Adsorption and penetration of enveloped and naked vaccinia virus particles

Area of Science:

• Virology
• Cell Biology
• Molecular Biology

Background:

• Vaccinia virus exists in two forms: intracellular naked virions (INV) and extracellular enveloped virions (EEV).
• Understanding the distinct entry mechanisms of INV and EEV is crucial for comprehending viral infection and developing antiviral strategies.

Purpose of the Study:

• To compare the adsorption and penetration kinetics of INV and EEV.
• To elucidate the environmental factors and cellular mechanisms influencing the entry of each virus form.

Main Methods:

• Comparative analysis of adsorption kinetics for INV and EEV under varying environmental conditions.
• Measurement of plaque-forming units (PFU) to particle ratios to assess infectivity.
• Kinetic studies of viral penetration at 37°C and 22°C, and after incubation in phosphate-buffered saline (PBS).
• Assessment of the impact of sodium fluoride and cytochalasin B on INV and EEV penetration.

Main Results:

• Adsorption kinetics were similar for INV and EEV, but INV adsorption was more environmentally sensitive.
• EEV exhibited approximately twice the infectivity of INV, based on PFU-to-particle ratios.
• EEV penetrated cells more rapidly than INV at 37°C.
• EEV penetration was robust, minimally affected by PBS incubation or lower temperatures, while INV penetration was significantly inhibited by these conditions.
• INV penetration was sensitive to sodium fluoride and cytochalasin B, indicating an energy-dependent and actin-dependent process, unlike EEV.

Conclusions:

• INV and EEV utilize distinct mechanisms for cell entry.
• EEV penetration appears to be a more rapid and less environmentally constrained process compared to INV.
• INV entry is dependent on cellular energy and the actin cytoskeleton, suggesting a different pathway than EEV.