A Comparison of Plasmid DNA and mRNA as Vaccine Technologies

Liu, Margaret A.

In related observations to the equine WNV DNA vaccine, in a human clinical trial of a WNV DNA vaccine in humans, all subjects generated titers of antibodies that were considered protective in the horses [82] . In a subsequent study using a construct with a stronger promoter, older adults (who generally are considered to have senescent immune systems and respond to licensed vaccines such as the influenza vaccine more poorly than younger persons) had neutralizing antibody responses as good as the younger adults [83] . In a clinical trial of a DNA vaccine for Ebola and Marburg viruses, the individuals likewise generated antibodies that were boostable [84] . These observations demonstrate that DNA vaccines are capable of inducing antibodies in humans of relevant titers, suggesting that it is not a limitation of the technology per se to generate effective antibodies, but rather the target and the optimized constructs are key elements (much as finding the right target for monoclonal antibodies (MAbs) was needed for MAbs to become such effective anti-cancer agents). Also of note is that the first two Zika vaccines brought to human clinical trial were DNA vaccines [85] . This underscores the point made earlier about how the ease of making both DNA and mRNA vaccines is considered a tremendous advantage for rapid responses to emergent or epidemic diseases.