Brachyspira hyodysenteriae Infection Regulates Mucin Glycosylation Synthesis Inducing an Increased Expression of Core‑2 O‑Glycans in Porcine Colon

Brachyspira hyodysenteriae causes swine dysentery (SD), leading to global financial losses to the pig industry. Infection with this pathogen results in an increase in B. hyodysenteriae binding sites on mucins, along with increased colonic mucin secretion. We predict that B. hyodysenteriae modifies the glycosylation pattern of the porcine intestinal mucus layer to optimize its host niche. We characterized the swine colonic mucin O-glycome and identified the differences in glycosylation between B. hyodysenteriae-infected and noninfected pigs. O-Glycans were chemically released from soluble and insoluble mucins isolated from five infected and five healthy colon tissues and analyzed using porous graphitized carbon liquid chromatography tandem mass spectrometry. In total, 94 O-glycans were identified, with healthy pigs having higher interindividual variation, although a larger array of glycan structures was present in infected pigs. This implied that infection induced loss of individual variation and that specific infection-related glycans were induced. The dominating structures shifted from core-4-type O-glycans in noninfected pigs toward core-2-type O-glycans in infected animals, which correlated with increased levels of the C2GnT glycosyl transferase. Overall, glycan chains from infected pigs were shorter and had a higher abundance of structures that were neutral or predominantly contained NeuGc instead of NeuAc, whereas they had a lower abundance of structures that were fucosylated, acidic, or sulfated than those from noninfected pigs. Therefore, we conclude that B. hyodysenteriae plays a major role in regulating colonic mucin glycosylation in pigs during SD. The changes in mucin O-glycosylation thus resulted in a glycan fingerprint in porcine colonic mucus that may provide increased exposure of epitopes important for host–pathogen interactions. The results from this study provide potential therapeutic targets and a platform for investigations of B. hyodysenteriae interactions with the host via mucin glycans.

猪痢疾短螺旋体（Brachyspira hyodysenteriae）可引发猪痢疾（swine dysentery, SD），给全球养猪业造成巨额经济损失。感染该病原体会导致黏液素（mucins）上的猪痢疾短螺旋体结合位点增多，同时结肠黏液素分泌量上升。我们推测，猪痢疾短螺旋体会修饰猪肠道黏液层的糖基化模式，以优化其宿主定植生态位。

本研究对猪结肠黏液素O-糖组（O-glycome）进行了表征，并鉴定了猪痢疾短螺旋体感染组与非感染组猪只的糖基化差异。研究人员从5头感染猪和5头健康猪的结肠组织中分离可溶性与不溶性黏液素，通过化学方法释放O-聚糖，并采用多孔石墨化碳液相色谱-串联质谱（porous graphitized carbon liquid chromatography tandem mass spectrometry）进行分析。

本研究共鉴定出94种O-聚糖；健康猪个体间糖基化异质性更高，而感染猪的聚糖结构种类更为丰富。上述结果提示，感染可导致个体间糖基化异质性丧失，并诱导产生特异性感染相关聚糖结构。主导聚糖结构从非感染猪的核心4型O-聚糖，转变为感染猪的核心2型O-聚糖，这与C2GnT糖基转移酶水平升高相关。

总体而言，感染猪的聚糖链更短，中性结构或主要含N-羟乙酰神经氨酸（NeuGc）而非N-乙酰神经氨酸（NeuAc）的结构丰度更高；而岩藻糖基化、酸性或硫酸化结构的丰度则低于非感染猪。因此，我们得出结论：在猪痢疾发病期间，猪痢疾短螺旋体在调控猪结肠黏液素糖基化过程中发挥关键作用。

黏液素O-糖基化的改变会在猪结肠黏液中形成一种聚糖指纹图谱，该图谱可能会增加宿主-病原体互作相关表位的暴露量。本研究结果为潜在治疗靶点的筛选提供了依据，并为探究猪痢疾短螺旋体通过黏液素聚糖与宿主的互作机制搭建了研究平台。