HUMAN-MILK K-CASEIN AND INHIBITION OF HELICOBACTER-PYLORI ADHESION TO HUMAN GASTRIC-MUCOSA

Readily digested caseins, which account for almost half of the protein content in human milk, are important as nutritional protein for breast-fed infants. It has also been advocated that part of the antimicrobial activity of human milk resides in the caseins, most likely the glycosylated kappa-casein. To explore this possibility, we purified kappa-casein from human milk to homogeneity by a two-step size-exclusion chromatography procedure. Purified human kappa-casein, in contrast to kappa-casein purified from bovine milk, effectively inhibited the cell lineage-specific adhesion of fluoroisothiocyanate-labeled Helicobacter pylori to human gastric surface mucous cells. The inhibitory activity was abolished by metaperiodate oxidation and considerably reduced by preincubation with alpha-L-fucosidase but not with alpha-N-acetylneuraminidase or endo-beta-galactosidase. These results strongly support the view that fucose containing carbohydrate moieties of human kappa-casein are important for inhibition of H. pylori adhesion and, thus, infection. They also suggest that breastfeeding may protect from infection by H. pylori during early life and that species-specific glycosylation patterns, as illustrated by human and bovine kappa-casein, partly determine both the narrow host spectrum of this human gastric pathogen and the capacity to resist infection.