Photo by Einar Fredriksen
Three types of investigational vaccines can protect monkeys from Zika virus infection, according to research published in Science.
Investigators found that an inactivated virus vaccine, a DNA-based vaccine, and an adenovirus vector-based vaccine induced immune responses and protected against infection in rhesus macaques challenged with the Zika virus.
In addition, there were no adverse events observed with any of the vaccines.
The investigators first tested the inactivated Zika virus vaccine in 16 rhesus macaques. Eight animals received the experimental vaccine, and 8 received a placebo injection.
Within 2 weeks of the initial injection, all vaccinated animals developed neutralizing antibodies as well as antibodies specific to the viral envelope protein, a key vaccine target on the Zika virus. A second dose was given 4 weeks later, which substantially boosted antibody levels.
The monkeys were then challenged with Zika virus. Following exposure, the vaccinated animals had no detectable virus and showed no other evidence of infection, while the group that received the placebo injection developed high levels of virus replication in the blood and other tissues for 6 to 7 days.
In another experiment, the investigators administered 2 doses of a DNA vaccine, 1 dose of an adenovirus vector vaccine, or a placebo injection to 3 groups of 4 monkeys each. The group that received the DNA vaccine received a booster shot 4 weeks after the initial vaccination.
Minimal levels of antibodies were detected after the first injection of the DNA vaccine. However, after the second injection, investigators detected Zika-specific neutralizing antibodies in the animals.
The adenovirus vector-based vaccine induced Zika-specific neutralizing antibodies 2 weeks after the single injection.
The animals were exposed to Zika virus 4 weeks after the final vaccination. Both the DNA vaccine and the adenovirus vector vaccine provided complete protection against infection.
The investigators said these encouraging findings suggest a path forward for clinical development of Zika vaccines in humans.
