Aims: Human milk contains a 46 kD mucin-associated glycoprotein(lactadherin) that binds to rotavirus (RV) and inhibits RV replication in vitro and in vivo (J Clin Invest 90:1984,1992). The binding and inhibition appears dependent upon an intact carbohydrate moiety. Our aims were to study the nature of the carbohydrate moiety of lactadherin and the association between variations in lactadherin concentrations in breast milk and RV infection of the suckling infant.
Methods: Characterization--Lactadherin was purified from human milk fat globule by aqueous partition into Triton X-114. Carbohydrate was hydrolyzed enzymatically, derivatized with fluorescent label, resolved by PAGE and visualized (Glyko FACE). Clinical Significance--Nursing dyads from Mexico City were studied throughout lactation. Matched milk and stool samples and clinical histories were obtained weekly and stools were monitored for RV. Milk samples obtained from 44 mothers 13±9 days (range 2-41 days) prior to the appearance of RV in the stool were analyzed by solid phase immunoassay for their content of lactadherin.
Results: Three bands of carbohydrate were released from lactadherin, indicating the presence of N-linked oligosaccharides. A positive correlation (p<0.001) exists between lactadherin and mucin concentrations. Infants ingesting milk whose combined lactadherin and mucin levels were high had a lower chance of developing symptomatic RV infection over asymptomatic RV infection (p<0.05).
Conclusions: Lactadherin contains an N-linked oligosaccharide. Breastmilk containing high concentrations of lactadherin and mucin appears to protect infants against symptomatic RV infection. Supported by HD13021, HD30444, CA39932
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