Anti-dengue antibodies may prevent Zika infection

An anti-dengue antibody-based drug could potentially protect a mother and her foetus from the deadly Zika virus as well, suggests new research.

In experiments with mice, the researchers found that an antibody that protects against dengue virus is also effective against Zika.

"We found that this antibody not only neutralises the dengue virus but, in mice, protects both adults and foetuses from Zika disease," said Michael Diamond, Professor at Washington University School of Medicine in St. louis, and senior author of the study published in the journal Nature Immunology.

Antibodies remain in the bloodstream for weeks, so one or a few doses of an antibody-based drug given over the course of a woman's pregnancy potentially could protect her foetus from Zika, with the added benefit of protecting her from both Zika and dengue disease, the researchers said. 

Dengue causes high fever, severe headaches, and joint and muscle pain in children and adults but does not directly harm foetuses.

Since dengue and Zika are related viruses, the researchers reasoned that an antibody that prevents dengue disease may do the same for Zika. 

In collaboration with Gavin Screaton of Imperial College london, who had generated a panel of human anti-dengue antibodies years before, the scientists infected nonpregnant adult mice with Zika virus and then administered one of the anti-dengue antibodies one, three or five days after infection. 

For comparison, another group of mice was infected with Zika virus and then given a placebo.

Within three weeks of infection, more than 80 per cent of the untreated mice had died, whereas all of the mice that received the anti-dengue antibody within three days of infection were still alive, and 40 per cent of those that received the antibody five days after infection survived.

To find out whether the antibody also could protect foetuses from infection, the researchers infected female mice on the sixth day of their pregnancies with Zika virus and then administered a dose of antibody or a placebo one or three days later.

On the 13th day of gestation, the amount of Zika's genetic material were significantly lower in the placentas and in the foetal heads from the pregnant mice that were treated one day after infection, compared with mice that received the placebo.

However, administering the antibody three days after infection was less effective, the findings showed. 

These findings suggest that for the antibody to effectively protect foetuses from Zika infection, it must be administered soon after infection. 

Such a goal may be unrealistic clinically because women rarely know when they get infected.

However, giving women the antibody as soon as they know they are pregnant could provide them with a ready-made defence against the virus should they encounter it. 

"We mutated the antibody so that it could not cause antibody enhancement of dengue infection, and it was still protective," said Diamond.

"So now we have a version of the antibody that would be therapeutic against both viruses and safe for use in a dengue-endemic area, because it is unable to worsen disease," Diamond added.