Mammary immunity in mothers of infants with respiratory syncytial virus infection.

Seven of 230 breast fed infants followed prospectively from birth through their first winter contracted RS virus infections. The colostral from five of the mothers of these infants contained antiviral IgA antibodies. In each case antibody levels were above the mean for a group of 36 mothers whose infants were age matched to infected infants but for whom there was no evidence of RS virus infection in their first winter. Four colostral samples from mothers of infected infants also contained antiviral IgG antibody. Colostral lymphocyte reactivity to RS virus antigen was tested in three mothers of infected infants and two showed significant proliferation. There was, therefore, no evidence that mothers of infected infants lacked mammary immunity to the virus. Maternal mammary IgA and IgG responses following diagnosis of RS virus infection in the infant were followed for the seven cases identified prospectively and for a further 23 infants admitted to hospital with RS virus infections of varying severity. There was no evidence that the mothers of more severely affected infants were deficient in IgA or IgG milk antibody.