Work on a human vaccine for the Zika virus is progressing well, it was announced last night.
Two experimental Zika vaccines have been tested on mice and found to be protective, given in a single dose, when the animals were exposed to the virus four or eight weeks after having the vaccinations.
Dr Dan Barouch of Harvard Medical School, Massachusetts, USA, and colleagues believe similar vaccines could be similarly protective for humans. The team developed one of the two vaccines, a DNA vaccine, which is composed of portions of DNA from a Zika virus strain that recently circulated in Brazil.
The second vaccine was developed by a team led by Dr Stephen Thomas at Walter Reed Army Institute of Research, Maryland, USA. This version is made from a purified and inactivated Zika virus which circulated recently in Puerto Rico.
Tests show that antibodies specific to the virus could be induced by the DNA vaccine. Both vaccines led to a lack of virus replication in mice four weeks after the inoculation when exposed to the Brazilian strain of Zika virus, which is known to cause foetal birth defects in mice.
A separate group of mice who had the DNA vaccine were exposed to virus eight weeks later and were also protected from infection. Zika-specific antibody levels in the mice appeared to link closely to the level of protection against infection.
Both vaccines are intended to prevent infection by other viruses in the same family as Zika, including West Nile, dengue and tick-borne encephalitis viruses. They conclude in Nature yesterday (28 June) that: "Taken together, our findings provide substantial optimism that the development of a safe and effective Zika vaccine for humans will likely be feasible."
Larocca, R. A. et al. Vaccine Protection against Zika Virus from Brazil. Nature 28 June 2016; doi: 10.1038/nature18952
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