Influenza vaccine uses insect cells to speed development

Using a strategy involving a genetically modified baculovirus and caterpillar cells scientists from Protein Sciences Corporation have been able to speed up a key step in the development of an experimental cell-based influenza vaccine. They report their findings today at the 2005 American Society for Microbiology Biodefense Research Meeting.

“The bird flu may become the next flu pandemic strain. It could happen at any time,” says Keyang Wang, a scientist at Protein Sciences Corp. and a researcher on the study. “The most effective method to control such an outbreak is the widespread use of a vaccine. The traditional egg-based method requires 3 to 6 months to develop the vaccine. With our cell-based method, the time from receipt of the virus strain to the final vaccine product would be shortened to approximately 1 to 2 months.”

Today’s flu vaccines are prepared in fertilized chicken eggs. The eggshell is punctured, and the influenza virus is injected into the fluid surrounding the embryo. The egg is then resealed, the embryo becomes infected, and the resulting virus is then harvested, purified and used to produce the vaccine. In addition to the long development time, another drawback to this method is the possibility that an avian influenza virus would be lethal to embryos in the eggs.

The vaccine strategy pursued by Protein Sciences, known commercially as FluBlok, does not rely on whole vaccine virus. It uses a purified concentration of a key molecule on the surface of the virus, called hemagglutinin, to elicit an immune response against that specific strain of the virus.

Wang and his colleagues have developed a methodology for rapidly producing and purifying hemagglutinin from an influenza virus. They extract the genes responsible for the production of hemagglutinin from the virus and insert them into a baculovirus. Caterpillar cells are then infected with the virus and begin to produce the hemagglutinin.

The FluBlok vaccine has recently finished phase II clinical trials, where it has established safety and the ability to elicit a strong antibody response in humans.

“Since all the media used here are chemically stable and commercially available, the process can be easily scaled up for commercial manufacture,” says Wang. “New FluBlok vaccines can be developed quickly and safely to address late appearing influenza viruses and to reduce the impact of a potential flu pandemic.”