Fungal exposure had been repeatedly associated with a wide range of harmful health effects. The first association between mould exposure and asthma exacerbations was reported almost 300 years ago and since then, they are numerous data on the link between mould sensitization and asthma severity. Most of the data on fungi and asthma concern A. alternata, C. herbarum and A. fumigatus. However, some mould species are known for their more pronounced indoor tropism and since people tend to increase their time spent indoors, the impact of exposure to these “indoor” species cannot be neglected. In the first part of this work, we developed and validated a dot-blot assay for the detection of mould sensitizations against a panel of species. We worked with the classical A. alternata, C. herbarum and A. fumigatus but in addition, we included indoor-related species such as P. chrysogenum, P. brevicompactum, C. sphaerospermum, C. cladosporioides, A. versicolor and more ubiquitous A. niger, and A. flavus. The development of such an assay allowed us to detect sensitizations against species that are not routinely investigated or not available for testing with classical methods such as skin prick tests or CAP tests. In addition, to cope with cross-reactions, a well-described phenomenon with regard to response against moulds, we developed and validated the concept of “major sensitization”, defined as the antigenic response with the highest difference as compared to the variation of response of the negative control. As there are few data on mould sensitization in healthy individuals, the dot-blot assay was used in a large cohort of healthy subjects. The most frequent sensitizations were observed against A. alternata, A. flavus and A. niger and the commonest “major sensitizers” were A. niger and A. alternata. Of note, in this cohort, no “major sensitization” against A. fumigatus was detected while “major sensitization” against a group of species more specifically linked to the indoor environment (Penicillium spp, A. versicolor, C. cladosporioides) reached more than 25.1% of all sensitizations.These findings were quite surprising and since our laboratory had previous expertise with mouse-model of A. alternata-induced asthma, we investigated the inflammatory and allergenic properties of several fungal species to determine if they display different inner inflammatory potential. Six species were included in the panel A. alternata, A. fumigatus, C. cladosporioides, C. sphaerospermum, A. versicolor and P. chrysogenum. Results showed real differences between moulds and while the classification is not clear-cut, A. fumigatus or P. chrysogenum triggered a typical pro-Th2 response, A. alternata and C. sphaerospermum rather induced a neutrophilic inflammation and A. versicolor and C. cladosporioides induced a mixed Th2/Th17 response. In parallel, the sensitization rates and profile were also investigated in a group of mould-sensitized asthmatics and they both differed notably with the healthy cohort. Indeed, in asthmatic patients, the two most frequent major sensitizations were against A. fumigatus (32%) and A. alternata (28%). The last part of the work consisted in a case-control study to evaluate and compare asthma severity markers and indoor mould exposure between the group of mould-sensitized asthmatics (cases) and a group of asthmatics without mould sensitization (controls). Some interesting findings emerged from this study. First, the overall mould contamination (airborne, in settled dust or through visible mould marks) was very high and more than 90% of the visited dwellings were contaminated by at least one mould species/genus (Penicillium spp, A. versicolor, A. fumigatus and C. sphaerospermum) in at least one type of sample (air, dust and visible mould imprints). Of note, overall “indoor mould exposure” was not associated with markers of asthma severity. Second, exposure and sensitization but also sensitization alone to A. fumigatus in asthmatics were associated with asthma severity markers compared to the absence of mould sensitization which confirmed its noxious potential. This contrasted with the absence of significant severity markers associated with other sensitizations. Lastly, we observed a positive link between overall indoor exposure to Penicillium spp and a reduced lung function in asthmatics even in the absence of sensitization. / Doctorat en Sciences biomédicales et pharmaceutiques (Médecine) / info:eu-repo/semantics/nonPublished

La contamination fongique des produits laitiers est à l’origine de pertes économiques conséquentes et de gaspillage alimentaire. Dans un contexte de demande pour plus de « naturalité », les cultures de bioprotection et leurs métabolites représentent une alternative d’intérêt aux conservateurs chimiques pour lutter contre ces contaminants.Les objectifs de cette thèse étaient i) de sélectionner des micro-organismes présentant une activité antifongique, pour élaborer des cultures de bioprotection applicables dans des produits laitiers, et ii) d’étudier les composés potentiellement supports de l’activité antifongique observée. Dans un premier temps, l’activité antifongique de 32 souches de bactéries lactiques et propioniques a été étudiée en modèles « fromage » et « yaourt ». L’étude de combinaisons de souches et de leur innocuité a conduit à sélectionner 2 combinaisons binaires de lactobacilles (A1 et A3). Leur efficacité et applicabilité a été évaluée à l’échelle pilote en fabrication de crème fraîche et de fromage.Les challenges tests et tests d’usages ont montré que selon le produit laitier, A1 et A3 ont une activité antifongique similaire ou supérieure que les cultures bioprotectrices commerciales. Selon l’inoculum ajouté, ces cultures n’impactent pas les caractéristiques technologiques et organoleptiques des produits laitiers. Des méthodes chromatographiques des composés antifongiques suivies d’analyses statistiques ont permis de mettre en évidence des « cocktails » de 2 à 17 composés, selon la matrice et la culture considérée, qui sont probablement supports de l’activité antifongique.Ces travaux contribuent à une meilleure compréhension des mécanismes d’action de l’activité antifongique et devraient conduire au développement de cultures antifongique pour remplacer les conservateurs dans les produits laitiers. / Fungal contamination of dairy products is responsible for economic losses and food waste. In a context of “preservative-free” product demand, bioprotective cultures and their metabolites represe,t an alternative of interest of chemical preservatives to control these spoilers.The objective of this study was i) to select microorganisms exhibiting an antifungal activity, in order to elaborate bioprotectivecultures applicable in dairy products, and ii) to study the compounds potentially supporting the observed activity. Firstly, the antifungal activity of 32 strains of lactic acid and propionic bacteria screened in cheese model and yogurt. Strain combinaison study and safety assessment led to the selection of 2 binary lactobacilli combinations (A1 and A3). Their efficiency and applicability were then evaluated in pilot-scale productions of sour cream and cheese.Challenge and shelf life tests showed that depending on the dairy product, A1 and A3 have a similar or higher antifungal activity than the commercial bioprotective cultures. In addition, depending of inoculum, A1 and A3 did not impact the technological and organoleptic characteristics. Chromatographic methods and statistical analyses allowed identifying cocktails of 2 to 17 compounds, according to the considered dairy product and culture that probably support the antifungal activity.The obtained results contribute to a better understanding of the antifungal activity action mechanisms and should lead to the development of antifungal cultures to replace preservatives in dairy products.