Bioengineered Norovirus S₆₀ Nanoparticles as a Multifunctional Vaccine Platform

Homotypic interactions of viral capsid proteins are common, driving viral capsid self-formation. By taking advantage of such interactions of the norovirus shell (S) domain that naturally builds the interior shells of norovirus capsids, we have developed a technology to produce 60-valent, icosahedral S₆₀ nanoparticles through the E. coli system. This has been achieved by several modifications to the S domain, including an R₆₉A mutation to destruct an exposed proteinase cleavage site and triple cysteine mutations (V₅₇C/Q₅₈C/S₁₃₆C) to establish inter-S domain disulfide bonds for enhanced inter-S domain interactions. The polyvalent S₆₀ nanoparticle with 60 exposed S domain C-termini offers an ideal platform for antigen presentation, leading to enhanced immunogenicity to the surface-displayed antigens for vaccine development. This was proven by constructing a chimeric S₆₀ nanoparticle displaying 60 rotavirus (RV) VP8* proteins, the major RV-neutralizing antigen. These S₆₀-VP8* particles are easily produced and elicited high IgG response in mice toward the displayed VP8* antigens. The mouse antisera after immunization with the S₆₀-VP8* particles exhibited high blockades against RV VP8* binding to its glycan ligands and high neutralizing activities against RV infection in culture cells. The three-dimensional structures of the S₆₀ and S₆₀-VP8* particles were studied. Furthermore, the S₆₀ nanoparticle can display other antigens, supporting the notion that the S₆₀ nanoparticle is a multifunctional vaccine platform. Finally, the intermolecular disulfide bond approach may be used to stabilize other viral-like particles to display foreign antigens for vaccine development.