Gangliosides in human, cow and goat milk, and their abilities as to neutralization of cholera toxin and botulinum type A neurotoxin

To elucidate the potential of mammalian milk as to protection of infants from infections, we determined the ganglioside compositions of human, cow and goat milk in relation with cholera toxin and botulinum type A neurotoxin-receptors. Gangliosides accounted for 1 to 2 μmol of lipid-bound sialic acid (LSA) in 100 ml of milk, and GD3 comprised about 69% of LSA in all milk samples. Among the milk samples examined, goat milk was found to contain an amount of gangliosides belonging to the b-pathway representing 15.8% of the total LSA. Accordingly, botulinum neurotoxin bound to GT1b and GQ1b in goat milk, but not to any gangliosides in human or cow milk. On the other hand, GM1, the cholera toxin receptor, was found to be present in all milk samples at concentrations of 0.02% to 0.77% of the total LSA and to be maintained at a relatively constant level in human milk during the postpartum period. Gangliosides from 1 ml of pooled human milk exhibited the ability to attenuate the binding of cholera toxin (30 ng) to GM1 by 93%, and those from 500 μl of goat milk completely inhibited the binding of botulinum type A neurotoxin 1.5 μg to GT1b.