Zika vaccine moves a step closer

Scientists in the US are reporting rapid progress towards a vaccination against the Zika virus, the mosquito-borne disease associated with a range of birth defects.

Two doses of a DNA vaccine candidate for Zika protected 17 of 18 monkeys from the virus, according to the study, published in Science.

The vaccine contains DNA that codes for specific proteins from a pathogen.

Once taken up by the host cells, the cells use the DNA to synthesise the pathogenic proteins, recognising it as foreign and triggering a protective immune response.

“What we want is to present the outer surface of the virus to the immune system so that it can recognise that with antibodies and make more of those antibodies, so, that if you see the real virus, those antibodies can block it from infecting,” Barney Graham, Deputy Director of the Vaccine Research Center at the US National Institutes of Health (NIH), told reporters.

Researchers at the NIH developing the vaccine say they chose the delivery system due to the urgency of the current Zika outbreak in South America.

“Advantages of DNA vaccines include the ability to rapidly test multiple candidate antigen designs,” they said.

The system also has an established safety record in humans, which has allowed the clinical trials to get under way so quickly.

The technique has been used in a range of other diseases such as Ebola, West Nile virus, SARS, influenza and AIDS.

While 17 of the 18 monkeys that got two doses of the vaccine were completely protected, all six monkeys given a single, weaker dose became infected with Zika.

Even so, those six had a lower viral load than a control group of animals that received no treatment, suggesting the low dose did provide some level of protection.