The Molecular Basis of Serotype 1 Reovirus Glycan Interactions and the Function of Glycan-Binding in Pathogenesis

Abstract

Virus-receptor interactions govern the susceptibility of cells to infection and dictate viral tropism in the host. Mammalian reoviruses display serotype-specific neurotropism in newborn mice, with serotype 1 (T1) strains causing hydrocephalus and serotype 3 (T3) strains causing encephalitis. However, the basis for serotype-specific disease is not clear. All reovirus serotypes bind the same proteinaceous receptors, but T1 and T3 strains engage different glycans, suggesting a function for glycan binding in serotype-specific disease. Prior to these studies, the specific glycan bound by T1 reovirus and function of glycan engagement in T1 reovirus tropism were not known. Using glycan array technology, we identified GM2 as a receptor for T1 reovirus. I demonstrated that preincubation with GM2 specifically inhibits infection of mouse embryonic fibroblasts (MEFs) by T1 but not T3 reovirus, demonstrating that GM2 is a serotype-specific receptor. Crystallography studies performed in parallel showed that the head domain of the T1 attachment protein σ1 interacts with the GM2 glycan. I used structure-guided mutagenesis and reverse genetics to engineer mutant viruses incapable of binding GM2. Mutants deficient in GM2-binding displayed impaired hemagglutination capacity and infectivity in MEFs compared with wildtype virus. A mutant T1 reovirus strain incapable of binding GM2 induced substantially less hydrocephalus than wildtype virus, an effect phenocopied by wildtype virus infection of GM2-deficient mice. These findings enhance an understanding of reovirus-glycan interactions and illuminate the function of glycan engagement in virus-induced hydrocephalus. Moreover, since reovirus is being developed as an oncolytic and vaccine vector, understanding virus-glycan interactions may enhance reovirus targeting for clinical applications.