Effects of antibodies, trypsin, and trypsin inhibitors on susceptibility of neonates to rotavirus infection

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Abstract
Levels of antirotaviral secretory IgA were measured by enzyme-linked immunosorbent assay in colostrum and milk samples collected daily for the first 5 days postpartum from 49 mothers breast-feeding their infants. The trypsin-inhibitory capacity of these lacteal secretion samples was assessed by their ability to inhibit the hydrolysis of .alpha.-N-benzoyl-DL-arginine-p-nitroanilide by trypsin. Stools passed by these breast-fed infants and by an additional 43 bottle-fed infants were pooled by individual and examined by EM for rotavirus. Stool trypsin levels were estimated with the gelatin hydrolysis test. Breast-fed infants were significantly less likely to become infected with rotavirus and showed significantly lower stool tryptic activity than did bottle-fed infants. Breast-fed infants who did not excrete rotavirus over the 5 day period received milk of significantly higher antirotaviral secretory IgA of trypsin-inhibitory capacity or both than breast-fed infants who were infected with rotavirus. A case of probable maternal rotavirus infection during pregnancy, producing greatly elevated lacteal antirotaviral secretory IgA levels lasting for 2 yr, was detected. Both antibodies and trypsin inhibitors in human milk can be associated with the protection of neonates against rotavirus infection in the first 5 days of life.