DNA Flu Vaccine

Scientists Create DNA Flu Vaccine

Allows for build up of reserves

EVERY YEAR, SCIENTISTS cross their fingers, hoping that the avian flu doesn't mutate into a human-to-human version. But one group of researchers has some good news to offer. They say that a new way of delivering the avian flu vaccine-through DNA constructed to build antigens against the flu-will make it possible to stockpile the vaccine in case of a pandemic.

"This is a new way to approach flu vaccines," says study author David B. Weiner, PhD, a professor of pathology and laboratory medicine in the University of Pennsylvania'S School of Medicine. The team'S work was published in the June 25 issue of PLoS ONE. (Laddy DJ, Yan J, Kutzler M, et al. Heterosubtypic protection against pathogenic human and avian influenza viruses via in vivo electroporation of synthetic consensus DNA antigens. PLoS ONE. 2008;3(6): e2517.)

The avian flu, also known as the bird flu, is not only deadly, it also mutates quickly, which means that a virus targeted against one strain will not be effective if the virus mutates into a different strain. This makes it difficult to stockpile a vaccine that will be effective if it is ever needed. Currently, there are four known A subtypes of the influenza virus circulating among humans: H1N1, H1N2, H3N2, and H7N2.

"Right now, we don't have enough stocks should the bird flu spread," Dr. Weiner says. The Food and Drug Administration (FDA) has so far approved only one avian flu vaccine. The vaccine, from Sanofi Pasteur, protects against the H5N1 strain, which does not yet readily infect humans.

A CONSENSUS VACCINE

For this study, researchers used a computer program to align various influenza A matrix 2 and nucleoprotein sequences. Using this information, they generated an artificial consensus sequence similar in some way to each of the other sequences. The point was to provide some immunity against the various strains of the disease.

The researchers used a constant-current in vivo electroporation, an electric shock that opens up cell pores, to deliver the DNA vaccine into mice, ferrets, and monkeys. Traditional vaccines expose the body to a strain of the virus, allowing it to create antibodies against the strain. This DNA vaccine, however, is thought to provide the cell with guidance that enables it to create a response that targets diverse strains.

Researchers found two types of immune responses in all three types of animal models: T lymphocytes and antibodies. The animals reached hemagglutination inhibition titers greater than 1:40.

BENEFITS

A DNA vaccine offers several benefits, according to the study authors. Because it protects against several strains of the virus, the vaccine could be created and stockpiled prior to an outbreak. The DNA vaccine also offers greater protection to researchers because it does not involve the injection of a live virus. Another plus is that it does not rely on egg-based production methods, which can affect people with egg allergies.