Investigating the Effects of Glycochenodeoxycholic Acid on Mutant Murine Norovirus P-Domain Structure and Antibody Interactions
Viral gastroenteritis is most frequently caused by exposure to norovirus (NoV) through fecal–oral transfer resulting in severe vomiting and diarrhea lasting between 24 to 48 hours, yet for certain individuals, these infections can be fatal. With epidemic strains continuously emerging, it is imperative to understand how these viruses promote infection. NoVs contain 90 highly mobile P-domain dimers across their capsid surface with specific P-domain conformations known to facilitate host cell infection and promote immunological evasion. To understand these mechanisms, we investigated a novel murine norovirus (MNV) mutant and the effects of native gastrointestinal cofactor glycochenodeoxycholic acid (GCDCA) on its P-domain dynamics and antibody interactions. Cryo-electron microscopy and image reconstruction were used for structural determination of the MNV isolate, WU23. In the presence of GCDCA, we found variable dynamics across dimer pairs A/B and C/C. This result may support our hypothesis that WU23 is less sensitive to gastrointestinal cofactors such as bile salts. Additionally, we characterized the binding and neutralization capacity of three previously established anti-MNV monoclonal antibodies on WU23 in the presence and absence of GCDCA. Here, low GCDCA concentrations significantly increased infectivity and simultaneously promoted antibody escape. The three monoclonal antibodies isolated against wildtype MNV-1 were able to neutralize WU23, albeit with much lower efficacy. For future structural studies on antibody-mediated neutralization of MNV, we have developed and crystallized a recombinant single-chain variable fragment of the monoclonal 4F9. This is a particularly interesting antibody in that the only escape mutants isolated thus far act in an allosteric manner rather than directly contacting the bound antibody.
Chemistry, Biochemistry, Biology, Virology, Physics, Molecular
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The University of Texas Medical Branch at Galveston