Poster Presentation 12th Australian Peptide Conference 2017

Targeted delivery of cyclotides via conjugation to a nanobody (#188)

Christina I Schroeder 1 , Soohyun Kwon 1 , Joao N Duarte 2 , Zevang Li 2 , Jingjing J Ling 2 , Olivier Cheneval 1 , David J Craik 1 , Hidde L Ploegh 2
  1. Institute for Molecular Bioscience, The University of Queensland, Brisbane, Qld, Australia
  2. Boston Children’s Hospital, Boston, MA, USA

Most naturally occurring peptides have poor proteolytic stability, which limits their therapeutic application. Cyclotides are plant-derived cyclic peptides that resist proteolysis due to their highly constrained structure, comprising a head-to-tail cyclic backbone and three disulfide bonds that form a cystine-knotted core. This makes them potentially useful as scaffolds onto which peptide sequences (epitopes) can be grafted. We target delivery of cyclotides via conjugation to a nanobody to confer specificity. We chose VHH7, an alpaca-derived nanobody that targets murine Class II MHC class II molecules, for conjugation of cyclotides and examined their immunogenic properties upon delivery to antigen presenting cells. Two cyclotides, MCoTI-I and MCoTI-I with a HA-tag epitope (YPYDVPDYA) grafted in loop 6 (MCoTI-HA), were tested. A conjugation strategy using sortase A and strain-promoted click chemistry provides a straight-forward method for targeted delivery of cyclotides to antigen-presenting cells and could play a role in the development of peptide-based vaccines. More generally, these types of fusions might also be useful to direct cyclotides to other cell types, based on the specificity of the VHH fusion partner.