Structural basis of glycan specificity of P[19] VP8*: Implications for rotavirus zoonosis and evolution

Recognition of specific cell surface glycans, mediated by the VP8* domain of the spike protein VP4, is the essential first step in rotavirus (RV) infection. Due to lack of direct structural information of virus-ligand interactions, the molecular basis of ligand-controlled host ranges of the major human RVs (P[8] and P[4]) in P[II] genogroup remains unknown. Here, through characterization of a minor P[II] RV (P[19]) that can infect both animals (pigs) and humans, we made an important advance to fill this knowledge gap by solving the crystal structures of the P[19] VP8* in complex with its ligands. Our data showed that P[19] RVs use a novel binding site that differs from the known ones of other genotypes/genogroups. This binding site is capable of interacting with two types of glycans, the mucin core and type 1 histo-blood group antigens (HBGAs) with a common GlcNAc as the central binding saccharide. The binding site is apparently shared by other P[II] RVs and possibly two genotypes (P[10] and P[12]) in P[I] as shown by their highly conserved GlcNAc-interacting residues. These data provide strong evidence of evolutionary connections among these human and animal RVs, pointing to a common ancestor in P[I] with a possible animal host origin. While the binding properties to GlcNAc-containing saccharides are maintained, changes in binding to additional residues, such as those in the polymorphic type 1 HBGAs may occur in the course of RV evolution, explaining the complex P[II] genogroup that mainly causes diseases in humans but also in some animals.
Author summary Rotaviruses (RVs) are diverse, infecting humans and/or animals. Significant advances in understanding ligand-associated RV host ranges have been made but how such host ligands drive RV evolution leading to the diverse genotypes/genogroups already identified remains unclear. In this study, through solving crystal structures of P[19] VP8*-ligand complexes with two different ligands, we demonstrated how genetic variations could configure a totally new ligand binding site leading to a distinct new evolutionary lineage. Sequence comparison also identified further changes of the binding site which may occur over the course of RV evolution leading to different P[II] genotypes infecting different populations, including some animal species widely seen everywhere around the world. The elucidation of the genetic and evolutionary relationships among all members of the P[II] lineage including the two genotypes in P[I] is highly significant for advancing our understanding of RV host ranges, disease burden and zoonosis of human diseases.