Commercial vaccines leapt toward state-of-the-art on July 8 when the USDA granted a license for the world’s first DNA vaccine for any species. This equine vaccine springs from more than four years of collaborative research between Fort Dodge Animal Health and the Centers for Disease Control and Prevention (CDC). Fort Dodge, CDC, and the USDA jointly announced the achievement on July 18. The West Nile virus (WNV) vaccine, West Nile-Innovator DNA, should arrive on the market in early 2006.

“This is the first DNA vaccine approved by any regulatory authority in the world for commercial sales rather than just for experimental usage, laboratory studies, and scientific paper publication,” says Steve Chu, DVM, PhD, senior vice president of Global Research and Development at Fort Dodge.

A DNA vaccine for salmon protecting against infectious haematopoietic necrosis virus gained approval in Canada about a week after the Fort Dodge vaccine was approved.

According to Chu, the collaboration between Fort Dodge and CDC began officially in 2001, but it was brewing shortly after the disease was discovered in the United States. The CDC has led the basic research on the initial prototype DNA vaccine, while Fort Dodge has led the DNA vaccine development work and the USDA registration studies.

With a conventional vaccine, killed or weakened viral proteins are put in a product as antigens, and the vaccinated animal creates an immune response to the protein antigens to become protected. With a DNA vaccine, carefully selected small pieces of the virus’ genetic material are given to the animal, and they are taken up by its cells. Inside the cells, the DNA fragments are processed into RNA, then into proteins, which are used to stimulate antibodies and a white blood cell immune response. Theoretically, DNA vaccines should have fewer adverse reactions than conventional vaccines. (For more on DNA vaccines, see www.TheHorse.com/ViewArticle.aspx?id=5952.)

Advances in Many Areas

Four years ago, Chu says DNA vaccine technology was well understood, but it was not yet to a point where it could be clinically applied. He explains that Fort Dodge was able to improve the technology in several areas to make the vaccine a reality:

• Improved the growth of Escherichia coli bacteria, which host the WNV DNA plasmid as it grows in the lab. (West Nile virus DNA will not replicate by itself in the lab setting, so it needs some host to carry this DNA material–in this case, E. coli.)
  
• Improved the extraction of WNV DNA from the E. coli.
  
• Mastered purification of the WNV DNA (after removal from the E. coli), and invented creative ways to protect the WNV DNA during the production process.
  
• Enhanced the stability of the WNV DNA material.
  
• Developed a vaccine formulation that improves the DNA delivery and enhances the vaccine’s ability to produce an immune response in the horse.

“After we’ve worked for so long, my feeling is that the development from the original research materials into a final product is partially science, and partially art,” says Chu.

To be licensed by the USDA, the product had to be proven as pure, safe, potent, and efficacious. Specific vaccine trial information will be released when the vaccine goes on the market. Scientists presented preliminary study results at the 85th Annual Meeting of the Conference of Research Workers in Animal Disease in November 2004, which was held in Chicago, Ill. This study showed the DNA vaccine was capable of inducing an immune response to WNV in horses.

The vaccine will be marketed as an additional tool in the Fort Dodge WNV vaccine line rather than a replacement for West Nile-Innovator (killed-virus vaccine) or the West Nile-Innovator combination vaccines. When the DNA vaccine hits the market, veterinarians can contact Fort Dodge for technical advice.

CDC Director Julie Gerberding, MD, says the breakthrough vaccine “has potential benefits far beyond preventing WNV in horses. This science will allow for the development of safer and more effective human and animal vaccines more quickly.” Chu says the CDC is currently leading a clinical trial to determine if the vaccine technology can be used in humans.

Chu reflects, “We’re happy that we’ve accomplished an enormous mission, but our mission has not ended here–we will continue to work on the vaccine technology as a whole, furthering the knowledge and availability of even better products for the veterinary community.”