Study: 2 Types Of Vaccines Protect Against Zika Virus In Mice

"We hope that this news will electrify and galvanize the vaccine effort against Zika virus," says Dr. Dan Barouch of Beth Israel Deaconess Medical Center and Harvard Medical School.

Barouch is senior author of a paper just out in the journal Nature reporting some promising findings on potential Zika vaccines — at least, in mice. Researchers found that two different types of vaccines — one using DNA and one using an inactivated form of the virus — seemed to confer complete protection against the virus that has been declared a public health emergency through much of the Americas.

There's no timetable for when this research may translate into help for humans, but still, it's a clear step forward. WBUR's Jonathan Cain spoke with Dr. Barouch. An edited excerpt:

How would you sum up your findings?

In this paper, we show that two vaccine candidates -- a DNA vaccine and a purified inactivated virus vaccine — both provided complete protection against Zika virus challenge in mice.

Who has been developing the vaccines and what is the connection with Beth Israel Deaconess Medical Center?

We developed the DNA vaccine in-house. The inactivated virus vaccine was developed by the Walter Reed Army Institute of Research.

What are the next steps?

The protection seen in mice was striking, with all the control animals showing high levels of virus replication and all the vaccinated animals showing no detectable virus after challenge with the Zika virus from both Brazil and Puerto Rico.

We have to be cautious about extrapolating mice data to humans, but based on the robustness of the protection, the demonstration that the antibodies can protect, and the similarities with other viruses in this family, for which human clinical vaccines have been successfully developed — these findings raise optimism that the development of a safe and effective vaccine for Zika virus may be successful. And so clinical trials should proceed as quickly as possible.

When did you start this work?

We started work on these vaccine studies essentially four or five months ago, after the Zika virus epidemic had been made public and the World Health Organization declared this a global health emergency.

So concrete next steps?

Clinical trials would be a very natural progression of the current pre-clinical studies. There are a number of unresolved questions, including larger animal studies, human immunogenicity and eventual protection studies, as well as scientific questions about the role of antibodies against other flaviviruses such as Dengue.

What's the theory behind how this vaccine works to knock out the virus in mice?

More than just theory, what we showed in this paper is that the vaccine induces antibodies against the Zika virus coat protein, called envelope. And we demonstrated that it is the envelope-specific antibodies that can block infection from this virus. We showed that by doing what’s called an adoptive transfer study. In other words, taking antibodies induced by the vaccine out of one animal, purifying the antibodies and then infusing them into another animal that has not been vaccinated, and showing that those antibodies can protect.

How do you interpret these findings for people gravely concerned about Zika and hoping for a solution as quickly as possible?

The current findings are very promising because they show that two different candidate vaccines can protect against Zika virus in an animal model. Although that does not necessarily mean that these will work in humans, these data certainly suggest that the development of a vaccine for humans will likely be possible.

With reporting by CommonHealth editor Carey Goldberg