Location of antigenic sites recognized by monoclonal antibodies in the influenza A virus nucleoprotein molecule

1 D. I. Ivanovsky Institute of Virology, Gamaleya Str. 16, 123098 Moscow, Russia 2 Division of Virology, Department of Infectious Diseases, St Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105 3678, USA 3 Department of Pathology, University of Tennessee, Memphis, TN 38105, USA Correspondence Nikolai V. Kaverin labphysvir{at}mail.ru The locations of amino acid positions relevant to antigenic variation in the nucleoprotein (NP) of influenza virus are not conclusively known. We analysed the antigenic structure of influenza A virus NP by introducing site-specific mutations at amino acid positions presumed to be relevant for the differentiation of strain differences by anti-NP monoclonal antibodies. Mutant proteins were expressed in a prokaryotic system and analysed by performing ELISA with monoclonal antibodies. Four amino acid residues were found to determine four different antibody-binding sites. When mapped in a 3D X-ray model of NP, the four antigenically relevant amino acid positions were found to be located in separate physical sites of the NP molecule. A supplementary table showing the primers used in this study is available with the online version of this paper.