DNA-based vaccine guards against Zika in monkey study
"The vaccine universally elicited antibodies from all primates, but for the animals that got a full dose of vaccine, 17 of 18 were protected from infection," said study co-author Ted Pierson. He is chief of the Viral Pathogenesis Section at the U.S. National Institute of Allergy and Infectious Diseases.
Based on these findings, researchers have begun clinical safety trials in healthy human beings, Pierson said. These trials will show whether the vaccine is safe in humans, and whether it prompts an immune system response as it did in monkeys.
"When a vaccine is effective in a lower primate species, it is a good signal that it will be effective in humans," said Dr. Amesh Adalja, a senior associate at the University of Pittsburgh's UPMC Center for Health Security in Baltimore. "The NIH vaccine candidates have cleared an important hurdle, and we are awaiting results from phase 1 human studies."
This potential vaccine contains a piece of DNA created synthetically in the laboratory from the Zika virus, Pierson said.
When introduced into the body, the DNA causes small virus-like particles to be secreted from cells, Pierson explained. These particles are not full-fledged Zika, but are similar enough to the virus that the immune system might produce an antibody response that will also protect against Zika.
"This kind of vaccine, which we call a DNA vaccine, there's precedent for this," Pierson said, noting that similar technology was used years ago to create a candidate vaccine for West Nile virus.
To test the potential effectiveness of the Zika vaccine, researchers provided a single dose to six rhesus monkeys and two shots to 18 monkeys.
None of the monkeys that received a single dose was protected from Zika infection, but the vaccine did appear to create an antibody response, the researchers found. Their blood contained less Zika virus than animals who did not receive the vaccine.
The two-dose vaccine series protected 17 out of the 18 monkeys against exposure to Zika, and provided researchers with an idea of how much antibody response is needed to protect against infection. ■