Development of an enzyme‐linked immunoassay for the quantitation of influenza haemagglutinin: an alternative method to single radial immunodiffusion

BACKGROUND The current method used to measure haemagglutinin (HA) content for influenza vaccine formulation, single radial immunodiffusion (SRID), is lengthy and relies on the availability of matched standardised homologous reagents. The 2009 influenza pandemic highlighted the need to develop alternate assays that are able to rapidly quantitate HA antigen for vaccine formulation. OBJECTIVES The aim of this work was to develop an enzyme-linked immunoassay (EIA) for the rapid quantitation of H1, H3, H5 and B influenza HA antigens. METHODS Monoclonal antibodies (mAbs) selected for haemagglutination inhibition (HAI) activity were conjugated with horseradish peroxidase and used to establish a capture-detection EIA for the quantitation of HA antigen. Results were compared with the appropriate reference SRID assays to investigate assay performance and utility. RESULTS Quantitation of HA antigen by EIA correlated well with current reference SRID assays. EIA results showed equivalent precision and exhibited a similar capacity to detect HA antigen in virus samples that had been used in either stability or splitting studies, or subjected to physical or chemical stresses. EIA exhibited greater sensitivity than SRID and has the potential to be used in high-throughput applications. CONCLUSIONS We demonstrated the utility of EIA as a suitable alternative to SRID for HA antigen quantitation and stability assessment. This approach would lead to earlier availability of both seasonal and pandemic vaccines, because of the extended cross-reactivity of reagents.