Cholesterol effectively blocks entry of flavivirus.

Area of Science:

• Virology
• Cell Biology
• Biochemistry

Background:

• Japanese encephalitis virus (JEV) and dengue virus serotype 2 (DEN-2) are enveloped flaviviruses.
• Flaviviruses utilize receptor-mediated endocytosis and low pH-triggered membrane fusion for cell entry.
• Lipid rafts, cholesterol-enriched membrane domains, are critical for various cellular processes.

Purpose of the Study:

• To investigate the role of lipid rafts and cholesterol in flavivirus infection.
• To determine how cholesterol levels affect JEV and DEN-2 entry and replication.

Main Methods:

• Disruption of lipid rafts using cholesterol depletion (methyl-beta-cyclodextrin) and cholesterol chelation (filipin III).
• Analysis of viral infection levels after lipid raft disruption.
• Membrane flotation assays to identify flaviviral protein localization.
• Assessment of cholesterol's effect on viral adsorption and entry.

Main Results:

• Disrupting lipid rafts reduced JEV and DEN-2 infection, primarily impacting intracellular replication and secondarily viral entry.
• Flaviviral nonstructural proteins were found associated with detergent-resistant membrane structures, suggesting localization to lipid raft-like membranes.
• Cholesterol addition blocked flaviviral infection, contrasting with other viruses.
• Cholesterol significantly hindered early viral life cycle steps, including adsorption and entry (fusion and RNA uncoating).

Conclusions:

• Flavivirus infection exhibits a stringent requirement for specific membrane components, particularly cholesterol levels.
• Cholesterol plays a critical, multifaceted role in the flavivirus life cycle, affecting both entry and replication.