Identification and characterization of phage display-selected peptides having affinity to Peste des petits ruminants virus

Phage display is a well-established technique used for selecting novel ligands having affinity to a plethora of targets including proteins, viruses, whole bacterial and mammalian cells as well as lipid targets. In the present study, phage display technology was used to identify peptides having affinity to PPRV. The binding capacity of these peptides was characterized through various formats of ELISA using phage clones, linear and multiple antigenic peptides. The whole PPRV was used as an immobilized target in a surface biopanning process using a 12-mer phage display random peptide library. After five rounds of biopanning, forty colonies were picked and amplified followed by DNA isolation and amplification for sequencing. Sequencing suggested 12 different clones expressing different peptide sequence Phage-ELISA was performed using all 12 phage clones. Results indicated that four phage clones i.e., P4, P8, P9 and P12 had a specific binding activity to PPR virus. Linear peptides displayed by all 12 clones were synthesized using solid phase peptide synthesis and subjected to virus capture ELISA. No significant binding of the linear peptides with PPRV was evident which may be due to loss of conformation of linear peptide after coating. When the four selected phage clones displayed peptide sequences were synthesized in Multiple antigenic peptide (MAP) format and used in virus capture ELISA, the results indicated significant binding of PPRV to the MAPs. It may be due to increased avidity and/or better projection of binding residues in 4-armed MAPs as compared to linear peptides. MAP-peptides were also conjugated on gold nanoparticles (AuNPs). Visual colour change from wine red to purple was observed on addition of PPRV in MAP-conjugated AuNPs solution. This colour change may be attributable to the networking of PPRV with MAP -conjugated AuNPs resulting in aggregation of AuNPs. All these results supported the hypothesis that the phage display selected peptides were capable of binding to the PPRV. The potential of these peptides to develop novel diagnostic or therapeutic agents remains to be investigated.