HUMAN-MILK GLYCOSAMINOGLYCANS INHIBIT HIV GLYCOPROTEIN GP120 BINDING TO ITS HOST-CELL CD4 RECEPTOR

The binding of the HIV envelope glycoprotein, gp120, to its host cell receptor, CD4, is inhibited in a solid phase assay by a glycosaminogly can of human milk; this binding is the essential first step in HIV inf ectivity. The human milk glycosaminoglycans were identified in this st udy. Pooled, fractionated human milk contained dermatan sulfate, hepar in, heparan sulfate, and chondroitin sulfate. The ability of this glyc osaminoglycan fraction to inhibit binding was unaffected by digestion with lytic enzymes specific for heparin, heparan sulfate and dermatan sulfate, but was lost when the milk fraction was treated with lytic en zymes specific for chondroitin sulfate. Furthermore, a purified milk f raction with high specific inhibitory activity contained chondroitin s ulfate but not other glycosaminoglycans. This indicates that the abili ty of human milk to inhibit gp120 binding to CD4 may be attributed to chondroitin sulfate or to a chondroitin sulfate-like moiety rather tha n to other components of human milk. We speculate that this human milk glycosaminoglycan could limit the rate of postnatal vertical transmis sion of HIV in breast-fed infants of HIV-infected mothers.