London, Nov 4 (IANS) A DNA-based vaccine being developed against the dreaded West Nile virus, transmitted from animals to humans, would be equally effective after the onset of the disease.Existing live vaccines are merely preventive and carry a risk of provoking the disease, but DNA vaccines are absolutely biologically safe. They can also be stored without a fridge - which makes them ideal for use in subtropical and tropical climates.

Although deadly viral outbreaks like SARS, avian flu, Ebola are becoming commonplace, there are no vaccines for many of the pathogens responsible.

One of the most dangerous classes of viral diseases is the zoonosis, which can be transmitted from animals to humans sometimes with fatal consequences. One of these is caused by the West Nile virus (WNV), which was first identified in Uganda in 1937.

The virus was carried to the US in 1999 and had spread through the whole of North America within five years. There is now a risk that it will propagate worldwide. Since its first appearance in America, WNV has claimed 400 lives. A new vaccine promises to provide protection.

Scientists at the Fraunhofer Institute for Cell Therapy and Immunology IZI in Leipzig have developed the DNA vaccine, according to a Fraunhofer release.

“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,” explained Matthias Giese, the IZI’s head of vaccine development.

“We can thus replicate the virus’s natural infection route without actually triggering the disease,” he said.

Conventional 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.

“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.”

Giese expects the lab research to be completed by 2009. After that, another three 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.