A VLP vaccine platform comprising the core protein of hepatitis B virus with N-terminal antigen capture

Nanoparticle presentation systems offer the potential to develop new vaccines rapidly in response to emerging diseases, a public health need that has become increasingly evident in the wake of the COVID-19 pandemic. Previously, we reported a nanoparticle scaffold system termed VelcroVax. This was constructed by insertion of a high affinity SUMO binding protein (Affimer), able to recognise a SUMO peptide tag, into the major immunodominant region of VLPs assembled from a tandem (fused dimer) form of hepatitis B virus (HBV) core protein (HBc). Here we describe a modified form of VelcroVax, comprising monomeric HBc with the Affimer inserted at the N-terminus (termed N-VelcroVax). In contrast to the tandem form of VelcroVax, N-VelcroVax VLPs were expressed well in E. coli. The VLPs effectively bound SUMO-tagged Junin virus glycoprotein, gp1 as assessed by structural and serological analyses. Cryo-EM characterisation of N-VelcroVax complexed with a SUMO-Junin gp1 showed continuous density attributable to the fused Affimer, in addition to evidence of target antigen capture. Collectively, these data suggest that N-VelcroVax has potential as a versatile next generation vaccine scaffold.