Mark Fishaut

Bronchomammary axis in the immune response to respiratory syncytial virus

The products of lactation from 26 nursing mothers were sequentially examined over several months for the presence or appearance of antibodies directed against respiratory syncytial virus. Antiviral IgM and IgG were rarely identified in either colostrum or milk. RSV-specific IgA was found in 75% (18/24) of specimens of colostrum; 40% (6/15) and 59% (4/7) of milk samples obtained at three and six months still contained specific IgA antibody. The latter increase was felt to represent boosting of exposed individuals when the virus was present in the community. Infection with the virus was documented in two mothers. Both had specific IgG, IgM, and IgA antibody responses in serum and nasopharyngeal secretions, but response in milk was limited to IgA. These data confirm that antibody to a specific respiratory tract pathogen is present in the products of lactation, that the specific activity is mainly of the IgA class, and that booster responses in milk are exclusively of the IgA class. Since RSV appears to replicate only in the respiratory tract, it is suggested that viral specific antibody activity observed in the mammary gland may be derived from the bronchopulmonary lymphoid tissue.

942 IMMUNOLOGY OF BREAST MILK: ORIGIN OF ANTIBODIES TO RESPIRATORY SYNCYTIAL VIRUS (RSV) AND BOVINE SERUM ALBUMIN (BSA) IN THE LACTATING BREAST

Employing the techniques of immunofluorescence, radioimmunoprecipitation, and radioimmunodiffusion, the development of antibody responses to RSV and BSA and the localization of immunoglobulin containing cells in the mammary glands, was studied in groups of pregnant rabbits after intravenous (IV), per oral (PO) or trans-tracheal (IT) immunization with RSV and BSA during late gestation. A predictable IgM and IgG and no IgA antibody response to RSV was observed in the serum. The secretory response to RSV was characterized by the regular appearance of IgA antibody in the colostrum and milk after IT and PO immunization but not after IV immunization. The proportion of IgA staining cells in the mammary tissues was found to be 50% higher in the animals immunized by IT or PO routes than by the IV route. No infectious virus or RSV antigen was detected in the breast. Most animals elicited IgG anti-BSA response in the serum, colostrum and milk, and a few evidenced IgA in serum. However, IgA response to BSA was notably absent in colostrum and milk. These observations suggest independent contributions of bronchus associated and gut associated lymphoid tissue to the development of mammary immunity. More importantly, significant differences exist between soluble dietary proteins and particulate viral antigens in their ability to induce breast milk antibodies.