The effect of human milk fractions on rotavirus in relation to the secretory IgA content

Human milk from healthy Norwegian women was fractionated by ammonium sulphate precipitation and gel filtration. The protein content, lactoferrin and secretory IgA were measured. Specific antirotavirus IgA, detected by indirect immunofluorescence was found in one out of five milk samples before fractionation, while a more concentrated immunoglobulin fraction from the other four milk samples contained such IgA. Before fractionation, 3 of 5 milk samples neutralized human rota-virus infection of LLC-MK2 cells, whereas concentrated, IgA-rich fractions of all 5 milk samples neutralized human rotavirus. Some fractions without detectable IgA also neutralized human rotavirus. This suggests that human milk contains rotavirus specific IgA as well as rotavirus neutralizing activity of non-immunoglobulin nature.