Amino acid substitutions in norovirus VP1 dictate host dissemination via variations in cellular attachment

Viruses interact with receptors on the cell surface to initiate and coordinate infection. The distribution of receptors on host cells can be a key determinant of viral tropism and host infection. Unravelling the complex nature of virus-receptor interactions is, therefore, of fundamental importance to understanding viral pathogenesis. Noroviruses are non-enveloped, icosahedral, positive-sense RNA viruses of global importance to human health, with no approved vaccine or antiviral agent available. Here, we use murine norovirus as a model to study the molecular mechanisms of virus-receptor interactions. We show that variation at a single amino acid residue in the major viral capsid protein, VP1 301, has a key impact on the interaction between virus and receptor. This variation did not affect virion replication or virus growth kinetics, but a specific amino acid was rapidly selected through evolution experiments and significantly improved cellular attachment when infecting cells in suspension. However, modulating plasma membrane mobility counteracted this phenotype, suggesting a role for membrane fluidity in norovirus cellular attachment. When the infectivity of a panel of recombinant viruses with single amino acid substitutions at this residue was compared in vivo, there were differences in the tissue distribution of viruses in a murine host, suggesting a role for VP1 301 in dissemination in vivo. Overall, these results highlight how capsid evolution can influence infectivity and dissemination in the host.