In recent weeks, two potential Zika virus vaccines were given to a few dozen people in the United States and Canada – the first time an immunization against Zika has been tested on humans. Both are what researchers call DNA vaccines and their formulas are similar; they contain synthetic copies of a piece of Zika genomic material that codes for two proteins, which encase the protein in shells and which the body’s defense cells use to identify the invader.
This is the first of the three phases of a human clinical trial that are required for approval of the commercial sale and broad public use of drugs and vaccines. In the current phase, both vaccines are given to healthy volunteers to make sure they are safe and cause no serious adverse reactions. One vaccine was engineered by scientists at the Vaccine Research Center, part of the National Institutes of Health (NIH), while the other was designed jointly by South Korea-based GeneOne Life Science and the US firm Inovio Pharmaceuticals.
Little is known about the vaccine developed by GeneOne and Inovio. Labeled GLS-5700, it is undergoing animal testing in the United States and Canada, but no results have been released as yet. The NIH vaccine, called VRC-ZKADNA085-00-VP, is being given only in the United States, where it has proved to be effective in tests on rodents and monkeys. Data presented in Science magazine on September 22, 2016, showed that 17 of 18 monkeys that received two doses of the NIH vaccine acquired protection from Zika infection.
“We ascertained that there is a minimum concentration of antibodies needed to afford protection,” says Brazilian researcher Leda dos Reis Castilho, one of the study collaborators. Castilho is trained in chemical engineering and is a professor at the Alberto Luiz Coimbra Institute–Graduate School and Research in Engineering (Coppe), of the Federal University of Rio de Janeiro (UFRJ), where she had been working to develop a yellow fever vaccine, before the Zika epidemic exploded. She is now a visiting researcher at the NIH, where she focuses on the development of Zika vaccines and antibodies.
“Based on the animal results obtained in July, the NIH received approval to initiate clinical trials in humans,” says Castilho. In August and September 2016, NIH teams vaccinated 55 individuals ages 18-35 with the first dose. Eighty people are expected to receive two to three doses during this phase.
Both the NIH and the GeneOne/Inovio vaccines differ slightly from the DNA version developed by Dan Barouch’s team at Harvard Medical School. His group was the first to prove that this type of vaccine can protect rodents and monkeys from Zika infection (see reports at goo.gl/dUSjqm and goo.gl/9oiSsC on the Pesquisa FAPESP site).
“We are counting on the NIH’s DNA vaccine to be safe and undergo rapid development,” says Castilho. Scheduled to begin in January 2017, the phase 2 clinical trial will be conducted in several countries, including Brazil. If all goes as hoped, the vaccine may be available to the public in a few years. In São Paulo, the Butantan Institute, which is one of Brazil’s key centers for sera and vaccine production, is studying the possibility of producing the DNA vaccine developed by the NIH. “It may be possible to produce this vaccine at the Butantan Institute to start with,” says biologist Paulo Lee Ho, director of the Technological Development and Production Division at Butantan.
DOWD, K. A. et al. Rapid development of a DNA vaccine for Zika virus. Science. September 22, 2016