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Changes in the morphology of influenza particles induced at low pH
Abstract:
At low pH influenza virus causes membrane fusion. This phenomenon is thought to reflect a part of the infection mechanism of the virus. To obtain more information on the effect of low pH on the virus, the change in morphology of influenza virus particles was studied by electron microscopy. Further, the degradation of haemagglutinin (HA) after trypsin digestion as a function of pH was studied by gel electrophoresis. The results showed that a threshold value existed below which both a change in morphology and an increase in trypsin sensitivity were observed. This threshold pH was found to be strain specific. A number of strains showed a heterogeneity in the particle population with respect to the threshold pH. The various subpopulations appeared to differ genetically. Virus particles with uncleaved precursor HA, HAo, were not effected by the low pH treatment.
Insights
Influenza virus membrane fusion at low pH depends on a specific threshold, varying by strain. This pH sensitivity affects viral morphology and haemagglutinin (HA) protein degradation.
Area of Science:
- Virology
- Molecular Biology
- Biophysics
Background:
- Influenza virus infection involves membrane fusion, a process triggered by low pH.
- Understanding the low pH-induced changes in influenza virus is crucial for deciphering its infection mechanism.
Purpose of the Study:
- To investigate the morphological and biochemical alterations of influenza virus particles at low pH.
- To determine the specific pH threshold for these changes and its strain-dependency.
Main Methods:
- Electron microscopy was used to observe changes in virus particle morphology.
- Gel electrophoresis analyzed the degradation of haemagglutinin (HA) after trypsin digestion across different pH levels.
Main Results:
- A critical pH threshold was identified, below which significant morphological changes and increased trypsin sensitivity of HA were observed.
- This threshold pH was found to be specific to different influenza virus strains.
- Heterogeneity within virus particle populations regarding pH sensitivity was noted, suggesting genetic differences in subpopulations.
- Virus particles with uncleaved HA precursor (HA0) did not exhibit low pH-induced effects.
Conclusions:
- Low pH induces conformational changes in influenza virus, impacting its infectivity.
- The strain-specific pH threshold for fusion and HA degradation highlights the diversity in influenza virus entry mechanisms.
- Genetic variations within virus populations contribute to differential responses to low pH environments.