Researchers at the Washington University School of Medicine in St. Louis, and Vanderbilt University School of Medicine in Nashville, have identified a naturally-occurring human antibody which could protect the developing fetus from birth defects caused by the Zika virus. The article – which was published in the journal, Nature – could help in the development of a Zika vaccine.
While most people who become infected with the Zika virus after being bitten by the Aedes aegypti mosquito are asymptomatic, the virus can cause devastating effects on an unborn child. Pregnant women who are exposed to the Zika virus run the risk of giving birth to baby with microcephaly and vision problems, among other birth defects.
As there is currently no vaccine available to protect against Zika, pregnant women living in endemic areas are urged to avoid getting bitten by mosquitos. The newly-discovered antibody, named ZIKV-177, will put researchers one step closer to developing a more effective form of disease prevention.
To conduct their study, the researchers analyzed blood samples collected from those who had been infected with the Zika virus. They found 29 distinct anti-Zika antibodies, which they tested against a number of different Zika strains in vitro.
One of those antibodies tested – ZIKV-177 – was found to be effective against five different Zika strains. To determine whether this antibody was able to neutralize the Zika virus in animal models, the researchers administered ZIKV-177 to pregnant mice one day before, or one day after, they were infected with the Zika virus.
In both groups of mice, ZIKV-177 reduced Zika virus levels both pregnant mice and their offspring. Compared to mice who were not given the antibody, treated mice showed better outcomes.
“We did not see any damage to the fetal blood vessels, thinning of the placenta or any growth restriction in the fetuses of the antibody-treated mice,” said Dr. Indira Mysorekar, an associate professor of obstetrics and gynecology and pathology and immunology at Washington. “The anti-Zika antibodies are able to keep the fetus safe from harm by blocking the virus from crossing the placenta.”
The researchers also administered ZIKV-177 to male mice infected with a highly-lethal strain of Zika. In this case, even though the antibody was given to the mice five days after they were infected, it was still able to reduce levels of the virus.
“We stacked the deck against ourselves by using a highly pathogenic strain of Zika,” said Mysorekar, “and even in that case, the antibody protected the mice.”
The researchers say that these results suggest the antibody could be sufficient to protect against Zika virus in both adults and fetuses. As well as being a potential protective, the antibody could also treat fetuses that have already been exposed to the virus.
“These naturally occurring human antibodies isolated from humans represent the first medical intervention that prevents Zika infection and damage to fetuses,” said Dr. James Crowe Jr., of the Vanderbilt Vaccine Center. “We’re excited because the data suggests we may have antibody treatments in hand that could be developed for use in pregnant women.”