A simple slot blot for the detection of virtually all subtypes of the influenza A viral hemagglutinins using universal antibodies targeting the fusion peptide.

The fusion peptide of influenza virus hemagglutinin (HA) has a critical role in mediating the entry of the virus into the cells and is also the only universally conserved sequence in the HAs of all strains of influenza A and influenza B viruses. Therefore, it could be an attractive target for new vaccine development and a potency marker for existing influenza vaccines. The fusion peptide epitope is hidden inside the HA proteins, making it inaccessible for quantitative antibody binding. Our simple slot blot protocol highlights pre-treatment of HA samples with moderate concentrations of denaturant to maximally expose the fusion peptide on the protein surface, followed by detection using universal antibodies targeting the fusion peptide. The method is highly reliable, inexpensive and easy to follow. The entire procedure takes only 5 h and can be applied to the quantitative determination of virtually all influenza viral HAs using a single antibody targeting the fusion peptide.