Researchers in the Center for Biologics Evaluation and Research (CBER) have shown that antibodies from people who received high doses of a new type of vaccine against H5N1 (avian influenza or “bird flu”) block the activity of critical parts of this virus. The findings also suggest that the vaccine might protect against a variety of different H5N1 viruses, reducing the need to make new vaccines for each variety of this influenza virus.
Using laboratory tests, the scientists found that these antibodies effectively targeted critical parts of hemagglutinin (HA) and neuraminidase (NA)—the two major proteins on the surface of H5N1 virus. Since HA enables influenza viruses to infect cells and NA helps the infection to spread to new cells, antibodies that disrupt their activity could be effective in protecting against infection by this virus.
CBER previously approved an H5N1 vaccine in 2007. The current report by CBER scientists is the first to describe the quality of the antibody responses in humans to a new H5N1 vaccine that is still undergoing clinical trials sponsored by a pharmaceutical company and is not yet available to the public. Unlike vaccines made from weakened or inactivated whole viruses, the H5N1 vaccine used in these clinical trials is an artificial, virus-like particle (VLP) made up of specific viral proteins. These collections of proteins closely resemble the outside of the H5N1 virus but lack the genes needed for the VLP to reproduce.
Importantly, the VLP in this study was designed to produce several copies of the key section HA and NA linked together, much as they appear on the real H5N1 virus. The CBER scientists found that this arrangement appeared to greatly increase the ability of the vaccine to raise protective antibodies against critical parts of the virus.
Successful development of VLPs as influenza vaccines would offer a rapid, economical response to emerging influenza infections that might cause a pandemic, since it does not require growing viruses in eggs for use as vaccines. The results of the CBER study support further development of vaccines against emerging strains of influenza using this technology.
“H5N1 virus-like particle vaccine elicit cross-reactive neutralizing antibodies in humans that preferentially bind to oligomeric form for influenza hemagglutinin”
Journal of Virology 2011; 85:10945-10954
Ramadevi Raghunandan, Eloi Kpamegan, Steven Pincus, Gale Smith, and Gregory Glenn
Novavax Inc., Rockville, Maryland 20850
Surender Khurana, Jian Wu, Nitin Verma, Swati Verma, Jod Manischewitz, Lisa R. King, Hana Golding.
Division of Viral Products, Office of Vaccines Research and Review, Center for Biologics Evaluation and Research (CBER), Food and Drug Administration, Bethesda, MD 20892