Structural Basis of Rotavirus Strain Preference toward N-Acetyl- or N-Glycolylneuraminic Acid-Containing Receptors

Abstract

The rotavirus spike protein domain VP8* is essential for recognition of cell-surface carbohydrate receptors, notably those incorporating N-acylneuraminic acids (members of the sialic acid family). N-acetylneuraminic acids occur naturally in both animals and humans whereas N-glycolylneuraminic acids are present only through dietary uptake in normal human tissues. The preference of animal rotaviruses towards these natural N-acylneuraminic acids has not been comprehensively established, and detailed structural information regarding the interactions of different rotaviruses with N-glycolylneuraminic acids is lacking. In this study, distinct specificities of VP8* towards N-acetyl- and N-glycolylneuraminic acids were revealed using biophysical techniques. VP8* protein from porcine rotavirus CRW-8 and bovine rotavirus NCDV showed preference for N-glycolyl- over N-acetylneuraminic acids, contrasting with monkey rotavirus RRV. Crystallographic structures of VP8* from CRW-8 and RRV with bound methyl N-glycolylneuraminide revealed the atomic details of their interactions. We examined the influence of amino acid type at position 157, which is proximal to the ligand's N-acetyl- or N-glycolyl-moiety and can mutate upon cell culture adaptation. A structure-based hypothesis derived from these results could account for rotavirus discrimination between the N-acylneuraminic acid forms. Infectivity blockade experiments demonstrated that the determined carbohydrate specificities of these VP8* directly correlate with those of the corresponding infectious virus. This includes an association between CRW-8 adaption to cell culture, decreased competition by N-glycolylneuraminic acid for CRW-8 infectivity, and a Pro157 to Ser157 mutation in VP8* that reduces binding affinity for N-glycolylneuraminic acid.