Effects of weaning and infection with Teladorsagia circumcincta on mucin carbohydrate profiles of early weaned lambs

Abstract

Differences in mucin glycosylation in milk-fed and early weaned lambs may influence susceptibility to parasitism, particularly the greater cellular content and higher sulphation of mucins in young and unweaned lambs. Weaning also reduced the percentage of Gal (p<0.05) in fundic mucin and galactosamine (GalN) (p<0.01) in duodenal mucin, but had no noticeable effect on fucosylation or sialylation. Four experimental groups of lambs were studied (n=3): (1) 3 days old; (2) 9 weeks old milk-fed; (3) 9 weeks old weaned at 3 weeks-of-age on to lucerne chaff and cereal-based pellets (4) 9 weeks old weaned and infected with 1000 Teladorsagia circumcincta L3 twice weekly for 5 weeks. Fundic and duodenal mucin monosaccharides were analysed chemically and fundic, antral and duodenal tissues were stained with lectins, periodic acid Schiff (PAS), Alcian blue/PAS (AB/PAS) and high iron diamine. Age-related maturation of mucin glycosylation was prominent in young lambs: reduced total fundic mucins and increasing fucosylation and decreasing sialylation and sulphation of all mucins, as well as changes in the types of linkages of Fuc and sialic acids. By 9 weeks-of-age, there were no longer sialylated mucins in fundic surface mucus cells, only neutral mucins, while in Brunner's glands, there was reduced sialylation and large amounts of neutral mucins. In the neonates, both fundic and duodenal tissues contained only small amounts of mucins terminating with alpha-1,2-linked Fuc, which became the principal linkage in 9 weeks old lambs. Duodenal mucins in 3 days old lambs contained both alpha-2,6- and alpha-2,3-linked sialic acids, whereas the alpha-2,3 linkage was not present in older lambs. Parasitism increased the percentage of galactose, but reduced total and neutral fundic mucins, as well as sulphation and sialylation. There was both decreased sialylation and sulphation in duodenal mucins. Although no change in fucosylation was apparent from chemical analysis, infection reduced lectin staining for alpha-1,2-linked fucose in antral and duodenal tissues and alpha-1,6- and alpha-1,3-linked fucose in the duodenum. These changes in fundic and duodenal mucins were similar to those previously seen on Day 28 p.i. after a single infection of 4-9 months old sheep with T. circumcincta larvae.