Analysis of the interaction between a synthetic peptide of influenza virus hemagglutinin and monoclonal antibodies using an optical biosensor

The interaction between two monoclonal antibodies and their corresponding Fab' fragments with a synthetic peptide, corresponding to the C-terminal 23 residues oF the HA₁ chain of influenza virus hemagglutinin against which they were generated, has been examined using an optical biosensor employing the detection principal of surface plasmon resonance (Pharmacia BIAcore(TM)). The data obtained has been analysed in detail by linear transformation of the primary data and nonlinear regression analysis, as well as by analysis of equilibrium binding data. The 21 antibodies and their Fab' fragments displayed higher affinity than the corresponding 1/1 proteins. The IgGs were found to have equilibrium association constants (K(A)) 10-20-fold higher than the corresponding Fab' fragments. This appears largely to be due to differences in the dissociation rate constant (k(d)) and probably reflects increased avidity due to bivalent binding.