• Identification of a PA-binding peptide with inhibitory activity against influenza A and B virus replication.

      Wunderlich, Kerstin; Mayer, Daniel; Ranadheera, Charlene; Holler, Anne-Sophie; Mänz, Benjamin; Martin, Arnold; Chase, Geoffrey; Tegge, Werner; Frank, Ronald; Kessler, Ulrich; et al. (2009-10-20)
      There is an urgent need for new drugs against influenza type A and B viruses due to incomplete protection by vaccines and the emergence of resistance to current antivirals. The influenza virus polymerase complex, consisting of the PB1, PB2 and PA subunits, represents a promising target for the development of new drugs. We have previously demonstrated the feasibility of targeting the protein-protein interaction domain between the PB1 and PA subunits of the polymerase complex of influenza A virus using a small peptide derived from the PA-binding domain of PB1. However, this influenza A virus-derived peptide did not affect influenza B virus polymerase activity. Here we report that the PA-binding domain of the polymerase subunit PB1 of influenza A and B viruses is highly conserved and that mutual amino acid exchange shows that they cannot be functionally exchanged with each other. Based on phylogenetic analysis and a novel biochemical ELISA-based screening approach, we were able to identify an influenza A-derived peptide with a single influenza B-specific amino acid substitution which efficiently binds to PA of both virus types. This dual-binding peptide blocked the viral polymerase activity and growth of both virus types. Our findings provide proof of principle that protein-protein interaction inhibitors can be generated against influenza A and B viruses. Furthermore, this dual-binding peptide, combined with our novel screening method, is a promising platform to identify new antiviral lead compounds.
    • Identification of high-affinity PB1-derived peptides with enhanced affinity to the PA protein of influenza A virus polymerase.

      Wunderlich, Kerstin; Juozapaitis, Mindaugas; Ranadheera, Charlene; Kessler, Ulrich; Martin, Arnold; Eisel, Jessica; Beutling, Ulrike; Frank, Ronald; Schwemmle, Martin; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2011-02)
      The influenza A virus polymerase complex, consisting of the subunits PB1, PB2, and PA, represents a promising target for the development of new antiviral drugs. We have previously demonstrated the feasibility of targeting the protein-protein interaction domain between PA and PB1 using peptides derived from the extreme N terminus of PB1 (amino acids [aa] 1 to 15), comprising the PA-binding domain of PB1. To increase the binding affinity of these peptides, we performed a systematic structure-affinity relationship analysis. Alanine and aspartic acid scans revealed that almost all amino acids in the core binding region (aa 5 to 11) are indispensable for PA binding. Using a library of immobilized peptides representing all possible single amino acid substitutions, we were able to identify amino acid positions outside the core PA-binding region (aa 1, 3, 12, 14, and 15) that are variable and can be replaced by affinity-enhancing residues. Surface plasmon resonance binding studies revealed that combination of several affinity-enhancing mutations led to an additive effect. Thus, the feasibility to enhance the PA-binding affinity presents an intriguing possibility to increase antiviral activity of the PB1-derived peptide and one step forward in the development of an antiviral drug against influenza A viruses.