Detection of conservative and variable epitopes of the pandemic influenza virus A(H1N1)pdm09 hemagglutinin using monoclonal antibodies

: The goal of this work was to analyze the antigenic structure of the hemagglutinin (HA) of the pandemic influenza virus A(H1N1)pdm09 using monoclonal antibodies (MAbs) and to develop a sandwich ELISA for identification of pandemic strains. Competitive ELISA demonstrated that 6 MAbs against HA of the pandemic influenza A/ IIV-Moscow/01/2009 (H1N1)pdm09 virus identified six epitopes. Binding of MAbs with 22 strains circulating in Russian Federation during 2009-2012 was analyzed in the hemagglutination-inhibition test (HI). The MAbs differed considerably in their ability to decrease the HI activity of these strains. MAb 5F7 identified all examined strains; MAbs 3A3 and 10G2 reacted with the majority of them. A highly sensitive sandwich ELISA was constructed based on these three MAbs that can differentiate the pandemic influenza strains from the seasonal influenza virus. The constancy of the HA epitope that reacts with MAb 5F7 provides its use for identification of the pandemic influenza strains in HI test. MAbs 3D9, 6A3 and 1E7 are directed against the variable HA epitopes, being sensitive to several amino acid changes in Sa, Sb, and Ca2 antigenic sites and in receptor binding site. These MAbs can be used to detect differences in HA structure and to study the antigenic drift of the pandemic influenza virus A(H1N1)pdm09.