HS-AFM and SERS Analysis of Murine Norovirus Infection: Involvement of the Lipid Rafts

Studies on human norovirus are severely hampered by the absence of a cell culture system until the discovery of murine norovirus (MNV). The cell membrane domains called lipid rafts have been defined as a port of entry for viruses. This study is conducted to investigate murine norovirus binding on the mouse leukemic monocyte macrophage cell line. Lipid raft related structures are extracted from cells by detergent treatment resulting detergent-resistant membrane (DRMs) domains. The real-time polymerase chain reaction technique is performed to detect the viral genome, thereby the MNV binding on the DRMs. The interactions between MNV and DRMs are investigated by high-speed atomic force microscopy (HS-AFM) combined with surface-enhanced Raman spectroscopy (SERS). The inoculation of the virus onto cells results in the aggregations of detergent-resistant membrane domains significantly. The characteristic Raman band of MNV is found in inoculated samples. To be sure that these results are originated from specific interactions between DRM and MNV, methyl-a-cyclo-dextrin (MaCD) is applied to disrupt lipid rafts. The MNV binding on DRMs is precluded by the MaCD treatment. The cholesterols chains are defined as a key factor in the interactions between norovirus and DRMs. The authors conclude that the MNV binding involves the presence of DRMs and cholesterol dependent.