New Vaccine Protects Newborn Mice From Zika

Two vaccines against Zika virus under development protect newborn mice from the neurological ravages of the disease, a new preliminary study finds.

Scientists are racing to develop a vaccine against Zika, a virus spread primarily through the bite of an infected mosquito.

The virus is spreading at epidemic proportions in various parts of the world. Homegrown Zika is also present Florida, where health officials are trying to stop it from spreading.

When pregnant women are infected, the virus can pass to their fetus, which can damage the developing baby and cause severe neurological birth defects, including microcephaly, or an abnormally small head.

At the University of Pennsylvania, researchers have developed two vaccines which they say successfully conveyed immunity against Zika in a mouse trial.

But although two vaccines were tested, only one of them is an actual candidate for a Zika vaccine, the researchers noted.

One of the two vaccines uses a “microneedle array” to deliver the vaccine just below the surface of the skin through tiny crystals that dissolve after being affixed to the skin by a Band-Aid-like patch.

The other vaccine uses the traditional needle delivery format and adenovirus, a type of common cold virus, to present Zika antigens to the immune system to induce immunity.

Both vaccines used proteins on the “envelope,” or outer shell, of the virus as the antigen to prime the immune system so it can quickly recognize and fight off the actual virus. This approach has worked in the past to develop West Nile, yellow fever and dengue vaccines.

Mice do not develop microcephaly, so the researchers looked at other factors, including survival, as well as the development of neurological problems after the offspring were exposed to the virus at one-week old.

In terms of survival, only 12.5 percent of the pups survived in the control group.

Furthermore, all of the control group pups showed signs of neurological damage, including loss of balance, muscle weakness and hind-limb paralysis.

Five out of six of the microneedle array group pups also exhibited neurological issues, though they weren’t as severe as the control group’s symptoms.

None of the adenovirus vaccine pups showed significant neurological problems.

Although the adenovirus Zika vaccine definitely performed better in this study, this vaccine wouldn’t work well in humans because the vast majority of us have already had adenovirus colds so our immune systems would simply neutralize the vaccine and not develop proper Zika antibodies, the researchers say.

“We’ve not only developed a promising vaccine candidate to move toward larger preclinical and, eventually, human clinical trials, but also a delivery format that would be inexpensive to produce and distribute to hundreds of thousands of people,” says senior author Dr. Andrea Gambotto of the findings, which appear in EBioMedicine.