Human Milk Contains the Shiga Toxin and Shiga-like Toxin Receptor Glycolipid Gb3

Human milk antibody and nonantibody factors are thought to be important in protecting infants from diarrheal diseases. The nonantibody factors include host receptor analogues that bind to specific pathogen virulence factors, thereby inhibiting these bacterial products from binding to their intestinal target receptors. Globotriaosylceramide (Gb3), a glycolipid known to bind to both Shiga toxin and Shiga-like toxins, was found to occur in human milk with an average concentration of 73 nM (77 micrograms/L) for Gb3 containing hydroxylated fatty acids and 50 nM (53 micrograms/L) for Gb3 containing nonhydroxylated fatty acids. This human milk Gb3 was found to bind to Shiga toxin, consistent with the hypothesis that Gb3 could contribute to the protective effect of human milk against infantile diarrheas associated with Shiga or Shiga-like toxins.