St. Jude Scientists Develop New System for Generating Influenza A Virus

St. Jude Children's Research Hospital (ALSAC)
Thursday, 8 June 2000

(Memphis, Tennessee, June 8, 2000) New test-tube method can be used for development of safe and effective vaccines.

Each year influenza viruses cause serious, sometimes lethal, infections in humans. Because the virus is highly variable, it is necessary to change vaccine strains almost annually. Erich Hoffmann, Ph.D., a postdoctoral fellow in the Department of Virology and Molecular Biology at St. Jude Children's Research Hospital, along with Robert Webster, Ph.D. chair of the department, have devised an improved method of producing specific strains of influenza A virus, which can be used for a more rapid development of safe and effective vaccines to meet influenza epidemics. The findings of their study will be published in the journal Proceedings of the National Academy of Sciences (PNAS) on May 23.

The St. Jude research group developed a way of producing influenza A strains in the laboratory by manipulating the eight RNA segments of the virus. By this new method, virus is generated by using eight plasmids, or circular pieces of DNA corresponding to the virus segment. After the introduction of these eight plasmids into cells, cellular enzymes synthesize virus-like molecules. Ultimately, the interaction of these molecules will result in the generation of infectious influenza virus useful for vaccine production.

"The system will allow us to dissect the influenza virus gene by gene to better understand how some strains cause more disease than others," Webster said. "We also may learn to predict which strains can cross the species barrier and cause pandemics."

Because this approach uses a smaller number of plasmids than that used in other influenza virus-production systems, according to Hoffmann. "Therefore, this approach provides a simpler, less expensive system of virus production," he said, "and will allow scientists to improve the design of new influenza vaccines."

There are two ways to make influenza vaccines. The traditional method is by growing large amounts of the influenza virus in chicken embryos. After the virus is purified, treated and killed, it is given as a flu vaccine to humans. Usually the vaccine is administered as an injection in the arm. A more recent technique, still waiting approval for human use, generates a live, weakened, or cold-adapted, virus in the laboratory. The cold-adapted vaccine is administered as a nasal spray, rather than as an injection; this method of administration makes it easier to use and increases its potential for acceptance.

"The administration of this type of vaccine more closely resembles the common route of influenza virus infection, so the vaccine should be more effective than the traditional vaccine in inducing an immune response," Hoffmann said. "Our test-tube method for generating 'designer viruses' can now be used for the development of cold-adapted vaccines once they are approved for human use."

St. Jude was founded by the late entertainer Danny Thomas. The hospital is an internationally recognized biomedical research center dedicated to finding cures for catastrophic diseases of childhood. The hospital's work is supported through funds raised by the American Lebanese Syrian Associated Charities (ALSAC). All St. Jude Children's Research Hospital patients are treated regardless of their ability to pay. ALSAC covers all costs of treatment beyond those reimbursed by third party insurers, and total costs for families who have no insurance.

For more information, or to contact St. Jude Children's Research Hospital (ALSAC), see their website at: www.stjude.org