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

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. 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. NoVBPs conferring a high affinity to norovirus GII were successfully isolated from activated sludge micro-organisms. NoVBPs could be natural viral ligands and play an important role in the NoV transmission.