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Innovative Strategy Could Speed Approval of Influenza Vaccines
CBER scientists demonstrated how to speed production of the key component of tests used to evaluate the potency of new influenza vaccines and significantly reduce the time needed to approve them. Reducing the time needed to approve influenza vaccines could be especially important during a fast-moving pandemic, when they are urgently needed.
The scientists used genetic engineering techniques to produce a protein called Hemagglutinin (HA), which is found on the surface of influenza viruses. Currently, HA is removed directly from influenza viruses, a process that is labor and time-intensive, and does not always provide sufficient protein or protein in an appropriate form. HA is the target of immune responses to influenza viruses and is used to make vaccines against these viruses.
HA is also used to develop a critical reagent used for quality control tests that evaluate the quality of the HA in influenza vaccines. CBER scientists test samples from each lot (“batch”) of influenza vaccine to determine if the HA in the vaccine is likely to adequately stimulate the immune system of people receiving the vaccine so as to provide protection from influenza. The quality control tests use antibodies that recognize HA to determine whether the HA proteins in the vaccines are present and have retained their natural shape during the manufacturing process. In order to obtain the antibodies, CBER scientists inject the HA from the same viruses used to make the influenza vaccine into sheep to trigger production of antibodies against the HA. If the antibodies recognize and bind to the HA proteins in the vaccine sample, the vaccines in that lot are considered potent (in this case, potency provides an indirect measure of the vaccine’s ability to protect against influenza when injected into humans). If the antibodies do not recognize the HA proteins or bind poorly to them, FDA does not consider the HA in the vaccine to be potent and therefore will not allow the lot to be released for distribution to the public.
Since HA mutates readily, manufacturers must make new vaccines each year in response to the variation among influenza viruses. Likewise, the laboratory test to evaluate lots of each vaccine must use antibodies against identical influenza strains that can identify the new forms of HA.
Currently, CBER scientists chemically treat influenza viruses to remove HA proteins from influenza virus to make antibodies in sheep. However, in 2009, when CBER scientists tried to remove HA proteins from the pandemic (H1N1) 2009 influenza virus using the standard chemical treatment, the chemical disrupted the shape of the HA proteins. The scientists began to proactively prepare for a future pandemic by initiating work to develop an alternate way to produce HA proteins from a pandemic influenza virus that kept their proper structure and could be used to raise anti-HA antibodies in sheep.
The scientists showed that it is possible to insert the genetic material for the HA protein from an influenza virus into bacteria (E. coli). The bacteria then produce the recombinant HA protein that has structure and function similar to HA protein on influenza virus.
The CBER scientists genetically engineered bacteria to make HA from a variety of H1N1 influenza viruses. These genetically engineered HA proteins triggered strong antibody production in sheep and rabbits that worked as well in quality control tests as did those antibodies produced by injecting sheep with traditionally prepared HA obtained directly from chemically treated viruses. The time line for generation of recombinant HA1 in bacteria is significantly shorter from the traditional approach, which could be of great importance in the face of impending pandemic.
“Recombinant HA1 produced in E.coli forms functional oligomers and generates
strain-specific SRID potency antibodies for pandemic influenza vaccines”
Vaccine 29 (2011) 5657-5665
Surender Khuranaa, Christopher Larkinb, Swati Vermaa, Manju B. Joshib, Juan
Fontanac, Alasdair C. Stevenc, Lisa R. Kinga, Jody Manischewitza, William
McCormickb, Rajesh K. Guptab, Hana Goldinga*
aDivision of Viral Products, and bDivision of Product Quality, Center for Biologics
Evaluation and Research (CBER), Food and Drug Administration, Bethesda, MD 20892,
USA, and cLaboratory of Structural Biology Research, National Institute of Arthritis and
Musculoskeletal and Skin Diseases, National Institutes of Health, MD 20892