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Veterinary medical officers Juergen Richt and Kelly Lager of the center's Virus and Prion Diseases of Livestock Research Unit used a reverse genetics process to actually create new flu viruses whose individual components could be explored. It is hoped these components can in turn become the targets of vaccines.

The influenza that has spurred this research--a swine flu type that contains gene segments from birds and humans, as well as from pigs--has spread throughout North America since being detected in 1998.

Swine influenza presents a special challenge to genetics researchers because its virus stores its information in RNA, which is more susceptible to mutation and allows viruses to evolve far more rapidly than in DNA. Because of this, it is sometimes hard for an infected host to develop lasting immunity.

Since manipulations commonly done on DNA cannot be performed with RNA, reverse genetics is used to perform a procedure called reverse transcription, in which RNA viruses' genetic material is turned into a DNA state where modifications can be easily introduced. When the DNA is converted back into RNA, these modifications occur in the genome of the RNA virus as well.

Through this approach, the researchers in collaboration with scientists from Iowa State University, the Mount Sinai School of Medicine in New York and St. Jude Children's Research Hospital in Memphis, Tenn. used cloned DNA to generate swine influenza viruses.

Source: USDA Agricultural Research Service - 11th February 2004