FDA Develops New Potency Assay For Flu Vaccines

Scientists at the U.S. Food and Drug Administration (FDA) has developed a new laboratory assay that could speed up the launch of pandemic influenza vaccines to the public by cutting the length of time it takes to test vaccine potency. The Office of Vaccines Research and Review conducted the study assessing the new assay.

The new assay was developed by FDA scientists in response to the recommendation of a workshop organized by World Health Organization (WHO) and the U.S. Department of Health and Human Services’ Biomedical Advanced Research and Development Authority (BARDA) following the 2009 H1N1 influenza pandemic.

One advantage of the new vaccine potency assay is that it does not require the use of antisera to test vaccines. Antisera are solutions of antibodies against specific targets on the vaccine being evaluated. The new assay does not use antibodies but is based instead on the natural interaction between the influenza virus envelope protein hemagglutinin (HA) and the receptor molecule on the surface of target cells.

Researchers used artificial versions of the HA receptors (sialic acid [ SA]-glycans) usually targeted by pandemic avian influenza or human influenza. These were tested to find out whether HA proteins from influenza vaccines were recognized and attached to the artificial versions of the HA receptors. HA proteins that were identical to the viral protein and able to act as a vaccine were able to fit into the proper SA-glycan receptor sites. 

“The scientists used a technique called surface plasmon resonance (SPR) to measure the amount of HA proteins attached to the artificial receptors that were coated on special chips. In this way they were able to determine both how much HA was in vaccine samples as well as the stability of those proteins — key measurements for evaluating vaccine potency. This assay was also able to measure the amount of HA protein in vaccines that were mixed with substances called adjuvants — substances that are added to some vaccines to increase their ability to trigger immune responses,” the agency explained in its press release.

Results from SPR-based assay measurements indicated that the new vaccine potency assay might be reliable enough to replace the slower, standard one. The new assay and other alternative potency assays are currently undergoing further evaluation.