Proteinticle engineering for accurate 3D diagnosis.

In nature certain proteins are self-assembled inside cells to form nanoscale particles (named "proteinticles") with constant structure and surface topology. Unlike chemically synthesized nanomaterials (e.g., various metal, carbon, and polymer nanoparticles), a variety of functional proteinticles can be easily created through genetic modification of the proteinticle surface, i.e., by adding or inserting specified proteins/peptides to the N- or C-terminus or the internal region of the protein constituent. Here we present proteins/peptides that recognize disease-specific antibodies on the surface of human ferritin based proteinticles for accurate 3D diagnosis of human autoimmune and infectious diseases. The surface display of the extracellular domain of myelin oligodendrocyte glycoprotein (MOG) with native conformation successfully discriminated between autoantibodies to native or denatured MOG, leading to the reliable diagnosis of multiple sclerosis with enhanced accuracy. Also we simultaneously displayed different antigenic peptides from hepatitis C virus (HCV) on the same proteinticle surface with modulating the composition of each peptide. The proteinticles with the heterogeneous peptide surface detected anti-HCV antibodies in patient sera with 100% accuracy. The proposed method of proteinticle engineering can be applied in general to the sensitive and specific diagnosis of many other human diseases.