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Characterization of fungal exposure and dectin-1 expression in healthy horses and horses with severe asthma
Citation:
Di Pietro, R., V. Dubuc, E. Manguin, R. Giroux-Lafond, C. Bédard, R. Boivin, J. Lavoie, S. Vesper, AND M. Leclere. Characterization of fungal exposure and dectin-1 expression in healthy horses and horses with severe asthma. American Journal of Veterinary Research. American Veterinary Medical Association, Schaumburg, IL, 83(6):1-10, (2022). https://doi.org/10.2460/ajvr.21.09.0143
Impact/Purpose:
Asthma is the most common chronic disease of children in the US (about 7 million). Horses are the only animals, besides humans, that can develop asthma. In order to better understand human asthma, we conducted a study comparing low level vs high level mold, i. e., pasture vs barn, exposures for horses that were susceptible to asthma and those that were not. Low level exposures did not trigger asthma in either group of horses. High level of mold exposures triggered asthma in the susceptible group of horses but not the other group. These results suggest that horses, and by extension of the model to children, with a predisposition to asthma should not be exposed to high mold levels. This should be of interest to veterinarians, parents and physicians.
Description:
OBJECTIVE To quantify dectin-1 expression in bronchoalveolar lavage fluid (BALF), create polyclonal antibodies against equine dectin-1 and localize it in tissues, and quantify fungal exposure in pastured and stabled asthmatic and nonasthmatic horses. SAMPLES BALF samples from 6 controls and 6 horses with severe asthma. Stored lung and nasal wash samples. PROCEDURES Dectin-1 expression was quantified by quantitative PCR (qPCR). Purified peptide from equine dectin-1 was used to generate polyclonal antibodies and was confirmed with immunological testing. Fungal exposure was quantified in BALF samples by counting fungal-like intracellular particles in phagocytic cells, by qPCR quantification of the “universal” 18S rRNA fungal gene, and by quantifying 36 specific fungi in equine and dust samples using qPCR assays. RESULTS Equine dectin-1 was localized in tissues and cells, and functional isoforms were upregulated significantly in BALF after stabling. Pastured horses from both groups had low levels of fungi in BALF, and there was a significant increase in some specific fungi, most notably for Eurotium amstelodami, Wallemia sebi, and Aspergillus niger after stabling. However, stabled asthmatic horses had fewer phagocytized particles, less 18S rRNA signal, and fewer specific fungi compared to nonasthmatic horses. CLINICAL RELEVANCE Stabling increases exposure to fungi, but asthmatic horses had fewer fungi reaching their lower airways, presumably resulting from congestion and narrowing of the airways. Exposure to fungi could contribute to airway inflammation by increasing dectin-1 functional isoforms, and exposure to indoor molds should be avoided.
URLs/Downloads:
DOI: Characterization of fungal exposure and dectin-1 expression in healthy horses and horses with severe asthma