Transplacental genetic immunization after intravenous delivery of plasmid DNA to pregnant mice

A number of factors influence the development of tolerance, including the n ature, concentration, and mode of Ag presentation to the immune system, as well as the age of the host. The studies were conducted to determine whethe r immunizing pregnant mice with liposome-encapsulated DNA vaccines had an e ffect on the immune status of their offspring. Two different plasmids (enco ding Ags from HIV-1 and influenza virus) were administered Lv. to pregnant mice. We examined the uptake of plasmid DNA by the fetuses until the 21st p ostcoital day, but little such transfer occurred in early pregnancy. At 9.5 days postconception with cationic liposomes, injected plasmid was present in the tissues of the fetus, consistent with transplacental transfer. When the offspring of vaccinated dams were immunized with DNA vaccine, they moun ted stronger Ag-specific immune responses than controls, and were protected against challenge by homologous influenza virus after vaccination. Moreove r, such immune responses were strong in the offspring of mothers injected w ith DNA plasmid 9.5 days after coitus. These results suggest that DNA-vacci nated mothers confer the Ag-specific immunity to their progeny.