Analysis of the surface topology of respiratory syncytial virus particles that form on the surface of virus-infected cells

The surface topology of virus filaments on respiratory syncytial virus (RSV)-infected cells was examined using field emission gun-scanning electron microscopy (FEG-SEM) and atomic force microscopy (AFM). FEG-SEM analysis of the surface of RSV-infected cells labelled with an anti-G protein antibody revealed the presence of virus filaments and clusters of the G protein distributed intermittently along their surface. RSV-infected cells thinly coated with chromium were imaged using FEG-SEM and revealed a distinct structured surface topology consisting of closely packed surface domains. The G protein clusters were only associated within a subset of these domains which suggested that this structured topology was mainly derived from the host cell, and the presence of the cell glycocalyx that coats the virus filaments was further suggested. Imaging of RSV-infected cells using AFM was undertaken as a different but complementary approach to the FEG-SEM analysis. Imaging using AFM revealed a similar structured surface topology on the virus filaments to that observed in the FEG-SEM analysis, indicating the consistency in the appearance of the virus surface topology using these different methods. Collectively, this study provides the first detailed imaging of the surface topology of the virus filaments as they form on RSV-infected cells. The imaging data is consistent with the envelopment of the virus filaments by the glycocalyx and highlights the complexity of the spatial organisation within the viral envelope.