On page 1177, Lorenzen et al. report that a DNA vaccine encoding a recombinant antibody protected fish against viral pathogens, a step in developing safer and more efficacious animal vaccines. They prepared single-chain antibody (ScAb) gene constructs coding for neutralizing antibodies to the fish viral hemorrhagic septicemia virus (VHSV), and inserted them into a eukaryotic expression plasmid. They showed that rainbow trout fingerlings injected intramuscularly with the recombinant plasmid were protected against VHSV challenge. If immunoprophylaxis by DNA vaccines delivering antibody genes can be extended beyond aquaculture to mammals, it may provide a valuable tool in situations where conventional vaccination is ineffective or impractical (see also p. 1145).