Development of a Dot-Blot Assay for the Detection of Mould-Specific IgE in the Belgian Population

Aspergillus fumigatus Recognition by Dendritic Cells Negatively Regulates Allergic Lung Inflammation through a TLR2/MyD88 Pathway

Aspergillus fumigatus is an opportunistic fungal pathogen responsible for a spectrum of clinical manifestations. Dendritic cells recognize pathogen-associated molecular patterns of Aspergillus via two main receptor families, Toll-like receptors (TLRs) and C-type lectin receptors (CLR). Here, the importance of TLR and CLR signaling in the regulation of T-helper cell type 2 (Th2) responses was analyzed using a mouse model based on the transfer of bone marrow-derived dendritic cells (BMDCs) pulsed with A. fumigatus conidia. BMDCs were generated from mice deficient in either MyD88 or MALT1 (mucosa-associated lymphoid tissue lymphoma translocation protein 1). Both the MyD88 and MALT1 signaling pathway in BMDCs contributed to the production of inflammatory cytokines induced by A. fumigatus conidia. Mice sensitized with MyD88^-/- BMDCs pulsed in vitro with A. fumigatus conidia showed an exacerbated allergic inflammation, with stronger eosinophil recruitment in the BAL and higher Th2 cytokine production compared with mice sensitized with wild-type or MALT1^-/- BMDCs. This exacerbation was not observed when MyD88^-/- BMDCs were pulsed with Cladosporium sphaerospermum, a nonpathogenic mold. A lack of TLR2 signaling recapitulated the exacerbation of the A. fumigatus Th2 response observed in the absence of MyD88 signaling, whereas TLR2 agonist dampened the response induced with A. fumigatus and C. sphaerospermum conidia. IL-10 production by BMDCs in response to A. fumigatus was dependent on the expression of TLR2 and MyD88. IL-10^-/- BMDCs exacerbated, whereas MyD88^-/- BMDCs supplemented with exogenous IL-10 decreased the allergic pulmonary inflammation. These results indicate that TLR2/MyD88-specific recognition of PAMPs from A. fumigatus conidia can upregulate IL-10 production and downregulate lung eosinophilia and the development of a Th2 response.

Kids, Difficult Asthma and Fungus

Fungi have many potential roles in paediatric asthma, predominantly by being a source of allergens (severe asthma with fungal sensitization, SAFS), and also directly damaging the epithelial barrier and underlying tissue by releasing proteolytic enzymes (fungal bronchitis). The umbrella term ‘fungal asthma’ is proposed for these manifestations. Allergic bronchopulmonary aspergillosis (ABPA) is not a feature of childhood asthma, for unclear reasons. Diagnostic criteria for SAFS are based on sensitivity to fungal allergen(s) demonstrated either by skin prick test or specific IgE. In children, there are no exclusion criteria on total IgE levels or IgG precipitins because of the rarity of ABPA. Diagnostic criteria for fungal bronchitis are much less well established. Data in adults and children suggest SAFS is associated with worse asthma control and greater susceptibility to asthma attacks than non-sensitized patients. The data on whether anti-fungal therapy is beneficial are conflicting. The pathophysiology of SAFS is unclear, but the epithelial alarmin interleukin-33 is implicated. However, whether individual fungi have different pathobiologies is unclear. There are many unanswered questions needing further research, including how fungi interact with other allergens, bacteria, and viruses, and what optimal therapy should be, including whether anti-neutrophilic strategies, such as macrolides, should be used. Considerable further research is needed to unravel the complex roles of different fungi in severe asthma.

Relationship between mold exposure, specific IgE sensitization, and clinical asthma: A case-control study

BACKGROUND

Most of the findings related to the noxious effect of mold sensitization on asthma come from investigations based on Alternaria alternata, Cladosporium herbarum, and Aspergillus fumigatus. However, species such as Penicillium spp, Cladosporium sphaerospermum, Cladosporium cladosporioides, or Aspergillus versicolor display a more pronounced indoor tropism, and their potential harmful respiratory effects cannot be neglected.

OBJECTIVE

The goal of this work was to relate mold sensitizations with asthma severity and with the level of indoor mold contamination among mold-sensitized patients with asthma and nonsensitized patients with asthma.

METHODS

A case-control study was conducted and several asthma severity markers were compared between patients with asthma with and without mold sensitization. Indoor contamination of patients' dwellings was also investigated.

RESULTS

Our findings confirmed the association between sensitization to A fumigatus and severity for patients with asthma in contrast with sensitization to other species. Indoor mold contamination was detected in approximately 90% of dwellings. Overall mold exposure was not associated with asthma severity. However, regardless of the sensitization, exposure to A fumigatus and Penicillium spp in dust was linked to an increased risk of severe asthma.

CONCLUSION

The harmful nature of mold sensitization and mold exposure for patients with asthma was not confirmed in this study. However, sensitization to A fumigatus was associated with an increased risk for severe asthma. A better investigation of the properties of Penicillium spp is recommended because its exposure was found to be associated with a more pronounced impairment of lung function.

Investigation of inflammatory and allergic responses to common mold species: Results from in vitro experiments, from a mouse model of asthma, and from a group of asthmatic patients

Most studies on molds focus on Alternaria alternata and Aspergillus fumigatus. Here, we report on inflammatory and allergenic properties of more typical indoor species Aspergillus versicolor, P. chrysogenum, C. cladosporioïdes, and C. sphaerospermum that were compared to A. alternata and A. fumigatus. In a mouse model, after intranasal instillation, A. alternaria, A. versicolor, and C. sphaerospermum induced the early recruitment of neutrophils and the strong expression of inflammatory markers in the bronchoalveolar lavages fluids. A. fumigatus also induced the early accumulation of neutrophils but with lower levels of inflammatory markers. Chronic treatment induced variable response according to species: P. chrysogenum and A. fumigatus appeared strong pro-allergenic inducers compared to A. alternata and C. sphaerospermum while A. versicolor and C. cladosporioides induced a mixed pro-allergenic/pro-inflammatory response. In mold-sensitized asthmatics, mold-specific Immunoglobulin E (IgE) were detected with an in-house dot-blot assay. A. fumigatus and A. alternata were the most frequent sensitizers. Altogether, P. chrysogenum, P. brevicompactum, C. sphaerospermum, and C. cladosporïoides were the "major sensitizer" (defined as the strongest response against a single mold species) for almost 30% of the asthmatics. These results show that, not only A. alternata and A. fumigatus, but also indoor species have strong inflammatory and allergic properties and a harmful potency.