Researchers report progress in developing vaccine to protect against Zika. | Gordon Zammit/AdobeStock
Three different types of Zika vaccines are effective at protecting rhesus monkeys from the virus, according to analysis published in the 5 August, 2016 edition of the journal Science.
The research, which Science has made freely available to the public, describes scientific progress toward combating the scourge of Zika, which has been causally associated with fetal microcephaly, intrauterine growth retardation, and other devastating birth malformations in humans. A preventative vaccine is poised as one of the best ways to minimize the spread of the virus and its detrimental effects.
“Three vaccines provided complete protection against Zika virus in nonhuman primates, which is the best animal model prior to starting clinical trials,” said senior study author Dan H. Barouch, MD, PhD, Director of the Center for Virology and Vaccine Research at BIDMC, Professor of Medicine at Harvard Medical School, and Steering Committee Member at the Ragon Institute of MGH, MIT and Harvard. “The consistent and robust protection against Zika virus in both rodents and primates fuels our optimism about the development of a safe and effective Zika vaccine for humans.”
Whereas some similar techniques and vaccines have been tested in mice, monkeys are a much better model to determine how vaccines will work in humans. Previously, researchers had reported that both a DNA vaccine and a purified inactivated virus (PIV) vaccine were effective at protecting mice from the virus.
Now, Barouch and his colleagues have reported the efficacy of the PIV vaccine in 16 rhesus monkeys, eight of which were given sham vaccines as controls.
All PIV vaccinated animals developed Zika-specific binding and neutralizing antibodies two weeks following immunization, and were completely protected from Zika when exposed to the virus. When the researchers harvested antibodies from PIV vaccinated monkeys and transferred them to mice and monkeys, a technique called adoptive transfer, these animals also were protected against Zika virus, as long as therapeutically sufficient antibody titers were transferred.
The researchers also tested a DNA vaccine and a recombinant adenovirus (Ad) vector expressing the Zika pre-membrane and envelope protein. These two vaccines also raised antibody responses and provided full protection to monkeys, and the Ad vector even protected after a single immunization. Across all three platforms, no adverse effects were reported.
The work resulted from a collaboration of researchers with the Walter Reed Army Institute of Research (WRAIR) and the Beth Israel Deaconess Medical Center and Harvard Medical School.
In a news release, Col. Stephen Thomas, an infectious disease Army physician and a vaccinologist specializing in flaviviruses such as Zika and dengue said: “Results from both mouse and nonhuman primate testing are encouraging and support a decision to move forward with our U.S. government, industry and regulatory partners to advance our ZPIV vaccine candidate to human trials. It builds on technology WRAIR developed and successfully applied to other flavivirus vaccines. We hope that by leveraging a proven technology we increase our chances of developing a safe and effective Zika vaccine.”
In a 5 August news article in Science, award-winning journalist Jon Cohen noted that “A vaccine is sorely needed. The virus has blasted through Latin America, leaving severe birth defects and other maladies in its wake. Just this week, Florida health officials confirmed the first cases of local transmission in the United States; until now, all cases here involved people who had traveled to affected countries. These Florida cases were mainly infected by mosquitoes within a 2.5-square-kilometer area of northern Miami.”
The Science paper, by Peter Abbink and colleagues, is entitled “Protective efficacy of multiple vaccine platforms against Zika virus challenge in rhesus monkeys.”
[Associated image: Gordon Zammit/AdobeStock]