(530d) Repurposing Barley-Stripe Mosaic Virus As a Nanoparticle Vaccine Platform

Nanoparticle therapies can reprogram tumor-associated macrophages from cancer-supportive to cancer-suppressive (M1) phenotypes. Therapeutic outcomes depend on nanoparticle size, shape, cargo, and surface structure. The special class of rod-shaped plant viruses (RSPVs) allow rare control over all these properties. RSPVs such as tobacco mosaic virus (TMV) are already under investigation for vaccine applications, but their efficacy is limited by the presence of anti-TMV antibodies in human serum. We show that a related RSPV species, barley-stripe mosaic virus (BSMV), does not suffer from preexisting immunity and thus has immense potential for vaccine development. We leverage a bacterial platform to produce BSMV VLPs, non-infectious analogs in which the viral genome is replaced by a user-defined RNA template, for additional control over particle properties. By decoupling VLP production from native host infectivity, we enable high-density surface functionalization with diverse ligands via direct fusion and post-assembly conjugation methods. Through the introduction of specific residues, we achieve control over surface charge and other physicochemical properties. We also decorate the VLPs with immunogenic ligands including toll-like receptor agonists. To enhance decorated particle stability, we identify and remove a dispensable region in the coat protein that contains a cleavage site. Furthermore, we demonstrate that BSMV VLP size and aspect ratio can be tuned by varying the length of the RNA template. The finely tuned, functional VLPs are highly immunogenic and lead to robust M1 activation of murine macrophages. We investigate the mechanism of BSMV VLP immunogenicity, which is partly mediated by toll-like receptors. These scientific and technological advances set the stage for further BSMV VLP development as a nanoparticle platform for cancer immunotherapy and broader vaccine applications.