A Comparison of Plasmid DNA and mRNA as Vaccine Technologies

Liu, Margaret A.

Five plasmid DNA products (four of them vaccines) have received licensure for veterinary applications. These include a fish vaccine for infectious hematopoietic necrosis virus licensed in 2005, and a vaccine against salmon pancreas disease licensed in 2016 [72] . A dog cancer immunotherapeutic vaccine for melanoma was licensed originally based upon comparison with historic controls in the US in 2010. After submission to the European Medicines Agency, the application was withdrawn in 2014 by the company, stating that their priorities had changed such that they did not justify the investment in research and development to answer the remaining questions [73] . A vaccine for West Nile virus (WNV) prevention in horses was licensed in 2005 [74] , although it is no longer used in favor of the previously licensed killed virus vaccine for unpublished reasons. Yet, a promising observation was that the equine WNV DNA vaccine was able to protect various species of birds from WNV [75] [76] [77] [78] , including the California condor, and has been credited by U.S. Center for Disease Control (CDC) scientists with saving this endangered species from potential extinction [79] . A fifth plasmid DNA product was licensed in 2008 for veterinary use; this plasmid encodes growth hormone releasing hormone (GHRH) and is given via electroporation to pregnant sows, resulting in litters with an increased number of surviving piglets and of higher birthweights [80, 81] .