Discovery of IL-5-binding unnatural cyclic peptides from multiple libraries by directed evolution

Area of Science:

• Biochemistry
• Molecular Biology
• Immunology

Background:

• Interleukin-5 (IL-5) is a critical type 2 cytokine implicated in allergic conditions, notably severe eosinophilic asthma.
• Targeting IL-5 signaling presents a therapeutic avenue for managing IL-5-driven inflammatory diseases.

Purpose of the Study:

• To identify novel unnatural cyclic peptides with high affinity for human IL-5.
• To explore the potential applications of these IL-5-binding peptides in research, diagnostics, and therapeutics.

Main Methods:

• Directed evolution using systematic evolution of ligands by exponential enrichment (SELEX) on mRNA-displayed peptide libraries.
• Utilized the Escherichia coli-based reconstituted cell-free transcription and translation coupling system (PURE system) for peptide library generation.
• Incorporated genetically encoded unnatural amino acids with thiol-reactive linkers for ribosomal synthesis of cyclic peptides.
• Performed chemical dimerization to enhance the avidity of identified IL-5 binders.

Main Results:

• Successfully identified multiple novel unnatural cyclic peptides that bind specifically to human IL-5.
• Peptides were generated using diverse mRNA-displayed libraries and featured various cyclization strategies.
• Demonstrated the potential to increase binding avidity through chemical dimerization.

Conclusions:

• The discovered IL-5-binding unnatural cyclic peptides represent a promising new class of molecules.
• These peptides hold significant potential for advancing research, diagnostics, and therapeutic interventions targeting IL-5 signaling pathways.