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 anti-F and anti-G protein antibodies revealed the presence of virus filaments and clusters of the F and G proteins distributed intermittently along their surface of the virus filaments. 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. 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 cellular membrane microdomains and the concentration of the virus glycoproteins in other microdomains at specific locations on the virus filaments. Collectively, these data further highlight the complexity of the spatial organisation within the viral envelope during virus assembly.