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 acquired only through dietary uptake in normal human tissues. The preference of animal rotaviruses for 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* for N -acetyl- and N -glycolylneuraminic acids were revealed using biophysical techniques. VP8* protein from the porcine rotavirus CRW-8 and the bovine rotavirus Nebraska calf diarrhea virus (NCDV) showed a preference for N -glycolyl- over N -acetylneuraminic acids, in contrast to results obtained with rhesus 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* domains 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.