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Zika DNA Vaccine Proven Safe and Effective at Inducing Immunity
Ben Leach

Results are in from the first phase 1 clinical trial for a Zika vaccine, and they are very promising. A new generation DNA-based Zika vaccine, developed by Wistar scientists in collaboration with Inovio Pharmaceuticals and GeneOne Life Science, was found to be safe and well tolerated by all study participants and was able to elicit an immune response against Zika, opening the door to further and larger trials to move this vaccine forward.

“The Wistar Institute has been a leading developer of vaccines for the protection of children and families for decades,” said David B. Weiner, Ph.D., executive vice president of The Wistar Institute and director of Wistar’s Vaccine & Immunotherapy Center, who spearheaded the research team that developed the vaccine. “In light of Wistar’s history of vaccine creation and the work taking place in my lab and with collaborators, we hope to create a vaccine that will benefit humankind.”

Zika virus is a mosquito-borne infection associated with birth defects and neurological complications in adults, for which no approved vaccine or treatment is currently available. In the fall of 2015, after news of global Zika outbreaks was reported in Africa, Southeast Asia, the Pacific Islands, and many South American countries, Dr. Weiner and his collaborators got to work and put in place a plan to develop reagents, animal models, assays and potential vaccine candidates for initial testing.

The team had developed a new synthetic DNA-based vaccine technology that can be applied to a variety of infectious diseases and they set to implement this resource for the development of a Zika vaccine. The result of their combined efforts was GLS-5700, a DNA vaccine that contains the DNA instructions for the host to learn how to mount an immune response against a specific Zika virus antigen.

DNA-based vaccines brought about a revolution in vaccine research because they are much faster to develop and implement than traditional vaccines, which take several years from the start to the first tests. Weiner and his team were able create the Zika vaccine candidate in just about six months.

After it proved safe and effective in pre-clinical trials, the vaccine received FDA approval for clinical testing in June 2016, and participants were enrolled in the phase 1 trial between August and September.

The clinical study was conducted through a partnership among the Perelman School of Medicine at the University of Pennsylvania, Inovio Pharmaceuticals, GeneOne Life Science, and The Wistar Institute. The trial involved 40 healthy individuals. The vaccine was administered intradermally with the aid of an innovative device called Cellectra, which delivers small, directional electric currents into the skin to facilitate optimal vaccine uptake.

Two weeks after the final dose, 100 percent of the study participants developed Zika-specific antibodies and 80 percent developed significant neutralizing antibodies against the virus. Importantly, Weiner and colleagues were able to show that the vaccine-induced antibodies circulating in the blood of the study participants are effective in preventing disease in a mouse model of Zika infection. From a safety standpoint, the vaccine was well tolerated, with no significant side effects reported.

Development and first testing of the GLS-5700 vaccine provided a proof of concept that new generation DNA vaccines represent an ideal approach for emerging infectious diseases. This new class of vaccines can be designed and manufactured rapidly, and they are significantly safer and more stable than most traditional vaccines, making them exceptionally practical to distribute during outbreaks, especially in regions where resources are limited and a quick response is crucial to curb an emerging epidemic.

The clinical research was published in the New England Journal of Medicine. To learn more, read the press release on the study.