University of Pittsburgh researchers are working with a biotechnology company to develop a vaccine aimed at quickly countering outbreaks that could be caused by a deadly avian flu virus.

The vaccine, being developed by researchers at Pitt's Center for Vaccine Research and Novavax Inc., produced a strong immune response in mice and protected them from death following infection with the H5N1 virus, according to a study being published today in the online journal PLoS ONE.

The vaccine also has been tested in humans in early-stage trials. Last month, Novavax announced that the vaccine was well tolerated in 70 healthy adults and that it induced "good immune responses."

Researchers are conducting additional tests involving 320 people, said Dr. Ted Ross, lead author of the study and an assistant professor at Pitt's vaccine research center.

The vaccine uses a technology known as a virus-like particle, or VLP, that is recognized by the immune system as a real virus but lacks genetic information to reproduce, making it potentially safer.

Gardasil, used to protect against certain viruses that are a major cause of cervical cancer, is the first vaccine using VLP technology to be approved for human use by the U.S. Food and Drug Administration, Dr. Ross said.

No similar use of VLP is being made by other companies for flu, he said.

Outbreaks of H5N1 flu in birds were reported in Asia several years ago, and more recently in Europe, Africa and the Near East, according to the U.S. Centers for Disease Control and Prevention. The virus usually does not infect people, but more than 200 human cases have been reported.

Because all flu viruses can change, however, scientists are concerned that H5N1 could gain the ability to spread easily from person to person, which could trigger a flu pandemic.

Typically, flu vaccines have been grown in chicken eggs and can take six to nine months to develop. But Dr. Ross said the vaccine he and others are developing uses a cell-based technology that can eliminate months of production time, which could be crucial if a pandemic occurred.

Other companies are using similar technology to develop flu vaccines, he said.

The study was funded by Novavax. Other co-authors were Drs. Rick Bright, Niranjan Kumar, Peter Pushko and Gale Smith, all of Novavax; Donald Carter, Corey Crevar, Jonathan Steckbeck, and Drs. Franklin Toapanta and Kelly Cole of the Center for Vaccine Research; and Dr. Terrence Tumpey of the CDC.