Research on attachment of flagellin enhances immunostimulatory activity of hemagglutinin-ferritin nano-cage

Abstract

Hemagglutinin (HA) displayed on a ferritin nano-cage has been shown to be effective in generating a potent and protective immune response against a broad range of influenza infections in experimental animals. In the present study, I showed that the HA-ferritin cage produces mostly Th2 responses (class switching to IgG1), and serum IgG2a is not significantly increased. Attachment of flagellin together with HA to the exterior surface of the ferritin cage greatly enhanced not only total IgG but also Th1-type cytokine secretion and class switching to IgG2a, as a result of significant increase in Th1 responses. Moving the ferritin attachment site from the N-terminus to an internal site in flagellin had only a minor effect on immunostimulation, whereas moving it to the C-terminus completely abolished immunostimulation. I used a small immunoglobulin fragment VL12.3 as a convenient method for attaching HA and flagellin to the ferritin cage. This method can be used for rapid screening of a variety of protein cages and nano-assemblies to identify the most suitable carrier and adjuvant proteins for the target antigen.