The Levels of Brachyspira hyodysenteriae Binding to Porcine Colonic Mucins Differ between Individuals, and Binding Is Increased to Mucins from Infected Pigs with De Novo MUC5AC Synthesis

Abstract

c Brachyspira hyodysenteriae colonizes the pig colon, resulting in mucohemorrhagic diarrhea and growth retardation. Fecal mucus is a characteristic feature of swine dysentery; therefore, we investigated how the mucin environment changes in the colon during infection with B. hyodysenteriae and how these changes affect this bacterium's interaction with mucins. We isolated and characterized mucins, the main component of mucus, from the colon of experimentally inoculated and control pigs and investigated B. hyodysenteriae binding to these mucins. Fluorescence microscopy revealed a massive mucus induction and disorganized mucus structure in the colon of pigs with swine dysentery. Quantitative PCR (qPCR) and antibody detection demonstrated that the mucus composition of pigs with swine dysentery was characterized by de novo expression of MUC5AC and increased expression of MUC2 in the colon. Mucins from the colon of inoculated and control pigs were isolated by two steps of isopycnic density gradient centrifugation. The mucin densities of control and inoculated pigs were similar, whereas the mucin quantity was 5-fold higher during infection. The level of B. hyodysenteriae binding to mucins differed between pigs, and there was increased binding to soluble mucins isolated from pigs with swine dysentery. The ability of B. hyodysenteriae to bind, measured in relation to the total mucin contents of mucus in sick versus healthy pigs, increased 7-fold during infection. Together, the results indicate that B. hyodysenteriae binds to carbohydrate structures on the mucins as these differ between individuals. Furthermore, B. hyodysenteriae infection induces changes to the mucus niche which substantially increase the amount of B. hyodysenteriae binding sites in the mucus.

Neutrophil Elastase and Interleukin 17 Expressed in the Pig Colon during Brachyspira hyodysenteriae Infection Synergistically with the Pathogen Induce Increased Mucus Transport Speed and Production via Mitogen-Activated Protein Kinase 3

“…We previously reported that B. hyodysenteriae infection causes changes in the mucin environment that are characterized by a disorganized mucus structure and massive mucus induction with de novo expression of MUC5AC and increased production of MUC2 in the colon (12). The results from the present study show that several factors from the immune system are differentially expressed in the pig colon during B. hyodysenteriae infection.…”

“…1A). Pig 1 presented milder clinical signs of dysentery and an absence of de novo MUC5AC expression and increased MUC2 production; thus, this animal produced mucus similar to that observed in the control pigs (Table 1) (12). IL-17A expression correlated with MUC5AC mRNA levels (r ϭ 0.8, P ϭ 0.01) and the MUC5AC protein amount in the colon tissue (Table 1) (r ϭ 0.8, P ϭ 0.01).…”

“…In order to determine how factors from the immune system change in the pig colon during B. hyodysenteriae infection, we quantified the mRNA levels of 13 factors from the immune system, IL-1␤, IL-2, IL-4, IL-5, IL-6, IL-8, IL-12, IL-13, IL-17A, tumor necrosis alpha (TNF-␣), gamma interferon (IFN-␥), monocyte chemoattractant protein 1 (MCP-1), and neutrophil elastase (NE), by quantitative PCR (qPCR). These factors were chosen based on previous reports from experimental trials (13), associations with mucin production (5,(14)(15)(16), and/or in relation to histopathological findings, such as the neutrophilic infiltration observed in infected pigs (12). The colons of B. hyodysenteriae-infected pigs had a 7-fold increase in mRNA levels of the proinflammatory cytokine IL-17A compared to healthy controls (P ϭ 0.017) (Fig.…”

“…These changes are characterized by a disorganized mucus structure and massive mucus induction as a result of de novo expression of MUC5AC and increased expression of MUC2 mucins (12). The regulatory networks determining mucin expression in the pig colon have not been previously investigated.…”

“…We previously demonstrated that B. hyodysenteriae causes profound changes to the colonic mucin environment (12). These changes are characterized by a disorganized mucus structure and massive mucus induction as a result of de novo expression of MUC5AC and increased expression of MUC2 mucins (12).…”