title: Characteristics of fusion of respiratory syncytial virus with HEp-2 cells as measured by R18 fluorescence dequenching assay.
abstract: The characteristics of fusion of respiratory syncytial virus (RSV) with HEp-2 cells were studied by the R18 fluorescence dequenching assay of membrane fusion. A gradual increase in fluorescence intensity indicative of virion-cell fusion was observed when R18-labeled RSV was incubated with HEp-2 cells. Approximately 35% dequenching of the probe fluorescence was observed in 1 h at 37 degrees C. Fusion showed a temperature dependence, with significant dequenching occurring above 18 degrees C. The dequenching was also dependent on the relative concentration of target membrane. Thus, increasing the concentration of target membrane resulted in increased levels of dequenching. In addition, viral glycoproteins were shown to be involved in this interaction, since dequenching was significantly reduced by pretreatment of labeled virus at 70 degrees C for 5 min or by trypsinization of R18-labeled virions prior to incubation with HEp-2 cells at 37 degrees C. The fusion of RSV with HEp-2 cells was unaffected over a pH range of 5.5 to 8.5, with some increase seen at lower pH values. Treatment of HEp-2 cells with ammonium chloride (20 and 10 mM), a lysosomotropic agent, during early stages of infection did not inhibit syncytium formation or progeny virion production by RSV. At the same concentrations of ammonium chloride, the production of vesicular stomatitis virus was reduced approximately 4 log10 units. These results suggest that fusion of the virus with the cell surface plasma membrane is the principal route of entry.
authors.affiliation: Department of Microbiology, State University of New York, Buffalo 14214.
authors.forename: N
authors.initials: N
authors.lastname: Srinivasakumar
authors.forename: P L
authors.initials: PL
authors.lastname: Ogra
authors.forename: T D
authors.initials: TD
authors.lastname: Flanagan
mesh_terms: D000643:Ammonium Chloride / Q000494:pharmacology; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000382:microbiology*; D005976:Glutaral / Q000494:pharmacology; D006023:Glycoproteins / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D012136:Respiratory Syncytial Viruses / Q000187:drug effects / Q000502:physiology*; D013696:Temperature; D014357:Trypsin / Q000378:metabolism; D014759:Viral Envelope Proteins / Q000378:metabolism
chemical_list: D006023:Glycoproteins; D014759:Viral Envelope Proteins; D000643:Ammonium Chloride; D014357:Trypsin; D005976:Glutaral