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Salivary Scavenger and Agglutinin in Horses With and Without Severe Equine Asthma

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Title: Salivary Scavenger and Agglutinin in Horses With and Without Severe Equine Asthma
Author: Lee, Gary Kwok Cheong
Department: Department of Pathobiology
Program: Veterinary Science
Advisor: Bienzle, Dorothee
Abstract: Severe equine asthma (SEA) is a common, debilitating inflammatory airway disease of horses. Next-generation sequencing identified numerous differentially expressed epithelial genes in asthmatic compared to healthy horses, including downregulation of the gene for salivary scavenger and agglutinin (SALSA). In humans, SALSA has numerous functions in innate immunity and modulates inflammation. In horses, SALSA was poorly characterized. This thesis addressed the hypothesis that SALSA has anti-inflammatory effects on equine leukocytes as assessed in healthy horses and those with SEA. First, an antibody against SALSA was validated by western blotting, immunoprecipitation followed by mass spectrometry, and immunohistochemical analysis of 22 equine tissues in a tissue microarray. The equine SALSA gene was amplified and functional motifs predicted. Equine SALSA was found to have three to five scavenger receptor cysteine-rich domains, two complement C1r/C1s, Uegf, Bmp1 (CUB) domains, and one zona pellucida domain. There was interindividual variability in domain frequency. Immunohistochemical labeling was most prominent at mucosal surfaces of the duodenum and sections of the airways. Labeling was cytoplasmic and apical, consistent with a secreted protein. Second, gene and protein expression of SALSA in horses with and without SEA was evaluated, and bronchial brushing and biopsy were compared to bronchoalveolar lavage as in vivo diagnostic modalities. Quantitative PCR confirmed lower SALSA gene expression in horses with SEA while immunohistochemically SALSA did not significantly differ between affected and unaffected horses. Bronchial brushing but not bronchial biopsy was a good method for distinguishing affected from unaffected horses. In the third study, the effect of purified equine SALSA on neutrophil bacterial phagocytosis and alveolar macrophage cytokine production was determined. Neutrophils incubated with SALSA had a dose-dependent decrease in the phagocytosis of fluorescently-labeled bacteria. Alveolar macrophages incubated with SALSA had reduced production of CXCL1, IL-8, IL-10 and TNF-α and increased production of G-CSF, as measured with an equine-specific multiplex bead immunoassay. Overall, the findings from this research indicate that equine SALSA is secreted by mucosal epithelial cells, reduces neutrophil phagocytosis, and suppresses pro-inflammatory cytokine production. These features define characteristics of SALSA that are likely influential in dampening the host response to microbial components at mucosal surfaces.
Date: 2021-12
Rights: Attribution-NonCommercial-NoDerivatives 4.0 International
Related Publications: Lee GKC, Tessier L, Bienzle D. Salivary scavenger and agglutinin (SALSA) is expressed in mucosal epithelial cells and decreased in bronchial epithelium of asthmatic horses. Frontiers in Veterinary Science. 2019; 6:418.doi: 10.3389/fvets.2019.00418

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Attribution-NonCommercial-NoDerivatives 4.0 International Except where otherwise noted, this item's license is described as Attribution-NonCommercial-NoDerivatives 4.0 International
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