Amyloidogenic Propensity of Self-Assembling Peptides and their Adjuvant Potential for use as DNA Vaccines
De novo designed peptides that self-assemble into cross-{beta} rich fibrillar biomaterials have been pursued as an innovative platform for the development of adjuvant- and inflammation-free vaccines. However, they share structural properties similar to amyloid species implicated in neurodegenerative diseases, which has been a long-standing concern for their translation. Here, we comprehensively characterize the amyloidogenic character of the amphipathic self-assembling cross-{beta} peptide KFE8, compared to pathological amyloid and amyloid-like proteins -synuclein (-syn) and TDP-43. Further, we developed plasmid-based DNA vaccines with the KFE8 backbone serving as a fibrillizing scaffold for delivery of a GFP model antigen. We find that expression of tandem repeats of KFE8 is non-toxic and can be efficiently cleared by autophagy. We also demonstrate that synthetic KFE8 nanofibers do not cross-seed amyloid formation of -syn in mammalian cells compared to -syn preformed fibrils. In mice, vaccination with plasmids encoding the KFE32-GFP fusion protein elicited robust immune responses, inducing production of significantly higher levels of anti-GFP antibodies compared to soluble GFP or -syn tagged GFP. Antigen-specific CD8+T cells were also detected in the spleens of vaccinated mice and cytokine profiles from antigen recall assays indicate a balanced Th1/Th2 response. These findings illustrate that cross-{beta}-rich peptide nanofibers have distinct properties from those of pathological amyloidogenic proteins, and are an attractive platform for the development of DNA vaccines with self-adjuvanting properties and improved safety profiles.