The special feature of this vaccine is that it is also effective after onset of the disease, for it has therapeutic properties.
"In this type of vaccine, DNA molecules known as plasmids extracted from the pathogen are used for inoculation, instead of the whole virus. They contain the genetic code for the antigens that stimulate the body to produce antibodies. We can thus replicate the virus's natural infection route without actually triggering the disease," said Dr. Matthias Giese, the IZI's head of vaccine development.
Traditional methods of vaccination involve injecting a dead or weakened form of the pathogen into the patient's body, which responds by producing the corresponding antibodies and developing immunity to the disease.
An alternative is to inject a serum that already contains these antibodies. Such vaccines are merely preventive.
By contrast with live vaccines, which carry a risk of provoking the disease, DNA vaccines are absolutely biologically safe.
Moreover, they activate all existing defence mechanisms in the body, are cheap to produce and can be stored without a refrigerator - which makes them ideal for use in subtropical and tropical climates.
"Since the human immune system is very similar to that of other mammals, we are developing a cross-species vaccine for use in both veterinary and human medicine. And unlike conventional vaccines, DNA vaccines can be used both as prophylactics and as therapeutics, i.e. in cases where the disease is already present," said Dr. Matthias Giese, citing the further benefits.
The WNV vaccine has already passed initial tests. Giese expects the laboratory research to be completed by the end of 2009.
After that, another 3 years or so will be needed for the approval procedure including clinical trials.
Then, it is hoped, the world's first therapeutic WNV vaccine will be ready for market.