Two New Vaccines Protect Mice From Zika Virus Infection

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Two new experimental vaccines protect mice against the Zika virus, a study out Tuesday shows.

Researchers from governments, academic labs, and biopharma companies have been rushing to develop Zika vaccines since global health experts started warningabout the previously unknown dangers wrought by the mosquito-borne virus,  including serious birth defects. Just last week, the Food and Drug Administration approved the first human testing of a Zika vaccine candidate from the company Inovio Pharmaceuticals.

For the new study, which was published in the journal Nature, scientists tested two kinds of vaccine on mice — one made from DNA and one from an inactivated form of the virus. With one dose, both vaccines prompted the creation of antibodies that shielded the animals from becoming infected when they were exposed to the virus.

“The protection was striking,” said senior author Dr. Dan Barouch, the director of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center in Boston.

Just because the vaccines worked in mice does not mean they will work in people. And even if the vaccines are ultimately successful, they still have to be tested in other animals and small groups of people before they could be deployed widely. Complicating the challenge is that the main goal of any vaccine will be to protect pregnant women — so the inoculation will have to pass rigorous safety tests.

The US Army developed the vaccine made from the inactivated virus and hopes to start testing it in people later this year, said Col. Nelson Michael, an author on the Nature paper and director of the US Military HIV Research Program at Walter Reed Army Institute of Research. Michael said the research group was partnering with a pharmaceutical company to advance the vaccine through clinical development, but would not yet disclose which company.

Inovio’s vaccine is a DNA vaccine, as is a fourth vaccine being designed by the National Institute of Allergy and Infectious Diseases. In those vaccines, patients would receive DNA that produces a protective protein.

The vaccines presented in Tuesday’s paper provided at least two months of immunity in the mice, researchers said. They are exploring if and how that could be extended and are also conducting experiments in pregnant animals. Barouch did not offer a timeline for when the scientists hope to start testing the DNA vaccine in people.

The researchers also need to tease apart if and how well the vaccine would function in patients with existing antibodies from a former dengue infection, Barouch said. Dengue, a related mosquito-borne virus, previously swept through much of the same territory Zika is now moving through, and some scientists have speculated a prior dengue infection could make the impact of Zika worse.