNA. These PCR products were sequenced and analyzed. The coding sequences of Mal f 7, Mal f 8 and Mal f 9 encode proteins with ORFs of 141 (16.2 kDa), 179 (19.2 kDa) and 126 (14.0 kDa) amino-acid residues, respectively. None of the putative proteins showed significant sequence homology with other known proteins in the searched database. The proteins encoded by the complete cDNA sequences were expressed in E. coli as recombinant proteins. Immunoblotting and radioallergosorbant test data showed that all of the expressed recombinant proteins have the ability to bind serum IgE from atopic dermatitis patients and furthermore, the M. furfur extract could specifically inhibit this IgE binding.