Eye-drop DNA can induce IgA in the tears and bile of chickens

DNA vaccines protect chickens against lethal virus infections but whether they induce local antibody which is associated with preventing viral entry, is unknown. We were able to show how avian DNA vaccines can induce local IgA. 65 μg plasmid DNA encoding the reporter protein beta-galactosidase induced antigen-specific IgA in the tears of 6/10 birds, IgA in the bile of 4/10 birds and IgG in the serum of 2/10 birds. Giving the DNA by the intramuscular route, as is more usual, induced lacrimal IgA in 2/8 birds, biliary IgA in no birds and serum IgG in 4/8 birds. Eye-drop DNA therefore favoured local IgA whereas intramuscular DNA favoured serum IgG. Further to this preliminary work eye-drop DNA should be improved by adjuvants and cytokines as a way of inducing protective IgA at the mucosal surfaces of the alimentary and respiratory tracts.