Harnessing the activation of toll‐like receptor 2/6 by self‐assembled cross‐β fibrils to design adjuvanted nanovaccines

Abstract

Protein fibrils characterized with a cross‐β‐sheet quaternary structure have gained interest as nanomaterials in biomedicine, including in the design of subunit vaccines. Recent studies have shown that by conjugating an antigenic determinant to a self‐assembling β‐peptide, the resulting supramolecular assemblies act as an antigen delivery system that potentiates the epitope‐specific immune response. In this study, we used a ten‐mer self‐assembling sequence (I10) derived from an amyloidogenic peptide to biophysically and immunologically characterize a nanofibril‐based vaccine against the influenza virus. The highly conserved epitope from the ectodomain of the matrix protein 2 (M2e) was elongated at the N‐terminus of I10 by solid phase peptide synthesis. The chimeric M2e‐I10 peptide readily self‐assembled into unbranched, long, and twisted fibrils with a diameter between five and eight nm. These cross‐β nanoassemblies were cytocompatible and activated the heterodimeric Toll‐like receptor (TLR) 2/6. Upon mice subcutaneous immunization, M2e‐fibrils triggered a robust anti‐M2e specific immune response, which was dependent on self-assembly and did not require the use of an adjuvant. Overall, this study describes the efficacy of cross‐β fibrils to activate the TLR 2/6 and to stimulate the epitope‐specific immune response, supporting usage of these proteinaceous assemblies as a self‐adjuvanted delivery system for antigens.