Researchers have developed a vaccine that provides protection against the Zika virus in mice without increasing susceptibility to Dengue virus infection
The two viruses belong to the same family, known as flaviruses, and share genetic and structural similarities, which can lead to a type of immune cross-reactivity called antibody-dependent enhancement of infection (ADE) if a person is infected with both.
This means that prior exposure to Dengue can result in a more severe response to Zika infection and previous attempts to develop Zika vaccines indicated they might increase the risk of Dengue.
In an attempt to overcome this, researchers developed a recombinant vaccine targeting a viral envelope sub-unit specific to the Zika virus.
They showed that in mice the vaccine induced strong antibody and cellular immune responses, with antibody titres indicating that it would confer protection against Zika virus infection. Furthermore, by incubating blood serum samples from vaccinated mice with Dengue fever virus, they showed that there was no detectable ADE.
“All flaviviruses have the envelope protein on the outside part of the virus. It has three domains,” explains lead author Qiang Chen from Arizona State University, Tempe, Arizona. “The domain III has a unique stretch of DNA for the Zika virus, and we exploited this to generate a robust and protective immune response that is unique for Zika.”
The team says the results indicate that their vaccine could confer robust immunity to Zika while potentially being safer than vaccine candidates explored in research so far.
They also say that their approach could help improve the cost-effectiveness of Zika vaccination as they produced and purified their vaccine in large quantities using plant-based expression in the tobacco plant.