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Studies of membrane fusion. I. Paramyxovirus-induced cell fusion, a scanning electron-microscope study
Abstract:
Fusion of erythrocytes and HeLa cells with Sendai and Newcastle disease viruses has been studied by scanning electron microscopy. Most virus particles are spherical but vary in diameter from approximately 200 to approximately 600 nm. At 4 degrees C virus particles bind randomly to the cell surface and at high cell densities cross-linking of adjacent cells by virus particles results in cell agglutination. Cell-cell fusion takes place when the agglutinated cell suspension is warmed to 37 degrees C. Fusion is initiated at sites of cell-cell contact and is accompanied in all cases by cell swelling. In the case of suspension HeLa cells, virally mediated cell swelling involves an 'unfolding' of cell surface microvilli and results in the formation of smooth-surfaced single or fused cells. With erythrocytes, swelling results in haemolysis. There is a dramatic reduction in the numbers of virus particles bound to cells following fusion.
Insights
Sendai and Newcastle disease viruses mediate cell fusion by cross-linking erythrocytes and HeLa cells, causing agglutination and subsequent fusion upon warming. This process involves cell swelling and a reduction in bound virus particles.
Area of Science:
- Virology
- Cell Biology
- Microscopy
Background:
- Sendai virus and Newcastle disease virus are known to induce cell fusion.
- Erythrocytes and HeLa cells are commonly used model systems in cell biology.
Purpose of the Study:
- To investigate the mechanism of virus-induced cell fusion using scanning electron microscopy.
- To characterize the morphological changes in erythrocytes and HeLa cells during fusion mediated by Sendai and Newcastle disease viruses.
Main Methods:
- Scanning electron microscopy was employed to visualize the interaction between viruses and cells.
- Erythrocytes and HeLa cells were incubated with Sendai and Newcastle disease viruses at different temperatures.
- Cell agglutination and fusion were induced by temperature shifts.
Main Results:
- Virus particles, 200-600 nm in diameter, bind to cell surfaces at 4°C, leading to cell agglutination at high densities.
- Warming to 37°C induced cell-cell fusion initiated at contact sites, accompanied by cell swelling.
- HeLa cell swelling involved microvilli unfolding, forming smooth-surfaced cells, while erythrocyte swelling resulted in hemolysis.
- A significant decrease in bound virus particles was observed post-fusion.
Conclusions:
- Sendai and Newcastle disease viruses effectively mediate fusion of erythrocytes and HeLa cells.
- The fusion process is temperature-dependent and involves distinct morphological changes in different cell types.
- Scanning electron microscopy provides valuable insights into the dynamics of virus-cell interactions and fusion mechanisms.