The development of inhibitors for the infection using phage library

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Influenza HA is known to bind sialylgalactoside having α2-3- or α2-6- linkages on host cells at the first step of infection. We attempted to design peptides as a universal inhibitor that bind to the receptor-binding pocket of HA.In order to obtain peptides which are a mimic of sialyl oligosaccharide, a phage-displayed random pentadecapeptide library have been employed. phage-displayed method is a selection technology using a pool of phage. It was expected that HA-binding peptides selected from the phage library would serve as inhibitors of influenza A virus. In this study, the HA-binding peptides and glycolipid-binding peptides were selected from the phage-displayed peptide libraries, and they inhibited the infection of both HA1 and HA3 subtypes of influenza virus to MDCK cells. Although the theoretical molecular diversity of pentadecapeptide is calculated to be 3.3x10^<19>, the phage library employed has only 2.5x10^8 kinds of diversity. Therefore, in order to obtain improved the HA-binding peptides, sublibrary generated from a selected sequence was prepared. The directed evolution approach was employed to prepare the sublibraries.The two kinds of sublibraries were constructed to obtain HA1- and HA3-binding peptides. Through the affinity selections for HA1 and HA3 using the sublibraries, several peptide sequences having mutations were obtained. Many of the mutant phage clones showed higher binding affinity for both HA1 and HA3 subtypes than the original A-1 phage. The evoluted peptides inhibited the infection of influenza virus to MDCK cells more efficiently than the original A-1 peptide.