Sialic acid and sialyl-lactose glyco-conjugates: design, synthesis and binding assays to lectins and swine influenza H1N1 virus

The terminal parts of the influenza hemagglutinin (HA) receptors α2,6- and α2,3-sialyllactoses were conjugated to an artificial carrier, named sequential oligopeptide carrier (SOC₄), to formulate human and avian receptor mimics, respectively. SOC₄, formed by the tripeptide unit Lys-Aib-Gly, adopts a rigid helicoids-type conformation, which enables the conjugation of biomolecules to the Lys-N^εH₂ groups. By doing so, it preserves their initial conformations and functionalities of the epitopes. We report that SOC₄-glyco-conjugate bearing two copies of the α2,6-sialyllactose is specifically recognized by the biotinylated Sambucus nigra (elderberry) bark lectin, which binds preferentially to sialic acid in an α2,6-linkage. SOC₄-glyco-conjugate bearing two copies of the α2,3-sialyllactose was not recognized by the biotinylated Maackia amurensis lectin, despite its well-known α2,3-sialyl bond specificity. However, preliminary immune blot assays showed that H1N1 virus binds to both the SOC₄-glyco-conjugates immobilized onto nitrocellulose membrane. It is concluded that Ac-SOC₄[(Ac)₂,(3′SL-Aoa)₂]-NH₂ 5 and Ac-SOC₄[(Ac)₂,(6′SL-Aoa)₂]-NH₂ 6 mimic the HA receptors. These findings could be useful for easy screening of binding and inhibition assays of virus–receptor interactions. Copyright © 2011 European Peptide Society and John Wiley & Sons, Ltd.