By Betsy McKay
The Wall Street Journal
Scientists have identified a potential treatment for Zika—one that might protect both pregnant women and their fetuses, who are at risk of severe birth defects that the virus can cause.
A human antibody isolated from the blood of people who had been infected with Zika “markedly reduced” Zika infection in pregnant mice, their fetuses, and their placentas, according to a study published online Monday in the journal Nature.
More research needs to be done to determine whether the antibody works similarly in humans, the study’s authors cautioned. It’s likely to be several months before it can be tested in humans, and as a therapy, antibodies are expensive, though advances in engineering are bringing the costs down.
But if it does work, it could be given either as a preventive measure to pregnant women who are living in areas where Zika is circulating or as a therapy to pregnant women who are infected, the study’s authors said.
“This is the first evidence that antibodies can protect against fetal transmission” of Zika, said Michael Diamond, professor of medicine at Washington University School of Medicine in St. Louis and a co-senior author of the study.
Scientists also recently identified several existing drug compounds that may also work as therapies against Zika. But commercial drugs are rarely tested on pregnant women, so it isn’t known whether they could be all used for that group.
Antibodies, by contrast, are already in the human body. “This is essentially a naturally occurring biological drug,” said James Crowe, director of the Vanderbilt Vaccine Center, at Vanderbilt University Medical Center, and another co-senior author of the study. While they would have to be carefully evaluated for pregnant women, he said, “There’s a long history of the safety of antibodies.”
The researchers have raced to get this and several other antibodies they believe hold promise into manufacturing so that they can move forward quickly with further testing, Dr. Crowe said. “We have moved several into preliminary manufacturing,” he said.
Dubbed ZIKV-117, the antibody diminished levels of the virus in the pregnant mice, infecting fewer of the cells in their placentas, and thereby blocking or reducing transmission of the virus to their fetuses, according to the study. It had that effect when mice were injected with the antibody one day before they were infected, as well as when they were injected one or five days afterward.
That suggests that the antibody could be administered to pregnant women both before exposure, or to treat existing infections, Dr. Crowe said. A man who had been diagnosed with Zika might even be given it to prevent sexual transmission to a partner, he said.
The findings could also help scientists develop a Zika vaccine by showing how the powerful antibodies work, the authors said.
“I think that’s the most exciting part of this work,” said Hongjun Song, a neuroscientist at Johns Hopkins University School of Medicine in Baltimore, of the implications for vaccine development. He was a lead author on the study identifying potential drug compounds to treat Zika and wasn't involved in the current study.
ZIKV-117 worked against five Zika samples that represent a global range of strains—from Africa, Asia and the Americas, the study’s authors said.
Zika can cause a constellation of birth defects, including brain damage, in the fetuses of infected pregnant women. The defects are often signaled by microcephaly, an unusually small head. Hundreds of babies have been born with microcephaly over the past year, mostly in Brazil, but in other countries throughout the Americas as well.