Effect of breast feeding on responses of systemic interferon and virus-specific lymphocyte transformation in infants with respiratory syncytial virus infection.

In order to elucidate the mechanisms of breast-feeding-induced resistance to respiratory syncytial virus (RSV) infection, groups of breast-fed and bottle-fed infants with this infection were tested at the onset of illness and then again 1 and 2 weeks later for the presence of interferon (IFN) as well as of virus-specific lymphocyte transformation (LTF) activity. Alpha-IFN was detected in nine out of ten breast-fed infants, while it was found in only 11 out of 21 bottle-fed subjects. The rate of the detection of IFN was significantly higher in the former group (P less than .05). Mean levels of IFN activity were also higher in breast-fed infants than in bottle-fed subjects during the course of the illness. It was noted, however, that previous breast feeding elicited little enhancing effect on the IFN response of infants with RSV infection. Combining the two feeding groups, suppressed LTF activity to RSV seemed to be related to a positive IFN response, although the association was not statistically significant. These observations suggest that breast feeding has unique mechanisms for modulating the immune response of infants with RSV infection.