A potential treatment against Zika virus

A new experiment involving mouse models may have uncovered an antibody treatment for the Zika virus. Made up of blood cells from people who recently recovered from the virus, the treatment could potentially protect developing fetuses against Zika, leading to a possible vaccine and therapy for pregnant women.

Spread by mosquitos, the Zika virus can cause severe birth defects, such as microcephaly, a condition where babies are born with small skulls and underdeveloped brains. While the virus usually causes mild illness, including during pregnancy, an unusual increase in cases of congenital microcephaly in areas with Zika outbreaks has caused international concern.

According to a paper published in the journal Nature, a team of researchers was able to successfully isolate antibody-producing immune cells from the blood of three people who had been infected with the virus. After screening 29 different anti-Zika antibodies from the isolated cells, one of them, called ZIKV-117, was found to efficiently neutralize five different Zika strains that represent the existing known varieties of the virus.

To determine whether the antibody would also protect living animals, researchers injected it into pregnant mice either one-day before or after they were infected with the virus. Researchers found that just a single dose of ZIKV-117 not only significantly reduced the amount of Zika virus in the mother's blood but also shielded the fetus from the virus.

“The antibody, called ZIKV-117, protected fetal mice from a Zika infection in their pregnant mothers. It will clear the virus in the mother, and also protect the fetus, which is very important,” said co-senior researcher Dr James Crowe, director of the Vanderbilt Vaccine Center in Nashville, to WebMD.

This is the first antiviral that has successfully been shown to work during pregnancy to protect developing fetuses from the Zika virus, at least in mice, said Dr Michael Diamond from the Washington University School of Medicine in St. Louis, one of the lead researchers, in an NBC News report.

At the moment, if a pregnant woman is diagnosed with Zika, she only really has two options – terminating the pregnancy or take it to term, said Professor Laura Rodrigues from the London School of Hygiene and Tropical Medicine to BBC. But Dr Wong Sin Yew, Infectious Disease Physician at Gleneagles Hospital in Singapore, told Global Health and Travel (GHT) that it’s also important to emphasise that a women infected with Zika during pregnancy does not ‘automatically’ transmit the virus to her fetus.

But Dr Wong also warns that, in fetuses infected with Zika, the effects of the virus can extend beyond just the brain. “There is convincing scientific data that Zika virus infects the neuronal stem cells and can cause damage to nerve cells. One consequence of such damage is microcephaly and it is important to state that there are many other descriptions of damage in the brain and spinal cord due to Zika virus,” he said. “The congenital Zika syndrome also demonstrated that the virus affects not only the brain, but the eyes, limbs and other organs may also be involved.”

The big question going forward is how the antibody will act in humans. “Whether this monoclonal antibody performs similarly in humans and can prevent the negative effects of Zika infection in fetuses is currently unknown and would require further study,” according to the World Health Organization (WHO).

"If this study, done in mice, can be replicated in human models and the antibody developed for commercial use, it could be an important way to mitigate the damage Zika causes," Dr Amesh Adalja, a senior associate with the University of Pittsburgh's UPMC Center for Health Security, told WebMD.

Meanwhile, scientists are focusing on developing a vaccine, with some 30 Zika candidate vaccines currently in the pipeline, three of which are being evaluated in phase 1 trials. Several additional candidates are expected to move to phase 1 trials in the coming months.

“There are several models for the development of a Zika vaccine for humans. These are early days in vaccine development and a vaccine for general use is likely to take another three to five years. In addition, the different types of vaccines focus on different subsets of the population. For example, a live attenuated viral vaccine is not likely to be tested in pregnant women but could be used in healthy children,” Dr Wong said.

Researchers are also planning to test the antibody treatment in monkeys and hope to conduct clinical trials on humans within a year.

The WHO currently advises pregnant women residing in Zika-prone areas, or returning from such areas, to see their health-care provider to closely monitor their pregnancy.

This story was originally published in the 2017 March issue of Global Health and Travel magazine.