New DNA weapon against avian flu identified

Washington, July 2 : Scientists at the University of Pennsylvania School of Medicine have identified a potential new weapon against avian flu.

Researchers have immunized experimental animals against various strains of the virus by delivering vaccine via DNA constructed to build antigens against flu, along with a minute electric pulse.

Such an approach could allow for the build up of vaccine reserves that could be easily and effectively dispensed in case of an epidemic.

"This is the first study to show that a single DNA vaccine can induce protection against strains of pandemic flu in many animal models, including primates," said David B. Weiner, Ph.D., Professor of Pathology and Laboratory Medicine.

"With this type of vaccine, we can generate a single construct of a pandemic flu vaccine that will give much broader protection," he added.

Traditional vaccines expose a formulation of a specific strain of flu to the body so it can create immune responses against that specific strain.

Conversely, a DNA vaccine becomes part of the cell, giving it the blueprint it needs to build antigens that can induce responses that target diverse strains of pandemic flu.

Avian flu is tricky. Not only is it deadly, but it mutates quickly, generating different strains that escape an immune response targeted against one single strain.

Preparing effective vaccines for pandemic flu in advance with either live or killed viruses, which protect against only one or few cross-strains, is therefore very difficult.

How to predict which strain of avian flu may appear at any time is difficult. "We are always behind in creating a vaccine that can effectively protect against that specific strain," notes Weiner.

Instead of injecting a live or killed virus, the researchers injected three different species of animal models with synthetic DNA vaccines that are not taken from the flu microbe, but trick the immune system into mounting a broad response against pandemic flu, including strains to which the immune system was never exposed. Antibodies induced by the vaccine rapidly reached protective levels in all three animal species.

"The synthetic DNA vaccines designed in this study customize the antigen to induce more broad immune responses against the pathogen," said Weiner.

Researchers found evidence of two types of immune responses - T lymphocytes and antibodies - in all three types of animal models. Two types of animal models (mice and ferrets) were protected from both disease and mortality when exposed to avian flu.

To ensure increased DNA delivery, the researchers administered the vaccine in combination with electroporation, a small, harmless electric charge that opens up cell pores facilitating increased entry of the DNA vaccine into cells.

The study has been published in PLoS ONE.

ANI