DO THE BINDING-PROPERTIES OF OLIGOSACCHARIDES IN MILK PROTECT HUMAN INFANTS FROM GASTROINTESTINAL BACTERIA

The oligosaccharide fraction of human milk, the third most abundant so lid constituent, consists of hundreds of structures, many of them fuco sylated. Oligosaccharides may bear structural homology to cell surface glycoconjugates used as receptors by pathogens, thus protecting nursi ng infants. The ability of human milk to protect against heat-stable e nterotoxin of Escherichia coil in suckling mice has been attributed to neutral fucosylated oligosaccharides of milk. The same phenomenon has been found in human T84 cells, allowing the mechanism of inhibition b y the oligosaccharide to be studied in vitro. The oligosaccharide bind s to the extracellular domain of guanylyl cyclase, thereby inhibiting the binding of stable toxin. The protective oligosaccharide is a large structure present in too low a concentration to be routinely measured directly; however, its concentration in milk may be inferred by measu ring smaller, more plentiful, structurally homologous oligosaccharides . The adhesion by invasive pathogenic strains of Campylobacter to thei r enterocyte target is also inhibited by human milk fucosyloligosaccha rides. Because Campylobacter binds H-2 type oligosaccharide structures , the concentration of protective oligosaccharide may also be inferred from the total oligosaccharide profile. The relationship between olig osaccharide profile heterogeneity in human milk and the incidence of s pecific gastrointestinal bacterial disease in infants consuming these milks could indicate the significance of these oligosaccharides to inf ant health. The efficacy of synthetic analogs of active oligosaccharid es will confirm their clinical relevance and define minimum structural features essential for activity.