Nucleic acid vaccines induce 2 immune defenses to protect against infection and disease
Inoculations developed to combat COVID-19 in humans brought forth greater awareness for messenger RNA (mRNA) vaccines. Although mRNA vaccines were already in clinical trials for other diseases, its use for COVID-19 tested the technology and proved it was ready. “They were most efficacious, and they were the fastest to the finish line,” said Deborah Fuller, PhD, a professor at the University of Washington in Seattle.1
In her lecture at the American College of Veterinary Internal Medicine (ACVIM) Forum in Philadelphia, Pennsylvania, Fuller provided an overview of mRNA and DNA vaccines and discussed their value to the future of veterinary medicine. “mRNA vaccines were long in development, over 30 years, before COVID-19,” she said.
According to Fuller, nucleic acid vaccines induce 2 immune defenses to protect against infection and disease by essentially instructing the body to make microbial proteins. “They both induce antibody and T-cell responses,” she said.
The antibodies from mRNA and DNA inoculation types can block a virus from infecting a cell or clear a virus from the blood, and T cells in these vaccines can destroy cells that become infected. mRNA and DNA vaccines are also developed quicker, more efficiently, and less expensively on a large scale than traditional and viral vectored inoculation types.1 “There are a lot of veterinary vaccines based on that traditional technology,” Fuller said.
However, mRNA and DNA vaccines are different in genetic material and in other ways. For example, in their immunization delivery, mRNA must enter only the cytoplasm to produce microbial protein while DNA needs to enter the cell’s nucleus.1
Additionally, DNA vaccines are more stable at room temperature. That benefit may lead to DNA vaccines being more widely distributed and used on a global scale, according to Fuller.
These nucleic acid vaccines have the potential to be even more advantageous to veterinary medicine. RNA and DNA inoculations are currently being developed to prevent or treat infectious diseases such as rabies, influenza, zoonotic mosquito-borne flaviviruses, coronaviruses, and foot-and-mouth as well as multiple swine viruses. Veterinary RNA and DNA vaccines are also under development to address certain types of cancers in animals such as mammary tumors in dogs, according to Fuller.1
In concluding her presentation, Fuller surmised that mRNA and DNA vaccines could potentially prevent a future pandemic of a coronavirus, which originates with bats, on the scale of COVID-19 with help from a human ring immunity. These vaccines could potentially be used for universal inoculations with advantages that include rapid discovery of new antigens, combining multiple antigens in a single vaccine, and the ability to induce both antibody and T cell responses.
Fuller cited viral vectored vaccines in humans as a comparative example. “The current inactivated vaccines take 9 months, once you define the new variant to produce, and get that into people. In a pandemic, deaths will occur in the first 3 to 6 months,” she said.
Alternative vaccine delivery methods including spraying and oral administration are also being studied for veterinary use and may have benefit for wildlife and livestock populations. A spray vaccine could quickly inoculate a flock of chickens, Fuller noted.1
“You can take the current flu vaccine and inject 1 chicken at a time, which is a lot of work and a lot of time to do that,” she said.
Fuller D. State of the art (SOTA): the future of RNA and DNA vaccines in veterinary medicine. Presented at: American College of Veterinary Internal Medicine (ACVIM) Forum Specialty Symposium; June 14, 2023. Philadelphia, PA.