Discovery of Proteinaceous Attachment Factors for GII.4 Norovirus from the Diarrheal Sample of a Norovirus-Infected Patient.

Human norovirus (HuNoV) is the leading cause of acute nonbacterial gastroenteritis globally. Histo-blood group antigens (HBGAs) have been recognized as attachment factors for HuNoV. However, the receptors or other potential attachment factors for HuNoV have not been fully elucidated. A bacterial cell surface-displayed system was used to express GII.4 HuNoV protruding domain (GII.4 P) to capture attachment factors from a diarrheal sample of a patient infected with GII.4 HuNoV. A library of candidate HuNoV proteinaceous attachment factors was constructed. Through a database comparison, a literature review, the predicted protein subcellular localization, the protein-protein interactions (PPIs) network analysis, the molecular simulation and the protein docking analysis, four candidate attachment factors were selected for further investigation from the initial 118 candidates. Finally, two proteins, namely myelin-oligodendrocyte glycoprotein (MOG) and leucine-rich repeat-containing protein 15 (LRRC15), were demonstrated strongly binding to GII.4 P by both in vivo and in vitro assays. The binding between MOG/LRRC15 and GII.4 P can be blocked by GII.4 HuNoV antibody. Immunofluorescence showed that MOG/LRRC15 and GII.4 HuNoV co-localized in the cytoplasm in transfected cells. However, GII.4 HuNoV did not proliferate in the newly constructed MOG/LRRC15 overexpressing cells. This study describes attempts to identify HuNoV proteinaceous attachment factors from the diarrheal sample. Findings from this study will aid in understanding of HuNoV infection in humans, enrichment of GII.4 HuNoV from various environments and construction of cell lines for HuNoV cultivation in vitro.