Norovirus-binding proteins recovered from activated sludge micro-organisms with an affinity to a noroviral capsid peptide.

AIMS Transmission routes of noroviruses, leading aetiological agents of acute gastroenteritis, are rarely verified when outbreaks occur. Because the destination of norovirus particles being firmly captured by micro-organisms could be totally different from that of those particles moving freely, micro-organisms with natural affinity ligands such as virus-binding proteins would affect the fate of viruses in environment, if such microbial affinity ligands exist. The aim of this study is to identify norovirus-binding proteins (NoVBPs) that are presumably working as natural ligands for norovirus particles in water environments. METHODS AND RESULTS  NoVBPs were recovered from activated sludge micro-organisms by an affinity chromatography technique in which a capsid peptide of norovirus genogroup II (GII) was immobilized. The recovered NoVBPs bind to norovirus-like particles (NoVLPs) of norovirus GII, and this adsorption was stronger than that to NoVLPs of norovirus genogroup I. The profile of two-dimensional electrophoresis of NoVBPs showed that the recovered NoVBPs included at least seven spots of protein. The determination of N-terminal amino acid sequences of these NoVBPs revealed that hydrophobic interactions could contribute to the adsorption between NoVBPs and norovirus particles. CONCLUSIONS  NoVBPs conferring a high affinity to norovirus GII were successfully isolated from activated sludge micro-organisms. SIGNIFICANCE AND IMPACT OF THE STUDY  NoVBPs could be natural viral ligands and play an important role in the NoV transmission.