Immunogenicity and immunomodulatory activity of bovine surfactant (SF-RI 1)

Respiratory distress syndrome in preterm infants can be treated successfully by endotracheal administration of a bovine surfactant preparation (SF-RI 1). Before the routine use of xenogenic surfactant preparations can be recommended, their immunogenicity as well as their in-vivo and in-vitro immunomodulatory activity have to be investigated. High titers of anti-surfactant antibodies were detected by a sensitive ELISA after immunizing rats, rabbits and mice with SF-RI 1. Repeated endotracheal administration of SF-RI 1 resulted in a humoral antibody response in three out of eight rabbits. After treatment of 34 preterm infants with SF-RI 1 (50-200 mg/kg), a humoral immune response to SF-RI 1 could not be detected. In-vitro restimulation of peripheral blood lymphocytes with SF-RI 1 after primary in-vivo administration did not result in cell proliferation as measured by 3H-thymidine incorporation. SF-RI 1 did not stimulate peripheral blood lymphocytes of neonates in vitro. The mitogenic response of these cells to stimulation with PHA, ConA or PWM was heavily impaired in the presence of SF-RI 1 concentrations increasing from 0.04 to 4 mg/ml. These data indicate that SF-RI 1 is immunogenic and that it may have an influence on lymphocyte proliferation in vivo.