FDA Develops Alternative Assay to Increase Availability of Influenza Vaccines

A laboratory assay developed by scientists at FDA could speed the release of pandemic influenza vaccines to the public by shortening the time it takes to test vaccine potency. The FDA scientists developed the new assay in response to the recommendation of a workshop organized by the World Health Organization (WHO) following the 2009 H1N1 influenza pandemic and aninitiative by the US Department of Health and Human Services’ Biomedical Advanced Research and Development Authority (BARDA).

One advantage of the new potency assay is that it does not require the use of antisera for testing influenza vaccines. The current standard potency assay for influenza vaccines uses antibodies against hemagglutinin (HA), a protein on the surface of the virus that is an important component of influenza vaccines. In order to make the antibodies, vaccine viruses aretreated with enzymes to release HA proteins from their surface. If the anti-HA antibodies recognize and bind to the HA, the two molecules form tiny visible rings, demonstrating that the HA is suitable for use in influenza vaccines.Drawbacks to the current assay are that the use of enzymes to release HA from influenza viruses does not reliably produce sufficient amounts of HA and the resulting proteins are difficult to purify before injecting into sheep. The new assay does not use antibodies that attach to HA, instead it is based on thenatural interaction between the influenza virus envelope protein, HA, and the receptor molecule on the surface of target cells lining the human respiratory tract.