Related Experiment Videos
Fusion of influenza virus membranes with liposomes at pH 7.5
Abstract:
Influenza virus X-31 (H3N2) membranes fuse with liposomes containing ganglioside GD1a at pH 7.5. Fusion was demonstrated by electron microscopy and also can be measured by counting the labeled virus proteins incorporated into liposomes after bound virus has been removed. Liposomes composed of lipids that have no net charge behave as reported by other investigators and do not fuse with influenza X-31 membranes at neutral pH, but they do fuse at low pH. Therefore, the liposomal composition is a factor in whether liposomes fuse with influenza virus membranes at neutral pH, probably by determining whether binding occurs. The liposomal composition necessary for fusion at neutral pH needs to be individualized for each influenza subtype. To establish that a virus requires low pH for membrane fusion, it is first necessary to establish that fusion does not occur at neutral pH under conditions where adequate binding occurs.
Insights
Influenza virus X-31 (H3N2) membranes fuse with ganglioside GD1a liposomes at neutral pH. Liposome composition influences fusion, with neutral liposomes requiring low pH for fusion with influenza virus membranes.
Area of Science:
- Virology
- Membrane Biology
- Biochemistry
Background:
- Influenza virus membrane fusion is critical for viral entry.
- The role of liposomal composition in influenza virus fusion is not fully understood.
- Ganglioside GD1a is implicated in influenza virus binding and fusion.
Purpose of the Study:
- To investigate the influence of liposomal composition on influenza virus X-31 (H3N2) membrane fusion.
- To determine the pH-dependent fusion requirements for influenza virus X-31 with different liposome formulations.
- To establish criteria for assessing pH-dependent fusion in enveloped viruses.
Main Methods:
- Fusion assays using influenza virus X-31 and liposomes containing ganglioside GD1a.
- Electron microscopy to visualize membrane fusion events.
- Quantification of labeled viral proteins incorporated into liposomes post-fusion.
- Varying liposomal lipid composition and pH conditions (neutral and low pH).
Main Results:
- Influenza virus X-31 membranes fused with liposomes containing ganglioside GD1a at neutral pH (7.5).
- Liposomes with no net charge did not fuse with influenza virus X-31 at neutral pH but did fuse at low pH.
- Liposomal composition significantly affects the pH at which fusion occurs, likely by influencing viral binding.
Conclusions:
- The composition of liposomes is a critical determinant of whether influenza virus membranes fuse at neutral pH.
- Influenza virus subtypes may require specific liposomal compositions for neutral pH fusion.
- Establishing lack of fusion at neutral pH under binding conditions is essential to confirm low pH dependence for viral fusion.