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The agency announced that FDA scientists have developed candidate vaccine viruses that may be used to produce influenza vaccines.
FDA announced on Oct. 10, 2019 that agency scientists have developed two candidate vaccine viruses (CVVs) that FDA says have protected laboratory animals against a highly pathogenic strain of Influenza A (H7N9). The agency says the CVVs may be used as starting material for commercial production of inactivated influenza vaccines.
The scientists genetically modified hemagglutinin (HA), a viral protein the influenza virus uses to bind to cells, to develop the CVVs. The agency stated that a study showed that this modification could allow for the large-scale production of CVVs in chicken eggs and animal cells through its effects on the activity of both HA and neuraminidase (NA), which are located on the surface of influenza viruses.
In order to prepare for the possibility of a pandemic, agency scientists looked to overcome the challenge posed by the fact that avian CVVs do not grow well in mammalian cells or chicken eggs, which makes it difficult to mass produce vaccines in an emergency. To address this, the scientists substituted an amino acid glycine with a glutamic acid at position G218E in HA. This change affected the activity of both HA and NA during virus amplification in cells. The FDA-developed CVVs facilitated the release of influenza viral particles from infected cells by cutting off sialic acid molecules on the viral surface. FDA stated in a press release that this change “could enhance viral replication for yielding more vaccine.”