A study revealed that ZIKV-117, anti-Zika antibody, can protect developing fetuses from the virus and its most common consequence: Microcephaly. The antibody was also advantageous to protect the placenta and adults, opening a window to improve the current trials of the Zika vaccine.

Researchers at Washington University School of Medicine in St. Louis and Vanderbilt University School of Medicine discovered the antibody that managed to protect both the fetus and the placenta in pregnant mice that were infected with Zika virus. The study was published on November 7 in the journal Nature. ZIKV-117 is the first antiviral that has shown to work to avoid microcephaly and other consequences of Zika virus in pregnancy.

A researcher holds a tray of Zika virus growing in animal cells at Washington University School. Image Credit: Huy Mach/Outbreak News Today

Michael Diamond, MD, Ph.D., and the study’s co-senior author screened 29 anti-Zika antibodies from people that already had the virus. Diamond worked with co-senior author James Crowe Jr., MD of Vanderbilt and other colleagues, whose work later led to discover antibody ZIKV-117. The antiviral efficiently neutralized five Zika strains -the five subtypes of the Zika virus- even when the carrier was pregnant, protecting the fetus from microcephaly and death.

After finding ZIKV-117, doctors had to test it to see if the antibody could protect living animals from Zika. Thus, they used pregnant mice to see if the fetus could not be harm by the virus and avoid microcephaly. The researchers gave the antibody to the mice one day before or after they infected them with Zika.

In both cases, the antibody managed to protect the animal from the virus, including the fetus growing inside them. ZIKV-117 reduced the levels of the virus in the mice, the fetus, and their placentas compared to the control group that did not receive the antiviral.  

Diamond is also a Professor of Medicine at Herbert S. Grasser and stated in the press release of his study that his team finding is the proof that Zika can be treated during pregnancy, at least in mice. Co-senior author Crowe stressed that the naturally occurring antibodies isolated from humans who had recovered from Zika are the first medical intervention that prevents the virus infection and damage to fetuses.

Co-author Indira Mysorekar, Ph.D. and associate professor of obstetrics and gynecology at Washington University confirmed that the team did not see injuries to the fetal blood vessels, any growth restriction in the fetuses nor thinning of the placenta in the pregnant mice that were giving the ZIKV-117 antibody.  Mysorekar explained that the antibody keep the fetus intact by blocking the virus from crossing the placenta. 

Indira Mysorekar is also a professor of pathology and immunology at Washington University and co-director of the university’s Center for Reproductive Sciences.

The study compared the placentas of the group that received the antiviral with the group of mice that did not and found significantly different results. The females treated for Zika showed a normal and healthy placenta, but the females that did not receive the antibody showed a destroyed placental structure. Damage to the placenta is the the cause of slow fetal growth -microcephaly included- and even death.

The ZIKV-117 not only can protect fetus and their placenta but adults as well

During research, the antibody also proved to be capable of protecting adult mice against a lethal dose of Zika virus. Zika has not been characterized for being lethal for humans, but the study needed to prove the antiviral with a lethal dose to understand how well the ZIKV-117 works under extreme conditions. The results were positive to keep adult male mice safe from Zika virus, even when they received the antibody five days after been infected.

The study proves that antibodies alone can protect adults and fetuses from the Zika virus, a relief for humanity that wants to end the virus effects on babies. The finding suggests that vaccines using the ZIKV-117 antivirus could protect women and their fetuses in current or future pregnancies.

A vaccine against Zika is already being tested in humans although it has not been injected to pregnant animals. Thus, the new study promises that antibodies could protect adults and fetuses if they are used in the vaccine against Zika.

The Zika vaccine is the best method to prevent Zika, although it has a main side effect. There is a phenomenon known as antibody-dependent enhancement commonly provoked by vaccines. The phenomenon worsened the symptoms of a disease in people that had a shot at it. This has happened with the Dengue virus, related to the Zika strains.

The good news is that scientists of the study already tried the possibility to avoid antibody-dependent enhancement of Zika injections and the results were positive. Researchers modified the antiviral to prevent it from participating in the process, and the results showed that the modified antibody worked as well as the original protecting the placenta and fetus.

How can pregnant women be protected while the vaccine against Zika is developed?

There is the possibility to protect fetuses and their placentas if expectant mothers are administered antibodies against the virus. It is an attempt to protect the women and her babies, but it has not been tested yet. Pregnant women living in a Zika-endemic area could receive the antibodies throughout her pregnancy to avoid the virus. The future mother does not necessarily have to be infected with Zika to be treated. Their partners could also get antibodies to prevent infecting the mother, causing microcephaly and other Zika consequences to the fetus.

Crowe will continue to work in the development of the antibody as a potential therapeutic production for human studies. Diamond is focusing on determining if the antibodies could be used to cure a persistent Zika infection.

“We know that Zika can persist in certain parts of the body, such as the eyes and the testes, where it can cause long-term damage, at least in mice,” Diamond said. “We showed that the antibody can prevent disease, and now we want to know whether it can clear the persistent infection from those parts of the body.”

Source: Washington University